A couple weekends ago I put a new drive belt on my Craftsman lathe, and it promptly ate it. After some help from Bernie in this thread, I contacted Palmgren (the makers of this Sears lathe) and learned that there was a newer pair of toothed drive wheels available. Apparently the ones from the era my lathe was built had a tendency to chew up belts, so they were redesigned. I ordered the new parts from Sears, and they showed up last Thursday. Thursday night I spent about 4 hours with the lathe in surgery. I don't really like working on mechanical stuff. I can usually figure it out, but it always involves lots of unprintable words and bloodied knuckles.
One of the new drive wheels is attached to the motor shaft, and the other to the shaft that spins the reeves drive (which in turn spins the lathe spindle). The reeves drive shaft is relatively easy to get out of the lathe, but replacing the wheel on the motor shaft was much more of a pain than expected. In order to get (read: heat 'n beat) the old wheel off, I had to completely remove the motor from the inside of the headstock housing.
In the process of removing the motor, I discovered what I suspect was my REAL problem all along. The motor is held in place in the headstock housing with two long bolts. When I got things about halfway stripped down, I realized that one of those bolts was not connected to anything. It had come loose, and had not been apparent in the various times I've had the lathe taken apart in the past. (I'd never stripped it down this far.) This loose bolt was allowing the motor to move, which was causing the drive belt to slip, which in turn ate the belt. Ever since I bought this lathe (used), I'd noticed a "clunk" sound whenever I turned on the lathe. I always thought it was simply slack in the belts, but as it turns out, it was the torque of the motor banging it into the headstock case.
Here are a few pics...
You can see in this pic that the motor is pretty buried inside the headstock housing. Opening up this lathe requires removing the spring from the reeves drive. Not too tough with a piece of all-thread running through the spindle, some spare 1/4" bolts, and a piece of scrap steel tapped to fit. Here's the outboard side, after removing the snap ring and releasing some of the spring tension:
Here's a look at the inboard side of the contraption. I slip a deep socket over the nut and turn it by have to tighten or release the spring on the other side of the headstock:
In this pic I've removed the reeves drive wheels. You can see the drive belt and a little bit of the toothed wheels it engages on. The bigger wheel is relatively east to get to, since the shaft it's on pulls out straight to the left in the pic. The little wheel on the motor shaft is the real target. Little bitty sucker and a real bear to get to.
After removing virtually every screw from inside the headstock housing, I got the motor out so I could remove the drive wheel. All that was left in the headstock was the spindle. I ended up chewing up the old drive wheel pretty badly in the process of heating and beating it off the shaft. At one point, I had heated the metal up quite hot, then while prying on the edge of the wheel a chunk broke off the lip, flew up, and went over my head and down the back of my shirt. Nothing quite like having burning hot metal chunks on your back. Did I mention I'm not fond of working on mechanical stuff?
Here's a shot showing the old wheel and the new one before I tapped in into place. The new wheel is on the left:
And for comparison, the old design big wheel vs. the new design. The new one is on the right, although it's not much different.
I didn't take any pics of the reassembly, nor did I take any of the piles of wood chips that resulted in the post-assembly testing, but suffice to say, the lathe is running better now than it ever has in the time I've owned it. No "clunk" when I turn it on, and no belt slipping, even when I manage to stall the motor by making intentionally excessive cuts. I don't really like tearing apart machinery, but for once, the end result is better than I expected, and the biggest surprise of all was no bloodied knuckles. (Bad words were still spoken, though. Especially during the burning metal on the back episode.)
Gotta run...there's a few dried rough-turned hollow forms calling my name.