I Tried to Make a .00001" Graduated Screw Jack
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- čas přidán 5. 09. 2024
- This is a video about differential screws. It's about what the mechanism is, how it works and how it can be used. It's about how I sometimes take things too far.
Leveling Plate STLs and info:
www.thingivers...
(it ended up on thingiverse anyway!)
You need 3 precision ground guide rods, holes reamed to match, a differential screw turned down perfectly to keep it linear, and perfectly vertical tapped threads for it to mate with. The readings you are getting are a wobble resulting from your screw being ever so slightly bent, and would definitely make more sense if you placed more than one indicator around the circumference of the jack
I did have ground rods with reamed holes but I agree, three makes a lot more sense. I also agree with everything else you said. The location of the adjustment knob also allows for a lot of influence from the operator while rotating it ad that could be improved. I still doubt any off the shelf threaded rod is going to be accurate enough to get this working. I also wasn't willing to buy more than one tenth indicator for a a project that isn't actually useful. Haha. It was a good excuse to buy one since I only had .0005" indicators at home, previously. Thanks for the good advise, all the same. Hope you enjoyed the video.
Despite having a lifetime in engineering, have only at 70 Yr old heard of differential screw threads. Absolutely fascinating. Love also the way you go from metric to imperial measurement. Some things just make more sense in thousandth of an inch. This will no doubt totally confuse our European friends. Thank you, Dave from Uk😅
I live in the US but work in medical manufacturing. I'm used to having imperial machines and metric prints and my brain goes back forth quite easily. Add to that that in the home shop I have a metric lathe and an imperial mill and I end up with a terrible mix of the two systems that would probably make anyone else insane. 😅
You had it there, all of your calculations and math is correct - search out some high precision, close tolerance threaded parts to complete it - you didn't fail and it's a very impressive effort indeed
Thermal expansion is more than 10 uInch. Also, your jack would need to be supported by three synchronized points to remain stable in a horizontal plane.
Correct on both accounts but those still aren't the only reasons this didn't work. I frequently work down to +/-.0001 professionally so I was well aware that my efforts weren't really up to the task of gaining a whole order of magnitude. I've gotten a lot of feedback on the design but my inspection is just as shoddy.
It was really just meant to be a fun little thing to help explain differential threads and give the video a little bit of a hook. I might revisit the design one day because there a lot things that could be greatly improved and these kinds of videos seem to be relatively popular on my channel.
Thanks for watching and commenting!
Nice attempt! This would be a neat project to try to make work at that resolution. It encompasses everything. Pitch accuracy, backlash (or better to preload perhaps), guide accuracy, hand knob influence, probably even need a breath guard. ha ha.
Yeah, this is really it. We are talking about laboratory tolerances and I'm just winging it in my basement with off the shelf parts and a low effort design. It's a fun idea and fun to think about but I'd probably be better off refining the printed indicator than trying to make this work. Thanks for watching!
and, indeed, maybe a compliant mechanism, driven by a differential screw, that 'gears down' the travel of the screws, to drive the 'jack'
I wonder if you lathe cut your own screws for a tighter tolerance and use a form tap if you would get better results
There are definitely things that might help but .00001" can be affected by a finger print or even your breath. It would be cool to get closer but it was never really a practical goal, in my mind.
I guess I have a bad habit of making interesting things with questionable usefulness. 😎
Well it looks cool and the idea is insane plus that brass pointer....
Maybe picking up some error the the indicator tip not being at the 11 degrees or whatever is spec'd for that one? Might be some odd motion in the internal mechanism when it's not under the tip right. TOT has a video on that somewhere, and I've seen a couple others, stefan I think has one as well related to that type of indicator measurement.
The tip should be 11° from the surface it's checking so I'm actually pretty close, probably +/-5°.
The problem we are talking about with test indicators produces a sine error, which at shallow angles would only be a small fraction of the overall measurement. It couldn't account for the measurements we're seeing.
In hindsight, I believe a lot of the error we are seeing is just me influencing the setup as a turn the adjustment wheel. There are some good comments identifying issues with the device too.
each of the differential screws needs to have linearity near the level of the desired pseudo-pitch...not so easy, but might improve with some kind of mechanical averaging over a longer thread, with a bit of compliance in the threaded body, to allow a bit of squish..
I think that would be a useful tool if you got the thread ratios right.
About 0.1mm per turn would make it very handy and could be graduated in finer than 0.01mm lines.
Nice experiment. Subscribed.
Thanks and welcome
what it looked like to me was stick and slip. The screw threads have some clearance in them which needs to be eliminated by preloading the whole assembly, IE make all the clearances stay on the same side of the V.
Ironically, it's the printed plastic nuts that keep the differential bolt from runout.
If you're talking about the leveling plate, there are embedded grade 8 nuts in the printed parts. I made that before I had a lathe or mill at home, but I'd do just about anything to avoid printed threads.
@@makerunderground I'm only talking about the printed nut. Everything else in the mechanism, of course, must be made of metal. This is the only solution that allows you to cheaply get rid of runouts of all kinds.
Very cool!
I think if you had put your indicator on the center line of the jack, instead of out near the edge, you would have eliminated virtually all of the reading jumps.
That's a very fair point. There were actually a lot of issues with the inspection. The piece being aluminum made it too light to manipulate without moving it around and the adjustment knob being on the two threaded shafts allowed a lot of human error to be imparted too.
I've gotten a lot of great feedback since I put this out. I haven't decided if I'll revisit this yet, since I don't have a practical use for it. I always appreciate more input though! Thanks for the comment!
@@makerunderground This would make a great educational/learning tool. As Landon mentioned in his post, three guide rods would probably stabilize the lifting platform more. Once pre-loaded, and measured in the center I think you wold get amazing readings. Great work!
@@sinkhole40 again, thanks for all the feedback. I really should do an update video at some point.
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