Bearings in Sheet Metal

[AdamHeard]

Originally Posted by sanddrag

With holes that much smaller there's no chance the bearings will fit. Did you leave out a zero?

With Material that thin it works no problem. If you were pressing into material the same thickness as the bearing it'd be a different case.

[JamesCH95]

Originally Posted by squirrel

Another thing you can do if you want to have some fun, is press the bearings into polycarbonate sheet. We discovered that a Forstner drill bit will make a hole just the right size for this press fit.

This works well for smaller mechanism type gearboxes, and I think it has been used by AM to make drivetrain gearboxes too.

We did this for our 2012 shooter. A total of 10 flanged bearings pressed into polycarbonate sheet. Worked great.

To put some numbers to the OP question:

Using a bearing like this one in 5052 aluminum (28KSI YS):

YS*(bearing OD*sheet thickness)=bearing load at material yield

28KSI*(.875*.0625)=1530lbf to reach yield in 5052 aluminum, assuming the bearing is seated properly and nothing is grossly misaligned. This is at least double the working load rating for most bearings of this size.

[MichaelBick]

Originally Posted by AdamHeard

With Material that thin it works no problem. If you were pressing into material the same thickness as the bearing it'd be a different case.

Is undersizing .003-.005 better for thin sheet, or is reaming out to .001 undersized still better?

[Michael Hill]

Originally Posted by IndySam

Exactly or even a little emery paper does the trick. On thicker materials we note which side is tapered by the water jet and a quick hit with a deburing knife usually results in a perfect fit.

Water jets taper the material? Hmm...I didn't know that. You learn something new every day!

[Andy Baker]

Originally Posted by Michael Hill

Water jets taper the material? Hmm...I didn't know that. You learn something new every day!

Yes, and no.

Waterjetting naturally cut a taper in the material. However, if the waterjet machine has an angle compensating head, then the cut can be straight on one side of the cut.

Andy B.

[JamesCH95]

Originally Posted by Michael Hill

Water jets taper the material? Hmm...I didn't know that. You learn something new every day!

It's called a 'kerf'. A skilled waterjet operator such as the gut I use for work can do a really good job minimizing the kerf's taper, even without a multi-axis head like Andy describes.

[DampRobot]

Originally Posted by JamesCH95

It's called a 'kerf'. A skilled waterjet operator such as the gut I use for work can do a really good job minimizing the kerf's taper, even without a multi-axis head like Andy describes.

Last summer, I was trying to cut some 1 module (metric) gears with a waterjet in about .4" thick material. Unfortunately, the kerf that yo mentioned prevented the gears from meshing properly.

Could you elaborate as to the methods used to help eliminate kerf? We tried cutting extra slow, but it didn't seem to help much. If you can cut propper bearing press fit holes with a waterjet using proper methods, to seems like cutting gears of at relatively large module would be trivial.

[R.C.]

Originally Posted by DampRobot

Last summer, I was trying to cut some 1 module (metric) gears with a waterjet in about .4" thick material. Unfortunately, the kerf that yo mentioned prevented the gears from meshing properly.

Could you elaborate as to the methods used to help eliminate kerf? We tried cutting extra slow, but it didn't seem to help much. If you can cut propper bearing press fit holes with a waterjet using proper methods, to seems like cutting gears of at relatively large module would be trivial.

You could just cut .125 plates and stack the gears. That would help quite a bit. Most places that we've used for work just compensate for the kerf via rotating head.

-RC

[AdamHeard]

You can also waterjet both gears, and run them opposite. We've done this in numerous places.

[JamesCH95]

Originally Posted by DampRobot

Last summer, I was trying to cut some 1 module (metric) gears with a waterjet in about .4" thick material. Unfortunately, the kerf that yo mentioned prevented the gears from meshing properly.

Could you elaborate as to the methods used to help eliminate kerf? We tried cutting extra slow, but it didn't seem to help much. If you can cut propper bearing press fit holes with a waterjet using proper methods, to seems like cutting gears of at relatively large module would be trivial.

No idea how he reduces the kerf so effectively and I've never asked. I assume it's a trade secret of his so that we'll keep sending work to his shop.

He uses a pretty old 3-axis machine with no fancy features.

If I had to guess it's that he adjusts the pressure of the jet in conjunction with travel rate to reduce the kerf, but that's pure speculation.