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Bearing Replacement
Bearing Replacement
My inherited Craftsman belt-disk sander (Model number 113.22580) was showing classic signs of bearing wear: poor belt tracking, noise, and vibration. The problem turned out to be the idler pulley (on the right in the picture).
Here's the nameplate on my sander:
- Model number : 113.22580
- Serial number : 8282.00082
Below is the idler pulley removed from the machine; the bearing are mounted internally in an inner "core." The bearing on one end had wobbled on the internal axle, so that it was very loose.
Idler pully
Bearing mount core (one end) - not too much wear.
Bearing mount core (other end) - severe wear.
Upon removing the bearing and axle, it was clear that deep wear on the axle was allowing the bearings to wobble, causing further wear on the pulley.
Internal axle - shown above the idler pulley.
Closeup showing severe wear on the axle.
The standard bearings for the idler shaft have a 0.5" ID with a 30mm OD and a snap ring. Supposedly these can be replaced with a 6204-2RSNR equivalent, but that would not work in my case as the replacement would wobble in the worn pulley.
I therefore decided to purchase the following bearings: 163110-2RS Deep Groove Ball Bearing Rubber Sealed 16 x 31 x 10mm
My plan was as follows:
- Bore out the inner core of the idler pulley to fit the slightly larger bearings.
- Make a "sleeve" to cover the worn sections of the idler shaft, and to fit the larger internal diameter of the replacement bearings.
Unfortunately, the snap rings on the axle would now be too small to retain the new bearings; I will attempt to address this by adding a thin washer before the snap ring.
The washers (0.050" thick) were made from O-1 drill rod, hardened and tempered. The hardening was probably not necessary, but I wanted to see how it would work. The heating process caused a slight cupping in the washer, but nothing significant. However, this tells me that if I want to do this in the future and get a completely flat washer, I would need to surface grind after hardening.
The idler pulley was bored out for the new oversize bearings by mounting in a four jaw chuck on the lathe.Initially I tried centering by indicating on the outside of the pulley; however the outside was slightly out of round (by about 0.004"), so I switched to a coaxial indicator on the inside. This gave better results.
Both ends of the inside were bored out for a very close slip fit on the bearings.
The bearing adapter (pictures below) was bored out for a close slip fit on the shaft. I had a 1/2" adjustable reamer in among my tools, so I used this to get the final diameter. The outer ends of the shaft were turned down to within 0.001" of the required diameter, and then polished down to final diameter with abrasive paper to give a very close slip fit on the bearing.
The bearing adapter was locked to the shaft with Loctite 263. I considered also putting in a roll pin, but decided it was probably not necessary, and would also weaken the axle somewhat.
Shaft (top) with bearing adapter (bottom).
Bearing adapter mounted on shaft.
The axle was reassembled with the bearing inside the idler pulley. The inner and outer surfaces of the bearing were also locked in place with Loctite 263 - probably not necessary since the beraring are held in place with the washers and circlips but I wanted to make sure there wasn't even the slightest amount of wobble in the bearing.
At this time I have re-installed the idler pulley in the sander and it appears to be working as hoped. If there are any problems in the future, I will note them below.
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