Belt Sander
When I buy a power tool from Harbor Freight, I always expect that I will need to fix it. This doesn't bother me as long as it is cheap enough. I enjoy building and fixing most things more than actually using them. If the tool isn't cheap enough, I don't buy from Harbor Freight. My little 1" belt sander was no exception to this rule. It worked fine for a while, but I smelled burning plastic when I was using it the other day. The motor smelled fine, so I took off the side panel that is used to change sanding belts. I saw that the drive wheel was loose and had walked partially off the motor shaft. It was rubbing the [plastic] side panel and melting it. Upon further investigation, I saw that it had a D-shaped bored that fit the flatted motor shaft and had a set screw at an angle (approximately 30 degrees off perpendicular to the motor shaft). The drive wheel is plastic and the threads for the set screw were stripped, so I couldn't tighten it anymore. The bore that was molded into the wheel had a real sloppy fit on the shaft. Combined with the angled set screw, it was a poor design that was destined to work itself loose.
I didn't want to make a whole new wheel, so I figured I would try fixing the broken one. The fix was dependent on being able to machine the wheel. I wasn't sure it would work since the plastic has a rubbery feel to it, but I had nothing to lose. I chucked it up in the lathe and faced the flange off to make room for the flanged bushing that I would create. The wheel was not the ideal plastic to machine, but it worked well enough, so I continued the repair. I opened up the bore to 0.850" halfway through the wheel. I wanted to leave some of the D-shaped bore in the wheel so the new bushing and set screw weren't taking all the torque from the motor.
I turned a flanged bushing out of aluminum, with the flange thickness equal to the amount I faced off the wheel to bring it back to the original thickness. I turned the bushing to 0.852", which pressed in the wheel by hand, but stayed in place due to the grip of the plastic. I bored the bushing for about a 0.0005" press fit on the motor shaft. It will probably require a gear puller if I need to remove it, so it's not going to walk off the shaft again. I drilled and tapped the bushing (perpendicular to the shaft this time) for a 1/4"-20 set screw.
I used the mill to remove the portion of the molded wheel where the old set screw was. This was needed to create clearance for the new set screw. I probably could have finished the repair here, but a wise man (Oxtoolco on Youtube) said "Nothing too strong ever broke." This is only a 1" belt sander with a 1/3HP motor and the molded D-shaped bore should handle the torque, but I decided to make it stronger. I drilled 2 holes through the flange and into the wheel hub, and pressed 1/8" drill rod in to pin the bushing to the wheel. This will help transmit some of the torque through the set screw and bushing to the wheel, and it isn't totally dependent on the integrity of the molded bore in the wheel. I felt this was a good option since I only had a plastic to metal press fit. If the wheel was metal, I could have relied on a solid metal-to-metal press fit, used Loctite sleeve retainer or added a set screw. It took some hits from a mallet to seat the wheel on the shaft and it feels solid now. The sander runs much smoother and a little quieter.
Click on the pictures for larger images.
I didn't want to make a whole new wheel, so I figured I would try fixing the broken one. The fix was dependent on being able to machine the wheel. I wasn't sure it would work since the plastic has a rubbery feel to it, but I had nothing to lose. I chucked it up in the lathe and faced the flange off to make room for the flanged bushing that I would create. The wheel was not the ideal plastic to machine, but it worked well enough, so I continued the repair. I opened up the bore to 0.850" halfway through the wheel. I wanted to leave some of the D-shaped bore in the wheel so the new bushing and set screw weren't taking all the torque from the motor.
I turned a flanged bushing out of aluminum, with the flange thickness equal to the amount I faced off the wheel to bring it back to the original thickness. I turned the bushing to 0.852", which pressed in the wheel by hand, but stayed in place due to the grip of the plastic. I bored the bushing for about a 0.0005" press fit on the motor shaft. It will probably require a gear puller if I need to remove it, so it's not going to walk off the shaft again. I drilled and tapped the bushing (perpendicular to the shaft this time) for a 1/4"-20 set screw.
I used the mill to remove the portion of the molded wheel where the old set screw was. This was needed to create clearance for the new set screw. I probably could have finished the repair here, but a wise man (Oxtoolco on Youtube) said "Nothing too strong ever broke." This is only a 1" belt sander with a 1/3HP motor and the molded D-shaped bore should handle the torque, but I decided to make it stronger. I drilled 2 holes through the flange and into the wheel hub, and pressed 1/8" drill rod in to pin the bushing to the wheel. This will help transmit some of the torque through the set screw and bushing to the wheel, and it isn't totally dependent on the integrity of the molded bore in the wheel. I felt this was a good option since I only had a plastic to metal press fit. If the wheel was metal, I could have relied on a solid metal-to-metal press fit, used Loctite sleeve retainer or added a set screw. It took some hits from a mallet to seat the wheel on the shaft and it feels solid now. The sander runs much smoother and a little quieter.
Click on the pictures for larger images.