In this post, I will talk about removing the old motor bearings and ordering new ones for a Craftsman 115.6962 capacitor start 1/2 -HP electric motor (115 V, 60 cycles, 1750 RPM). Here’s the original Craftsman manual at VintageMachinery.org.
The first step in restoring the motor was to remove the stuck-on pulley on the left side (terminal side) shaft of the motor. First, I removed the set screw, but from there, the pulley wasn’t budging. At all. I think the problem was a little corrosion between the pulley and the shaft, plus some galling of the shaft from the set screw. There wasn’t much room to get a puller in behind the pulley, and I was very reluctant to use a puller anyway, lest I damage the very soft metal of the pulley.
In the end, I set up an adjustable wrench on the fan side shaft to prevent the shaft from turning. Then I applied as much elbow grease as possible and tried to turn the pulley on the shaft. After a lot of grunting, cussing, and shots of penetrating oil, I got it to turn about a few mm. Then, I reversed the adjustable wrench and tried to turn the pulley in the other direction. Back and forth I turned it, getting it to move a few mm one way and then the other, slowly loosening it up. After a point, I tried to pull it out with a homemade puller and got it to move outboard a half inch or so. Progress! Then it was a few more rounds of turning against the adjustable wrench, work with the puller, and finally I got the *$^#@%% pulley off, basically intact.
The left shaft was rusty, dirty, a little galled, and basically just a mess.
I ran the motor a little and applied some fine grit sandpaper to the shafts to clean them up a bit. I also used a little simple green on a shop towel to get some of the grime off the bearing housing.
Ok, so at this point, the bearing itself was really all that was holding the end frames together. To separate the frames, I used a Gearwrench bearing separator to push into the rotor shaft while pulling on the frame. I do not necessarily recommend this approach – it could easily crack the end frame casting. It worked for me, but I am sure there’s a better way to go about this.
The right side (fan side) end frame is bored so the bearing can pass straight through, but the left side has a lip on the interior surface of the bearing housing and the bearing can only be installed or removed through the outside (it won’t push through).
Once I had the end frame open, I had my hands full and forgot to take pictures, but I basically just pulled it apart gently and worked the rotor assembly out the right side. I simply lubed and pulled the bearings off a little roughly, as I was planning on replacing them. They didn’t put up much resistance.
The motor originally housed two New Departure 8000 series N-D-Seal bearings. Specifically, each bearing was an ND model 8502. The following information is based on the 1943 New Departure Hand Book, 16th ed.:
The N-D-Seal bearings featured an extended inner ring housing a permanently fitted felt seal intended to keep dust and debris out of the race. The opposite side of most N-D-Seal bearings (including the 8502) has an inset on the opposite side of the inner ring, for use in blind housings without necessitating a counterbore to fit the bearing. Smaller N-D-Seal bearings, when run at high speeds, work better under a light thrust load, and a small steel spring may be used. Under medium and low speeds, like we see in fractional HP electric motors, it is recommended to leave 0.015 to 0.020″ of clearance between the bearing face and the housing shoulder to limit excessive thrust load on the bearings. The ND Hand Book also suggests using a thin metal washer and felt ring to close off the shaft extension end, which we see was done on this motor.
The modern equivalent to this bearing is Acurate Bearing p/n 87502. Lynne from Accurate provided me with IKS (Japan) bearings in that size (87502 IK) for about $12/ea (including shipping). This is a single row radial bearing, single shielded and single sealed. Specs for a 87502 are as follows (refer to the diagram which follows):
- Bore (d): 15 mm (0.5906 in)
- Outer Diameter (D) : 35 mm (1.3780 in)
- Total Width: 12.700 mm (0.5000 in)
- Inner Ring Width (Bi): 12.192 mm (0.4800 in)
- Outer Ring Width (Be): 11 mm (0.4331 in)
- Radius (r): 0.600 mm (0.0236 in)
And here are the new bearings (top row) alongside the original bearings (bottom row):
In the next post in this series, I’ll detail more about disassembly, cleanup, and reassembly, including installing the bearings into the motor.
Did any of this help you? If so, toss a buck in my Paypal tip jar on the home page!