Advice on press-fit bearings

D

Drhender

Registered
Registered
Joined
Mar 24, 2017
Messages
20
I am mentor for a high school robotics team and need some advice on of fitting bearings. Our drive and wheel shafts run in a 1-1/8" flange bearing, housed in either the wall of 1x2" aluminum rectangular tube (1/8" wall) or in a 1/4" aluminum plate. We recently purchased a CNC router table and have been getting really good results/precision. We'd like to buy a reamer to perfect the fit of our bearings-- the CNC gets it really darn close, but I know a ream would really bring it home. What size reamer should we be looking for? 1.126, 1.124, or dead on 1.125?

Also, same question for a smaller bearing: I am told it's a 7/8" OD, but my guess is that it's really 22mm.
 
Ok, but can I buy a 1.1248 or 1.1252 reamer? We’d rather not spend hundreds on a couple of reamers.

Is 0.0002” 2 tenths larger than the bearing diameter?
 
Bore them to size . Or , buy the nominal size reamer and stone the edge in a lathe . If you knock .0001 off each edge you have your 2 tenths press fit . :) They also sell adjustable blade reamers !
 
Wow, I appreciate all of the advice!

Boring requires a lathe or a mill. We don’t have either. I was hoping to get away with reamers in a drill press. However, our drill press isn’t a particularly precise piece of machinery. Is attempting to ream beyond our capabilities?
 
It's easy to get caught up with the professional documentation and be preparing tolerances intended for precision machinery. Stay away form high
ABEC number as a few microns of bearing play is nothing to worry about for your purposes.
I don't know if you have a milling machine with boring head or should your parts be small enough to to be turned on a lathe face plate, so reaming may be your only option.

Go for the ABEC-1 or non rated bearings in inch sizes. Measure the bearing, set the reamer to size .001 under and use precision ground shafting or drill rod for you shafts. Looking at the generic flange bearing, the tolerances of the bearing are way too loos to warrant the tolerances mentioned above. https://www.mcmaster.com/6383k234

Adjustable reamers would be the easiest way to go
http://www.grizzly.com/products/Grizzly-11-pc-Adjustable-Reamer-Set/H5942
These you can set to size with the aid of a micrometer. Tighten a tap handle at the stub, set a presision square to the blades and the work, then ream by hand.
 
The press fit that a radial ball bearing will tolerate, (I assume that you are using ABEC 1 off the shelf radial bearings, assuming is never a good idea however) is dependent on it's size and internal clearances.
You will find that an ABEC1 annular ball bearing of say 1/2" OD will have a visible clearance if the outer race is held in one hand and the inner race is wiggled by the other hand, try it.

On a practical note if the press fit does not exceed the internal clearance then you are good to go. If you are trying to create an annular ball bearing bore using circular interpolation in a CNC router pressing the outer race into a bore with the typical 12,3,6 9 o'clock deviations will often cause the outer race to become out of round.
 
You must log in or register to reply here.
Back
Top