06-20-2016, 07:10 AM
I've used 6-jaw chucks before but never really felt to be lacking because I don't own one. My D1-6 mount 10" Pratt-Burnerd Super Precision 3-jaw chuck runs with less than 0.0005" runout with anything it can hold, regardless of size or orientation of the top jaws. When I did use the very nice 6-jaw chucks I found that not all the jaws exert the same pressure. I know this may have been just the one I was using. The way I found this was using 6 little squares of 0.003" brass shim stock to protect the finished surface I was clamping and two of them (not opposite each other) had fallen out while I was working the part.
When you only have three, all have to be clamping at equal pressure. ;)
When you only have three, all have to be clamping at equal pressure. ;)