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- Nov 27, 2012
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- 7,864
Amazingly, after I posted that, I finished troubleshooting and repairing a 8" Bison 4 jaw chuck, with an integral D1-4 mounting, for a friend. I went to test it on my lathe, which is also D1-4, and I cannot get more than one pin to engage with the cams at a time, and that is due to the spindle taper on my lathe will not letting it seat. It may have mounted to my lathe if I let off the pins one revolution each, but it still would have only been seating on the taper, not on the chuck face. I will have to take the chuck back to his shop and take a close look at his lathe before taking any action. I really hope someone did not trim the spindle taper on his lathe to fit the chuck... Well, I DID say in my post earlier this morning that THIS IS A COMMON PROBLEM! If you have a D1 series spindle on your lathe, you should take a very close look at how the chuck(s) fit the spindle and if they are registering on BOTH the spindle taper AND on the spindle face.
BTW, this is the first Bison chuck I have worked on, and it had some serious problems with fit from the factory. The tenons that guide the jaws were sloped high toward the chuck center equally on all three jaws, and required major effort to close the jaws. It is an older chuck, with zero other information on it other than the Bison badge inlaid in the face and 8/4 over 82 below the inlay. It must have been made on Friday evening or Monday morning, for sure.
I've had 2 Bison chucks now, well 3, but only 2 with D1-4 back plates. From the factory they fit my spindle absolutley perfect. However they are not more than 10 yrs old. Not sure about the older Bison stuff but my backplates are blanchard ground. Some people like to to skim the face the mounting surface of the adapter where it meets the chuck mounting face to true it up but I didn't even need to do that.
If the face of the D1-4 mounting surface does not meet the spindle face, sounds like someone might have taken a skim cut there on the Bison. Can you tell if it looks like it has a turned finish rather than ground? I've seen people do this & that creates a big problem as you were pointing out.
I had a Chinese D1-4 back plate that had this issue. No visible gap but it pulled too tight onto the spindle. Needed a mallet to release it from the taper. I fixed it by massaging the taper on the adapter with emory cloth. I still need to tap it ever so slightly only by hand to get it release but at least it's usable. I don't worry about it cause it's for the stock 3-jaw that came with my lathe that I only use when polishing or sanding parts (beater chuck).
Hopefully they didn't try cutting the taper on the lathe's spindle like you mentioned, that's a big no no in my book. I would never touch the taper or mounting face on my spindle except for light stoning if ever needed. With normal & proper use, the spindle should never need to but touched.