View Full Version : Bearing interference fit / press fit
29-09-2012, 08:40 PM
Good day all.
I would like to know how I go about working out the right size hole to press a bearing into it.
I need to press fit 5200 & 5204 bearings into aluminium.
Thanks for your time.
29-09-2012, 09:20 PM
30-09-2012, 01:34 AM
How are you intending to measure the holes you've bored to fit these bearings? The only realistic and sufficiently accurate process to machine the holes is to bore them, but since the interference distances are in the order of a few micrometers, you need an expensive bore gauge to measure it.
When boring something for a bearing on the lathe, for myself, which requires a press fit I slowly approach the required diameter and machine the first few milimeters of material to the size where the bearing only just slides in. Then back off the appropriate amount for the press fit and machine the rest of the hole, then machine off the first few mm or sometimes leave them to make it easier to press the bearing in...
In steel you normally aim for 1 thou per inch undersized for a press fit. In Ali, if the parts are going to get hot, you'd maybe aim for 2 thou so the bearing doesn't slacken off when things warm up.
30-09-2012, 09:20 AM
In steel you normally aim for 1 thou per inch undersized for a press fit. In Ali, if the parts are going to get hot, you'd maybe aim for 2 thou so the bearing doesn't slacken off when things warm up.That sounds a darn tight for a bearing. I'd use that sort of fit betwixt a 3 1/2" or 5" gauge loco wheel and axle. I suspect that amount of interference is going to crush the outer race on to the BBs?
1 thou per inch is at the tighter end of the interference scale, but still within limits for steel.
Ali won't apply the same pressure as steel, and will also expand more with heat, so the forces are far less.
The other option is to bore marginally oversize, then peen/crimp the bearing in place, or just rely on some stud/bearing fit loctite. The loctite option can actually be better if you need a little bit 'give' in shaft alignment.
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