I just finished the backplate to mount the Sjogren collet chuck. I purchased a 1 3/4"-8 backplate from 800Watt one EBay. I was originally going to make the whole thing and even ordered the cast iron, but took the easy way out because I didn't have a internal threading tool large enough. I mounted the back plate in a four jaw and indicated it best I could with a tenth's dial. Both axially and radially. I turned the register to size, never had to use the telescoping bore gages before, what a pain. It was a hair under size so I finish ground it with a tool post grinder. I also faced the register with the grinder. Then I mounted it on the Clausing spindle and turned it to size a touch large. The thread in the backplate was very loose compared to the other tooling that came with the lathe. A tight fitting register makes it run true. I ground the OD and the face to give a smooth surface. Drilled and tapped the bolt holes. Chuck on the hot plate and backplate in the freezer. And it went together perfectly on the second attempt. I knew I was going to use the bolts to guide the backplate, but forgot to do it before the chuck grabbed the backplate. I can't be happier. I have about 2 10ths runout in the collet taper. I was worried this was not going to turn out well for my first attempt at doing this. Sorry the carriage is in the way of the chuck in the photo.
I don't think grinding is absolutely required, but it was available and gave a very smooth finish to the mating surfaces. I think this helped reduce runout.
I don't think grinding is absolutely required, but it was available and gave a very smooth finish to the mating surfaces. I think this helped reduce runout.
