Bearings in Sheet Metal
 

Most of my experience with sheet metal was in non-power transmission applications.

How do folks typically handle bearings when working in sheet metal? If you're working in .060" or something, do you build up around the bearing with additional sheet? What about thicker materials like .090" or even .120"?

Re: Bearings in Sheet Metal
 

We use .09 for our gearbox sideplates. It works fine without extra material. We also make the holes .003-.005 smaller so the bearing fits tightly which prevents slop in the gears.

Our 2012 collector had bearings in .063 sheet which supported bevel gears. There were no problems with the bearings all year. Just make sure the bearing flange is flush with the metal - it's not like its going to rip out or anything. I wouldn't suggest going this thin for a gearbox though.

Regards, Bryan

Re: Bearings in Sheet Metal
 

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

Re: Bearings in Sheet Metal
 

For what it's worth, 2815 has had good luck with flanged bronze bushings for 1/2" shaft inside 1/16"-wall square tubing. In each case, the bushing only went through one side of the square tubing.

We ran them in our 2011 roller claw, and on our ball elevator and shooter axle this year. Any issues we had with any of these were unrelated to the bushings.

Re: Bearings in Sheet Metal
 

We've done the same.

Re: Bearings in Sheet Metal
 

If you use a flanged bearing, make sure it is well retained in the plate, and pinched axially on the shaft, you'll be fine even in something as thin as 063.

-John

Re: Bearings in Sheet Metal
 

Nope, we just use a deburring tool or ream them out to make them a little bigger after they are waterjetted. I agree that they wouldn't fit unless you make the hole bigger.

Re: Bearings in Sheet Metal
 

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.

Re: Bearings in Sheet Metal
 

It's funny that me and Akash just had a discussion about this the other night.

Last year 772 used 1/8" sheet (0.125") for everything and didn't thicken the area's where bearing went. Though it isn't needed we WILL be adding extra material around them this year. I am also probably going to make a "press" mechanism that will make the bearing become perfectly flush with the sheet. This year we went with cutting the bearing holes to the exact size, though with the "press" I would make it about 0.005" smaller. Along with press fitting the bearings I want to Bolt them in, the exact same way IFI bolts the bearings onto their wheels (plastic small washer to space washer, and washer on top of bearing, bolt and nut holding the washer down). The holes for the bolts would also be used to press the bearing into the metal.

You can see what I designed for a bearing press below. You need an Arbor press for it to work.

Re: Bearings in Sheet Metal
 

I have seen two cases where flanged FR8s (pressed in 1/8 plate) and flanged FR6s (pressed in 1/16 tubing) have had pretty great success. The most recent application was done with the FR6s for the 973 Hodgepodge Bot. So far, there hasn't been any records of the bearings or tubing failing.

Re: Bearings in Sheet Metal
 

We added extra material in the drivetrain, but straight .09 gave us zero issues for the rest of the bot.

Re: Bearings in Sheet Metal
 

On our intake, we needed to press in FR6 bearings in 2 places. The sides of the intake were made from 0.060" 6061 so we weren't totally sure how the press would hold up. We decided to play it safe and added 2 bearing plates that simply acted as a carrier for the bearing and would then bolt onto the intake.

The little plates actually ended up being a bit of a celebrity on the team and we ended up making them into little NUTRONs logos just for some extra flare (bottom right):



They worked out great. It was actually a cool feature too, because it allowed us to disassemble part of the intake from the opposite side where if a bearing were permanently pressed in place, we'd be unable to.

-Brando

Re: Bearings in Sheet Metal
 

So your bearings were never pressed into the actual intake, they were only pressed onto these plates? I like that idea alot actually. Were they pressed in? Or bolted on to these plates? If they were pressed how much smaller, if any, were the holes made for the bearings?

Thanks, great idea btw.

Re: Bearings in Sheet Metal
 

Yeah the bearings were only pressed into the bearing plates. The bearing plates were then bolted to the intake.

For any part that we are making in-house we can reliably undersize the press fit to 0.0005" under and press with no issue. The most reliable way to get good press fits is to invest in the 2 reamers you would need to do 3/8" bore and 1/2" bore bearings (0.8745" and 1.1245"). This becomes a very repeatable process for your team, where you size bearing holes slightly under and ream to the final diameter. You will have much more consistent press fits this way. This will also help you where you may be using a process besides a CNC mill where the tolerances on the diameter may be a little bigger (ie: waterjet). Again, you'd undersize for the waterjet, and just finish with the reamer.

-Brando

Re: Bearings in Sheet Metal
 

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.

Re: Bearings in Sheet Metal
 

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.

Re: Bearings in Sheet Metal
 

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.

Re: Bearings in Sheet Metal
 

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

Re: Bearings in Sheet Metal
 

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

:cool:

Re: Bearings in Sheet Metal
 

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.

Re: Bearings in Sheet Metal
 

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.

Re: Bearings in Sheet Metal
 

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.

Re: Bearings in Sheet Metal
 

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

Re: Bearings in Sheet Metal
 

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

Re: Bearings in Sheet Metal
 

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.