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Chuck Adapter Plate For Rotary Table

petertha

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#1
I bought this 5" 4-jaw plain back chuck because it was the right size for my 6" rotary table. Its a Gator & seems pretty decent for the cost. Here is how I machined an adapter plate to marry the two. I decided to turn a close fitting male boss protrusion that fits the chuck recess as opposed to flat surface relying on bolts & friction to stay put. I'm not convinced its 100% necessary because right now that's how the plate attaches to RT platen anyway but figured it cant hurt either. If I do experience any plate movement I have one more trick - an MT stub located in the RT bore with a machined disc that fits the center hole of the plate.

Ideally I would have preferred cast iron or steel for durability but I had this 5/8" cast aluminum tooling plate stock so figured I'd give it a go. I'll just have to have to be careful not to ding it up, but accuracy wise it turned out decent. I was a little apprehensive about turning the rough stock with those standoff donuts sandwiched between the faceplate (another reason I was kind of chicken of iron). It went clunkety-clunk until stock became round but nothing moved or flew off. Now I'm more confident CI or steel could be done the same way as long as the cuts & speed was moderate.
 

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petertha

H-M Supporter - Premium Content
H-M Supporter-Premium
#2
After seeing how 5" Gator 4-jaw chuck turned out on 6" RT as an assembly stack, I decided I liked it a lot & ordered the 3-jaw. Its a bit of a nice-to-have vs. need-to-have but, 3J makes for rapid RT setups where centering within a couple thou is ok. I also want to make a 3J adapter plate for mill table (or maybe vise held) for holding circular objects because its so compact.

The 3J shares the exact same RT adapter plate because both 5" plain backs have identical recess ID. But according to specs, the 3J has 3 M8 mount holes whereas the 4J has 4. I was aware of this when I drilled the 4 holes & considered doing the 'shared' pattern at that time. But I've gotten burned on this issue before where there was a typo in the spec sheet, either bolt pattern or bolt size. Turns out all was good specs wise, so that meant I had to re-indicate the adapter center, re-establish alignment of a pair of 4-bolt pairs along mill X or Y axis & drill the new holes on their coordinates. That would have been better to do in one operation but it worked out great. Just mentioning in case anyone decides to go down this path.

What I really like about this combo is lots more headroom for my mill which was a problem before. Pic shows ~6" from drill chuck bottom to chuck face top & I probably have another couple more inches to raise the mill yet. I'm very pleased with the quality of Gator especially for the price. I don't have a surface plate yet, but just resting chuck on my mill table & traversing the dial indictor on every jaw surface, its within 0.0005" unloaded. I have one small issue & that's the insignia plastic lens looking part stands proud of the chuck face. So if you happen to put a spacer parallel across that it would not sit correctly. It doesn't look like it can be pressed further so either will have to remove or sand flush.
 

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