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Planing Forms - Entire Process Notes

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I finally finished my steel forms... thanks, list, for your help.  The archives were also a tremendous resource, as was Thomas Penrose's web site.  There are other rookies out there like myself who I know are making forms right now, and have asked for a heads up on ways to avoid mistakes, or ways to make the job easier, so here goes:

Drilling & Tapping

I did not break a drill bit or a tap, I used cutting fluid.  My threads were all 5/16”-18, and I used an F size bit.  I started the threads with a 4 flute tap, then finished them with a 2 flute tap.  Bought the bits and taps from McMaster-Carr.  I read somewhere that the Home Depot variety were of lower quality and susceptible to breaking.

Draw Filing

The Vixen file is worth spending $20-$30 on, I think Nicholson‘s  Vixen copy is called a curved tooth mill file.  I can file my forms from end to end in about 15 now.  Filing is much easier if you glue or screw a block of wood on one side of the file.  Keep the file as parallel as possible to the forms, and alternate sides with each pass (file crosses over the top half of the form on first pass, file crosses over near side on second pass, and so on).

Groove Filing

I did the entire groove with a triangular file.  The thread cutting tool would have made the job go much faster.  You need to make sure the file is cleaned every 5 passes or so with a tooth brush or wire brush.  I learned the hard way that filings can accumulate in the teeth and cause lines/gouges to be formed.  Also, I ruined a file this way.

Measuring the Groove

I considered several different methods before I settled on this one which worked best for me.  I would set a gap in the forms and measure the depth of the form with the indicator and attached 60 degree point.  I used one side of a small machinists square to set the gap in the forms, making sure the pressure on the square was as consistent as possible when tightening the cap screws.  When you take an indicator reading you will be measuring the groove depth, plus the amount the 60 degree contact point drops below the groove due to the gap.  Since the gap distance is known, and the target groove dimension is known, you can estimate by calculation what the indicator reading should be:

I = d + g*0.5/tan(30)
   = d + g/1.15
   = groove depth + how far the point drops below the groove

  • I = indicator reading of form when filing, with a known gap distance
  • d = desired groove dimension
  • g = gap distance

You need to calibrate this equation to make sure your readings will be accurate.  To do this I filed the groove for a station on one end until I hit the target dimension, then compared what the equation predicted to my actual measurements.  I then used this indicator reading to solve for the gap distance.  The square I used to set the gap had a thickness of 0.0625, but when I took the actual measurements of that first groove and used this as the term “I” in the equation and solved for g, the equation yielded a gap distance on 0.0619.  I then used 0.0619 as the gap distance g to determine what my indicator readings should be for all the rest of the stations.  You can use a spreadsheet to setup a table that shows the station number, the desired groove depth, and the corresponding indicator reading with a known gap distance.  For example, if I want a groove depth at the second station from the butt to be 0.150, and my gap is 0.0619, then the indicator reading should be = 0.150 + 0.0619/1.15 = 0.2038

I would file the groove to within 2 mils of what the equation predicted for each station, close the forms up and take measurements, and write on the forms at each station what the actual depth was.  I found I could get within 2 or 3 mils of my desired depth without over shooting.  I then opened the forms back up, carefully set the gap, and filed at those stations that needed a little more depth.  If you need 3 mils to hit the target dimension, file until the indicator reading changes by 3 mils.  Using this method I could file to an accuracy of +/- 1 mil.  This may not be perfect, but it was good enough for me.  The alternative to this method is to file some, close up the forms and measure, open the forms back up and file some more, close the forms and measure, etc. etc.  Seemed like that was going to take a lot more time.

Correcting Filing Mistakes

I started filing on the tip of the tip end and quickly learned that 0.020 inches is not very deep! I ended up overshooting my tip end by about 15 mils.  I thought I was going to have to toss the forms and start over.  Fortunately, the Vixen file bailed me out.  If you swab layout dye on top the forms, and file the forms flat with the Vixen until the dye is removed, you can remove approximately 4 mils of depth on the forms at a time.  I filed the tip side of the forms 4 times over to get the groove depth back under 20 mils.  The same thing happened on the butt side, I over shot by about 3 mils on one station.  I swabbed it, filed the entire form, and was back in business.  It is critical to check the gap distance at each station before you start filing.  What I found was that the gap would slightly change as I would file from station to station.


The center gauge sets nicely in the forms, but I'll just have to wait and see.  I am sure I just confused the bejeebers out of somebody, so send me an email if you want clear something up.

Thanks again everyone, this is a great list!  (Kyle Druey)


Things I learned building my forms:

  • Taps break so go slow.
  • Check and recheck the level of the drill press bed CONSTANTLY.
  • File the form from both sides to prevent a lean on your groove.
  • Cutting oil or WD40 makes the groove cutting easier, and saves file blades.
  • File blades are usually one direction, so sawing away with them like a hacksaw just ruins them.
  • Finally learn to love the vixen.  (Mark Bolan)


OK, I have planned for a long time to buy vs. make my own forms. I'm trying to take the advice I see a here a lot - "just get going".

Anyway, I was reading the Thomas Penrose instructions again and it really doesn't look that complicated or expensive - the main costs being tools I need/want anyway (dial indicator, base, 60 degree tip, drill press).

So, I think I'll spend a couple of hundred bucks and keep the tools, Vs. buying forms and still having to buy the tools.

Here's the question: Did you guys mail order the shoulder bolts, etc....or should these be readily available at some sort of local supply place.

I found a place online for the cold rolled key stock..

Is this the best kind of place to buy this stuff? I'm sure I'll be looking around for binder and beveler parts soon as well.  (Greg Holland)

    Getting the holes drilled correctly is the single most important step in creating a form that works well over the long haul.  I have built several forms, and IMHO one of the best steps I have taken is to:

    A) smooth the two inner surfaces with files

    B) Clamp the bars together, mark the locations, and take them to a machinist to drill and ream on a Bridgeport drill machine.

    Unless you buy a $500+ drill press, you'll wrestle with it all the way through drilling the holes.  A doweling jig and hand drill is even more tricky to use.

    You can get the bolts at your local fastener supply house.  Look in the Yellow Pages for construction fasteners and stop by there.  (Harry Boyd)

      I couldn't agree with Harry more.  I was lucky, I used a Bridgeport at work for the three sets of forms I made.

      A good place to check is your local technical school.  You can probably get the forms drilled,  reamed & tapped for a nominal charge.  (Ron Larsen)

    Look up the phone number for your nearest McMaster-Carr and memorize it!

    If you have a local metal supply, give them a call, otherwise just use the Ouija board method and order from the place that gives you the best feeling. If you find a place that is 1/2 the cost of most of them, make sure they are pricing key stock, and not CRS that they happen to call key stock. Steel is purchased by the pound/hundredweight/ton at the wholesale level, and there isn't much variance from distributor to distributor when comparing apples and apples.

    Hardware - does not matter what store it comes from, but the country of origin does make a difference. Don't buy junk hardware or junk taps. Very few hardware stores carry good taps, unless you know the difference, go to MSC or a local tooling distributor. If you visit the local hardware, we will know it, because you will be back asking how to remove a broken tap.

    Pay attention as you go, you can apply the lessons learned to the other toyls.  (Larry Blan)

    After you get the forms drilled, pinned & screwed together you'll need the tools to cut the groove.  I sent my set of gap gage, triangular scraper & file plane to Todd Talsma to loan out to whoever needs them to build forms.

    Check with Todd, I'm sure he'll loan them to you.  (Ron Larsen)

    I made my own. I wouldn't do it again but I too had a hard time with parts. The steel was the easy part. I just called a bunch of steel yards until I hit pay dirt. The bolts where harder. I finally found some at a tractor supply  (not THE Tractor Supply) place in the central valley.  (Jim Lowe)

    I purchased all the bolts and alignment pins from Fastenal, per Penrose's dimensions.  (Bob Gansburg)

    For metals I use:

    Online Metals


    Metal Express

    Both of them deal with small orders and are ideal for binders, bevelers and any other small project.  (If only they were good sources for NS round bar or tube.)

    Besides McMaster-Carr mentioned earlier, I've also picked up stuff from:

    J & L Industrial

    MSC Direct

    I have a drill press and one thing I had to deal with is that when you are drilling the center station you have an equal amount of steel hanging off either side of the table.  But when you are drilling station number one you got 6 foot of steel hanging out there in mid air.  (I'd like to see Garrison's stress curve on that).  That puts a lot of torque in the table and makes it a lot tougher to hold the work.  Support that far end and you've got half the battle won.

    Someone mentioned high quality taps and I would agree.  I would also recommend using three fluted taps.  I don't know if it is true, but it seemed as though they took less effort.  My guess is because they have 75% fewer cutting teeth than the 4 fluted ones.  Since you aren't tapping blind holes, get taps with a long taper of as much as 7 threads.  I think they help you get started easier and straighter.  You might also pick up one with a short taper to follow the long taper once the threads are started.  Get a good tapping handle.  (Tim Wilhelm)

    I found steel keystock at Potomac Steel, right on Loisdale Road in Springfield.

    If you're looking for somebody local.  (Kurt Wolko)


I am new to the list and new to bamboo rodmaking. I have built quite a number of graphite rods and really enjoyed it. I have gone as far as doing my own cork grips,  and developing a personal style. But I seem to have come to the end of it, unless I was willing to go commercial,  which I am not. Fancy thread weaves and inlays, and what I call "calico" grips, leave me cold. Bamboo rodmaking seems to have the interest and depth to it that I am looking for. Retired a couple of years now, I need projects with some staying power. It seems to take me no time at all to do a graphite rod -- not much of a project at all. That can't be true of bamboo.

I have just been through the exercise of making a planing form using the Waldron variation of the Penrose approach. I used 7/8" cold rolled steel. The drilling and tapping went quite well -- no broken drills or taps. I did it on a $40 Harbor Freight bench top drill press with a 2 inch stroke -- about the limits of what it could do. Knowing it was going to be serious work, I got the drills, taps and reamer that I needed from McMaster. I had to shorten the shank on the reamer so I could swap it in for a drill without moving the work. I used a two flute "gun" tap, which works quit well with through holes. Drilling and tapping sure produced an industrial quantity of cuttings. A Vixen file for dressing the surfaces was the way to go.

I wasn't sure I could accurately set the reverse taper for filing the groove using the inner jaws of my caliper. It occurred to me that the ideal way would be to use a set of gauges, accurately ground pins in steps of 0.001" over the range of interest. I didn't have that, but I did have a numbered drill index which has sizes in the necessary range. It's from those patrons of economy (sometimes false) at Harbor Freight, so I didn't trust the nominal diameters but miked each one. They were off a thousandth or two here and there. I did a spread sheet to figure out the locations along the form where the spacings should be the actual size of each drill. To set it up, I used the pull bolt to capture the drill shank, and tightened the push bolt to just release it.

I made file plane and a bit plane for cutting the groove. Here's where the trouble started. It came down to a miscalibrated dial indicator -- The stop was held in place with funny little screws with very narrow slots -- very hard to get tight -- it had slipped. By the time I figured that out, I was 0.020" too deep on the butt side. Fortunately I hadn't started on the tip side. Looking at tapers of interest, I concluded this was going to be pretty limiting. That 0.020" had to come off. I attacked with a Vixen file. After about a hundred strokes in a short region I measured -- maybe a quarter to half a thousandth gone. My limitations as a human milling machine were obvious. It did give me some insight into what life is like for those Pakistani tribal gunsmiths, who produce whole revolvers and automatics with files and hand drills. There was on hand a clunky old Miller Falls belt sander borrowed from my brother. It was too heavy to use on anything but a horizontal surface. A couple of hours, several belts and an impressive pile of cuttings later, I was back in range. A straight edge test showed the surface was a bit domed, but no worse than the original surface before I did anything to the material. A half an hour with a Vixen file put it right.

So it was back to filing the groove with paranoid attention to calibration of the dial indicator. This time it went OK. With a certain amount of tweaking and tuning, the form is within 0.001" of target all up and down. A thread gauge seems to think the shape is good too. Overall the experience yet again validates Hofstader's Law -- It always takes longer than you think, even when you take account of Hofstader's Law -- but I'm not complaining.  (Mike McGuire)

    Welcome to the list.  You just made the most important and the most time consuming tool.  You were able to notice your errors and correct them which is a big part of rod making.  It sounds like you are well on your way to a hobby with some staying power. Again welcome to the list and ask as many questions as you can and give as many answers as you can. That is what helps the list survive and be so productive to all of the readers.  (Greg Reeves)

    Now sit right down and wait a while -
    What's all this "personal" jolly style?
    With bamboo rods there is a norm
    And you'd better bloody well conform!

    Do NOT develop novel stuff
    That makes all other rods seem rough -
    No calculations algebraic
    Can change old rules, though so archaic.

    Just make a rod, or be afraid,
    Just like all others ever made:
    Or suffer now the lofty dudgeon
    Of many a bleary old curmudgeon!

    So get yourself in line, my friend,
    While down the bamboo road you wend -
    There is no unpalatable sensation
    Like a successful (shudder) innovation!  (Peter McKean)


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