Newbie- How to create a hole for a bearing

[Futterama]

Hi forum,

I have a general metalworking question.

How is a hole for a ball bearing created in a thick aluminium plate without a CNC machine? The ball bearing should be press-fit into the hole.

Let's say the bearing outer diameter is 8mm. The hole should then be a bit smaller to make the bearing fit tight in the hole. So it's not possible just to use a 8mm endmill on a milling machine, the bearing will fit, but it will easily pop out.

I know it will be easy if the part that the bearing should be mounted in was round, you could use a lathe to create a hole of the exact dimensions. But when it is a big plate that cannot be mounted in a lathe, then how is it done?

I know this is a CNC forum, I guess it wouldn't be a problem to mill a round hole using a CNC mill, but I don't have access to a CNC machine, so how is it done with "normal" machines (lathe/mill).

Thanks.

[CNCRim]

Do the old fashion way, drill hole close to want you want then file it by hand to the size you want.

[fatal-exception]

You would drill a pilot hole then finish to size with a boring head.

Paul

[Oldmanandhistoy]

Hi,

Can you use a bearing block; will save you a world of trouble?

John

[Futterama]

Originally Posted by fatal-exception You would drill a pilot hole then finish to size with a boring head. Paul

Oh, some kind of adjustable end mill type of thing. Do they come in small sizes too?

[ee_t]

Originally Posted by Futterama Oh, some kind of adjustable end mill type of thing. Do they come in small sizes too?

Do you see the one being held in the bottom of the picture, it looks to be quite small .

Or you can drill and ream.

[Futterama]

Originally Posted by ee_t Do you see the one being held in the bottom of the picture, it looks to be quite small .

Yeah, but it seems that it should be attached to the big one in the middle and I need it to fit a mini mill.

I found the danish word for the tool and will now look for one that will fit my mini mill. Thanks for the replies!

[Oldmanandhistoy]

Originally Posted by Oldmanandhistoy Hi, Can you use a bearing block; will save you a world of trouble? John

Sorry didn’t realise you had a manual mill.

In that case I would defiantly go with drill and finish with an adjustable boring head (how I do it). The adjustable boring head with care will give very good control of the tolerance (fit) of the bearing.

Don’t forget to research the necessary fit from the bearing manufactures specifications.

Good luck,
John

[BobWarfield]

Depending on the side of the plate, a lathe will also do a very accurate job with a boring bar. It's effectively the same operation as with a boring head on a mill, except you're spinning the plate in the lathe chuck instead of a boring head.

Be careful that the press fit is not so tight as to damage the bearing. They're more delicate than you'd think.

Cheers,

BW

[shanon]

this is very tricking the right size hole may not really be the answer. Depending on this situation I would worry about too small, too large, and because its in alum. the wearability when the bearing fails. My suggestion would be to first mill out a square or rectangle recess in alum. plate to allow for a bearing cover to be drilled, tapped, and then attached flush with the face of the alum plate. this will allow more tolerance on the actual bearing hole aswell as easier replacement of ware bearings.

[Futterama]

Again thanks for the answers.

My application it not VERY critical, and I wanted to use cheap china bearings because of the price and because the bearings may need to be replaced often due to operation in very dusty conditions - that's why the bearing price is a bit critical.
The cheap bearing I have access to have VERY much internal tolerance - so much that I can move/tilt the inner part of the bearing with my fingers.

shanon, I have thought about the plate thing, but it's too much work I think.
I would like you to further explain what you mean by this: "Depending on this situation I would worry about too small, too large, and because its in alum. the wearability when the bearing fails."
Do you mean that the hole in alum. wound "wear" when replacing the bearing? So after a number of bearing replacements, the press fit will no longer be "press fit" but only "fit"?

[shanon]

I was referring to thickness of alum. plate, clearance between alum. plate and any thing else. You may be able to attach bearing cover w/o milling recess. perhaps w/ thru holes and bolts??. Exactly what will you do if hole does ware?? and if hole is tight enough to press in cold but not under some operation heat or stress. something to take into consideration..