Sunday, June 30, 2013

Getting Started: Table Saw Repair, Part I

First, I should probably explain the name "Ghetto Luthier." In the strictest terms, a luthier is a lute-maker, but the word has come to encompass the makers of all stringed instruments. I'm going to give it a shot. but I'm going to start by making Cigar Box Guitars, which are not the high-rent district of luthierville. Maybe some day, if the cigar box versions work out, I'll make a few "real" guitars. OK, on to the table saw.

About ten years ago or so, I got an ancient Craftsman table saw from one of my neighbors. His wife wanted it out of the garage, and free is a great price, so I snapped it up. It served me well until one fateful day about five years ago when the drive pulley fell off the saw shaft. This is an unusual situation, because normally you need a gear puller to remove it. Unfortunately, this one just fell off by itself.

Since this sort of thing 'never' happens, the shaft and pulley are nearly impossible to get to without completely dissembling the table saw. As a result I sort of ignored the problem for years by doing work with my other saws that would be better done on the table saw. But now I really need to get the table saw working again for my luthier work.

Step one: Find a Woodruff Key that fits. When the pulley fell off years ago, there was very small part that I never found, the woodruff key. It's a little bit of metal, half-moon shaped, about 1/8th of an inch thick and maybe 3/4 of an inch wide. The rounded part of this "key" locks into a rounded depression in the shaft and a notch in the pulley wheel slides over the straight side so that the three effectively become one. When the wheel took a dive, the key flew off into the sawdust somewhere in the garage and I never found it. First I checked for a replacement part Home Depot. They had no idea what I was talking about. So I checked at McLendon's Hardware. They had them, and knew right where they were, but the fit is very precise so it took me a couple of trips to the store to find exactly the right one.

Step two: Replace the Woodruff Key. This involved a lot of cursing. I eventually found that the best strategy was to gently flip the table saw upside-down so I had better (but not great) access. There is a small setscrew on the pulley to secure everything, but the shaft, the key and the pulley all "friction fit" together. After dropping and misaligning several times I finally got the key partially set in the shaft by compressing it into place with pliers, then finished by tapping it into place with a small ball-peen hammer.

Step three: Reset the pulley. This involved a only a bit of cursing. If the saw was fully disassembled I could just tap it into place with my hammer. No such luck here. Using a couple of scraps of plywood (I broke the first one by applying too much pressure) I finally coaxed the pulley into place on the shaft. Tightening the setscrew was child's play. I hooked up the v-belt that connected the motor pulley to the drive pulley for the saw blade and I was ready to rock.

I made about five cuts before I heard the annoying sound of a pulley falling off the saw, and the blade stopped turning. Arghhh! I walked around to the back of the saw, picked the pulley up off the floor and looked inside the saw. My newly-replaced pulley was still there, but this time the pulley on the motor shaft had fallen off. For whatever reason, the motor pulley has a straight spline rather than a woodruff key, or at least it used to. The spline flew off and now I can't find it. This is not starting auspiciously.