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Form Setup - Measuring Differences


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When I set  my dial  depth indicator,  (standard it came with is .101), I get different readings from the form setting to the actual planed cane. I've learned to adjust my numbers OK, but why does that happen?  (Jerry Andrews)

    With what method are you measuring your strips? In what way do the strips measure differently from the form measurement? Larger? Smaller?  (Martin-Darrell)

    Short answer is, I don't know.  Longer answer is that it happens to all of us.  I set my forms and plane one strip till I'm shaving metal the entire length of the strip.  Measure the strip, and adjust the forms accordingly.  Most often, I find that I squeeze the forms together an extra thousandth or two.

    If you somehow figure out why this happens, let me know.  (Harry Boyd)

      Strips are measured with calipers. I'm careful not to crush the apex, and, the final dimensions show the discrepancy also.  (Jerry Andrews)

        As Harry said, it could be several things, and it happens. You may be pulling the strip up out of the forms when planing; the point of your indicator might be resting on the bottom of your standard; you may be crushing the apex more than you realize; the forms might no be a true 60°, etc., etc. Curious that your final dimensions show the same smaller discrepancy, since the adhesive usually adds to the overall dimension.  (Martin-Darrell)

    I had the same problem this weekend which threw me for a loop until I realized by calibration methods were off.

    I have a digital depth indicator that I bought a test indicator from Jeff Wagner for.  I also made my own test indicator by reaming a hole (1/8") through a piece of metal.  A few months ago, I wasn't able to get those two to agree so I assumed that the test indicator I bought was wrong and calibrated the depth indicator accordingly.

    I have a Vee Block on my caliper with a drill rod for calibration.  The math in the instructions was a little off but once I sorted that out, I feel the caliper is accurate.  (The instructions assumed a test rod of .0625" but the rod is actually .0620.  That resulted in a .001 difference  in the desired reading for the caliper.  Please if I am wrong, don't correct me.  It is working!)

    Like you, I kept coming up with a strip that was 1 or 2 thousandths off but I couldn't scrape the difference off the strip.  So I put the depth indicator on the form and calibrated to the value that the caliper was giving me.  I figured I wanted to work to the accuracy of the caliper.

    Now the kicker.  I then went back to the test block I bought from Wagner and lo and behold it read the number that he said it would.  It wasn't off!  My home made test block was off by 1.5 thousandths though.

    Now, whenever I pause to sharpen blades, I take a moment to check that the tools are still calibrated correctly.  Have found that both tools can be knocked off  a thousandth or so just by handling them.

    I hope now everything is right, but worst case is that I am consistently wrong and that at least is in agreement with what my wife and kids tell me which reinforces the feeling that everything is right.  :^)  (Tim Wilhelm)

Rule

I have the following:

  • A set of store bought forms, and a set borrowed from a friend. .
  • A bought base and 60 degree point.
  • I have 2 depth gauges.
  • A store bought wedge to calibrate my calipers.

So I have gone around with these things to check that they are measuring properly, depth gauge and calipers.

When I set my forms at the large end of the butt section side to something like .10 or .15 or .20  and plane a strip they come out at  .03 bigger than what the forms are set at than the.

If I go to the tip of the same side and do the same thing it is out .02.

If I turn them over and set the tip side to the same settings .10, .15 , .20 I get much the same error  of .02 and .03.

Because the error is not consistent I can not use it to zero it out.

I have used the drill bit method to check the depth, which matches with the depth gauge.

If I set the butt section, the larger side, to try and use this correction the forms will not close enough to make a butt section for a 5 wt.

I have tried to check the V to see it it is 60 degrees but it is not all that accurate with the little gauge for checking strips.

I have used the borrowed set of forms and get much the same very close to the same error, which keeps me thinking it is the measuring tools, but I have checked them many times and compared them with others or duplicated the part. 2 60 degree points, 2 depth gauges, 2 bases, 2 calipers and forms.

I have been going around with this for a long while now, my build a rod or two this winter has been consumed with messing with this problem.

Is there something obvious that I have missed.  (Ron Petley)

    Just to clarify, did you mean to say that your strips are 20 to 30 thou oversize or 2 to 3?

    20 to 30 seems like a lot.

    I use MHM rather than forms and a plane, so don't have the direct experience to help, but was wondering if you are using a plane with a groove.

    Are the forms flat?

    What you describe seems very puzzling.

    Hope someone with more experience can help you. I'll be watching to see the outcome.  (Pete Bates)

      .02 to .03 thousandths of a inch,  If the dial goes around once passing through numbers 1 to 10 it is out 2 to 3 of these numbers, which is a heck of a lot.

      I have also marked the V with felt pen and run a planed strip along it to see if their are any hi/low spots but it does not show any, trying to check and see if the V is 60 degrees.

      I have a few planes, all are standard flat bottomed planes. The strips feel flat in the V if I run my finger along them.  (Ron Petley)

    When you use your calipers to measure all three flat to apexes, are you getting the same measurement, or are they different.  Are you planing until you are removing metal from the forms and no more bamboo?  Have you tried to use a scraper or razor blade to finish off the  strips to ensure that you are level with the forms?  .030 sounds like a lot left.

    Are your depth gauges calibrated? Have you checked it against your calipers?  I would take my set of calipers and open them up to .1155, set the depth gauge on the them and zero the depth gauge.  Then test your strip.

    The only think I can think of would be to check your measuring devices as many ways as possible and make sure you are getting 60 degree angles.  (Greg Reeves)

      Are your depth gauges calibrated? Have you checked it against your calipers?  I would take my set of calipers and open them up to .1155, set the depth gauge on the them and zero the depth gauge.  Then test your strip.

      When you set your dial  indicator  with  the  caliper  method (0.1155") you are setting the indicator to 0.100", not 0.00.  (Neil Savage)

        Thanks for the correction.  Sorry I left out that info.  (Greg Reeves)

          One other consideration:  unless you have one of the really expensive dial indicators, they read backward.  That is,  you read the (usually) red numbers, not the black ones.  (Neil Savage)

    I have a cheap dial indicator that does exactly what you are describing and I've had no problem working with it for years making good rods without glue lines and accurate tapers.  You can deal with this by setting the calibration to an "offset" of your average error of 0.0025. Then set your final taper dims say 3 thousandths too deep (strip oversized).  Plane your first strip, check the dims, write the error with a sharpie on your forms at each station, and then close your forms at each station based on the amount the strips are oversize. Plane out the strip to final size, double check it, then do all the same strips with that setting.  I guess maybe I could try buying a more expensive dial indicator, but what's the point - I would still want to make my strips as above, just as a safeguard in case my calibration is off.

    What you will find though is that even with this you will get some variation in your strips, with errors some times higher than 0.003.  Know what? Your rods will come out fine, if your geometry is good you probably won't even get glue lines.  Despite what you might read about what kind of error to strive for, even 0.002 is a really close tolerance for say 3-sigma overall error (i.e. 99 percent of errors less than that amount), in reality it is very difficult to achieve, 0.003-0.004 is a more realistic goal. Getting all your strips within 0.001 IMO is not worth the effort.  (John Rupp)

    Couple more quick thoughts:

    I am assuming you meant to say your error is 2 thou vs 3 thou, not 20 Vs 30 that is completely out of whack and not going to get the job done.

    Another thing put a mark on your indicator base and point your indicator base to the same place on your forms and keep your forms flat so you aren't dealing with bumps that can throw off the measurement. Even then you may get some variation hence my suggestion to always work your way down to final dim on your first strip stepwise.  (John Rupp)

      NO the error is  20-30 thousandths it is a huge amount that is making me cracker dog, I would happily live with .003.  (Ron Petley)

        I would think it is how you are zeroing the indicator in the standard or reading the indicator wrong. If your indicator has large and small numbers read the small numbers on the face of the indicator after you "zero" the indicator in the caliper set at .1155. Actually you are setting the indicator at .100. .1155 is the width of a 60 degree angle at .100 up from the point. Are you sure you have a 60 degree point and not some oddball point.  (Tony Spezio)

          You have received some solid procedures and information from the list members. My suggestion: Take the forms back to the person you borrowed them and have them show you what you are doing wrong. My guess, you are the problem not  the equipment.

          Sorry to sound so harsh.  (Don Schneider)

        First thing to do is check your depth gauge on the calipers after you check the calipers on a drill bit. After you check your depth gauge and set it against the calipers check the accuracy of your depth gauge setting. Make a note on the standard of what your gauge is reading.  (Timothy Troester)

        Just a suggestion but lets take a few of the variables out of the equation. The advantage of this test is that only one measuring device is involved so you don't have multiple sources of possible errors.

        1.  Find a reasonably good quality drill bit, or chunk of drill rod, or a dowel pin of about 1/8" diameter.

        2.  Using the drill bit set the middle four stations of your forms by placing the bit in the groove and adjusting until a straight edge laid across the form just kisses the drill bit.

        3.  Over the four middle stations, plane out and hand scrape a 15 - 20" long strip as best you can until no more bamboo can be removed.

        4.  With a selected caliper, measure the drill bit and all three apex's of the strip at each station.  The bit diameter should be within .001 of label and you should end up with consistent apex dimensions of 1.5 times the measured drill diameter.  If you are within ,002 the form groove is good enough.  If the three apex dimensions are not equal within that same 2 - 3 thousandths, work on planing technique.

        5.  AFTER steps 1 - 4 are done, set your depth gauge by placing it in the form groove you have just planed over and adjusting it to read the average of the test strip apex dimensions.  Use this adjusted gauge to set your forms for an actual rod taper and see how it works out.   If all goes well, you will have eliminated questions about the forms and can sort out the other issues one at a time.  (Rick Hodges)

    New forms and questions about calibration can be frustrating issues. First pick one depth gauge or the other. Two depth gauges compound the issue. Check your calipers against a standard like a drill bit. Check the depth gauge against the caliper setting. Use that setting as your standard.  I haven't looked but the closed setting at the very butt end of my planing form may well be too big for lots of rod tapers. That's okay you can move on up the form to start. That's how we all do it.  If you are measuring .03 out on your planed butt ends and .02 out your tip ends. You are in the money. That's good! Before I would assume your form isn't right or your gauges are uncalibrated I would, as suggested, scrape down to the form with a razor blade and remeasure. I would check and compare all 3 peaks to flats. There is enough room for error there to make up most or all your found error in measuring depth. Work on planing with the flat of your plane parallel with the surface of the form. A slightly cocked plane also is a source for much more measured error than what you are dealing with. Next, quick screwing around and measuring a remeasuring and remeasuring. You are just going to make yourself bald. Plane out a rod and glue it up. Perfection comes from much practice. (Timothy Troester)

      I was going to suggest it may also be an issue with a plane that needs tuning or how you are using it. I think Harry recommended practicing with a mirror to get your technique right  (Nick Kingston)

    Have you checked the 60 degree point to be sure it is actually 60 degrees?  I have seen some off brand points which were not even close to the 60 degrees.  You can check this with a center gauge.

    Also, you didn’t mention anything about a standard for setting your depth gauge.  (Scott Grady)

    First, settle on ONE set of forms, ONE dial indicator, ONE method of calibrating or setting up your indicator.  Playing with two things at once is like trying to date two girls without them knowing about each other... disaster awaits.  Take the borrowed forms back and work on your problems with ONE complete and permanent setup.  Get the other forms and one of the two indicators OUT OF THE GAME!  COMPLETELY!!!  You're pretty much just beating your head against the wall messing with multiple setups.  You need to know what YOUR tools do, not what a borrowed set of forms do.

    I'm going to fly into this assuming a couple of things... I'm going to assume that you're using a quality set of forms like Larry Swearingen's, Jeff Wagner’s, Lon Blauvelt's, Bellinger's, etc, and I'm going to assume that you're planing method is sound and that your holding correct angles.  I'm also going to assume that your using a good quality 60 degree point, which I'll talk about in just a minute and I'm going to assume that your point is snugly screwed into your indicator stem (one that's loose can drive you NUTS... personal experience) and that your indicator is firmly mounted in your base.  Note I said firmly, not "cranked down".  You can crush the tube on the indicator even ever so slightly and cause the stem to stick and not move freely.  I'm assuming these "mechanical" things, but these are things you should check every time you set up your forms to cut a strip.

    I know you've gotten some great advice during this thread on calibrating, but you can calibrate until you go crazy if you don't have a quality 60 degree indicator point.  Use nothing but Starrett!  I've owned more supposed 60 degree points that are anywhere from 55 to 65 degrees than I can count.  Even the Starretts aren't all EXACTLY 60 degrees.  Why?  60 degree points are NOT made for rodmaking and they really aren't made to measure 60 degree grooves.  In my former career with Owens Corning years ago, I had access to an Optical Comparator and a gentleman that knew how to use it correctly.  I took MANY of those so called 60 degree points to the plant and had him check them.  Very few of the Non Starrett points were even close to 60 degrees... I'm talking 5 degrees or more off angle. Trying to maintain a .001" precision with a point that's 5 degrees off angle will put you in the Looney Bin in a short time.  The Starrett points were the closest we could find to 60 but even most of those are off a degree or so.  That's not much, but it's enough to make it VERY difficult to set forms precisely... keep the term, precise, in mind... I'll talk more about precision vs accuracy in a minute.  Before I do, I want to apologize in advance to those who are going to get mad at me or think I'm a jerk  for my upcoming rant about precision vs. accuracy, but sorry, that's the way I feel and the premise  upon which I've built rods for 23 years.

    Back to the problem... If you don't already have a Starrett point on your indicator, then purchase one.  Good tools are required to do good work! Few things will light my fuse faster than someone buying a $90 reel seat then complain about spending 8 or 10 dollars on a good 60 degree indicator point!!!

    Calibration:  Figure out which calibration method is best and easiest for YOU... settle on it and stick with it... don't change around doing one thing then another, or you're going to end up RIGHT BACK IN THE SAME BOAT.  Consistent methods... very important.  In my opinion, it doesn't matter so much how you calibrate as long as it's a repeatable process.  Most all the methods out there are great and work very well, but I can't stress this enough;  SETTLE ON ONE METHOD AND STICK WITH IT.  When you calibrate, insure that you are setting your indicator right and reading it to the correct side (red numbers unless you spent the money on a reverse dial indicator).

    When I use forms, which is not very much these days since I run a Miller, I mark lines on the forms with a Sharpie permanent marker.  I mark right above the dowel pin in the forms (using Bellinger forms). It doesn't matter where you mark them, as long as it's consistent from station to station... over the dowel pin, over the push screw, over the pull screw, doesn't matter.  Just use a small square and make an easy to see marker line at the same place on each station... this is the line that you'll measure your strips on and align your indicator with to make changes in your forms.

    Now, time to set up your forms correctly for your strip. Initially, you need to set them INCORRECTLY.  We're doing this intentionally.  Set your forms at .005 OVER your target, plane a strip.  Plane it until you take steel powder off of your forms on the final pass on both sides of the strip... you should have a small "pile" of steel powder on either side of the strip in your plane, laying on the blade, when you've reached the RIGHT place to stop. You need to watch that plane blade cutting as it goes down that final pass and make sure your "hitting steel" ALL THE WAY DOWN THE STRIP.   Of  course,  you  should  be taking off 0.001" or LESS on each pass at this point.  Before I go further, NO, you will NOT wear out your forms or get your next strip out of dimension doing this... you are taking off a VERY small amount of the forms when you do this.  I call it "shaving the form", but you MUST get down to a touch, or shave, on the metal or you won't get a well planed, well dimensioned strip.  If you're taking fine enough of a pass and have properly sharpened good quality plane blades, you won't get chatter on your forms, just a nice shiny line on each side of the groove.

    Next step, measure your strip at EVERY station.  Mark the station locations on the bamboo with a pencil so you insure you're measuring in the same place every time.  Make your pencil mark on the enamel side of the strip (just my way of doing it) and make the mark in line with the sharpie marks you made at each station.  I simply take the strip out, put it back in the form, enamel UP and mark the enamel side with a mechanical pencil.

    I measure each strip flat to apex on all three sides and record the measurements of each station in my build book (just a spiral notebook that I keep going for a rod during the entire build process).  Be careful about how much pressure you put on the calipers when you measure.  You do NOT want to use so much pressure that you crush the apexes on the strips, but you want to be firm enough that you can get a consistent measurement.  This is just ONE of the reasons why I prefer to use ratcheting micrometers instead of dial calipers. I'll get into the most important reason very shortly.  Now, calculate your average of the three measurements from each station.  You SHOULD be within 0.001" on the three measurements if you're getting your angles right,  so you can figure your average very easily.  For now, let's assume your angles are correct and you've planed until you take the 'powder' off of the forms.  Remember that you set your forms 0.005  over,  so  your  strips,  theoretically,  will   be 0.005" oversized at each station.  I can just about promise you that they will not be .005" over.  They may be .004 over at station one, .006 over at 2, .009 over at 3, .003 over at 4 and actually, that's pretty good for tip strips.  On butt strips your probably going to find your error to be even larger.  The only explanation I have for this is if the groove is off 1/4 of a degree and the point is off 1 degree, then the error is inevitable and it's nearly impossible to get "perfect" angles on forms.  They can be damn close, but perfect is tough to attain, and we've already talked about the indicator points and their slight inaccuracies, even with the BEST points available.

    By the way, there's no particular reason that I set  mine .005 over... It's just my favorite number, but you can set them .005 or .008 or whatever you choose, but settle on ONE number and use it ALWAYS!  Get a routine and keep it from now on.  In this craft, I don't feel like I can stress how important it is to develop a "building routine" and stick to it.

    Now, take your permanent marker and note how much over you are at each station.  Write the "oversize" right on the forms near each station, but in a place that you can physically see that number with your indicator base centered over the lines you marked at each station.   If it's .030 over, then mark .030 over.  I hope it won't be that much over, but it could well be, especially if your calibration is flawed or your indicator point is way off angle.  Be sure and mark EVERY station how much oversize the strip is at that station.  Now, here's where I go away from standard.  I don't care about calibration at this point. I calibrated to get my strip in the form and get the form set for an initial run.  I put the indicator in the groove , center it over the line that I marked at that station and set it at ZERO.  If it's in the groove at station one and station one was over .005" then I tighten it down until the indicator reads that I "tightened" that station by 0.005".  Move to the next station, make sure the point is in the groove, aligned with your station mark and zero the indicator again, tighten the screws and close the form to your target (the amount that station was oversized).  No, that's not in the books, or the rodmaker's bible, but it consistently works, it's quick, it's not confusing.  Do the same thing at every station.  Put your strip that you just planed back in the forms and take it down until you're getting powder on the final pass on BOTH FLATS.  Take it out, measure it again.  If the Rod Making Gods are smiling on you, then your strip will be dead on... usually this is NOT the case.  Measure the strip at each station again, record it in the notebook.  Again, if you're planing level and your angles come out right, you should be within 0.001" on flat to apex measurement at each station.  Once again, we're going to assume that you are "on angle" and I'm betting you'll still be off dimension, but not by much.  You may have to tweak each station a thousandths or two and some of them you won't have to move at all. Good news is that once you get that first strip set, you can plane strips in that groove until hell freezes over and they'll stay in spec.  I still measure each strip at the 5 inch stations, but again, I'm pretty OCD, and I'm not going to change!

    Basically, repeat this process until you get that first strip to whatever you consider acceptable numbers.  For me, that's within .001" per station, others have larger over/unders than I do and that's fine.  Keep in mind it takes about .010 to change a rod one line weight, so if you're off 2 or 3 or 4 thousandths then that is going to be acceptable to most rodmakers, most flyfishers.  For me... will I'm an Obsessive Compulsive Son of a Bi#$* and I insist on mine being + 0.001"/ -0.000".  Again, that's MY standard and is considered by many to be unreasonable, but I'm in my rut, have my way of doing things, and probably wouldn't change if the Rod Gods came down and said "Bob, it's OK to be off .004 on a glued up section.  It may well be OK, but it is NOT ok for me! Smile  As a matter of fact, I only use dial indicators for ROUGH measurements.  Don't trust them, don't feel like they're made for making PRECISE measurements.  I use Micrometers... Starrett Micrometers, which I check with a 1" standard EVERY time I get them out for a session of strip measurement.  My particular Starrett micrometer is precise to .001... My Starrett Dial Calipers are Accurate to within 0.002".  It will tell you that on the spec sheet, which doesn't come with most cheap dial calipers, but I don't figure they're really any more or less accurate than Starretts... I just like Starrett tools.  My point here is that there is a difference between PRECISE and ACCURATE.  I know we aren't building Space Shuttles, but ask a machinists what tool he would use to measure to within a thousandths of an inch.  If he says calipers, go shopping for another machinist.  If he says Micrometers, then he knows how to do PRECISE work.

    My opinion, we should , in rodmaking, strive for PRECISION, not ACCURACY.  Don't misunderstand, I know that it's not necessary to be within .003 on measurements (I really do NOT know that, but I'm going to say I do so I don't get called an Anal Retentive Ass), but if you use a tool that is Accurate, then you could get an inaccurate rod.  Keep in mind that if you're off .002 on a strip, then your error is doubled on the glued up section and you'll be off .004"... that's nearly half a line weight.  If you use an instrument that will allow you to make PRECISE measurements, like Micrometers, then your doubled error is MUCH LESS... More precise measurements equates to a more consistent product.

    Now, that I've gone through all of this, until you get a feel for YOUR forms and for YOUR indicator and YOUR 60 degree point and again, I'll stress, get a good Starrett point and save yourself a  lot  of  heartache,  then  I  would  set my original settings at 0.008" over, then plane the strip, measure and reset for  0.004" over, see how much movement your ACTUALLY getting when you move the indicator .004, then move them a third time to dimension.  Start a "build book" and make notes in it like Moved Dial Indicator 0.003" and actual dimension moved 0.002".  If you make these notes and keep track of what your tooling does, then you will very quickly learn to predict your movements and cut your setup time in half.

    Best of luck getting this problem worked out, Ron, but you've gotten plenty of great advice from the list and have plenty of things to look for, but I'd take back the borrowed forms and use your own, your ONE indicator, one set of calipers (or a micrometer if you have one) and work this down to find the error.  (Bob Nunley)

      You mention "loose point" That really gave me fits one time. I could not figure why I was getting different readings each time I rechecked a station.  (Tony Spezio)

    Thanks to Bob and all the others who have helped me out with this problem. People have offered so may ideas it is just a matter of working through them.

    I will follow up on Bob's and the others great advice.

    Bob I do not have the best 60 degree, but I will order one and start in on this I have a micrometer but did not think to use it, I will dust it off. I have a good quality dial and base. I have quality planes and have experience using them from years of woodworking.

    People have offered so may ideas it is just a matter of working through them.  (Ron Petley)

Rule

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