8x12 Mini Lathe Timing Pulley Lubrication and Replacement Belt Size · Jan 29, 02:09
Our stock 8×12 minilathe belt was fraying around the edges and was getting close to shredding apart. Instead of taking further chances on its useful life without a replacement, we looked at the various catalogs for a suitable replacement v-belt. The closest imperial belt (since MSCDirect didn’t have metric belts) was a 3L size with a 290 length. Once we installed it, we found it to be rather tight. We went ahead and posted a message on the minilathe Yahoo! group:
Original email:
“
fyi (can’t remember if this had been mentioned before) – we just installed a 3L290 belt on our 8×12 to replace the stock belt that was becoming frayed and twisted. it’s not the same depth as the stock belt, but it works just as well.
“
Well, we think that it’s better to get the next size up or go metric with the original or OEM replacement. The reason is that due to the tightness of the belt tension, it causes premature wear of the timing belt pulley and results in binding (seizing) of the non-bearing’d shaft and pulley.
We found out the hard way when the lathe all of a sudden started making violent stripping noises.
After removing the timing pulley from the lathe (you have to remove the back of the electric switch box to access the two screws (of four total) that hold the motor cover in place. Once the sheet metal cover is removed, take the timing pulley out and remove the remove the circlip pin that holds the shaft onto the step pulley assembly:
Since the shaft was seized onto the pulley, we had to put it under a 2-ton arbor press and press it out:
Next, we clean up the inside of the pulley and the outside of the shaft with acetone and then lubricate liberally. Since our use of white lithium grease (and regular lithium grease) ended up seizing up on us again (the longer replacement belt is enroute), we had to perform this procedure twice. The shaft and inside of the pulley was marred a bit, so some fine wet-dry sandpaper was used to smooth down the little globs of metal. The second time around, we just used oil, not grease.
Still, the moral of the story is that while a 3L290 belt works in a crunch, a longer belt is more appropriate (since the lathe has a tension mechanism to take the slack out of a long belt).
Update! We bought a “Bando” brand 3L300 and it was too loose in 210 RPM configuration even with the tensioner in max swing. We haven’t tried it in other speed configurations yet. Does this happen to your 8x?
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