# RF31 mill drill



## mocaquita (Mar 12, 2011)

I have a RF31 mill drill and I need to replace the spindle bearings. A little stiff and heat build up. The mill has always left a scalloped finish when side milling only a few tenths deep. Easy enough to remove with emery or a file, but I would like to improve or eliminate it. I don't expect it finish like a Bridgeport class mill. Don't know if this is caused by the class of bearing used in this machine or a vibration problem or both. Really doubt if precision bearings are used in this machine, and it certainly could be something else. Has anybody run into this problem and was able to fix, or improve it?

Thanks,
Dave


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## DaveH (Mar 12, 2011)

Hi DaveB

I have RF30 mill/drill, and over approx 12 years changed the bearings twice the last time about 4 years ago.

Both times I used precision bearings  mainly because I think they are worth the extra cost.

Improvement to the milling finish I didnt notice any marked improvement.

The poor finish is nearly always caused by vibrations. These vibrations can be caused by loose bearings

So first just check the X and Y movements, make sure there is very little play. Turning the hand wheel a drag should be felt.

Also check if milling in the Y direction gives a better finish than in the X direction and /or visa versa.

When you say few tenths deep is that tenths of a thou or tenths of an inch?

Dave


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## mocaquita (Mar 12, 2011)

Got the spindle out of the machine, relatively easy to pull out. Looked up the bearings on Motion Industries and P5's are available at an impressive price. Looks like I'll go with a name brand standard tolerance bearing. Top cup was a slip fit in its bore, about .0005" or so, does not look like it was spinning. Bottom cup was a light press. Probably locktite the top cup on reassembly.


Dave H~
When you say few tenths deep is that tenths of a thou or tenths of an inch?
--In US machine shops, a tenth is .0001"

I agree with you that it is probably a vibration issue. The finish looks worse than it actually is. Might try a linked belt.

Dave


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