Press Fit
 

I had a few questions about press fitting, Specifically bearing's. Lets say I want to press fit a bearing into and 1/8" plate, the bearing's OD is 5/8. Do I drill a 5/8" hole? Because we tried that this year and we needed epoxy to keep it in place. Next question, Can you press fit into 0.09" sheet? or is that to slim? Any information is very appreciated!

Re: Press Fit
 

You should be able to press fit a bearing into a sheet that thin. To make a hole the correct size, get the exact size of the bearing, then subtract a few thousandths for the press fit, and make a hole exactly that size. Usually this requires using a reamer, or CNC machining.

Re: Press Fit
 

WE would be getting this laser cut, does that make a difference?

Re: Press Fit
 

This year we had our chassis water-Jet. There was no problem press fitting into it when i made the hole the exact size. NOTE: we also had it painted so that may have affected it). But when we got our off-season Chassis laser cut it was also press fitted and stayed perfectly (wasn't Painted). you shouldn't have a problem with 0.09", as long as you have a support all around the outside of the sheet-mteal and bearing, so that the metal doesn't bend. we had that happen, but we just hammers it back in place :/

Re: Press Fit
 

Your would have to find out the kerf (width of cut) of the laser, and try to compensate accordingly.

You might run into problems with eccentricity of the circles being cut, and/or the accuracy and repeatability of the hole itself. Maybe try to get some samples cut and see if it's sufficient.

But the easiest method would be to just cut them undersize on the laser and then ream them as squirrel suggested. Anything that requires a precision fit should be drilled undersized and then reamed or bored to the final diameter.

Re: Press Fit
 

"A few thousandths" is FAR too much interference unless you have a really big bearing. Ideally, you're looking for something in the neighborhood of 4 ten-thousandths undersize for that size of bearing. You can get special undersize reamers to do press fit bores.

Let me ask, why do you need a press fit anyhow? In FRC, they're often more trouble than they're worth. Just make a good close slip fit and use part geometry to keep everything in place (flanges, shoulders, counterbores, snap rings, etc).

Re: Press Fit
 

If the hole is just a little too loose sometimes you can make the hole smaller by whacking the edge of the hole with the ball end of a ball-peen hammer. That will result in a little bit of the edge sticking into the hole creating a slight interference.

ChrisH

Re: Press Fit
 

If you are looking at thin sheet (.062 or less) be aware that Flanged bearings sometimes have an undercut at the flange. It is possible that a hole of "proper" size is loose because the sheet falls into the relief groove.

Laser cutters and water jet cutters tend to have compensation for cutter kerf. You just have to make sure the part program uses the compensation. It would a shame to have nice holes well located by a CNC cutter and then have to try to keep the accuracy with an expensive hand reamer.

Also, look at parts from Spyraflo. These are self clinching self aligning bearings made to go into sheet metal (or thin wall tubing).

Re: Press Fit
 

to elaborate on sanddrag's post for a press fit it is a pretty simple process....look at this chart: http://www.turnedoutright.com/wp-con...rill-sizes.jpg

You select a drill size two sizes smaller than your desired hole size, go one step up to ream out the hole, and then press it on

for example: if I want to press onto a 0.250" shaft, I would go down two steps to a size D drill (0.2460"), then ream out the hole one with one size larger (0.2480"), then press....and you are done

Re: Press Fit
 

Thanks for catching that, I've been working on cars lately....

Re: Press Fit
 

for example: if I want to press onto a 0.250" shaft, I would go down two steps to a size D drill (0.2460"), then ream out the hole one with one size larger (0.2480"), then press....and you are done[/quote]

0.250" is the same as an E drill. D is one size down. Two sizes down would be a C = 0.242"

Re: Press Fit
 

Before CNC this was done in any of several ways, from a file or sandpaper to a lathe with a 4-jaw chuck. It is not necessary for CNC equipment to be used.

Re: Press Fit
 

Getting students to hand size a hole for a press fit bearing...now that would be a neat thing to see! We used to get to learn craftsmanship like that in machine shop class.

Thanks for the added info Don.

Another way to do it is to use a boring head on a mill.

Re: Press Fit
 

You can put a lightly loaded bearing in a .09" plate. If there is a lot of load you would want to use a doubler plate to get more bearing area. The difference from a loose running fit (clearance) to a too tight press is less than a couple thousands of an inch on 5/8" dia. Not a lot more if you are talking about a ball bearing with a OD of 1.125 or so.
Most unpracticed people cannot measure that with a micrometer. Drill tolerance is way more than that. Reaming tolerance is more than that.

What to do?
1) Use a new quality drill bit. Clamp the work well Probably be a little loose. Use bearing mount loctite to take up the clearance. I am not sure how well that will work with thin plate.
2) Drill it undersized and use an adjustable reamer get the right fit.
3) Drill undersize & use a deburring tool to get the right size. Only works with relatively thin bores.

Re: Press Fit
 

he isn't talking a generic drill set, he is talking a real machine shop's drill set where they have the drills accurate to tenths of a thou. An E drill is a generic and it is typically .250, accurate to the thou. If you are pressure fitting with generics... be really careful and take plenty of measurements.