Press Fit

[MattC9]

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!

[MrForbes]

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.

[MattC9]

Originally Posted by squirrel

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.

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

[akoscielski3]

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 :/

[scottandme]

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.

[sanddrag]

Originally Posted by squirrel

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.

"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).

[ChrisH]

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

Originally Posted by sanddrag

"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).

[Big Ideas]

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).

[Stephen Kowski]

Originally Posted by sanddrag

"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).

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

[George C]

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"

[Peck]

Originally Posted by George C

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

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

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.

[DELurker]

All of your bearing fit information (radial ball) can be found in the chart on page 131 at http://catalog.timken.com/WebProject...ookcode=eng11#, with the codes defined on pages 132-145.

If you can't make the holes to the specifications listed there, 0.001" undersized should work. I've found that Loctite Retaining Compound 641 works well in other applications, if you want to make the hole right at the bearing diameter.

As for press fits into thinner materials, I would recommend a flanged or snap-ring bearing with either retaining compound under the lip or 3 screws at 120-degree intervals.

[MrForbes]

fwiw, we made a couple gear boxes this year using flanged bearings and polycarbonate side plates, we discovered that drilling a hole with a Forstner bit will provide a sufficient press fit. There are lots of ways to do things like this.

[pmangels17]

Also note that polycarb cracks when you put loctite on it.

[AdamHeard]

This is an area where standardizing in design can make things a lot easier. If you only use a few common sizes of bearings, then you can get the appropriate reamers for these bearings (at some expense, but not awful; and due to design standardization they're used almost everywhere on the robot).

We have a press fit and slip fit (press being .0005 to .001 under depending on the availability of the reamers) for most bearings and bushings we use.

Most 973 robots over the past few years have most gearing running on plates that were waterjetted then reamed out by a reamer in a hand drill.

The reamer is really the best compromise between precision and the ability to use it on any given part and machine. It also allows "fixing" of damaged or out of tolerance parts.

Originally Posted by squirrel

fwiw, we made a couple gear boxes this year using flanged bearings and polycarbonate side plates, we discovered that drilling a hole with a Forstner bit will provide a sufficient press fit. There are lots of ways to do things like this.

Materials like polycarbonate that are much softer/weaker than the bearing itself will allow a much greater range of bore sizes without undue damage to or efficiency loss in the bearing.