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I have just finished drilling the holes on my second set of Penrose forms. The first set?? Lets just say its always a good idea to check and recheck the drill press for perpendicularity, and make sure your drilling on the correct side of the form.

When tapping the holes, will it matter which side I tap from? I think I should be tapping down from the middle side, as opposed to the bottom side toward the middle. Is this correct, or does it even matter.  (Mark Bolan)

    I don't know that it matters, but if you have built the forms to accept shoulder bolts then one side of the form has a larger diameter hole (the shoulder side) then the other side (the threaded side).  If that is the case then tap the holes before you remove the clamps.  Place the tap through the larger hole which will help align the tap to the smaller hole.  This works for bolts that are pulling.  The push bolts, you are one your own.

    Also use good quality taps.  I have found, having made 3 forms to get a good one, that a three fluted tap cuts easier.  The tap I use also has a 7 thread taper to it which helps getting it started.  The taps you typically find at places like Home Depot and Lowes are 4 fluted taps that are tapered about 3 threads.  It just takes too much effort to get those started and therefore they become misaligned and you are at risk of breaking them.  Break one and it is easier to start over then to remove that broken tap.  Ask me how I know.  (Tim Wilhelm)

    One way to start/keep the Tap/Thread aligned and perpendicular to the form is to put the tap in your drill press and TURN IT BY HAND. You may even want to unplug the drill press just to make sure. Also use a good cutting oil and clean the tap often.  (Don Schneider)

      What Don says is what I would do.  I use a spring loaded tool to put pressure on the tap instead of putting the tap it in the chuck.  Drill the hole and do not move the form before tapping, that will keep the hole lined up.

      Check Todd's site (here) for some tapping shots with the spring loaded tool. I think he has  them listed  under my name.  (Tony Spezio)


If you are building forms, and WOULD happen to break a tap that sticks in the hole (where else is it going to go!!!!!!), you can remove it by smacking it a good blow with a punch or something along those lines. It will break into pieces, being that it's composite is very hard. Might take a few whacks, but it works. Used that technique many times from the days of gunsmithing works. You can't drill em', that's for sure! (Jerry Andrews)


I feel like such a klutz.  With all of the advise given on taking one's time with tapping the 5/16-18 treated holes for the "Penrose" forms.  I managed to break a tap - in the last hole, no less.

Any advice as to what I can do now (regarding the broken tap, I mean)?  It's a 4-fluted Vermont American.  We won't discuss the fact that Rick Crenshaw was kind enough to loan me one of the good (spiral point) taps that he had so much success with.  No, I had to use one of the cheap ones from Lowes,  but that's another lesson learned.

Newbies beware - Take the advise that's given by these guys!!!  (Denis Dunderdale)

    I am not a machinist, but once I did the same, and took a very hard chisel, and struck the broken part with a mighty whang.  It broke to pieces.  However, I hope some better informed listers will answer you before you try such a drastic stroke.  (Ralph Moon)

    I have removed broken taps by drilling into the tap with a slightly undersized tool tapping in a tapered reamer and backing out the broken tap, much the same way as removing a broken bolt.  (Doug Losey)

    You really only have 2 choices. Pick up a quality tap extractor and give it a try or do as Ralph suggested and drive the broken piece of tap out. The tap (even a cheap one) is hard and will usually break with minimal damage to the threads. After it is removed, just run a tap back through the hole. Find a good tap, even if you have to order it and wait for it to arrive. 

    Oh, and one other thing, use a good cutting fluid when retapping the hole. It goes without saying that it is critical for the initial hole as well.  (Larry Blan)

    Well, I had the same problem when I made my set.  Extractor didn't work so I used a punch and hammer to punch it out.  The threads were damaged so I went down to the hardware and bought a 1/2" rod.  I drilled it and threaded it to the size I wanted.  I then drilled out the ruined hole just smaller than the 1/2" rod.  I adjusted the rod diameter but the hole can be adjusted with drill bit choice.  I then cut a piece of the threaded rod to fit in the hole in the form and used  a vise to press the rod piece in.  Worked great.  (Onis Cogburn)

    Someone wrote in, some time back, to use some kind of acid on a broken tap.   Said the acid would eat away the harder metal of the tap before the softer  metal of the forms. Does anyone remember this post?  (David Dziadosz)

      Yes, that was me. You mix a small amount of water with Nitric acid. Nitric acid by itself won't eat metal, but when you add a little water to it, it eats like crazy.

      It eats the hardest metal the first. I've used this trick many times, when I get a broken tap in a rifle receiver. The best way would be to plug the other side of the hole with modeling clay and fill the hole up about 1/2 way or so, with the acid. It will fizz for a while. After the fizzing slows down, rinse out with water and turn the form upside down. Tap on the form with a plastic mallet.  If the tap doesn't drop out, then add more acid and try again.

      This usually works very well. If you can locate some Nitric Acid.  (Dave LeClair)

    I'm assuming that the last hole is on one or the other ends and not in the middle.  If that is the case, an the other methods don't work, cut the last six inches off of your form and make a 5 foot 6 inch long form.  Might limit you a little in what you make but not a lot.  Use it, abuse it, and make another form once you got a few rods under your belt.  By that time you will have figured out what you dislike about it and will be wanting to make a new form anyway.  (Tim Wilhelm)

    Just a quick comment on using taps.  At the time I was making my steel forms there was  a lot of comment about breaking taps. I decided to be cautious and only taped the " push" side of the forms. To obtain the closing action I took a bolt all the way through both sides of the form and achieve the closing action with a nut on the end of the bolt.

    It is quite easy to use and just as accurate, and saves one lot of tapping.  Also by using a bolt with only a small amount of thread on the end (there is probably a technical name for such a bolt) the main part of the bolt acts as another dowel to assist alignment.

    Denis you may be able to use the same technique when you get the tap out of the hole, even if only for that station if you are dealing with the pull action of the form.  (Ian Kearney)

    I broke 3 taps in the last set of forms I made.  Each time I was able to separate the form halves and there was always a "stub" of the tap sticking out.  I just used the tapping tool to back it out.  (Kyle Druey)

    If it were me, I'd move the hole to the other side of the station and start again.  Leave the broken tap there as a reminder that we're not building nuclear reactors, just fishin' poles.  (Harry Boyd)


I drilled and tapped all the holes today.  On about 4 of the 13, the shoulder bolt doesn't seat all the way and is really difficult to turn.  I think I was having a problem getting perfect alignment on the tapping or maybe on the 3/8" bore after I drilled the 1/4" all the way through. So, what's done is done, but is there a way to salvage this or is it garbage and I have to start over?  Somebody please have the saving advice.  (Kris Fox)

    Don't despair. That happened to several of my holes, as well.  I took my forms to a machinist friend who stuck a tap bit in a drill and reamed the sucker out.  Basically, he opened up the hole with the tap bit and gave it just enough slop so that the shoulder bolts could fit in without hanging up. The threads were fine, just opened up a bit more.  It wasn't precision machining, but it did the trick, and it took him about 10 minutes to do about 7 holes.  I don't think I would trust myself to do that (I did break my first bit in the hole, and it took me about an hour to pound the dang thing out with a hammer and a filed down screw driver), but you might know someone who could do it.

    If you did this stuff in one day, then don't stop now!  BUT, where I really messed up was making the groove.  Be sure to take your time with that job. It is much harder to fix a bad groove.  (Jason Swan)

    If I understand you, the absolute worst thing that could be happening is that the tops are not level due to the holes being off-center. As long as the strips aren't moving up-and-down as you tighten the screws (that would be a disaster), you should be able to drawfile the tops (when assembled) so they're again level with each other. The may not be perfectly straight and level when disconnected, but they should be and stay parallel and level when attached, no? I can't remember the name of the file guys use for that job, but it used to be used for shoeing horses. We all went in on a special group-buy a few years ago. Somebody'll recall the name.  (Art Port)

      Ain't that a vixen file?  (Dennis Haftel)

        I believe Vixen is a brand name.  Its also called a curved tooth mill file... mine was worth every penny.  (Kyle Druey)

      That would be a Vixen file, or body file.  (Larry Blan)

      It is called a Vixen File. Also used in aircraft sheet metal work.  (Tony Spezio)

        Why cannot a regular Mill Bastard File be used to true up the tops? A Vixen File sounds like a "girly man" file.  (Marty DeSapio)

          A curved tooth file is a more aggressive file than a mill file.  From what I have seen, Vixen is a trademark or brand name used by Simonds files.  Nicholson, and others, just call their's curved tooth.  I personally like the one without a tang that can be attached to a special file holder.  I mounted mine on the bottom of a 1x1 then added some handles and knocked off the rough edges to protect my "girly man" hands.  ;^)

          I think a good process is to first use the curved tooth file to take out the major differences between the two bars and the deformations in the bars that are caused when the material is cold rolled.  Follow that with some drawfiling using a mill file.  Traditional drawfiling, leaves a very smooth surface on a piece of metal.  It is done by holding the file 90 degrees to the work piece with the tang to the left and pulling the file towards you.

          Kris, as far as your bolt problem, not seeing it, I'm not exactly sure what is causing your problem.  If the two holes aren't aligned with each other you might try wallowing out the 3/8" diameter hole with a round file at one or the other ends of the hole.  I wouldn't try to enlarge the hole for it's entire length, but just one end might give you enough slop to prevent the bolt from binding while still giving it good contact through the rest of the hole.  If the holes are aligned with each other but are not at 90 degrees to the bars, you might find that putting a washer on the bolt could give you better contact.  I think you'll be fine, as is.  Chances are you'll have some other problems crop up as you complete the form.  (We all did)  Finish this form, use it to make a rod and decide if you would like better forms or not.  Once you have made a rod, you can judge how your forms work or where they need improvement.  If you decide to make another attempt at forms, you've at least gone through the whole process once and will know all of the pitfalls you will need to avoid the second time.  It was three times for me, since I am a slow learner, and because I  cut the groove for the tip too deeply, I expect I will build a fourth one day.  (Tim Wilhelm)

            If the tip groove is too deep, couldn't you just draw file that side of the form?  It seems to me that would be easier than making a new set of forms.  (Unless you just like making forms???)  (Neil Savage)

          The mill bastard can be used and is used. I find the Vixen (girly file) does a lot faster job with about 1/3 the effort.  You do have to learn to take light pressure cuts. We are making a set of 72" forms now, took 25 minuets on one bar and 30 minuets on the other bar to file the inside of the bars smooth. After drilling and tapping it took less than an hour to smooth the top and bottom.  (Tony Spezio)

            I also used this kind of file back in the day when I worked in the body shop.  I was the guy who did the antique cars and vettes and I used a vixen file to do lead work on the older cars.  (Bret Reiter)

    The vixen file can be ordered from Snap-On. The part # is V14 or 14V can't remember which. I do remember it was $40+ and worth every penny.  (Don Schneider)


I'm working on my forms and I have come to the part where I need to drill and tap the bar stock that I have.  Problem is that I'm not all together sure about how to tap a hole.  I am using the Thomas Penrose plans.  If you have a bolt with a 1/4" diameter bolt can you use a 1/4" drill bit to drill the initial hole?  If any of you know of a web site that might give the basics for tapping that might work best for me.  It doesn't look that complicated, I just don't want to end up drilling some metal out that can be easily replaced!  Also, I'm not sure about how to match the threads of my bolts with the right tap.  (Sean Morris)

    If you are tapping into wood, a drill size of .201" (a number 7 drill), which gives a 75% thread depth will work, but if you're tapping into steel, you should use a .2188"  drill  (7/32")  for a 50% thread depth.  (Mark Wendt)

      Reread the directions on the Penrose site.  He says to drill 1/4" holes to tap for 5/16-18 bolts.

      Bolts/machine screws are marked by diameter and number of threads per inch.  Therefore, if you are using 1/4-20 bolts, the large diameter of the thread is 1/4" (actually it's a tiny bit less so the bolt doesn't bind up in the nut or threaded hole) and there are 20 threads per inch.  Penrose used 5/16" diameter bolts, thus a 1/4" pilot hole to tap.

      It is NOT necessary to use a #7 drill bit (.201") unless you have one, or it comes with the tap.  A 13/64" (.203") will work fine and is a lot easier to find in most hardware stores these days.

      Remember not to force the tap, they are extremely hard, which also makes them brittle.  Back it out AT LEAST every 1/2 turn, and use a good lubricant.  Cutting oil is best, but you can get by with motor oil.  (Neil Savage)

      Look for the US Army manual that is online.  Go to chapter 4 there is a section on tapping holes.  (Mark Babiy)

      I've built two steel forms so far.  And one set of failed wooden form (1st attempt at forms).

      Here is where I got my stuff:

      • Local steel supplier had the 3/4" stock - $15
      • Used my Dad's drill press.  8" Delta
      • Drill press vise - YOU MUST HAVE THIS! - Harbor Freight $5
      • Various bits and tap - approx $20 - Lowes, but I'd buy them form Sears next time.
      • Files - Bought a cheap file from Harbor Freight. $ down the drain.  The Craftsman file worked much better. $8
      • Fasteners and dowels - ordered them from a local industrial supplier, but I think MSC does a lot better on price. $25

      I'm planing out the tips on my third blank and no screw ups have been because of the form.  2nd rod dimensions were dead on and no glue lines.

      One word of caution.  Don't cut the groove too deep on the tip side.  You will have trouble hitting smaller tapers.  (Lee Orr)

      Go to your local hardware store and get a 1/4-20 tap.  They're often packaged together with the required tap drill.  You'll need both.  The drilled hole is .201"  (Tim Preusch)

    The Penrose instructions give you all the information you need.  Simply walk into your local hardware store and tell them you need a tap, give them Tom's size specs (5/16 by 18 threads if I recall correctly.) You really don't need to think about this, simply follow the instructions. When you get ready to tap the holes, use a drill press to align the tap and make the first initial threads by hand turning. Take the form out of the press and use your hand tap to finish. This way you get straight holes and not one's that of at an angle.

    My suggestion would be to drill the and tap the push holes then put the bars together and do the rest. As I recall the instructions say to drill the pull holes first, then take the bars a part and drill the pull. I found I had problems putting the bars back together.  (Jim Lowe)

      Yeah, bad karma ensues.  Ask Denis Dunderdale what happens when you use a hardware store bought tap.  I LENT him a good tap, but NOOOOO!  He had to use one of those 'Vermin'  - I mean - Vermont brand taps.   Bad juju, Bwana! Run like all H#!! from those pieces of cr--, I mean tap.  Locate a machine supply shop or ORDER one over the net.  HECK, I'll lend you one - but DO NOT use a hardware store bought tap for this job.  (Rick Crenshaw)

        Guess I should have said, "walk into a good hardware store". I guess I'm fortunate to have a real old fashion hardware store around the corner. No little red packages here.  (Jim Lowe)

        I was advised to stay away from the hardware store bits and taps as well. The tools I've purchased from the machinist supplier in Little Rock are better quality than the ones at the hardware store and less expensive.  I'm not sure I understand why they're less expensive.  It might have something to do with their interest in fishing.  I've been in several specialty shops the past year looking for stuff.  Everyone gets really helpful when I tell them I'm making a fishing pole.  Well, there was one exception - the ladies at the sowing place didn't show much interest in helping me find glazed cotton thread for my binder.  (David Bolin)

          A good place to get good quality bolts and taps and drill bits was my local Fastenal store. When I built my forms the most important part seemed to be high quality hardware, taps and bits (and cutting oil). I had no problems with the process at all (did take a lot of elbow grease on the files, though). Can check under "Fasteners-Industrial and Construction" in the Yellow pages for the same or similar in your home town.  (Jon McAnulty)

      If you use the drill press to align the taps, DON'T tap the threads with the drill press, you'll break the tap. (Jim Lowe)

    I built my forms based on the Thomas Penrose (TP) plans last summer.  I ruined a perfectly good pair of cold rolled steel bars drilling those holes. I got close enough with the second attempt.  I'm an accountant, not a machinist.  If you're like me, you might benefit from some of my mistakes. If you've worked with metal before, you'll get a good laugh out of my comments.

    1.    Make sure you've purchased cold rolled  steel - not hot rolled.  It makes a difference.  Also, Harry Boyd suggested I use leaded steel.  I got in a hurry and didn't follow his advice.  Several weeks (and files) later, I was wishing I had.  You can order it on-line at several steel supply web sites.  I hope I never have to build another set of forms, but if I do, I'll use leaded steel.

    2.    If you're using a drill press, check the run out with the chuck fully extended.  If it's floppy, better work on that problem before you drill any holes.  Check the owners manual and the List archives for suggestions.

    3.    Steel will destroy a dry drill bit.  You must use cutting oil if you're going to get more than one hole out of each bit.  Don't even try to drill the holes with a dry bit.

    4.    Run your drill press on the slowest speed.  High speed will also destroy a bit.

    5.    Even with a drill press, your bit is going to walk around a well placed mark in the center of the steel bars.  Punch your start point with something or purchase a center drill to start the hole.  I did both - on my second attempt.

    6.    Don't underestimate the importance of having the drill bit square with the bars.  Your entrance and exit holes must be pretty close to centered. Drill some test holes in a wood test block - or steel if you have some scrap pieces.  TP makes that point quite clear.  I just wasn't paying attention the first time.

    7.    Use an 11/64th bit to pilot your holes for the steel dowels.  Use a 3/16th dowel reamer to finish them up.  That'll give you good snug fitting dowels.

    8.    You're going to use a 5/16th tap with #18 threads to thread the push pull bolt holes.  I know TP says to use a 1/4" bit, but a wire gauge "F" bit was recommended for that tap by the supplier that helped me.

    9.    When you get ready to tap the holes, you'll need some kind of tap lubricant.  I used Tap-It.  I didn't break a single tap - not bad for an accountant.  Also, make sure your tap wrench is plum with the hole.

    One final note:  I've mentioned several items that you probably won't find at your local hardware store (e.g. center drills, dowel reamers, cutting oil, Tap It and wire gauge bits).  If you live in a major metropolitan area, you should be able to find a local machinist supplier that will have all that stuff plus some helpful advice.  You'll also probably get much better taps and bits at better than hardware store prices.

    I think that covers everything I did wrong on my first attempt to drill the bars.  My last set of bars turned out okay.  If you want to hear about the beveling process, send me a note when you're ready to get started and I'll send you pictures of the custom files I built based on advice from Harry and others.

    Special thanks to Thomas Penrose for sharing his plans on-line and to Harry for patiently responding to all my e-mails.  (David Bolin)

      Good advice but you must have had some tough steel. I ran all my drill holes dry and had no problems. I did end up buying a longer drill bit than the standard 6 inch but that was it. The holes drilled true, first time. No muss, no fuss.

      I did break a tap, but that was because I became lazy after a couple of hours of running taps. For tap lube I simply used Tri-flow, which is a non silicon based lube used for bicycles. Sean, what ever you do, don't use WD-40 as a lube, you'll get silicon all over your shop.  (Jim Lowe)

      May I add that I was just tapping some tough holes and used something called Tap-Free II.  No silicone, no oil, and made things a heck of a lot easier.  I use it as a cutting "oil" for my metal lathe as well.  (Joe West)

      I use a product call Energy Release Cutting/Tapping Fluid that works really well. Grizzly carries it.  # G7896. Works better than anything else I've tried.  (Don Schneider)

    Look at this site for more information about drilling & tapping metals than you'll probably ever need.

    From the table you'll probably need the info on proper drills to use for the tapped (1/4-20?, 1/4-28?, 1/4-32?) hole as well as the drill to use for the bolt clearance hole.  Both the proper tap & clearance drills are specified in the table.  (Charles Schoettler)

    I do not know if anyone has replied to your request since it appears that the list has been down for a while. Check this chart out.

    Thomas Penrose called for 5/16 18 taps and you should use the letter F drill. It is slightly larger than 1/4 and really makes a difference in the ease of tapping the threads. I used this size and plenty of cutting oil and I had no problems.  (Bill Bixler)


Just broke a tap in one of my forms holes.  Tell me it gets easier guys!  (Ren Monllor)

    Sure it gets easier now you have it down you should be able to break them at will. (Ronnie Rees)

    Get a stout punch that will fit thru the hole and knock it out, drill the hole the next size up and retap it with the next size larger tap. Buy the best taps you can find, cheap ones from the hardware store break easier.  (John Channer)

      This sounds like a good idea, but depending on the size of the hole and where the broken tap is, on the form, a larger hole might be getting close to the groove? Maybe? Adding a "Heli Coil" insert would put you back on track with the same size of the original bolt.  (David Dziadosz)

        Yes, but the STI tap will be just as big as the next size up, so nothing is gained if your goal is to stay away from the groove. Now, if your goal is to have those lovely near indestructible inserts, that's another story!  (Larry Blan)

      If the broken tap is in one piece, the extractor might work.  Otherwise, Channer is absolutely correct.  Get a stout punch and knock it out.  You may shatter the tap and be able to salvage the threads.  I have one hole in my forms like that.  (Robert Kope)

        Actually, if the tap is a quality tap, it is very possible that it will break, and not really damage the threads. If it isn't a quality tap, go get some, now, and then retap the same hole before you drill out the hole.  (Larry Blan)

        John Channer gives good advise.  I would add starting the tap straight is essential. If the tap is not started straight the farther it goes into the hole the more pressure is exerted on the tap. An easy way to start the tap is after you drill the hole in your drill press, without removing the clamping, remove the bit and put the tap in the chuck, turn the tap into the hole by hand until it has a good start. Then loosen the chuck leaving the tap in the hole and finish the job with a "T" handle. Also use a good quality tapping fluid such as  (Don Schneider)

          Let me add this. Use a spring loaded tap guide to take up the slack as the tap is tapping the hole. This lets you lock the quill in place and keeps pressure on the tap as it is threading the hole. Photos of this can be found on my article in "Power Fibers".  (Tony Spezio)

            When I made my forms one other piece of advice was given to me that I have not as yet seen. That was to make sure I used the proper drill size for the tap I was using. I am no machinist and I followed all the advice to the letter and was able to drill and tap all my holes without any problems.  (Bill Bixler)

    When I was making my forms there was a similar flurry of discussion on how to extract broken taps and all the things that can go wrong when doing the tapping process.

    I took the cowards way out and did not tap the "pull" part of the planing form. I put a bolt all the way through the form with a nut for tightening ( pulling the forms together) on the outside of the form. I used the type of bolt with a short screw section so that there were flush surfaces where the bolt went through the forms. (that is an accountant's description of some named type of bolt).

    I did tap the "push" bolt. The result was that the amount of tapping was halved and the forms work really well.   (Ian Kearney)

    Just venting a little frustration.  I got a couple of the set screw holes done already.  I think possibly I should have stopped before the hand started to lose feeling. I'm going to order an extraction tool from MSC and go from there. I know I probably sound psychotic, but I really am enjoying making the planing forms. I guess I just wanted to keep going.

    Some days it's chicken...some days feathers.  (Ren Monllor)

      If you use a nail set, hammer and light blows you can sometimes loosen up the broken tap in the hole.  Then you can use a scribe to work it out.  It helps to countersink the drilled holes before starting to tap.  I use a block of metal wit a hole just larger than the tap to start it straight. Back the tap all the way out often and clean the chips off it.  Use a good lubricant, I use "tapping wax" that was given to me by a machinist years ago, but wheel bearing grease works well.  (Ron Larsen)

      It has been a long time since I did any metal work, but I seem to recall that when I pulled the same stunt.  I got rid of it by breaking up the tool.  It is very brittle steel and if done carefully can be shattered without screwing up the work you have already done.  Maybe someone can be more precise. Best of Luck.  (Ralph Moon)

      Here is another trick, to remove a broken tap. If the tap is a quality carbon steel tap, this will work.

      Get a small amount of Nitric Acid  and add  just a little bit of water to it. If the hole goes all the way through, then plug one side with modeling clay or anything like that. Then, fill the hole with the Nitric acid and let it sit.

      The nitric acid will eat the hardest metal first, which is the tap. After the acid stops bubbling, rinse it out with water and check and see if the tap piece is loose yet. If not, then fill the hole with the acid again and let it sit more.

      You may have to do this a few times, but it works. Being a gunsmith for thirty years, I have broken some taps off and when they are in a blind hole, on a $5,000.00 shotgun, you have to get it out and you can't drill the hole to the next size larger.

      Hope this comes in handy for someone.  (Dave LeClair)

    Well, my neighbor came over today to check on my progress with the forms and as is his way, began piddling about with the broken tap in spite of me asking him not too. He went home and got his long nose pliers, a pair of mini dykes and a pair of huge honkin' tweezers. I swear it was right out of an Abbott and Costello movie. I'm telling him not to because he's ruing the threads already cut, and he's replying "but I'm almost done". Have you ever wanted to kick your best friend in the ass? Well, I saw that the cut threads were getting pretty chewed up so the moment he got up from his chair, I placed a pin in the hole, and smacked that piece of tap out the other side. Tap never shattered guys, instead it cut grooves perpendicular to the threads. I filled the hole with JB weld and am going to redrill it out tomorrow. If it works great, if it doesn't. I can always redrill next size up and retap.

    Man, I hope it works.  (Ren Monllor)

      You can also redrill right beside the existing hole.  It shouldn't make any difference.  I would be more inclined to do that rather than increase the size.    (Lee Orr)

        I've been wondering about drilling next to the existing hole, only because "the reading" is taken at the 5" interval, and ideally that's where to put the adjustment bolt, but why does it have to be there? I don't think that the bamboo will sink or rise to  any degree just because the adjustment is 5/16" above or below the measurement point. Any feedback???  (Ren Monllor)

          You don't need to take your measurements right at the middle of the bolt.  Your 5" stations could be halfway between your bolts, or an inch to either side.  The main thing, if you are goign to use 5" as your center to center measurement, is that your centers are 5" apart.  (Mark Wendt)

            On my forms, the push bolt is on one side, then the dowel pin, then the pull bolt so I use the dowel pins for the centers.  You could just move the bolt about 1/2" to the side and redo.

            However, I'm guessing the JB Weld can be drilled and tapped without a problem.  Just be sure to let it have enough time to really get hard.  In my basement in the winter, that's 36-48 hours.  Depends on the ambient temperature.  It's 62 degrees F down there.  (Neil Savage)

          If the broken tap is near the shallow groove end, it might be worth tapping larger as you won't interfere with the groove depth. The irritation with this will be having to change spanner/allen key size for this station each time you set the forms. If you can find special bolts or fashion something which would obviate this I would go this route. If not I am sure shifting the station slightly and tapping a new hole will not affect setting the form depth at the 5" interval in the slightest.  (Stephen Dugmore)

            Well, I WOULDN'T move the hole toward either groove.  That would be apt to cause binding.  If you need to move the hole, move it sideways (toward or away from the pin).  (Neil Savage)

              I think Stephen was talking about the shallow end of the form and moving the bolt horizontally.  I didn't see anything in his post about changing the vertical orientation of the bolt.  In fact, he was talking about making the hole larger, tapping for a larger bolt and not interfering with the groove depth.

              I agree that you should have the bolts all in the same plane vertically so that you don't torque the bars though.  (Todd Talsma)

                I was indeed referring to moving the bolt horizontally. Moving it vertically would probably be impossible unless  the forms were extra thick.  (Stephen Dugmore)

                  I just realized the forms wouldn't have a groove at all yet..... so I would tap one size bigger, adapt the bolt head to fit the same spanner/key as the others and make sure when doing the grooves that this station is at the shallower end of the forms.

                  BUT BEFORE DOING SO it would be worth doing a scale drawing or calculation to make sure the bolt won't interfere with the grooves themselves or the strip when the forms are opened up. I doubt it would interfere even if the station is in the middle of the forms but it would be wise to check first anyhow.  (Stephen Dugmore)

                    If you place a bolt  midway up the form, say 1/2 inch up from one face for a 1 inch thick form, you're bolt diameter could be as big as 0.500 before you interfered with a groove or a strip set for  0.250 deep.  A  0.250 strip would give you a butt of 0.500 inches.  Quite the monster Rod!!!  So if your form is 1 inch or thicker you don't have to worry.  (Al Baldauski)

          As long as you have the adjustment correct at the 5" intervals you are good.  Doesn't really matter how you get there.  (Lee Orr)

            There are several other things you could do:  If this is the "push" location you could drill & tap the other side of the for and push from there.  If this is the "pull" location you could use a longer bolt with a nut on the end & still pull.  (Ron Larsen)

          I have a set of forms that were sold to me because the bolts were not on 5" centers. They vary from 5 1/8" to 5 1/2". I use these forms a lot by just setting the forms at 5" intervals. This is the set of forms that I use for tip sections. Rods come out just fine. Setting the 5" spacing does not have to be at the bolts.  (Tony Spezio)

          I may have missed it but with all this discussion about broken taps we should probably publish some place handy for all to see a list and/or description of "tap extactors". These tools really work quite well if you get the right one. There are some made that aren't worth a pinch but there is a set of 3 flute and a set of 4 flute finger type extractors that actually work quite well and were used in the machine shops I used to manage. They are shown in the McMaster-Carr Supply Company Catalogue and available at some industrial tool stores.  (Ray Gould)

          I would suggest drilling and retapping that 1/4" hole to 3/8". Then screw in a 3/8 bolt as far as it will go.  Then hacksaw off both ends of the bolt flush with the planing form.  Take a center punch and punch a few divots around the circumference of the plug locking it in place. You have just formed a plug patch in the form and you can then  redrill and tap to your  original specs in the correct location.  (Larry Swearingen)

          Here's an even easier way to fix the problem: drill out the existing hole and retap it oversize then screw in a threaded insert which has the newly tapped oversize thread on the outside  and the original thread on the inside. These inserts are commercially available and often carried by major hardware stores. For example if your original thread was 1/4"-20 NC you can tap the hole out to 3/8"-16 NC and install  a threaded  insert  that  has 3/8"-16 NC on the outside and 1/4"-20 on the inside. These inserts can be glued in place with "Loctite" although some of them come furnished with a little plastic plug built into the outside thread that automatically locks the insert in place when it is screwed into place. The inserts have a screw driver notch in one end to facilitate screwing it into place. These inserts are available in all kinds of different thread sizes both coarse and fine thread, just pick the one suiting your need.  (Ray Gould)

    You might look for metal based JB Weld. There is such stuff and it would be good for plugging your hole before redrilling. I think the material is laced with metal powder - I think it is aluminum, but not sure. MSC might have this stuff as well. (Frank Paul)

    One way to get around the tap issue is to drill your holes to fit your bolts, then if you have access to any welding equipment (a local high school with a metal shop is a great place to find someone to do it for cheap, or free), weld your nuts onto the outside of the forms for pull screws and weld the push nuts on the near side. Just be sure to have the nuts attached to the bolts before welding, to both make sure the nut is centered properly and to be able to remove the nut after welding to rethread everything in case there was any minor heat damage to the threads. This will save you hours of time and headaches you are experiencing while tapping the threads. A guy who knows how to weld can do this in less than 10 minutes and if they know what they are doing, they won't get the forms too hot to do any damage.  (Wade Turner)

    A lot of good stuff on tapping steel,  but I don't think anyone said,  for the benefit of newbies,  DON’T use a hardware store tap. They will  break off in a steel bar, it's just a question of when. Get a quality  tap from an industrial supplier. They are made from superior steel,  and are also sharper. The inconvenience of ordering them is nothing  compared to the trouble of dealing with a broken tap.  (Tom Smithwick)

    Thanks again for all the input on the broken tap thread.

    For the record, I received two new taps last night from MSC along with a straight tap wrench instead of the T-tap I was using before. I re drilled and tapped the original hole after refilling it with JB Weld. and the repair went without a hitch. I ran bolts through the holes and everything is working smoothly. The JB Weld is holding up beautifully (time will tell).

    Hi ho, hi ho, it's back to work I go.... (Ren Monllor)


I'm working on a set of steel planing forms and think I may have a problem.  I am following the Penrose instructions - and am about halfway through drilling/tapping.  I drilled all of the dowel holes (3/16") and put them in along the way.  Then I moved on to the shoulder bolts - drilling 1/4" all the way through, drilling 3/8" 1 inch shoulder, tapping and finally screwing in the bolt.  That is where the problem arises.  I've drilled 10 of the 15 shoulder bolts.  I can't hand tighten at all.  I can get them fully seated - but only with some serious elbow grease.  I assume the problem is either that I've tapped at an angle - or - that my shoulder 3/8" hole is not centered on the 1/4" hole.

I am using a doweling jig and hand tap rather than a press - I know that could be the cause of the problem - but I don't have a drill press - so my real question is what the potential problems are at this point.  Since I have shoulders and dowels (every 5") to aid in maintaining alignment - is it still possible that the misaligned holes could cause one bar to raise in relation to the other when I am setting the forms?  (Tim Aaron)

    There are different tolerances for taps and you might have a super tight tolerance on the tap and a not so tight tolerance on the bolt threads.

    If I were you I’d lose the jig and go to harbor freight and pick up their bench top drill press (30-40 bucks). By the way, you can’t tap at an angle, the tap will break.

    As to your question about misalignment…..yes.  (Ren Monllor)

      I thought about buying a drill press about 4 holes ago - then I figured I had gone this far with the jig so I might as well finish with it.  I figure that if I switch now - I still can't undo the problems I may have already created without going to larger bolts and dowels - if I go to a larger bolt - I don't think I will have enough clearance over the shoulders for butt sections because I started with 3/4" stock.

      Is there a way to test for misalignment prior to filing the faces?  (Tim Aaron)

        Oh yeah, forgot to mention, if the holes are just unbearable to look at then you can plug them with some JB Weld. That stuff is absolutely incredible.  (Ren Monllor)

        You could buy the drill press and redo the holes and taps on the other side of the existing holes, the only one who will see the holes is you.

        As far as going to larger bolts you’re right and also, the new drill bit will follow the existing hole, so don’t go there. If I were you, you already thought about the purchase of a drill press, I’d go that route, then just re-drill and tap. If you’re afraid of weakening the bars to the point that they might shift under the pressure of plane and bamboo, it just ain’t  gonna happen. Just for information’s sake, here is the tap I used to make mine: GTD 5/16-18 NC HS G H3. H3 is the indication of tolerance and 3 is right in the middle.

        One more thing, if you take the time now to do it correctly and go S-L-O-W-W-W, You’ll end up with forms just as accurate as any of the commercial ones. I’m telling you this because I purchased a set of Bellingers a while back and the truth is, they are no more accurate than my handmade ones; not taking away anything from the Bellingers.

        You’ll do fine, you’ll see.  (Ren Monllor)

          I'll be the oddball here, as is so often the case.  Rather than concerning myself with re-drilling holes for shoulder bolts I would simply switch to regular hex head bolts -- no shoulder.  If (big IF) your dowel pins are accurately drilled and reamed they will hold the bars in alignment.  Less holes to drill.  Plenty accurate.

          No question, it will look better with shoulder bolts, etc.  But one of my forms is made as described above and works plenty good.  (Harry Boyd)

            The only problem with this is, that should you decide to go with a mild swell by the grip, you will have weakened the threaded area and it would be more susceptible to breakage at that point. You would have to remove the thread from all around the screw in order not to mar the surface of the cane. At least that is how it would appear to me.

            Besides if there is a misalignment issue, it doesn’t matter what type of screw mechanism  you try, it just ain’t gonna go through because the threads are misaligned.  (Ren Monllor)

              Not at all Ren.  Have a look at a set of Lon Blauvelt's forms.  His are made exactly the way I tried to describe.  (Harry Boyd)

                Maybe I didn’t catch what you were trying to say. All I’m saying  is that if the holes are misaligned and not tapped properly, ain’t no screw gonna work.  So he has to re-drill and tap.  (Ren Monllor)

                  The first set of forms I made didn’t open & close smoothly. It took me a while to figure out why and how to correct the problem. I’ve made forms this way ever since.

                  The problem was the holes were not parallel so the dowels and bolts were binding on each other. To correct the problem I did the following:

                  First: I “tuned” my drill press so that the drill and the table were perpendicular or as close as I could get them to each other. To test this I marked and  drilled a piece of square stock to see if the entry and exit hole were at the same relative place on each side of the block.

                  Second: With the rails of the forms clamped together I drilled all of the holes in the forms except the holes for the push setscrews with the same orientation to the drill press. My thinking was even if there was a slight difference from perpendicular at least the holes would be parallel.

                  I clamp the rails together with two “C” clamps at each station initially before drilling. One clamp to hold the rails together and the second to clamp top to bottom over the seam between the rails to assure parallel alignment of the rails resulting in less metal removal later on when flattening the surfaces.

                  With the forms supported on each side of the drill press starting in the middle remove the clamps at that station as necessary to drill the dowel hole. Insert the dowel. Next drill the dowel holes and insert the dowels on either side of the middle dowel and so on till you have all of the dowels installed.

                  I use new 1” square cold roll stock for forms. Yes, they are 1/3 heavier and yes they are more work to build. I just like the added width when using them and the extra weight keeps them from moving around when in use.

                  It helps to start all threading with the tap in the drill press. If you have a big enough drill press you can power tap the threads. For the “Pull Bolts” I would recommend using countersink bolts. It’s another form of alignment and besides you don’t beat up your fingers on bolt heads when using the forms.  (Don Schneider)

                The "drilling accuracy' problem is certainly not uncommon. Drills do have a tendency to 'run'. Straight holes usually require first drilling the hole undersize (about 1/64th), then reaming to size ~ with a good sharp full size reamer, and slow feed! Then for sinking socket head screws a counterbore tool with the correct size pilot should be used. Counterbore tools are usually three fluted flat bottomed cutters (similar to an end mill), with a hole in the end to accommodate the shank of a 'pilot'. Should be available at any good tool supply firm. It's surprising that mention of this important tool hasn't been previously made.  (Vince Brannick)

                  Unfortunately, reaming will not straighten a wandering drill hole. The reamer will follow the wander, after all, it's not much thicker than the drill bit used to make the hole in the first place.  It will, however, make an out-of-round hole   round,  unless  the  opening  is bell-mouthed too much.  The only way you can straighten a wandering drilled hole is by boring the hole out.  (Mark Wendt)

                    Mark is correct, a reamer will not straighten a wandering drill hole. To minimize wander use a good aircraft quality drill, properly sharpened,  no longer than necessary to drill through the stock. Rack job drills from HD won’t cut it. Spend the little extra for a high quality drills and taps, makes life easier. A reamer should only be used to get the proper fit of the dowel pin. With high quality drills chances are good you won’t need a reamer. Or better yet, drill a hole in a piece of scrap stock and take it to a supplier and find a dowel pin that fits it.  (Don Schneider)

                    Your contractor status gives credence to your suggestion that the reamer will follow the 'errant' hole's path ~ thus the admonition to use a reamer with sharp cutting lips, and slow feed. We aren't reaming for a 'slip fit' or a 'press fit', and .015" stock removal (.007+" each side) should suffice to provide enough material for the reamer to make its own track. However, it's acknowledged that an end mill (if long enough) might be a better solution, but it would seem somewhat difficult to set up long bars to perform a boring  (literally) operation.  (Vince Brannick)

    You could check for squareness of your tapped holes easily enough by just placing the tap back in a tapped hole.  Check visually or with a square to see if you are perpendicular to the surface.  If you are out, just drill out the clearance hole of the shoulder bolts a bit larger to compensate for the error. You have the dowel to keep everything in place.

    For the misalignment, if you drilled the .250 drill first and then followed with the .375 drill, the .375 drill will follow the center of the .250 drill. I doubt  would you have misalignment. Do a visual look. You should be able to tell if there is a mismatch between the 2 holes.  (Al Anonymous)

      I echo Al's comment.  You could also use a length of drill iron in the untapped holes (or a drill I guess).  I purchased a couple of small machinist's squares (Lee Valley I think) - about 2" long model.  I used a drill press, but the principle should be the same.  I raised the bas to the point that the drill was almost touching the bars and checked that the drill bit was perpendicular to the bar.  I did at least two checks. on either side of the drill.  I compensated for what little I knew about what I was doing by being anal about checking what I was doing.  Given that your holes have been drilled, checking the square will verify the perpendicularity (???) of the holes to the bars.

      I tapped by hand and I trusted my "feel" that the tap was sitting well in the pilot hole.  BTW, I purchased drills specifically for the size of tap I used.  I did not use the standard 1/4" drill bit for example.  I did not recess the bolt heads at first.  Later on, I did change from shoulder bolds to countersunk bolts (I got tired ow bashing my fingers on the bolt heads) and I then countersunk the bolt heads for the "pull" bolts.  I replaced the "push" bolts headless allen-keyed bolts (can't think what they are called).

      Have you run your tap through the already-tapped holes to verify that the threads are clean?  I found that gunk came out even with the second tapping.  (Greg Dawson)


With several posts about planing forms, it seems like a good time to ask a question about making them and about hand taps.

In the archives, a number of folks warn against using cheap taps when following the Thomas Penrose instructions.  So here's the question:  for those of us with no practical experience in metalworking or metallurgy, what makes a good tap or, more specifically, a tap that's good to use when making planing forms?

In my case, I skipped the Vermont American taps from home improvement stores and have gotten two taps from Enco (one is made by OSG, a 3-fluted plug tap, and the  other by  Cleveland, a 4-fluted plug tap). I'm not sure I've exercised much intelligence in selecting these.  I know the  taps in  the big  box stores  sold for $2.99 and the taps I got from Enco cost me just a bit less than $8 each.

With a good tap wrench, cutting fluid, and care, attention, and patience, are these taps going to work for me?  (Al Boehm)

    They should work just fine. I am a firm believer that you pay more for quality.  Good luck, take your time with the tap, use a good cutting fluid such as Tap Magic and remember to back it out often to clear the chips.  (Don Green)

    I went through the exercise of making my forms a few months ago. I got a couple of 2-flute gun taps from McMaster.  They seem to be best for tapping through holes, which is what I had using the Waldron variation on the Penrose forms. I actually ended up using only one of the taps for the whole job. That aspect went very well -- no problems, no breakage.  (Mike McGuire)

    Hand tapping can be helped by using a cylindrical (or square) block with the tap body size hole drilled/reamed through, and high enough to keep the tap straight ~ at least until about a 1/3 of the full threads have been started.  (Vince Brannick)

    It looks like you have the same luck I do. Enco has two flute spiral point taps on sale now for 4 bucks or less.

    I plan to convert from wood to steel forms this summer, so I haven't done forms yet, but I have tapped a lot of holes in materials like alloy steel and air hardening tool steel. You can reduce  the torque necessary and extend the life of your taps by using a taper style tap and finishing, if you need a bit more length, with the plug taps. Enco has three tap sets (bottom,plug, and taper) for about 10 bucks. You probably have H-3 diameter taps, which are pretty standard for those sizes. The tap sets are available in H-2 diameter for 1/4 inch. H-2 produces a tighter mesh and would reduce backlash.

    And finally, you are making forms that have substantial market value. Enough so that you might hedge your bets with a hand tapper, available from our Enco friends for about 90 bucks. It makes running straight taps much easier... break a tap deep in the hole and you will cry.  (Larry Lohkamp)

      I'll second Larry's last comment.  Buy yourself a hand tapper for a couple of reasons; to keep holes consistent and to save your hands!  I bought one from Enco and it made tapping a breeze.  (Scott Bahn)

        In case you don't want to spring for the hand tapper here is another way to get taps started straight.

        When you drill the hole on the drill press, (I hope you have a drill press) leave the bar clamped in position, remove the drill bit and put the tap in the chuck.  With light pressure on the down feed, turn the chuck by hand about 3 revs to get the threads started.  Loosen the chuck, then raise the quill and finish by hand with a tap wrench.  It is hard on the hands and there are a lot of tool changes but you get straight holes and threads.

        I made my steel forms last year and It worked for me.  (Rick Hodges)


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