Turning, Heat Treating,and Grinding a Special Dividing Head Pin

[@Digital-Dan]

Your gauge pin exercise was a perfect demonstration of what computer scientists call a binary search. Great fun. Your pedagogy is beyond compare. Really enjoyable.

[@jeromeleach9316]

Very good video Keith. Like your shop. Own one myself here in Indiana. We opened (grandfather and partner) in 1946. About as vintage as one can get. No DROs, mostly flat belt, four lathes, three mills, couple shapers, etc, etc. Did our own castings in aluminum. Shop is complete. Go out and do a few jobs occasionally. Since I am on the far side of 60 now, figure that when I retire from my toolmaker job, will re-open again.

[@newtonmiller8810]

Alas a nurse, I’m not an engineer, machinist or tool maker, but thanks to your explanations and detail back ground information, I find I’m able to follow quite well, even found another channel to other night and was able to keep up with the jargon based on my learnings from you, so kind sir, thank you for exposing me to the world of machinery, metal work and foundry works, not something I’d do but I thoroughly enjoy watching and learning.

[@DavidKutzler]

I'm a nurse who retired in 2017. I became fascinated with the machining KZbin channels. I took a couple of courses on machining and welding at the local community college and have been slowly adding to my hobby machine shop. Thoroughly enjoying my retirement.

[@newtonmiller8810]

David Kutzler David, I’m very much into wood work, but am really enjoying the precision in these tasks.

[@ShainAndrews]

Tom Lipton is probably the most accurate in both his work, and detail.

[@newtonmiller8810]

Shain Andrews Shaun, thank you, I’ll have to look him up, I’ve also started watching Blondiehacks last week, she’s quite detailed as well, but I’m still in the beginning stages of this journey

[@cameronchild6146]

Adam Booth (abom79) is really entertaining too. He's very smart and puts in the extra mile. Lots of cool projects (check out the fireball fixture plate project!)

[@garthbutton699]

Thanks for letting me look over your shoulder once again.

[@paulfromupstateny8065]

I love the fact that you used a tool, to make a tool part for your tool, so that you could make another tool part.

[@seansysig]

Necessity is the motherhood of invention. Operating old mills & lathes will eventually require the making of fixtures or parts of them to perform specific funtions.

[@AdrianPardini]

Nice way of doing a binary search for the right gage pin :)

[@TrPrecisionMachining]

very good video..thanks for your time

[@andrewevans1658]

I just went over and looked at my collection of plates and eventually I will have to build 2 more catch pins. Thanks for the tutorial!

[@C2DSolutions]

Time permitting... I would suggest making the whole pin/spring/housing assembly... save time in the future not having to swap out pins... and easier to find in the toolbox.

[@michaelcurtis9287]

Always enjoy your videos.

[@fredclark4033]

Great to see a tool being made for a machine that parts are unavailable, thanks.

[@FredMiller]

I enjoyed seeing you use the surface grinder and spin-indexer to shape the pin. Well done!

[@frankdeegan8974]

much better than say a lathe and tool post grinder

[@ramsay19481]

I have a model H dividing head and a set of plates but did not know about the smaller index pin needed for the high number plates.. I looked in my 2h book and it does indeed make reference to a high number pin.....Learn something new every day! Love your vids... Cheers! Mike in Louisiana

[@TinkerInTheShop]

Great video. I considered making mine with a radius nose to reduce the wear/galling sometimes seen on the dividing plates from operators dragging the indexing pin unnecessarily. All the best from the UK.

[@SunnnyDay]

Great project and very nicely filmed ! looking forward to seeing the 57 tooth gear cut !

[@AGEngineering]

I like the cylindrical grinding method 👍

[@davidhudson5452]

Good Job Hope It Works Out

[@homeryoung7436]

Thank you Keith

[@TheDippoo]

remember forging cold chisels as part of my degree course our black smithing tutor was old school he only taught through the use of the colours it was good miss doing that stuff

[@kennydebique6192]

Thanks for sharing your work. I really appreciate it.

[@84953]

Nice job Keith!

[@MrValhem265]

What an interesting Project Thanks Keith :)

[@elsdp-4560]

THANK YOU...for sharing. Watched and very much enjoyed.

[@listerine-pr5lt]

Excellent job from a experienced and expert in the field.

[@assessor1276]

Very interesting Keith - well done. I really liked your discussion of the heat treatment process: you explained what you were Dong and why but avoided all the chemistry and phase diagram stuff which most people would find pretty dry.

[@jackgreen412]

Really enjoy watching your work and expertise.

[@jerrycoleman2610]

Keith, Awesome video, enjoyed watching, great content, thanks for sharing your video.!.!.!.

[@mikeadrover8825]

Verry-Cool Thanks Teach

[@dwightcarlson7136]

To which book are you referring to regarding heat treatment? Also very nicely done video. No superfluous wording!

[@rexmyers991]

Fascinating! Your depth of knowledge and your skills combined with your ability to teach are perfect. Thank you

[@johnwallace9002]

When I made my pin for the dividing plate on my turntable I used a Bristol spline wrench and it was tough enough not to bend but easy to machine with carbide. I could have used an Allen hex wrench but I don't use the Bristol spline wrenches as wrenches so it was perfect material for the pin.

[@chrisshake23]

"Just the tip" I can't help but laugh like a fraternity boy!🤣😂

[@hitoortega1616]

Excellent like always!!!!!

[@WilliamTMusil]

Hiya Keith

[@tpobrienjr]

When will you add forging and casting to the shop? Smelting? Thanks for a nice demonstration.

[@TheKnacklersWorkshop]

A good job done Keith...

[@erichoff7926]

Beautiful work as always. What is the trick for successful parting? I always have problems. Eric

[@jimad]

What is the narrow insert you're using to turn near the live center at 10:30? Thanks for the video - always learning something new!

[@outsidescrewball]

Enjoyed

[@GeorgeWMays]

Very interesting. Thanks for a really good video. Your project is appreciated.

[@CraigLYoung]

Thanks for sharing!

[@tomp538]

I would like to see the 57 tooth gear cut and where it goes when finished.

[@tropifiori]

Pretty slick

[@stanhobbs5292]

If you quench in oil rather than water can you avoid the final anneal and still get both acceptable hardness and toughness?

[@FinboySlick]

I don't think it really matters for this but what is the concentricity register on the pin? The larger diameter or the shank itself? In the former case, I feel I would have turned the larger diameter a little oversize and ground it in the same setup to make sure the pin is in the same place regardless of how it's turned.

[@bradlilly8603]

Cool build might I suggest using oil instead of water. Mineral oil is a pretty good quenching oil, water is pretty aggressive medium. Not everyone has a tank of parks 50

[@WobblycogsUk]

Very good, did you grind a radius on the end of the pin?

[@RobertKohut]

Nice!!

[@SciPunk215]

This was beautiful. Such a well defined and well contained project, from beginning to end.

[@techno_mesh]

Hi Kieth, could you share the amount of holes that each disk has? You mentioned one, but I would like to know the other ones if it is not to much hassle.

[@wmcwings4343]

At 23:20 "to get it down to a PRECISION measurement....my measurement needs to be ABOUT 93 thousandths". LOL You crack me up.

[@jcs6347]

Question Keith: You keep mentioning 'The book'; what book are you referencing? Thanks!

[@rennkafer13]

More than likely Machinery's Handbook.

[@kurtarmbrust]

Custom gears, your new side gig.

[@monadking2761]

This is a great video of showing how to make things. Would have it been easer to just regrind the orginal pin as a step so, it would have 2 diameters. This way you would never have to change pins when you change dividing plates.

[@frankdeegan8974]

I could not see how far in the plate the pin must go for a secure hold but watching the videos of making gears and such I don't feel as though I would be comfortable with a pin that didn't have a secure hold only to get to making the last tooth and oh look not enough material to make the last face of my gear.

[@hilltopmachineworks2131]

@@frankdeegan8974 You lock the dividing head after you have the pin in the hole so the pin is not taking any force.

[@erneststorch9844]

I thought of using a 7/16" drill blank but It would too hard for such a small pin. If you found a how much would it cost and how long till you could get it. You made the right call . By the way nice job!

[@samuraidriver4x4]

No door safety switch on the oven to shut the coil off? You should wire one in so you dont electrocute yourself by accident.

[@garybrenner6236]

Do you have any idea when you are going to resume work on the stoker engine?

[@alanturner3546]

93tho is 3/32 - why didn't you use some 3/32 drill stock or even a 3/32 drill?

[@paulcopeland9035]

How would 3/32 drill stock /drill mount in the divider? Turning down from larger stock is the only solution.

[@davidhoward2237]

what ever happen to the furance or the safe rebuild? Ty for another great vid

[@Hoaxer51]

David Howard, and the ice cream makers! I guess everybody has some old projects sitting around, it makes him human!

[@gregfeneis609]

25:55 If u leave the wheel runnin', u have to be wheelie wheelie careful 😉

[@chrisc4088]

Started to get worried when it didn’t clean up at first when grinding. Clearly Worried for nothing. Nice work.

[@farmalltomf]

Keith, I really like the approach to make a matching pin vs. making a new plate. Well played.

[@Bobbywolf64]

Considering it would actually take a 57 hole dividing plate, to make a new 57 hole dividing plate, I also think he made the right choice lol.

[@stevespra1]

Looks like somebody needs a collet chuck for Christmas. I would think we need pretty good concentricity for this pin.

[@paulwomack5866]

Any accuracy (or lack) will come from the final grinding process, where a collet was indeed used.

[@Bobbywolf64]

@@paulwomack5866 Exactly. The pin tip actually had quite a bit of runout due to using the 3-jaw chuck, and the heat treating process. You can see it when he was grinding, as it took almost 5 thou before the wheel was hitting all the way around. However, the end product was perfectly concentric due to the collet he was holding it in while grinding.

[@stevespra1]

@@Bobbywolf64 Yep it's all good. Keith knows what he is doing but it's a good excuse to get another tool.

[@StreuB1]

You don't need the level of concentricity that you might think for a dividing head in this arrangement. Plus, the final concentricity was delivered by the grinding process. The lathe was just roughing things in.

[@paulwomack5866]

@@StreuB1 +1 on the accuracy. Any plate/pin error is reduced by a factor of FORTY!!

[@morgan19811]

Keith how do you get the dividing head square on the table?

[@freemanfreed1581]

helical gear cutting and worm cutting video please??

[@mixedgas2]

When you parted off the pin, what rpm were you running?

[@budgenatorP]

I always wondered why dividing heads were generally geared 40:1 instead of 30, or 45 which would more divisible in degrees minutes and seconds

[@jdmccorful]

Good learning project.That is , for us that are learning.

[@jadney]

It would have been better if you had ground both the 3/32 and 7/16 diameters to final size in the same setup. That would have been easy and it would have assured concentricity and fit for both. Those are both necessary to get the full precision out of your dividing head.

[@StreuB1]

Not required. The level of deviation (fractional arc seconds) is beyond the resolution of the machine and the dividing heads gearing, even when brand new. People need to realize the difference between accuracy and precision as well as how tolerance stacking creates a virtual ceiling for delivered precision. What he did is WELL beyond the resolution of the system. He could have left it rough turned from the 3-jaw and been a few thou small and still been within the resolution of the machine system.

[@KG-yn9qi]

Will it be Mike? Or Lance? Hope Mike, have not seen anything from him in a long time. Hope all is well with him! 👍🎥, 👋🧙‍♂️🇺🇸, 👏🍻😎

[@PeterWMeek]

Do you think the plate was designed for a 3/32" pin? 0.09375" It seems awfully close for coincidence.

[@danielcobbins9050]

I have a machinists handbook that states one should use oil for quenching, not water, because water causes cracking.

[@littleworkshopofhorrors2395]

It can depend on the shape of the part you are heat treating. A simple shape like that should be fine but it would have been better to plunge tip first not sideways to prevent distortion. A complicated shape or say a plate with holes in it might indeed crack if not quenched with care due to differential cooling, oil slows down the speed of quench, but might not achieve the same degree of hardness. Generally with homeshop hardening the quicker the part is cooled the harder it is, brine being the quickest, then water and finally oil.

[@deathk26]

Did a small piece get chipped off the end of the pin?

[@rennkafer13]

Looking at that, and his minor bobble towards the end of grinding I think he had the wheel too low initially and nicked the end.

[@infoanorexic]

Making small parts with big machines, I found, seems more daunting to those with a lot less experience. I guess you get used to it over time.

[@markbernier8434]

If I had to crank that spinner for any length of time I'd chuck up a buffing wheel in my drill and let it spin the device. When I did something similar I just laid the drill on a bit of 4x4 and it worked with just gravity.

[@paulwomack5866]

When did you get that dividing head - I recently watched one of your old videos on "Disassembly and Assembly of a Brown & Sharpe Dividing Head", and that was a very different beast.

[@kris4362]

👍👍👍👍👍👍👍👍👍👍👍👍

[@williamsquires3070]

I wonder why it would need to be Rockwell C50? 🤔 It’s not like the pin has to resist a lot of torque, and it would take decades, maybe even centuries, of pulling it out and putting it in, to cause any significant wear on it, even if you just make it of 4140.

[@Peter_Riis_DK]

Drill larger holes. 😉

[@sleepib]

I kind of wonder why 40:1 is so common, I think 30:1 or 60:1 would work out better with fewer plates. Either would be able to do 57 teeth with a 19 hole plate. I guess larger powers of two would be easier. With 30:1 you'd need a 32 hole plate to make 64 divisions, but you can bootstrap that much more easily than a 57 hole plate.

[@MrRShoaf]

Although dividing heads with other than 40:1 ratios are made, this is the most common ratio.

[@billiondollardan]

5:18 it would have been pretty crazy if you would have cut the video to show you put in the exact right pin on the first try lol

[@petert3355]

Quench in water? I'd have thought an oil quench would be a better idea to reduce the internal stress that a water quench creates.

[@Peter-V_00]

W1 tool steel is designed for "water quench". www.hudsontoolsteel.com/technical-data/steelW1

[@bcbloc02]

Odd that they didn't use the same size pin for all the plates.

[@paulwomack5866]

Guess the bigger pin is more robust, for common use.

[@accessblaster7876]

Do we know if all the plates are OEM to the dividing head?

[@kensherwin4544]

The holes are too close together. There isn't room for the bigger holes.

[@paulwomack5866]

@@kensherwin4544 they could use the smaller hole/pin for the wider spacing if they wanted too. It's a valid choice.

[@OldIronShops]

To bad that the bin could not be made reversible so you don't lose the special one.

[@kentuckytrapper780]

Hello Keith ' I've got a model A monarch lathe 16×77. I gotta sale it if you no any one looking. Great video.

[@edwardsilva895]

What ever happened with the steam stoker engine?

[@tsw199756]

Abom dropped the ball on his part

[@danrabenhorst2549]

@@tsw199756 Abom is to busy traveling around now that he is a full time YOU TUBER

[@Hoaxer51]

Dan Rabenhorst, unfortunately that seems to be the case nowadays, one or two videos a week and stretch the project out!

[@tsw199756]

@@danrabenhorst2549 yup photographing every move and gets pissed when someone doesn't agree with his methodology. In his eyes its his way or the highway 🤣 🤣 🤣

[@tsw199756]

@@Hoaxer51 yeah 2 videos to make a freaking broach plug. Quantity over quality pays more I guess until people become annoyed and stop watching. I am already annoyed with the constant pop ups in the videos panhandling for money.

[@Andrew_Sparrow]

Wouldn't you want the pin to be softer than the plate? The pin being easier to replace than the plates with wear? I would have thought making out of brass would good. Obviously for your use it doesn't matter as unlikely to wear in your lifetime! :)

[@Blazer02LS]

You want the pin and plate to be about equal hardness so that the locations are repeatable with very little wear. Brass wouldn't be a good option because at those sizes it would be very easy to bend it and that would render it unusable.

[@staticfanatic6361]

Wasn't the original pin a 2 piece? I suppose that would have been a lot harder to make.

[@howardosborne8647]

Making the indexing pin from a drill blank inserted and loctited into a mild steel body would be a very acceptable option. The drill blank ensures the location end is hard enough to withstand wear and tear.

[@xmtxx]

Thanks for the video, it's always a pleasure to watch. no matter how difficult the project is. Your little schema got me thinking. I still can't wrap my head around the fact, that you guy's are using fraction for measurement. I know that it's engraved in your head and become automatic. But still. Stuff like 7/16, or even going down to /32, and then switching to though... It seems so hard to manipulate instead of straight going to decmial. Added to the fact, that you usually, still need to convert it for your instruments that are usually in though. Do you need to do some arithmetics in your head to know that, for example, 7/16 (0.4375) is greater than 11/32 (0.34375)?

[@MrRShoaf]

As to your question, what you do is change 7/16 to 14/32 by doubling both the numerator (7x2= 14) and the denominator (16x2= 32). Since 14 is more than 13, you know that it is 1/32" (.01525") bigger. Often fractions are easier to "do in your head" than having to deal with decimals. While using a measurement expressed in base 10 can be easier sometimes than base 12 or something else, each has their advantages.

[@xmtxx]

​@@MrRShoaf Yes I know, that's exactly the arithmetics I had to do in my head. I'm just asking if it's automatic, or if you have to do the maths in your head? For example, I work in CS, and I pretty much know my power of 2 by heart, up to 64k, but I really don't expect others to know them (it's pretty useless). When you have to handle /8 /16 /32 /64 (not so often I guess, for the last one), IMO it's way harder, than just comparing 2 decimal numbers. With decimal, you just have to read both number from left to right, and whenever one is different thant the other, you know which one is bigger than the other. No way multiplying your fractions, to have the same divider is easier. And, when you have to compare more than 2 it gets even harder with fractions. And what about the decimal conversion. You know all your fractions by heart? I'm just wondering how "automatic" it is, as I never ever been subjected to measurement in fractions.

[@xenonram]

@@xmtxx It is second nature to people using the fractional numbers a lot. Doing fractional +, -, *, and / are easy for someone like a contractor, but converting them to decimal are usually not. Converting fractional to decimal it's easy for a machinist because they did it a lot. I grew up in a family where my grandfather, father, and uncle all owned construction companies, so I grew up doing construction, and that mostly uses fractional inches and feet/inches. Somewhere in between that time I was a machinist in a prototyping shop, and I used decimal inches a lot. Then I went back to school to pursue a professional degree (professional degree are MD, DO, PharmD, DDS, etc, which usually are preceded by a science degree like chemistry or microbiology) and I studied using SI (similar to metric). So I'm very familiar with all three. Fractional inches + feet/inches, decimal inches, and metric/SI. Overall metric/SI is easiest to use, in a vacuum, but nothing is easiest as the thing you learned the first 20+ years of your life. It would be like telling a Chinese person, who grew up in China speaking Chinese, that French is easier. Well yeah, in a vacuum, French is easier than Chinese, but not for a Chinese person. For some reason people outside of the US get so confused about fractions. I don't know if they just don't learn them in school, or what, but their mind just gets so boggled. (Obviously I know they learned them, but maybe not as much emphasis is put on them as in the US.) If you're talking decimal inches vs metric, they're exactly the same except the units have a different name. So metric isn't any easier than decimal inches. They're both base-10 systems. Once you start going from decimal inches to feet/inches (which is base-12), or converting to other units like miles, it becomes more difficult. But it's still second nature to me to know there are 5280 feet in a mile, and rarely do you get to convert things like feet miles on-the-fly.

[@xmtxx]

​​ @Andrew Delashaw Thanks for the reply. I didn't talk about SI, because I know that it's another story. And decimal is decimal, whatever the unit you are using. And I didn't talk about inch and foot because adding base 12 to the fraction story, wouldn't plead for the easiness of the whole thing. I'm in france, and we never learn fraction as a way of measuring or quantifying things. It's always decimal, and SI of course. Except for broad stuff, like "half the population is blabla". For the use of a quarter I prefer 25%, and it's often used as so. Before we invented SI, everybody was counting by those "odd" bases and imperial units, but it's been almost completely abandonned here. Fraction are non existent, and base 12 is only used for buying eggs and oysters.

[@kindabluejazz]

@@xmtxx Fractional mechanics is the most natural way. Taking 1/2 of something requires no equipment. From there you can just as easily get 1/4. 1/8 etc. When someone says they want a half, quarter or eighth, it is very easy for the brain to picture that, and it's very easy operation to perform mechanically. It makes no natural sense to divide things into 10 parts. Take a rod and try to divide it into 10 equal parts - it's not so easy without external calibrated equipment. The decimal system is nothing special - we could have instead standardized on an octal system, which would have been more mechanically useful. That is why computers are based around powers of 2/4/8/16.

[@wAnubiSw]

Actually, when you grind that pin without water, you make him softer) But it still good job)

[@RCDinsmore]

Wouldn't you want the tip slightly softer than the plate? I would think that if it's harder than the plate, its going to cause your plate to wear. You can replace the pin, but replacing the plate would require buying a new one.

[@Bobbywolf64]

One would think that the plates are already harder. Since they are stationary, they could withstand being much harder without fear of breaking, unless you were to drop one, then I bet it would shatter.

[@RCDinsmore]

@@Bobbywolf64 That's what I thought, but unless I miss-heard him, I thought he said his goal was to make it just a little bit harder than the plate.

[@Bobbywolf64]

@@RCDinsmore Sure enough 9:12 he states hes making them harder than the plates. Definitely counter to what I would have thought. Interesting.

[@jimmurphy6095]

I think the theory is the pin is going into every single hole he aligns to, regardless of the division he makes. The individual holes in each plate will only be used once a session.

[@freddupont3597]

So many ads, it makes the viewing quite unpleasant!

[@Frankowillo]

Use Adblock for KZbin, I never see a single ad. It's a Chrome extension.

[@MrPossumeyes]

I reckon! Firefox has Adbloc Plus. The only ads I see are at the start and can skip those (although I'm cutting a cent or so off the channel providers income... but I hate the ads). Oh, some sites won't display stuff unless I switch adbloc off - Goodbye, I'm going somewhere else.

[@johnopalko5223]

@@MrPossumeyes I use AdBlocker for KZbin under Firefox on my Linux machine and I don't even see the ads at the beginning.

[@MrPossumeyes]

@@johnopalko5223 I'm on Macbook, perhaps the difference. I know I'm cutting a cent or two from the channel but I hate ads... at least I can click Skip.

[@paulcopeland9035]

@@MrPossumeyes .....Let's see, you hate ads but love the free machining content. I guess you are one of those that don't care to pay their way.

[@Mark-jp9dz]

These mid-video adverts are getting so obtrusive and badly timed that they destroy the enjoyment. I am starting to de-select those channels that allow them to continue.

[@Blazer02LS]

The channels creators have no options, it is KZbin that places the ads when and where they choose.

[@LightAndSportyGuy]

@@Blazer02LS Not true. As a "creator" you can opt out of the mid roll ads (that's what I do) or specify where they go (or just let youtube go advert crazy - which really sucks). I will mention that I believe Mr. Rucker earns every penny that he gets. But I doubt that the recent changes that youtube made to overwhelm us with mid-roll ads results in any real increase in income - supply and demand...

[@danielcobbins9050]

Try downloading the Brave Browser. It allows ads only when you want to see them. In my case, never.

[@wayned1807]

Get KZbin Premium, well worth it. No ads and Keith still gets paid for his work.

[@Frank-Thoresen]

Support the channel by joining it on Patreon. No ads there. www.patreon.com/vintagemachinery

[@vettepicking]

Most of those 5c spindex's runout a lot and are not precise for making good parts, kinda a waste of time.

[@ydonl]

I'm thinking that's probably not an issue for this application. Here's how I reasoned it out... First of all, the concentricity of the pin will have no effect on how it affects the rotation of the dividing head, because the pin will sit in each hole the same way each time. You could even have an intentional offset in the pin (i.e. huge runout), and it would still work fine. The only real issue for error would be slop in the hole, allowing the rotation to be a little plus or minus. You could "tune" that out by always pushing the pin in the clockwise direction as you locked the dividing head, but let's assume a "worst case" and say there was a thousandth of error, no matter where it came from. I'm going to estimate that the radius of the hole pattern on the plate is about 2 inches. So the error at that radius would be approximately the arctan of 0.001 / 12, or 0.00477 degrees. Then the ratio is 40:1, so the error at the dividing head would be 0.000120 degrees, which is... fairly small. Quite probably less than all of the other potential errors combined. Another way to look at it would be that 0.001 error at the pin would be reduced by the 40:1 ratio at the dividing head, so if the radius was the same 2 inches on the part, the error would be 0.001 / 40, or 0.000025 inches... or in other words, 0.25 tenths. But I didn't get the sense there was anything close to 0.001 slop for the pin in the hole; I could be wrong, it's just an impression. But if I'm right about that, then the error due to the pin in the hole would be down in the millionths of an inch range, which is a relatively small error for most machine work. On the other hand, I'm not trying to dismiss your comment. I assume you're right on; that runout is often poor on those devices. Then you wouldn't want to make precision parts with it in the case where the concentricity of the journal clamped in the collet and the journal being machined needed to be really good. For sure. You could be just fine if those two regions don't really need to be concentric (as in this pin), but maybe not when it really matters. I suppose for some jobs, you could mount the raw stock in the collet, and then grind two different journals that would indeed be concentric. Perhaps it depends on how the "good part" is being made.

[@ydonl]

@@vettepicking I don't think the error can accumulate -- the overall rotation is still defined by the 40:1 gearing between the crank and the chuck. The error would apply to each individual hole position, i.e., each individual tooth position... I'm pretty sure! Think of it this way: no matter how far off each hole is, it's not going to change the gearing. One revolution of the crank is still 9 degrees, as exactly as the gears (and everything else) will allow. And I've already tried to make the case that for this project, the runout doesn't matter, so while your spindex sounds pretty attrocious, it might have been okay for this particular project! What a world.

[@richardbradley961]

THINK YOU SPINNING IT OUT A LOT, NOT GOOD, SORRY....