Wednesday, December 10, 2014
During one of my dumpster diving forays at work, some time ago, I happened across this ancient 42 inch slip roll. I grabbed it and tossed it into the back of my truck, very pleased with my find. Upon further examination, I discovered why it was tossed. One of the gears was missing that operates the rollers. I stuck it in the shop and figured, I'll fix it someday. Someday arrived. I could have taken the easy way out and ordered a gear from Boston Gear or Browning, but that's no fun. Realizing that all the gears are the same, I took one of them and cut a blank on my lathe the same diameter. I have accumulated a few involute gear cutters, but I did not have one in the correct pitch. I took a piece of HSS tool stock and ground it to the shape of the tooth. I was able to get it close, but it is not perfect. If it was a gear for a transmission it would howl like a banshee, but for a hand cranked machine, it's good enough. I clamped the cutter in my fly cutter and mounted it on the mill spindle. I have a large dividing head, but I had never used it, so some self educating was in order. It turns out to be pretty basic math. No algebra or trig, just simple fractions. I put the blank on a mandrel and put it between centers on the dividing head. My math told me that each cut is three revolutions of the dividing head crank plus three holes on a 39 hole plate. So off I go. Thirteen cuts later, I have a new gear. The teeth are a bit wonky because of my poorly ground cutter, but when I assembled the roller, everything works as intended. Some will say that an aluminum gear is about as good as one made from clay but as often and as hard as I will use the machine, it will last forever. While I was at it, I sandblasted all the small parts. I also chucked up the rollers in the lathe and sanded off all the rust. I reassembled it and put on a few coats of hammertone paint. Should be good to go for another 70 or 80 years. Now, I just need a spot to put it. The sucker weighs a ton. A 48 inch slip roll sells new for around 15 hundred bucks. This one cost me the price of the fuel to get it home. I had to go home that day anyway, so it was a wash.