Back from the Dead

[RJSakowski]

Here is a post that might prove interesting to some members. I have a B&D multi-function sander, orbital, finish, detail,etc. that died. Yeah, I know, cheap product not intended to be rode hard and put up wet but it has served me well through fifteen years of remodeling and cabinet making and doesn't owe me a dime. The sander died because the rear bearing froze up and the bearing was bouncing around in the plastic housing and chowdered it resulting in the armature hitting the field core. I was going to chuck it but I have a bunch it pads for it and none of the new sanders that I looked at were muti-functional so I decided to take a stab at repairing it.

To build up the destroyed housing, I decided on using JB Weld. It had to be stronger than the original bearing seat. The plan was to use the motor armature to position the bearing correctly while forming the new seat. I measured the diameter of the armature and the i.d of the core and determined there was a difference of .040". A .020 shim would properly center the armature. I had some .010 aluminum flashing and I heated a piece to remove the temper. It turned out that a second piece was too tight a fit so I salvaged a piece of .006" aluminum from a beer can for a second shim which gave a nice snug fit with no wobble.

The next issue to be addressed was how to make a proper mold for the bearing. A bare bearing would undoubtedly bond to the JB Weld and most likely destroy the new seat when I dissembled it, I thought of using a thin film of grease as a release but rejected that idea as the bearing has negative draft
features the would still tend to lock the bearing in place. Then I thought of making a surrogate for the bearing from Delrin since nothing bonds to Delrin and it would be self releasing. The bearing is a 7x19x6 mm. The actual o.d. measured at .7478" or 18.994 mm. The motor shaft measured at .2736" or 6.975mm. The bearing thickness measured at .2355" or 5.982 mm. I turned a section of Delrin rod to .7484" or .0004" over 19mm. There was a gap on either side of the bearing which would have filled with JB Weld so I turned a short necked down region on either side of the surrogate to fill the gaps and prevent the JB Weld from bonding to the motor shaft. I drilled a 6.5mm hole for the motor shaft and enlarged it to 7.0mm which gave an interference fit on the motor shaft. The surrogate was parted off and fitted to the motor shaft.

I cleaned up the bearing seat and removed a little more of the housing to provide some thickness for the JB Weld seat. There were some slots in the housing at the bearing seat which would provide an anchor for the epoxy. I mixed a small amount of JB weld and filled the area, Next, I inserted the motor assembly, using care to ensure the motor field was properly seated. The surplus JB Weld oozed up around the bearing and I carefully cleaned it off and left the assembly to cure. Later that evening, the epoxy had set well enough that the motor assembly could be removed. I cleaned up any residual epoxy and repeated the process on the other half of the housing. After the JB Weld had started to set, I added the first half housing and fastened the two jalv3es together to ensure that the bearing registration between the two halves was good. The next day, I dissembled the housing and removed the motor. There was a very minor amount of cleanup needed to complete the job.

I reassembled the motor and did a short test to make sure that everything was good. Although the directions for the JB weld state that the part could be used after 24 hours, it was still flexible. Epoxy doesn't really cure all that quickly and at the point at which it appears solid, it is only about 10% cured. When I use epoxy, I always make a small test sample to determine its cure state. After 36 hours, the sample was rigid so the repair was deemed ready for use. As I write, my wife is using it to refinish some of our 110 y.o. doors.

Original bearing and Delrin surrogate. The necked down region to prevent epoxy intrusion to the motor is visible. (the black mark is a bit of epoxy remaining on the Delrin after use.)


The completed bearing seats with the motor at upper right, ready for assembly. The finish on the new seats is superb.

 

[john.oliver35]

Nice save RJ! I'm afraid that if I had started on this venture I would have lost patience long before you did and tossed the whole thing!!

 

[Eddyde]

Clever approach, nice work!
I used JB Weld to re-seat a bearing in my Bosch Brute, demolition hammer. Same failure, a gear bearing seized and tore up the aluminum housing. I used the first approach you mentioned, just using the bearing itself as a mold. As this was a straight in situation, not a split housing, it was feasible. Anyway, it was a desperation repair that I hoped would just get me through the rest of the job... That was 13 years ago and I've clocked at least a hundred hours on that repair since.

 

[WesPete66]

Good save!
This failure must be fairly common. I recently gave $10 for a 1/2" Milwaukee hammer drill with rear bearing issues. I found the bearing was froze, and spun in the plastic housing. I debated trying a JB repair, but found I could buy the housing for $8 so I did that. That drill runs like a champ today.

 

[pdentrem]

Same happened on our electric chain saw.

 

[RJSakowski]

Back in the '90's my wife was a sales rep for Black & Decker in the UK. She was told that the tools in their lineup were intended for occasional use by the home handyman. I have to say, though.that sander has done a lion's share of sanding and has held up well. Considering that sanding dust is a combination of very fine powder and abrasive, it is surprising that the bearing had held up as long as it did.

 

[projectnut]

Back in the '90's my wife was a sales rep for Black & Decker in the UK. She was told that the tools in their lineup were intended for occasional use by the home handyman. I have to say, though.that sander has done a lion's share of sanding and has held up well. Considering that sanding dust is a combination of very fine powder and abrasive, it is surprising that the bearing had held up as long as it did.

At one time Black & Decker made a line of tools they called their "Professional Line". One of our machine shops had a 14" chop saw from that line. It was originally purchased in the early 1980's. The first 20+ years it was used on a daily basis. When the shop closed, I bought it as part of a lot of tools. It doesn't get used much today, but it still works fine.

 

[RJSakowski]

At one time Black & Decker made a line of tools they called their "Professional Line". One of our machine shops had a 14" chop saw from that line. It was originally purchased in the early 1980's. The first 20+ years it was used on a daily basis. When the shop closed, I bought it as part of a lot of tools. It doesn't get used much today, but it still works fine.

In the eighties, I bought a B & D Wildcat 7" angle grinder that is a beast. Well built, no plastic and works great. My B & D 2 x 14 belt sander was only replaced because it was difficult to find new belts. The lever loosening the belt on the replacement Skil 3 x 21 belt sander gave up fairly early in its life. I have a DeWalt 4" angle grinder where the insert holding the handle ripped out of the plastic housing, stripping out the threads. Epoxy didn't work so I made a new threaded insert and tapped the housing for it.

Like so many other old standby tool companies, corporate decisions were made to be competitive on price, lowering the durability of the products as a result. What used to be quality brands that could be counted on for long and faithful service are now seemingly designed for an early demise.