I bought HF's 4 inch universal four jaw chuck to build my own indexing fixture.
On receipt, the jaws and scroll were way to tight and a little unvevn. Now I suppose a nice tight chuch helps you hold parts accurately, but this thing took all the rubber out of my forearm just running the scroll in and out to change jaws. I decided to lap it in.
I removed the jaws and ran the scroll at some hundreds of rpm for minutes using first my cordless screwdriver, then, when it showed promise, the drill motor. Got it loosened up nicely.
Then I removed backing plate, pinions, and scroll, and started lapping the jaws in by hand with 150 grit Clover brand lapping / grinding compound. Silicon Carbide. It proved _not_ to embed, something I was terribly worried about, since that would accelerate wear tremendously.
I tried each of teh eight jaws in the natural positions in each of the four slots. I made a chart. Four were most loose, and all on the 2-4 axis, so I started with them on that axis. Whew. At first it was tough going and I used the rubber hammer a lot. Then I learned that then need not go more that 1/3 out beyond the edge of the chuck. So I would bang them through to the other side then back. Once they got loosened up a lot, I was able to apply finger force down low on the chuck in between the guiding faces. That seemed to help. It was easier.
Eventually I got the loose jaws lapped in the the ways straightened. Let me add I pushed the jaws all the way through the 2-4 axis, not just to the center, and I wan't just using the 2 and 4 jaws either. I started work on the others and then loosened up.
I though of designing a fixture to hold the chuck and loosely pivoted arm to move each jaw back and forth to ease the effort and reduce rubber-hammering.
Now all four are pretty smooth, and I will leave the minor tight spots to avoid loosening the overall fit.
I got ready to do the 1-3 axis and got an inspiration. Turned to the MSC Big Book and found 50 mm long 20 mm dowel pins to fit the chuck bore. Let's 35mm work height plus 3/4 stock thickness, that would do. So they're sending me one as a sample! And I will cut a piece of 3/4 Formica coated chipboard, and make a hole for the pin. Then I'll clamp the board to the bench and that will ease things up even more.
So if you want a good chuck, buy one, but if you want to lap the jaws in yourself, buy HF. Cheap is as cheap does.
Actually the specs on the chuck looked pretty impressive. I think it can grip rounds, too! The scroll pitch is 6 mm so you can make 12 mm throw crankshafts (maybe) and grip rectangles that are in increments of 6mm. Too bad it's not 1/4 inch. That could be pretty useful here.
My senior project at ODU: Google Groups, then "dgoncz" and some of: ultracapacitor bicycle fluorescent flywheel inverter Equipped with BoBike Mini removable child seat, too!