# Chuck adapter plate for rotary table



## PeterT (Dec 9, 2016)

I got this 5" 4-jaw plain back chuck because it was the right size for my 6" rotary table. Its a Gator (Chinese) but 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 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. Tooling plate machines like the hard alloys (2024 or 7075) & holds tolerances well. 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 steel). 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.

Now with this under my belt I want to make a tooling plate with an array of threaded holes so I can clamp irregular parts & machine them on the lathe faceplate.


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## Dabbler (Dec 9, 2016)

nice work!


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## John Conroy (Dec 9, 2016)

That will be a handy piece to have!


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## PeterT (Dec 22, 2016)

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. I also ordered an import MT3 arbor with about 5" straight shank off ebay. The idea there is drop the bar into MT3 RT socket, lightly close the chuck jaws, clamp adapter plate in that position, hopefully pre-zeroed to RT center.

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 ok. 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 noticed 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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## John Conroy (Dec 22, 2016)

Nice job on that backing plate Peter.


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## Janger (Dec 23, 2016)

Is that a Bison-Bial rotary table? Looks pretty nice. Where did you get it?


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## PeterT (Dec 23, 2016)

Yup, Bison. Got it several years ago at healthy discount & currency was par and before Bison jacked their prices or changed NAm middleman, whatever the story was. They are stupidly expensive now. It hindsight I should have bought 10 & just stored them for investment - they would have outperformed most stocks 
http://www.ebay.com/itm/BISON-6-ROT...hash=item48452626f2:m:mNiLN1cm1UOMUyCfzr5CG2g

I wish the Asian copycater's would have picked this particular model/series to clone, it has a lot of nice features particularly for smaller mill setups. Low profile, big dial, detent stops for quick indexing, indexing plates available. Maybe it will happen one day. The tale goes that's how Gator got started, essentially grabbed Bison's dimensions & manufactured in far east at lower labor cost vs. Poland. I heard mixed reviews with Gator line, some liked them a lot & even interchanged parts with Bison. But also some (recent) QC issues. I decided to try the 5" Gator chuck & am totally satisfied for the cost. Put it this way, the 3J Gator was 275$U, the Bison is currently going for 1100$C at KBC. I don't have a surface plate yet but I put the chuck on my mill table & ran DTI across every jaw datum & surface. Its within 0.0005" (likely outside of accuracy of how I could measure). Same went for squareness gripping a dowel pin. Its at least as accurate as my machines & ability.

Sorry for the long answer. The RTs come up used on ebay once in a while, but not very often. There are dealers & occasional sales, but I think they all source from TMX = USA distributer. Ive heard Canada has their own distributer but there seems to be no advantage (or even disadvantage) as the prices can often be higher than buying from US & paying the dinger fees. One thing I would watch for. If Bison ever decides to drop making RT's or say only focus on the larger sizes, you will see inventory unloading sales. That's exactly how I got my 5" vise, they don't make that line anymore.


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## Janger (Dec 23, 2016)

Expensive! That doesn't begin to describe it.  I'll try other brands I guess!


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