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Pushing work w/ threaded rod + hand crank

Pushing work w/ threaded rod + hand crank

(OP)
I'm kind of having a brain fart here. I'm trying to design a fixture that can push/pull work by using a long screw + hand crank. The screw is threaded into a stationary block and at the end of the screw is the work piece that needs to move back and forth. What I am having trouble visualizing is how the screw can attach to the work piece by means of some swivel action so the screw just pushes/pulls the piece and doesnt attempt to rotate the work piece while also being capable of pushing/pulling with at least 100 lbf. A normal screw and thread should be able to handle that force but the means of connecting the screw to the work piece is what I cant visualize.

RE: Pushing work w/ threaded rod + hand crank

Drill a counter-bored hole in the work piece and a threaded hole in the end of the threaded-rod, and then attach the threaded-rod to the work piece using a shoulder-bolt.



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RE: Pushing work w/ threaded rod + hand crank

Sounds like a bearing attached to some sort of mounting device. Any further detail depends on the detail of the requirement.

Do you know how receptive the work-piece is to attachments (does it have a handy ferrous pad that could take a magnetic mount, or stud holes in just the right place), whether the device is going to have to support the weight of the work-piece, whether it will need to stop it tipping as well as pushing it and whether there is something to react the friction forces in the bearing (because otherwise the work-piece will still be prone to spinning)?

A.

RE: Pushing work w/ threaded rod + hand crank

You can do that with off-the-shelf components as well.

Say your threaded rod is 5/16" You get a 5/16" bolt and a nut and a threaded standoff, like: https://www.mcmaster.com/#standard-threaded-hex-st...

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RE: Pushing work w/ threaded rod + hand crank

Yeah, this is highly dependent on what you're trying to do, how much external guidance your load has, frequency of operation, what your precision of fabrication is, etc.

Anything you screw onto/into the end of the shaft will unscrew itself quite quickly as soon as you try to pull the load. In fact, anything with a threaded connection is a bad idea.

There will always be some torque transferred from the screw to the workpiece. If the workpiece is just hanging off the end of the screw it's gonna spin.

-handleman, CSWP (The new, easy test)

RE: Pushing work w/ threaded rod + hand crank

Through hole in work, cut grooves in the rod and circlip on both sides?

RE: Pushing work w/ threaded rod + hand crank

Hi

Have a look how a bench vice works.

“Do not worry about your problems with mathematics, I assure you mine are far greater.” Albert Einstein

RE: Pushing work w/ threaded rod + hand crank

I use J Baker's method often, when the load is constrained to move in a linear fashion. You can minimize the torque transmitted with thrust bearings if needed. You could also use something like a ball joint if you need more degrees of freedom for rotation of the load.

RE: Pushing work w/ threaded rod + hand crank

What you need is called a thrust bearing arrangement. That will allow the screw to rotate about its axis but not move laterally.

RE: Pushing work w/ threaded rod + hand crank

(OP)
Thanks guys. I am going to look into using the shoulder screws with thrust bearings to see if that can fit into my fixture dimensions. Can I clamp down onto thrust bearings or do I need to be somewhat gentle with them? I typically dont like being too rough with bearings but these seems like they would have a fair bit of force being pressed onto them.

RE: Pushing work w/ threaded rod + hand crank

Is one direction more prevalent ?

Got an OEM jack in your car for tire changing ? If it is some variation of a scissors jack, there will be some thrust bearings of varying complexity, retained in in various ways.

RE: Pushing work w/ threaded rod + hand crank

(OP)
Yes in this fixture the force will be mostly one direction, the opposite direction will probably just be a return.

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