Caliper Measurement Techique...?

[jrista]

I've been turning pens for a little while now. Didn't get a lot of time in the shop last year, but overall, I'd say I have about a year, or so, under my belt. I went TBC....well, I guess, around the end of 2021, based on things I learned here on these forums. I turn between 60 degree centers with TBC bushings, until I get close to the bushing, then put the blank directly between centers for final turning and finishing.

I'm wondering, for those of you who do things this way, how you measure your final diameters? I have a digital caliper, and am looking to improve my technique, accuracy, and speed at getting down to the right diameter at the ends of each blank. I have had some trouble, getting those measurements. Like most digital calipers of this class, I think, there are two ways to measure...outside diameter, and inside diameter. I've tried both. I have tried using the inner part of the outside diameter side of the calipers, as well as the tapered outer part. The inside part, if you have any kind of curve to your blank, is hard to get an accurate read with... However, using the thin tapered outer tips of this part of the caliper, is often very hard to get right at the end of the blank...so its not necessarily, at least in practice for myself so far, been much more accurate.

I've also tried to use the inside diameter tips of the caliper. I feel like that should be a more accurate way of measuring...but, it can be tough to actually get those tips at exactly the surface of the blank... Since you are not clamping down on anything...there is no natural stop for the tips, and getting an accurate read is still tough.

Anyway, I'm wondering if anyone has a particular technique that works really well, for caliper measurements. I still get a bit of wobble with bushings, even the high quality TBC bushings from TBCBushings.com. I am not real sure why, although I have several ideas. Anyway, in order to get optimal concentricity and roundness, I'm trying to do final turning and sanding without any bushings, with caliper measurement to try and get a perfect fit between the blank and kit parts.

 

[BULLWINKLE]

I've been turning pens for a little while now. Didn't get a lot of time in the shop last year, but overall, I'd say I have about a year, or so, under my belt. I went TBC....well, I guess, around the end of 2021, based on things I learned here on these forums. I turn between 60 degree centers with TBC bushings, until I get close to the bushing, then put the blank directly between centers for final turning and finishing.

I'm wondering, for those of you who do things this way, how you measure your final diameters? I have a digital caliper, and am looking to improve my technique, accuracy, and speed at getting down to the right diameter at the ends of each blank. I have had some trouble, getting those measurements. Like most digital calipers of this class, I think, there are two ways to measure...outside diameter, and inside diameter. I've tried both. I have tried using the inner part of the outside diameter side of the calipers, as well as the tapered outer part. The inside part, if you have any kind of curve to your blank, is hard to get an accurate read with... However, using the thin tapered outer tips of this part of the caliper, is often very hard to get right at the end of the blank...so its not necessarily, at least in practice for myself so far, been much more accurate.

I've also tried to use the inside diameter tips of the caliper. I feel like that should be a more accurate way of measuring...but, it can be tough to actually get those tips at exactly the surface of the blank... Since you are not clamping down on anything...there is no natural stop for the tips, and getting an accurate read is still tough.

Anyway, I'm wondering if anyone has a particular technique that works really well, for caliper measurements. I still get a bit of wobble with bushings, even the high quality TBC bushings from TBCBushings.com. I am not real sure why, although I have several ideas. Anyway, in order to get optimal concentricity and roundness, I'm trying to do final turning and sanding without any bushings, with caliper measurement to try and get a perfect fit between the blank and kit parts.

I've used a mandrel and bushings for the 20+ years I've turned pens. I never turned a pen that came out off center or lopsided. I've see many here prefer TBC. Is it better ? Maybe so. Does it make a huge difference? I don't think so.
Well if using bushings and you are getting great results then why change ? Is any customer going to check it with a micrometer ? I think it's possible to overthink it. If you get a satisfactory result that's all that matters. Why make something that's fairly simple more difficult ?
I don't see the point. Just my opinion.

 

[rixstix]

ID is easier, more accurate to measure OD and subtract 2X the measured wall thickness.

 

[jrista]

I guess I should be clear...I'm not having any huge issues. Nothing like when I was using any of the mandrels I have (which, admittedly, are not the best available...) My issues are pretty small...but, as a perfectionist, I want to do better. There is usually one side of my blanks that comes in just under the edge of the kit parts, and the other side just over. Its by a tiny fraction of an inch, but its still there...and, I just want to do better.

FWIW, a customer doesnt need to check with a micrometer...all they need to do, is feel those seams. You can FEEL the issue. You can also see if, if you look close enough.

Using TBC has definitely improved things, and I'm not really complaining about TBC.

 

[jrista]

I've used a mandrel and bushings for the 20+ years I've turned pens. I never turned a pen that came out off center or lopsided. I've see many here prefer TBC. Is it better ? Maybe so. Does it make a huge difference? I don't think so.
Well if using bushings and you are getting great results then why change ? Is any customer going to check it with a micrometer ? I think it's possible to overthink it. If you get a satisfactory result that's all that matters. Why make something that's fairly simple more difficult ?
I don't see the point. Just my opinion.

FWIW, I can see the same issue I have, in the blank in your photo here. This is something you can just feel...you can feel the lip of the blank when it overhangs the kit part it butts up against, when its misaligned like that. It is also clearly visible here. I know there are members here, who do not seem to have this issue with their pens...

Just wondering how to take my products to the next level. You can either settle for good enough, or keep pushing the envelope to do better, take things to the next level... I guess, I tend to take the latter path.

 

[jrista]

ID is easier, more accurate to measure OD and subtract 2X the measured wall thickness.

...hmm, I'm not sure I fully understand this. Subtract 2x the measured wall thickness? I am not following that...

 

[mark james]

When I glue in my tubes, I leave 1-2 MM on both ends, clean out the epoxy after taking out the dental wax. I then turn the blank down to 1-2 MM proud of the stock bushings.

I use both TBC and stock bushings, but I NEVER depend on them for final dimensions. I always measure my components, write down those dimensions. After turning to 1-2 mm proud, I take the blank off and go to my small second lathe with my Rherrell offset sanding jig. I use a metal face plate with a 2" block and sandpaper attached on the headstock side. I sand the blank ends down to the brass tube, clean the tube and remount on the lather for final turning.

I will stop 2-3-4+ times during the final turning and use calipers to get the blank to the components dimensions. I also feel that the repeated taking the blank on/off the mandrel will correct any slight 'out of round' of my mandrel - (which I do not detect with a roll on my bench; just being careful).

 

[jrista]

When I glue in my tubes, I leave 1-2 MM on both ends, clean out the epoxy after taking out the dental wax. I then turn the blank down to 1-2 MM proud of the stock bushings.

I use both TBS and stock bushings, but I NEVER depend on them for final dimensions. I always measure my components, write down those dimensions. After turning to 1-2 mm proud, I take the blank off and go to my small second lathe with my Rherrell offset sanding jig. I use a metal plate, 2" block and sandpaper attached on the headstock side. I sand the blank ends down to the brass tube, clean the tube and remount on the lather for final turning.

I will stop 2-3-4+ times during the final turning and use calipers to get the blank to the components dimensions. I also feel that the repeated taking the blank on/off the mandrel will correct any slight 'out of round' of my mandrel - (which I do not detect with a roll on my bench; just being careful).

Thanks, Mark.

Yeah, I see the taking the blank off several times and returning it, can help with OOR, since you'll rarely ever put it back on in the same orientation as before...

I;m curious more explicitly, about EXACTLY how you use the calipers to measure. When you are actually measuring the blank...what are you measuring, and how? The full OD of the blank at the very ends? Or do you try to measure the same diameter, but from with the ID tips of the caliper? Or, are you, say, measuring from the inside of the brass tube, to the surface of the blank, at the ends?

I have some trouble, getting a read on the very ends of the blanks. If I use the tapered parts of my OD caliper tips, its actually pretty hard to keep the blank steady, and keep the caliper tips exactly at the end of the blank... Sometimes its back a little ways, and the diameter measurement might not be totally accurate. If I use the ID tips, then, I'm not clamping down on anything, and getting an accurate read can still be a challenge. I've seen in some videos, where some guys actually measure from the inside of the tube to the outside of the blank...which is totally different than I've approached it, and I'm not real sure what measurement they are actually really trying to take, or what they are comparing to....

 

[mark james]

Thanks, Mark.

Yeah, I see the taking the blank off several times and returning it, can help with OOR, since you'll rarely ever put it back on in the same orientation as before...

I;m curious more explicitly, about EXACTLY how you use the calipers to measure. When you are actually measuring the blank...what are you measuring, and how? The full OD of the blank at the very ends? Ends. Or do you try to measure the same diameter, but from with the ID tips of the caliper? Never tried that. Or, are you, say, measuring from the inside of the brass tube, to the surface of the blank, at the ends? Nope.

I have some trouble, getting a read on the very ends of the blanks. If I use the tapered parts of my OD caliper tips, its actually pretty hard to keep the blank steady, and keep the caliper tips exactly at the end of the blank... Sometimes its back a little ways, and the diameter measurement might not be totally accurate. If I use the ID tips, then, I'm not clamping down on anything, and getting an accurate read can still be a challenge. I've seen in some videos, where some guys actually measure from the inside of the tube to the outside of the blank...which is totally different than I've approached it, and I'm not real sure what measurement they are actually really trying to take, or what they are comparing to....

My calipers (Home Depot and Harbor Freight) do not have a tapered tip that I remember, so my end-of-blank measurements are from a straight edge. I measure the very ends of my blank; my middle profile is just 'eye pleasing.'

 

[jrista]

My calipers (Home Depot and Harbor Freight) do not have a tapered tip that I remember, so my end-of-blank measurements are from a straight edge. I measure the very ends of my blank; my middle profile is just 'eye pleasing.'

Ok. Thanks.

 

[jttheclockman]

My turning of pens has not changed since the day I started. I am still using the same mandrel too. Never had an out of round blank. I have mentioned my process many times here over the years but will add it again. I use the stock bushings. At one time someone here was making BTC bushings and I bought a bunch. I really should sell those. Never used them. I turn one blank at a time. I am not a production turner. I am a hobbiest that makes one of a kind pens. I will purposely turn the bushings below required height so that I know I can control final outcome. I get close to bushings size and the correct shape I am looking for. Now I take the blank off and measure the very end of blank. I already measured the kits componets ahead of time and wrote them down. Now I compare that with my measurements of the blank and with my skew I can take off just what I need. I may have to take the blank off the mandrel 3 or 4 times to get it right but to me that is all part of a grade A++ pen hand made. and that is what I am shooting for. Calipers are used to measure OD of components and of blank. I use the front portion of calipers. I like to use MM measurements. Not feeling ends where components meet blank is a touch thing. Some kits like Sierras have a crown on the components and it keeps the blank from looking like it is touching the parts. That is done to prevent wear because the blank spins on the components. Next time you make one hold it up to a light and you will see what I am saying.

 

[rixstix]

...hmm, I'm not sure I fully understand this. Subtract 2x the measured wall thickness? I am not following that...

You mentioned difficulty measuring ID (I thought, maybe misread).

Yes, measuring ID with calipers is difficult. Instead, measure the OD. measure the wall thickness of the brass tube or tube and turned blank. Subtract twice the measured wall thickness & the result is the ID.

 

[jrista]

You mentioned difficulty measuring ID (I thought, maybe misread).

Yes, measuring ID with calipers is difficult. Instead, measure the OD. measure the wall thickness of the brass tube or tube and turned blank. Subtract twice the measured wall thickness & the result is the ID.

Oh, I was referring to the ability of my digital calipers to measure with outer-diameter tips, or inner-diameter tips. I'll get a picture of my calipers to explain better.

 

[jrista]

My turning of pens has not changed since the day I started. I am still using the same mandrel too. Never had an out of round blank. I have mentioned my process many times here over the years but will add it again. I use the stock bushings. At one time someone here was making BTC bushings and I bought a bunch. I really should sell those. Never used them. I turn one blank at a time. I am not a production turner. I am a hobbiest that makes one of a kind pens. I will purposely turn the bushings below required height so that I know I can control final outcome. I get close to bushings size and the correct shape I am looking for. Now I take the blank off and measure the very end of blank. I already measured the kits componets ahead of time and wrote them down. Now I compare that with my measurements of the blank and with my skew I can take off just what I need. I may have to take the blank off the mandrel 3 or 4 times to get it right but to me that is all part of a grade A++ pen hand made. and that is what I am shooting for. Calipers are used to measure OD of components and of blank. I use the front portion of calipers. I like to use MM measurements. Not feeling ends where components meet blank is a touch thing. Some kits like Sierras have a crown on the components and it keeps the blank from looking like it is touching the parts. That is done to prevent wear because the blank spins on the components. Next time you make one hold it up to a light and you will see what I am saying.

I don't know what mandrel you use, but every one I've bought since 2020 has problems. The shafts on every one at the very least, have an intrinsic bend or curve to them. One is particularly bad, got it from PSI, tried to return it and they never communicated with me at all over it. I had the same problem when I tried to return my PSI TBC centers set (which also has problems). I have several other mandrels, and they all have some kind of intrinsic curve or bend, although not as severe as the PSI one. I think that alone, causes problems. One has problems with the mandrel staying screwed in. Another has a kind of collet-like compression fitting that, I assume, is supposed to eliminate that problem, but it introduces its own issues. So, I've never had luck with mandrels, and finally gave up on trying to find one that wasn't problematic in one way or another. IMO, they are hit or miss, at the very least, more miss for sure in my case.

Hence TBC. The problem is not TBC though, which seems to be what everyone responding to this thread things.


The problem is how to actually use a set of calipers effectively, to get an accurate read on the diameter of the turned blank. Maybe i just have unsteady hands...not sure. But I have trouble keeping the calipers, right at the end of the blank, and measuring it accurately? Maybe no one else has that problem...

Regarding sierras, I know exactly what you are referring to. I don't think you quite understood the touch thing I was talking about. Its not feeling the gap. Its feeling non-concentricity or OOR in the turned blank, as it fits up against pen parts. If the blank is non-concentric or OOR, then on one side of the pen, you can feel where the blank shifts farther out than the pen part, and on the other in the opposite direction, you can feel where the pen part shifts farther out than the blank. Its not severe, probably totally nit picking, but I can still see and feel this issue with some of my pens...too many, although maybe not necessarily a majority. It bugs me. I feel that, if I want to sell a truly exceptional pen, at a high price...then this is something that I should find unacceptable, and work to eliminate.

 

[TDahl]

To answer you main question about measuring with calipers, I will measure using the OD flat portion of the Calipers and then lock it in place and then slide the caliper back and off the blank. I take at least three measurements, to make sure I have accurate readings. I have not had any issues with inaccurate measurements. I know some makers had began using micrometers for their measurements for the exact reasons you are talking about.

 

[1080Wayne]

I totally understand your problem with using calipers at the very end of the blank . If you are making your barrels dead flat , it is fairly easy to use them in the manner described above by TDahl . If you like to have a slight bit of curvature , like me , it is much harder . I do the best I can , but after that , I do a trial assembly , and then make adjustments as necessary .

There is one other variable which hasn`t been mentioned , and that is components which are not perfectly round . They do exist . Shouldn`t be too common on the nib end , but I`ve seen a lot of it on the ring to which the clip is attached on Luxor pens . I haven`t checked others , but would be surprised if they don`t have the same problem .

 

[jttheclockman]

https://www.amazon.com/Neiko-01407A...keywords=6+inch+caliper&qid=1678946709&sr=8-3

This is just for picture sake. I do not have this brand. I bought mine at a woodworking show from Peachtree years ago. Have a couple sets. I measure with the flat portion right after the indented ends. It is a larger surface to catch the edge. Never had a problem getting the edge. You do not want to squeeze the daylights out of it. Just close so it touches. Same goes for components and with some kits you have to be careful of the fancy designs on the nibs or center rings. I measure to the flat edge and never to the fancy designs. Those that round over the very ends so it transitions better to components may have a problem getting an accurate edge. I never round those edges over unless I really have to because I am cheating on thickness of blank because of casting parts. I understand about parts feeling as a perfect transition to components and blank. We strive for that. Again maybe it is just my technique or something but I do not have this problem because of the measurements I take for each kit. Not every kit has the same amount of plating material so that can vary that measurement. Each kit for each blank is measured.

As far as mandrel I have the oldest version of mandrels out there. I bought mine 15 years ago from Crafts Supply USA where I bought just about all my turning tools lathes, and chucks and other things needed for pen turning. Saw them at a woodworking show and talked with and now can not remember his name but he was or has been with them for a long time. Bought my turning tools from them and they showed me how to sharpen and all. They are a great source to watch a ton of videos on everything turning. Check them out. It is a morse taper with an adjustable rod that is moved and locked with a setscrew. I turn one blank at a time and as I said never ever had I made an OOR blank with it. If you are having OOR problems it is possible your lathe is not level or head and tailstock are not in line. Some people said that bushings could be a source for OOR turning because they are not drilled dead center. Again I must be the luckiest pen maker on the planet because never run into this either. Other factors can cause OOR blanks and you should do a search on that topic because it has been talked about many times. But sanding is a possibility and that is why I recommend to use a block of wood behind sandpaper to evenly sand with equal pressure all the time.

 

[jrista]

I totally understand your problem with using calipers at the very end of the blank . If you are making your barrels dead flat , it is fairly easy to use them in the manner described above by TDahl . If you like to have a slight bit of curvature , like me , it is much harder . I do the best I can , but after that , I do a trial assembly , and then make adjustments as necessary .

There is one other variable which hasn`t been mentioned , and that is components which are not perfectly round . They do exist . Shouldn`t be too common on the nib end , but I`ve seen a lot of it on the ring to which the clip is attached on Luxor pens . I haven`t checked others , but would be surprised if they don`t have the same problem .

Yeah, I often do a slight bit of curvature...I think that's partly where my troubles come from. I will usually do two-part pens with a flat pen blank, but a slightly curved cap blank. So I have the most trouble with my caps.

Good point about the components though... Its not necessarily just non-round parts, but sometimes the parts are actually a larger diameter than the blank should be as well. In fact, there are even kits I've turned where the diameter of the bushings is the same as the largest diameter of the pen kit parts, when they actually should be a fraction smaller (especially kits that have bands with a three dimensional profile, say something kind of like:

∩∩

The blank should actually be turned a bit thinner than the upper part of the bumps with a band like this, but sometimes bushings are the same diameter as the maximum height of the bumps, which just increases the challenge.

 

[jrista]

To answer you main question about measuring with calipers, I will measure using the OD flat portion of the Calipers and then lock it in place and then slide the caliper back and off the blank. I take at least three measurements, to make sure I have accurate readings. I have not had any issues with inaccurate measurements. I know some makers had began using micrometers for their measurements for the exact reasons you are talking about.

Hmm, you know....I think I lost the locking thumb screw for my calipers... Heck, I didn't even think about that, but, maybe that is part of my problem here... Not being able to lock them. Maybe its time for a new set here, something that has a working locking screw!!

it also just occurred to me...I guess there is no reason I couldn't put the blank, measured end down on a flat surface, put the calipers down on the same surface...that should make it easier to get a measure directly on the very end of the blank...

 

[jttheclockman]

And that is the reason I actually turn my bushings down. I do not trust bushings for exact measurements, I use them as a guide to get me close and then out comes the calipers. Most people hit the bushings anyway so after the first pen they are off. I never throw a set of bushings away. Now I do loose them and that is why I buy several sets.

 

[jrista]

https://www.amazon.com/Neiko-01407A...keywords=6+inch+caliper&qid=1678946709&sr=8-3

This is just for picture sake. I do not have this brand. I bought mine at a woodworking show from Peachtree years ago. Have a couple sets. I measure with the flat portion right after the indented ends. It is a larger surface to catch the edge. Never had a problem getting the edge. You do not want to squeeze the daylights out of it. Just close so it touches. Same goes for components and with some kits you have to be careful of the fancy designs on the nibs or center rings. I measure to the flat edge and never to the fancy designs. Those that round over the very ends so it transitions better to components may have a problem getting an accurate edge. I never round those edges over unless I really have to because I am cheating on thickness of blank because of casting parts. I understand about parts feeling as a perfect transition to components and blank. We strive for that. Again maybe it is just my technique or something but I do not have this problem because of the measurements I take for each kit. Not every kit has the same amount of plating material so that can vary that measurement. Each kit for each blank is measured.

As far as mandrel I have the oldest version of mandrels out there. I bought mine 15 years ago from Crafts Supply USA where I bought just about all my turning tools lathes, and chucks and other things needed for pen turning. Saw them at a woodworking show and talked with and now can not remember his name but he was or has been with them for a long time. Bought my turning tools from them and they showed me how to sharpen and all. They are a great source to watch a ton of videos on everything turning. Check them out. It is a morse taper with an adjustable rod that is moved and locked with a setscrew. I turn one blank at a time and as I said never ever had I made an OOR blank with it. If you are having OOR problems it is possible your lathe is not level or head and tailstock are not in line. Some people said that bushings could be a source for OOR turning because they are not drilled dead center. Again I must be the luckiest pen maker on the planet because never run into this either. Other factors can cause OOR blanks and you should do a search on that topic because it has been talked about many times. But sanding is a possibility and that is why I recommend to use a block of wood behind sandpaper to evenly sand with equal pressure all the time.

Ok. So this is a big part of the question. I have tried with the flat parts, after the indents. If the blank has a curvature though...I think that's where some of the challenge comes into play. Do you usually turns your blanks just flat, or do they ever have any kind of curvature, or other angle, to them? Not rounding at the end, like you mentioned...just a slight curvature to the overall turned blank.


You do sound rather lucky. I've had a number of issues since I started turning...BUT...I only started, well, my very first handful of pens were in 2020, then I had a pause, then started up again in summer 2021, and did some more last year (although last year was pretty sporadic). Getting back into it here. I wouldn't be surprised, if fifteen years ago, maufacturing of these kinds of things was just better in general. It seems like the general quality of lower end things like this, has taken a bit of a dive. I know there are some much higher quality mandrels out there, but they come with a corresponding price tag (hundreds of dollars). I've had pretty poor luck with most mandrels, and I've actually literally picked up normal bushings that visually had apparent roundness issues. I've also picked up normal bushings that were just incorrect sizes, based on the documented diameters in the pen kit data sheets as well as other sources. I just think the manufacturing for a lot of these things has declined in more recent years.

SO FAR...I've found the TBC bushings from TBCBushings.com have been phenomenal. Dead on for measurements. Perfectly round. Strong steel, so they don't scratch easily and last significantly longer. They are tighter tolerance, so they fit the tubes much better. Overall, I'm actually quite happy with all of these bushings.

I suspect my issues are something up with the lathe. I've been working on it, picked up a dial indicator and have been trying to dial everything in as best I can. On the lathe I usually turn pens with, there was some slight issue with the headstock and dead center...managed to clean out some stuck on gunk inside the spindle and that helped. I have found that I need to adjust the angle of the dead center to get the most optimal result. I am not yet sure about the alignment of the head to tailstock, though, and there may still be an issue there. I am not sure if that is a lathe bed issue, or if I might have to shim the headstock. I am not quite sure how to dial that in though, as I'm not real sure of the best way to measure that alignment.

 

[BULLWINKLE]

Jris

FWIW, I can see the same issue I have, in the blank in your photo here. This is something you can just feel...you can feel the lip of the blank when it overhangs the kit part it butts up against, when its misaligned like that. It is also clearly visible here. I know there are members here, who do not seem to have this issue with their pens...

Just wondering how to take my products to the next level. You can either settle for good enough, or keep pushing the envelope to do better, take things to the next level... I guess, I tend to take the latter path.

 

[BULLWINKLE]

Jrista, perhaps it appears that way in the photo I posted. I am admittedly a terrible photographer. I assure you that there is no OOR or overhang/ underhang between barrel and pen part. I can run a fingernail over it and it's a perfect fit. I totally understand the problem you are having. If TBC corrects it that's fine. Many people use mandrels and bushings with no such problem. I understand fully what you're saying with bad fit to pen kit. I wouldn't settle for that either. Just wondering what is causing it to happen with mandrel and bushings. It may remain a mystery.
Whatever works best for the individual is what they should go with.

 

[Mortalis]

To give you an answer to the reason for your question:
I use calipers all the time when turning pens. I turn TBC after having a few issues of overtightening the madrel setup and getting OOC.
I measure the hardware where it will butt up against the turned blank (on both end parts) and write those dimensions on a piece of paper (I use sticky notes and stick to the lathe).
I will then turn the entire body until I get the desired body diameter I want. I then concentrate on turning the ends. I measure using the thin part of the O.D. measure jaws and I use reading glasses to be sure I am measuring as closely to the end of the blank as possible.
I DO NOT try to match the hardware dimensions exactly. I will leave the blank a bit proud. How proud? I try to get within 0.005".

This is the important part of the TLDR
Once I get there I then apply my CA to 3-4 coats thin and 3-4 coats medium and once I start my finish sanding I will round the blank edge ever so slightly with a very ifinitesimal radius (An old timer taught me this). Once assembled, the radius hides any mismatch that the fingers can detect.

 

[montmill]

The problem is how to actually use a set of calipers effectively, to get an accurate read on the diameter of the turned blank. Maybe i just have unsteady hands...not sure. But I have trouble keeping the calipers, right at the end of the blank, and measuring it accurately? Maybe no one else has that problem...

I have that problem too and would love to see a picture or video of how it's done.

 

[Curly]

A suggestion or two for you.

You will get better and more consistent readings by using the calliper two handed. One hand lightly holding the calliper and the other gently squeezing the jaws together in to the part. When you hold it one handed and use your thumb to close the jaws you may not be consistent with the force you exert and it is harder to align the calliper to the work resulting in incorrect readings.

You said you lost the locking screw so this won't help unless you get another calliper or new screw. Set the calliper to a value over what you desire and lock it. As you turn offer the calliper to the blank from the end, lathe off. When it begins to slip onto the blank you are close to size and can reset the calliper to a few thou over desired dimension and continue doing the same. When you can just slip it on you have reached your desired size. You are likely going to sand the blank and will take it to size anyway.

I usually have my blanks a little oversize after sanding and very gently break/round the edge on the end of the blank with the fine paper. Then when finishing and buffing with the Beall wheels you have a "soft" edge at the end of the blank. When you assemble it a fingernail going towards the hardware will not catch and from the hardware to blank will gently ride up and over the difference unnoticed. You can't see the difference either.

 

[jttheclockman]

Ok. So this is a big part of the question. I have tried with the flat parts, after the indents. If the blank has a curvature though...I think that's where some of the challenge comes into play. Do you usually turns your blanks just flat, or do they ever have any kind of curvature, or other angle, to them? Not rounding at the end, like you mentioned...just a slight curvature to the overall turned blank.


You do sound rather lucky. I've had a number of issues since I started turning...BUT...I only started, well, my very first handful of pens were in 2020, then I had a pause, then started up again in summer 2021, and did some more last year (although last year was pretty sporadic). Getting back into it here. I wouldn't be surprised, if fifteen years ago, maufacturing of these kinds of things was just better in general. It seems like the general quality of lower end things like this, has taken a bit of a dive. I know there are some much higher quality mandrels out there, but they come with a corresponding price tag (hundreds of dollars). I've had pretty poor luck with most mandrels, and I've actually literally picked up normal bushings that visually had apparent roundness issues. I've also picked up normal bushings that were just incorrect sizes, based on the documented diameters in the pen kit data sheets as well as other sources. I just think the manufacturing for a lot of these things has declined in more recent years.

SO FAR...I've found the TBC bushings from TBCBushings.com have been phenomenal. Dead on for measurements. Perfectly round. Strong steel, so they don't scratch easily and last significantly longer. They are tighter tolerance, so they fit the tubes much better. Overall, I'm actually quite happy with all of these bushings.

I suspect my issues are something up with the lathe. I've been working on it, picked up a dial indicator and have been trying to dial everything in as best I can. On the lathe I usually turn pens with, there was some slight issue with the headstock and dead center...managed to clean out some stuck on gunk inside the spindle and that helped. I have found that I need to adjust the angle of the dead center to get the most optimal result. I am not yet sure about the alignment of the head to tailstock, though, and there may still be an issue there. I am not sure if that is a lathe bed issue, or if I might have to shim the headstock. I am not quite sure how to dial that in though, as I'm not real sure of the best way to measure that alignment.

Jon, when I turn my blanks I try to keep the edges flat. As I mentioned above unless I am cheating a clear cast blank that has parts that I need to avoid when turning I may do a slight round edge to get the components and blank to match up. But with all other blanks any rounding of the edges is done with MM when I go to polish to a finish. I always do my finishing between centers so no bushings are in the way. When I am talking about exact match of kit parts and blank, I do not use magnifiers or anything like that. I do the finger touch test and your fingers can feel even the smallest imperfections. I do the best I can There have been pens that I may have over sanded or over turned but I will take that over not turning enough. These are handmade objects remember that. We do the best we can.

I can not help with the dialing in on the lathe but that can be your problem. Also can not help with reading a caliper. Sometimes things come to others easier than some. This maybe the case here. Yes having rounded edges will have an effect of calipers slipping off. You may just have to compensate and live with it.

 

[leehljp]

I see different techniques here and each serves the respective maker well.
I measure with calipers basically the same way Pete does.

While I may have missed reading it above, my starting point for caliper measurements are not with the bushings but with the fittings: Nose cone, center band at the point the blank joins, and the clip end size. I measure this and write the numbers down. I measure each pen every time. On occasion there is a change from one pen to the same pen style a month later. Not much but still these things change. AS to your question how to measure: Like Pete does. One thing I learned for me - don't press too hard, sneak up on the size; measure it two or three times, maybe more if needed to see if you are getting the same measurements repeatedly. After a while the "feel" comes.

That said, on occasion you will find that even the nib end/nose cone ends or center band may not be perfectly round. I have found nose cones that are off by .003 from one side versus 90° from that side, and that has usually been on slimlines, but it happens.

My personal obsessive compulsive disorder in my brain makes me turn a blank down to about .003 - .005 or so MORE than needed and build back up with CA until the CA is + .004 or so. Then turn or sand the CA down to the precise size as the nose cone, CB and Clip end. My obsessive compulsion makes me make the fittings match the blank. I am not in a hurry when I make pens, I enjoy the journey. In most cases .002 or .003 won't matter that much, but it does once a pen's sale price goes beyond $150 or more. At that price many people run their fingers over the fittings and see if there is a transition point, or they check to see if the fittings match. I personally don't do it to get a higher price, I do it for my own peace of mind!

 

[sorcerertd]

Once I am close, with the brass tube directly on the centers, I just use these, often setting them by the parts, not the bushings. Certainly not supremely accurate, but I'm happy with my results this far.

 

[RunnerVince]

One thing that's helped me is to not rely on the readings of the caliper. Doesn't matter if you're going digital or analog. I use the calipers as a measuring tool, but the actual measurement is really irrelevant to me. It's been so long since I've actually turned my calipers on, I don't even know if the one set's readout even works. For anyone who's ever run into problems when following a set of plans, and you cut out all the parts to the dimensions specified, but then somehow a piece is too short/long, or something isn't square...it's the same thing. Certain parts should be cut to fit, not cut to size, because as humans we're really good at introducing errors that compound.

So whether the OD of my mating part is .2500" or .2501" or .2509" inches is irrelevant to me. I use my calipers to get the measurement, lock them down, and then don't mess with them. As I'm turning, I'm using those calipers as the measure. I'm not looking at the numbers or the scale. I'm just concerned with whether the calipers will fit over the part I'm turning. As soon as they are, I know the hardware and the turned blank are the same diameter.

Of course, if you're measuring technique is off, you'll still have issues, which I think is what the original poster was getting at. So my first advice would be to become consistent, and then use the scientific method. Do things the same each time (make a jig if you have to...in fact, I may just do that to make my caliper measurements faster, easier, and more consistent), and once you're consistent (which means getting the same end result, good or bad, each time), then start changing one thing at a time. If you're strapped for cash, buy some cheap domestic wood or get a piece of firewood to cut into blanks. You can turn the material off the tubes and start again if you want, and reuse the same kit multiple times. Just make sure your kit parts are actually round, or all your work will be pointless. Sorry, that was a terrible pun, but I couldn't resist.

 

[randyrls]

All the suggestions above are good ones. One I'll add; Use electronic / digital calipers on the fitting and press the "zero" button. This sets the target size you are looking for. I use the two handed method, and slide the caliper just onto the end of the blank. I have two calipers and set one to the right end of the blank and one for the left end of the blank.

 

[jrista]

One thing that's helped me is to not rely on the readings of the caliper. Doesn't matter if you're going digital or analog. I use the calipers as a measuring tool, but the actual measurement is really irrelevant to me. It's been so long since I've actually turned my calipers on, I don't even know if the one set's readout even works. For anyone who's ever run into problems when following a set of plans, and you cut out all the parts to the dimensions specified, but then somehow a piece is too short/long, or something isn't square...it's the same thing. Certain parts should be cut to fit, not cut to size, because as humans we're really good at introducing errors that compound.

So whether the OD of my mating part is .2500" or .2501" or .2509" inches is irrelevant to me. I use my calipers to get the measurement, lock them down, and then don't mess with them. As I'm turning, I'm using those calipers as the measure. I'm not looking at the numbers or the scale. I'm just concerned with whether the calipers will fit over the part I'm turning. As soon as they are, I know the hardware and the turned blank are the same diameter.

Of course, if you're measuring technique is off, you'll still have issues, which I think is what the original poster was getting at. So my first advice would be to become consistent, and then use the scientific method. Do things the same each time (make a jig if you have to...in fact, I may just do that to make my caliper measurements faster, easier, and more consistent), and once you're consistent (which means getting the same end result, good or bad, each time), then start changing one thing at a time. If you're strapped for cash, buy some cheap domestic wood or get a piece of firewood to cut into blanks. You can turn the material off the tubes and start again if you want, and reuse the same kit multiple times. Just make sure your kit parts are actually round, or all your work will be pointless. Sorry, that was a terrible pun, but I couldn't resist.

Thanks! I agree with you, that the actual diameter is irrelevant. How well it matches the parts you are going to be fitting against, is what matters, and what I am after.

I think part of my problem, is that my locking screw was lost for my calipers. So, I haven't been able to lock them down. I think I'm gonna pick up another set (or two) with a locking screw, and use this approach of locking them down and keeping them locked so I can measure each end against the proper fitting consistently.

I also like the idea of making a measuring jig. Cogitating on that... Not too concerned about cost, but I do like crafting my own jigs!

All the suggestions above are good ones. One I'll add; Use electronic / digital calipers on the fitting and press the "zero" button. This sets the target size you are looking for. I use the two handed method, and slide the caliper just onto the end of the blank. I have two calipers and set one to the right end of the blank and one for the left end of the blank.

I like this idea, of zeroing once you lock the part measurement. If you need then, you can easily get an accurate read of whether your blank is too large or too small, and by how much.

I'm gonna be picking up a couple new digital calipers with proper locking thumb screws today, so I can accurately measure each end of the blank (several of the kits I turn have different diameters at each end of one or both blanks.)

 

[monophoto]

my locking screw was lost for my calipers.

I lost the locking screw on the analog calipers that I keep on the lathe.

Actually, I know where it is - in the shavings under the lathe, I just haven't been able to retrieve it yet, even using a magnet in a plastic bag to separate metal from wood.

Those calipers were actually my father-in-law's - so they are probably more than 50 years old and don't owe me anything. Just too cheap to buy a replacement. And they are still working just fine as long as I don't need the locking function.

 

[TDahl]

I have to say this was an excellent posting!!!!!

You can tell by the numerous detailed responses from everyone. All the information was well written and covered in detail. It's questions and responses like this that improve the pen making skills of all of us.

Thanks for posting the question Jon.

 

[jrista]

I have to say this was an excellent posting!!!!!

You can tell by the numerous detailed responses from everyone. All the information was well written and covered in detail. It's questions and responses like this that improve the pen making skills of all of us.

Thanks for posting the question Jon.

Happy to inquire for my fellow man.