I've neen getting pretty antsy to actually cut something on my new machine so I went out to the shop last night. I had an old quartermaster triple disc racing clutch laying around that I had nearly tossed in the trash several times. The discs were shot, the flywheel was heat marked and shiny and the pressure plate and floater plates were warped. I started out thinking I would just see how well the flywheel would turn, and if it was history I would just dump the whole thing. The flywheel has a step in it, so i measured that depth first and then simply gripped it in the 3 jaw chuck jaws. I set the lathe speed at 80 and touched off on the highest point of the face and set my DRO to zero. I made my first pass by hand and was surprised how easy the hard surface cut away. On my second pass I started at the center and cut to the outside under power feed. With the power feed gearbox in low range and the spindle at 80, it moves pretty slowly, a lot like a brake lathe. I took 0.010 off the first pass, and then 2 more of the same until I had a completely fresh surface. I then turned the step back by 0.030 so the relationship would remain the same. That all went pretty quick, so i moved on to the pressure plate. It was also warped and had the heat marks. The ID is 5.25" which is right at the limit of the 3 jaw chuck, but it gripped fine and a couple of passes there got me a fresh surface. The floater plates are the real challenge as they warp like a belleville spring, probably due to the heating and cooling differential from the inner and outer diameters. They are also made from a harder material than the flywheel and pressure plate. They really need to be ground, but the amount of warpage makes that impossible- by the time you grind both sides they would be way below the wear limits. I decided to try and flatten them in my press between 2 sheets of 1/2 " plate. They would flatten, but then spring right back- in order to take a set they need to go beyond the 0 point. I traced out the outline of the floater on one of my steel plates and tacked a series of 1/2" nuts around the diameter to support the outer edge of the plate. I then found an old piece of pipe that was about the same diameter as the inside and turned it so it was a nice snap pit. I set the plate with nuts in the press and the floater on top, then put the pipe in the center diameter and pressed it until the plate went beyond the zero point. After a few tries I got both floaters pretty flat, but they still were not perfect across the surface and are too hard to turn. Now I needed to figure out a way to grind them. The floaters have 6 notched ears around the outside which engage the pressure plate and keep them from spinning- these ears do not make contact with the discs, so I decided to drill a hole through each one and countersink them for some 10-32 flathead screws. This would allow me to bolt the disc flat to one of my 1/2" steel plates and then clamp it to the mill table. Drilling 12 holes and countersinking both sides proved to be time consuming because of the hardness, but i got it done and drilled and tapped the 6 holes in my steel plate. I have a lot of small stones and carbides I use for head work, but the floaters called for a larger stone. I had a grinding wheel for my grinder that looked good enough to try, and I put it in the mill head with a 1/2" collet. I set my mill speed to 2400 and turned it on just to see how it all spun. When I was sure nothing was going to fly apart, I brought the mill head all the way down and locked it in place then moved the quill down until the stone mede contact with the floater. At this point I am a bit nervous that it might grab the plate or some other disaster, so i found an old piece of lexan windshield and held it up in front while I made a pass by hand. No big disaster, so I set my DRO to zero and set the cut a 0.001 and let the power feed do the work while I held the lexan up with 2 hands. End result was that it took about 4 passes at 0.001 to get a full surface on each side. I might have been able to take more each time, but I have little knowledge of grinding and how much those wheels can take. After I finished, I measured each disc with a caliper and I was within 0.002 all around in thickness. They were just above the minimum spec that quartermaster gives, so with 3 new friction discs I should be good to go. This whole process took about 4 hours, but those Quartermaster clutches sell for over 700.00 new, and now all I need to buy are the 3 friction discs at 60.00 each. So I made myself about 500.00 for my 4 hours work. Not bad for my first project.
Say that 5 times real fast