Very cool. Really enjoying this series.

28:06 - the equation for metric threads is far simpler, just pitch a - pitch b. I designed bed corner adjusters for my 3d printers using this principle, M4 is 0.7mm pitch, M6 is 1mm pitch. Difference is 0.3mm, so 0.3mm per 360° rotation of the adjuster wheel. Very cool!

Adding... I think Tom deserves an extra-big "atta boy." Cooking up demonstrations and making visual aids takes a ton of time. He's done this for all his hundreds of videos and got little thanks for it. Tom, if you weren't 950 miles away, I'd buy you a pizza and even help you eat it. That's how grateful I am for all your good works.

I can't afford a shop. Not even a small one (living in a block apartment and the noise would be too much). But I love to watch and learn. And I know I'm watching the right people when, after a while, I get goose bumps finding out I can anticipate the same solutions to the problems they propose as the ones they find themselves. Thank you, Tom!

Never cut a single chip. Never miss a single video. Your content is great...except the 3rd vid on lapping

One of the best videos on the subject I have ever seen. Thank you for the tutorial!!! Fred

Thanks for also giving the values in microns!

Priceless information for anyone designing fine adjustment into a device. Once again I have to say that this video alone would have saved me many days of head scratching back when I was designing and fabricating research instrumentation. Before I learned about differential screw mechanisms I used to go to swap meets and buy beat up old micrometers and use them for projects that required fine adjustment. I know the following remark betrays my prejudices and I in no way want to diminish the incredible power of software based design, but it is great to see design done in the shop with physical objects. Many thanks Tom!

Great video Tom, looking forward to seeing the final design and execution. Best, Robin

One of my favorite videos you have made. I would love to see more design iteration like in this video. It really gives a good sense of the reality of designing a product and what problems you have to solve along the way, and how you solve them. Thanks for the excellent videos.

This is the kind of thing that makes me look forward to your videos. So many idea's floating through my head right now.

Differential screws, never heard of them before now. Wicked cool. Thanks for the knowledge transfer. Keep them coming Dr. Ox

Tom, i consider you one of the smartest people on youtube. thank you again for a great lesson

Thank you mr Lipton, very educational episode! You might just as well build your own repeat o meter, as you are almost half way. Oh and thank you very much for the metric, screen shots, it really makes it easier to understand, and at the same time get to know the imperial sizes!! Ian South Africa

Another great video, Tom. Thanks for showing the various steps to getting finer and finer adjustment. The trick of using differential threads is awesome. An easy way of thinking of the differential movement is that the 1/4-28 thread is moving ~0.03571" per rotation, while the 10-32 thread is absorbing 0.03125" per rotation, making the resulting movement ~0.00446" per rotation, or about ~0.001" for every 90 degrees of rotation.

Fantastic video Tom, always interesting watching your stuff and I learn several new things from each video. Thanks for posting this.

Thanks Tom, that was fabulous. Have added this to my "mint" playlist for future reference!

There are some great tips in here. Loved the ball bearing /screw combination; that can have soooooo many applications. Detent applications are common for ball bearings but I don't recall seeing a ball bearing applied like that.

Very nice video. Thank you for sharing your knowledge and showing a design process. I'm particularly happy that you showed how you made some prototypes and tested the ideas. Very important for this type of work. Very cool to see.

Thanks Tom, great video. I found a use for the differential threads, I just finished making 3d printer bed adjusters using 0.7mm and 1mm pitch threads so the net difference is 0.3mm. Working perfectly!

Awesome video! Tom you are making baby nap time very enjoyable for this engineer! These principles of precision are fascinating and make us all better metal workers!

The description of the differential screw I found very interesting. I was looking for a way to hold a collet chuck in my pillar drill so that I could use it for light milling. The idea I came up also used two threads of unequal pitch to draw the arbor into the taper. Excellent video.

Great visual demonstration!

interesting stuff tom. i" learnt "a lot of new words today, and thanks to you and google i may even be able to use some to impress my buddies. the world beyond tenths is like looking for quarks to me. i really enjoyed the machining and the creative setups as always. i will forever remember the differential screw. thanks for another great video.

really cool stuff Tom! sneaky screws are the best screws :)

Excellent part on the Differential screws. I never heard of that before. Thank you.

You are an amazing teacher. Thank you!

Tom really liked these 2 videos. I always enjoy the thought process. and the info on flextures. Will

Sneaky? How about alternatively derived, I say your "Tomiszims" are just one of the reasons I enjoy your productions.You have a truly unique mindset.Thank You for the adventurous journey in machining, and satisfying culmination thereof!!!

When you finish this project, let the gentleman who calibrated your surface plate borrow it. Of course, if it performs better or equal you may not see it again. Your videos are really cool and show a wide range of interesting topics! Keep it up!

Another excellent video tom. Thank you.

Very enjoyable, watching your design work, from the drawing board to the final product.

thanks again Tom, very cool stuff to learn!

Great information Tom. I've learned a lot from these videos on the Rahn instrument.

Differential screws are awesome, never knew about them, or thought about it, but it makes so much sense!!!

I’m a little late to the party but knowledge like this doesn’t go out of date. Some fantastic elements to apply here. As someone just starting to try this video stuff, I really appreciate the work that goes into these.

Being an obsessive/compulsive type personality, this fine measurement series is fascinating. Especially like the fine thread, within a fine thread, differential screw. Thanks Tom.

That was tremendously educational! Thanks!

These are really nice videos Tom. Thanks for sharing.

Good ideas Tom. Thanks for the video.

Great series.

Man, I listened to the first minute of what you had to say, and thought it would be interesting to see you review/dissect the mechanics/precision of some home/hobby grade "precision equipment" - I'm thinking like 3d printer, or cnc machine. A lot of people don't understand the tolerances of their machines, and I just think it would be interesting to see you dissect one at that level.

That is super awesome. Thanks, Tom!

Brilliant! Thanks Tom.

Great ideas, Love the differential screw.

Fascinating video, thanks for posting

Machinist magic! Thanks so much for enlightening me. That really comes handy.

Great video Tom! I had never heard do differential screws before. Lots of interesting content in this one. 👍

Never heard of a differential screw. Very interesting. Thanks for the video, and the explanation of how they work ;-)

love this. this is a great example oh combining simple machines to make a much more complex one. it's one of the things I love about this trade. (note must add this to the build list.

Great info, we need a more "Tom's improvements" series. Go over random shop tools and redesign them. :)

Incredible content.

Holy shit Tom, that was very I interesting/brain challenging. Just about to look up my Black Book to get the inside on these differential fittings. Great series, thanks for sharing. Kindest regards. Joe.

Tom, that was a very informative video that just blew me away with the differential screw. Wow, what resolution.

Thanks Tom, really useful stuff.

Me Wizard... Great Video! Especially love the differential screw. I am going to use that somewhere... Someday!

Good stuff Tom. One of the benefits of your design (for me, at least) is that, since the flexure can be disassembled at will, there is a lot better chance of a home shop machinist getting through the fabrication without destroying it. If I were building the original design I would have to save the saw cut as the last op, and I would still probably wreck it before getting the limit straps in place. and the differential thread idea is brilliant! Regards, Dan

I was trying to do the math and I was putting the actual pitch values in the equation, whereas you really meant just the TPI values and I was getting crazy results!

Miss your videos Tom. Glad I have your books

Brilliant Tom!, thanks for sharing! Regards, MSFN

I hadn't seen that equation for differential screw pitch before. It's remarkably similar to the equation for parallel resistance, except in the case of right/right pitch there's a minus sign. Now I've got to make something with one of those setups. Cool.

Good stuff Tom.

That was a very interesting video. Thanks

Excellent information. That differential screw and parallel flexure mechanism would be a great improvement to the adjustment on a cheap comparator stand I have. Great, another project to do before finishing another project.

Thanks for sharing your knowledge.

thank you! , lots of inspiration and ideas for my version.

A very informative feature again. I would live to see your solution to increase the sensitivity of a 1/10000" indicator so we lesser mortals could look to build the meter for home shop use and negate the hi-end indicator requirement. Keep up the great series . All the best. mat

Enjoyed. Thanks Tom

GREAT VIDEO !!!

This and the last episode were both great. Your indepth analysis of the subtleties behind the mechanics of the tooling and design improvements were both damned interesting. You should do a whole series of "Tom Redesigns [foo]" where foo = industry standards like the Kurt vice (which is no doubt fairly good, but has it's flaws, i.e., overtorque will lead to canting your workpiece vertically, rather than keeping it flush).

Great video. Thanks

This video could and should be a guideline on when and how to use the "educational" tag! excellent video

Great content, I feel like I should be prepping for a midterm though :) . With the new knowledge I quickly tried to figure out how to get you a one-one turn with the tenths indicator you had even though you were close with the P(effective) of 224 as set up. With 0.0008" total indicator travel for a 360 degree turn you would need at P(effective) of 1250 which could be done with none standard hardware but that was not your point... so with standard gear it looks like that 224 is a good result that can easily be achieved. Just messing with some combinations and an formula, it appears the P(effective) increases as the individual TPI(s) increase and the difference between them decreases. With a custom set of hardware, 80 TPI and 79 TPI, you can get to 6320! Great lesson Tom, Thanks

Had not heard of that, very clever.

Great demo of the differential screw! Was playing with something similar recently, they're really neat things. You might know them already, but Thorlabs sells stock adjuster screws in various sizes (1/4"x80tpi is popular) along with drills+taps. Not the cheapest, but maybe handy to have.

Really outstanding

Instead of the bolt in the milled slot, use 1 or 2 metal dowels press-fitted into one side projecting out into larger holes on the other side. The size of the larger holes would dictate how much lateral movement you have. This would be simpler to produce. I hope this makes sense.

fantastic!

I came up with another simple way to increase the sensitivity of the indicator to the adjuster screw by making the lower limb thinner than the upper. After viewing the first video. I could hardly stop thinking about the differential screw. While calculating pitch multiplication factors, I noticed something in Rahn's design which can be further exploited for precision. Notice that both the upper and lower limbs are free to move relative to the base under the force applied by the adjuster screw. This means that the spreading distance from the adjuster screw is distributed between the two limbs in accordance to their springiness. If in the original, assuming the spread is equally distributed between the upper and lower limbs, the upper limb moves about half as much as the change in screw length. Since the indicator measures from base to upper limb, this effectively doubles the thread pitch since the upper limb only moves up by half the spread of the screw. My big idea (in my mind) is that one could further increase sensitivity by making the lower limb springier by making it even thinner. For example, to make an effective screw pitch 4x as fine, make the lower limb 1/3 the thickness of the upper. 1/3 thickness should move 3x further under the same screw force. For a total movement of 4 units, (1 upper + 3 lower) the upper would only move 1 unit. As long as the elastic properties of the limbs is not exceeded, the thinner the lower spring, (or thicker the upper) the greater the thread pitch multiplier. Your proposal (previous video) to make these limbs bolt together in the previous video, makes it easier to try out this idea. Thanks again for this awesome follow up video. I'm vary curious what you think of this.

Fascinating, The amount of time you have used to do the machining and design must be outrageous. Still I enjoy the knowledge that is provided.

Tom, fantastic followup video, lots of meat on the bone here!

Very interesting. Thanks.

excellent subject and presentation. Dan Gelbart has also nice video on flexures.

You just made differential threads cool! A p.s. to Andy Coakes, I am out in the boonies of Arkansas on an investor owned telephone co-op with a self-build PC that's 8 years old and I can play the video at 1080p just fine! Think you may have problems on your end.

Great video Tom! I see a lot of people in the US talking about 10ths of an inch as such a small amount. As soon as you converted it into microns. Its a sausage in a corridor measurement. I found the differential thread part really interesting. Project should have been a build off against SMW instead of a collaboration. Keep up the great work!

Very nice solution 👍

Quite enjoying this series and hope to see lots more about it. I really don't like nycnc's style, so this is the only side of the story I get to see.

More learnin' with Tom. That differential screw is very cool ... a gear reduction for threads 😉

Thanks Tom, interesting video. You described the Rahn solution as lame, but they have achieved a solution that does the job as well as required using a single saw cut. I would describe that as elegant. Your alternative would be many times the cost to implement and does not perform any better. As you are aware cost is an important part of the design decision!

VERY fine discussion of alternatives. I went overboar:d with my concerns with the fine Vs differential thread business. There are lots of alternatives: if 1/4 - 28 against 10 - 32 is too slow. 5/16 - 18 against 10 - 24 = 0.014"/rev or 5 degrees per 0.0001"; against 10 - 32 = 0.024"/rev or 8 degrees etc until awash with too many choices. Suggestion for drilling or punching spring steel sheet for flexure: chuck a wood dowel in the drill press on max spindle RPM, force it against the drilling site until friction heat draws the spring temper to machinability (wood smoke for 10 seconds?). Spritz with water to limit heat migration.

very cool ...thanks

1/4 turn of the wrench = 1/4 sweep of the dial makes adjustment nice and easy

A drop of weld on the tip of the screw also works. I've done that with an adjustment screw for an indicator base. I don't remember what filler i used tho. Hasn't lost its tip in 10 or so years i've done it.

Whoa that differential screw blew my mind. Didn't know that existed

Tom looks like you should have worked for the semiconductor industry.. it doesn't get more precise than that (except the IBM machine that can mess with single atoms)!

excellent video Tom. Thank You Matt C.

Even though I have no use for a repeat-o-meter and lack the equipment to build what you're creating, I really enjoy your explanations and ideas. John (+NYCCNC) better hurry up or he's not going have anything left to do but the Fusion model. ;)

That was cool.

Will you be making your own dial gauge ? For the repeat o meter

For those of you working with metric threads- all the reciprocals cancel out and you end up with pe=p1-p2.