Thread: Magnetic Chuck for thin round shim grinding

Originally Posted by jeepinmatt

In my mind, a logical extension of that roller process would be to simply use a press and squish it. It would be easy to calculate force required based on size and material properties, but nearly impossible to maintain flatness and consistent thickness.

A old Baldwin hydraulic universal testing machine would do the job. The hydraulic ram is 12 inches in diameter or larger depending on the model. The top and bottom platens would need to be resurfaced. The machine design will meet the accuracy requirements. You would need to install a dial indicator on the moving lower platen and increase the pressure of the ram very slowly to not overshoot the needed shim thickness The hydraulic testing machines do come up on university auction sites and sell for scrap prices. Your company may not want to devote the floor space or deal with the safety regulations that may be required when using the testing machine.

Originally Posted by jeepinmatt

Another thought branching off of that is to have 5 different thicknesses of shim stock, and a punch set for each of the 50 sizes. But I imagine 50 high quality, clean cutting punch/die sets would be pretty pricey, especially for the larger sizes.

Sounds like the best excuse ever to buy a small, high frequency, metal cutting fiber laser. Ideally one of the ablation versions, but I think those are still beaucoup bucks right now.

How 'bout these: McMaster-Carr

Or punch them from your own shim stock. No Grinding required. Just lap burrs between ground flat stones.

Best Regards,
Bob

Originally Posted by rjs44032

How 'bout these: McMaster-Carr

Best Regards,
Bob

Too compliant from the glue layers between shim elements. Also courser adjustment than what they want. But good for other applications.

Originally Posted by Robert R

A old Baldwin hydraulic universal testing machine would do the job. The hydraulic ram is 12 inches in diameter or larger depending on the model. The top and bottom platens would need to be resurfaced. The machine design will meet the accuracy requirements. You would need to install a dial indicator on the moving lower platen and increase the pressure of the ram very slowly to not overshoot the needed shim thickness The hydraulic testing machines do come up on university auction sites and sell for scrap prices. Your company may not want to devote the floor space or deal with the safety regulations that may be required when using the testing machine.

Yeah, I'm sure that's a no go, but another good idea

Originally Posted by Milland

Sounds like the best excuse ever to buy a small, high frequency, metal cutting fiber laser. Ideally one of the ablation versions, but I think those are still beaucoup bucks right now.

It's just money, they'll print more of it!

One piece at a time in the center of the chuck or a few spread around?
Rotary grinders have a whole extra problem from surface grinders as the part wants to spin inside it's keepers.
One option is super glue and keepers.
Holding the glue film to tenths is an art, you have to keep the drops the same size and use the same pressure when seating.
Then acetone soak to release.

As Cash said anything under .032 is very, very difficult. We draw the line at .0625.
Most metal cutting laser would induce warpage but maybe ok as it gets squished back to flat in use?
Cold (ablation) laser would be great but are 50K just for the laser head without any machine holding it.

Double sided grinder/lappers also very expensive and made for big runs.
There is always hand flat lapping or single side lappers but that is slow and very much art.

Why not just grind the bearing itself if you want to do your own preloads. Some machine builders did this long ago but now just simpler to by preloaded pairs.
Other option is to use a wider spacer that can be held easily for both inside and outside and make them offset as needed.

Doing your own bearing pair preload means micron level control and every bearing set involved needs a custom fit.
This is just not done any more. I wonder how you know what size you need for an assembly.
Measuring drag torque at a nut torque or a feeler gauge shim fit or the guess and fit method. Plastic gauge?

I do not understand the problem you are chasing that leads you down this rabbit hole.
If an internal product and a high desire to use low class bearings there are also wave springs
Bob