Bearings in Sheet Metal

[akoscielski3]

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.

[rcmolloy]

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.

[Akash Rastogi]

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

[Brandon Holley]

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

[akoscielski3]

Originally Posted by Brandon Holley

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

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.

[Brandon Holley]

Originally Posted by akoscielski3

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.

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

[MrForbes]

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.