Mounting a 160mm chuck on a 150 mm rotary table?

[DICKEYBIRD]

Awright then...I received my (early) Father's Day present Grizzly 150 mm. rotab and it looks very nice; better than I expected for the price. http://www.grizzly.com/products/h7527

It looks like it's a good match for the X-3 and mounts up great. Question: I want to mount my 160 mm 4 jaw chuck on it and am at a loss as to how to do that efficiently.

(1) The pics show one way I came up with ie: take the lathe adaptor plate off the chuck and just drill 4 - 8mm holes right through the chuck and bolt it down on the rotab using the t-slots in the table and long 8 mm bolts. 4 square keys bolted to the back of the chuck would prevent it slipping under load. Prolly be a be-otch to get 4 keys precisely machined and mounted so that the chuck drops in without a bunch of slop. I reckon 2 keys would be easier now that I think about it.

(2) Machine the keys deep enough to reach down into the slots and make them expandable with a tapered bolt of some sort so that it could lock down firmly without drilling holes in my chuck.

(3) Any other ideas; what say ye-all?

[lbender]

One method from Sir John

http://bbs.homeshopmachinist.net/showthread.php?t=20653

[DICKEYBIRD]

Yep, that'll do her! Thanks a bunch for the link.

I'm going to try to add Sir John's clever mount method to the existing chuck backplate adapter to keep from making an entire new one. My lathe is a little anemic for that task...although I guess my new rotary table could assist my mill in hewing out a big ol' round chunk like that!

[platypus2020]

Have the same rotary table, but with 6"-3 jaw chuck, used a 6" #2mt x #2mt ext, that was precision ground on the outside of the socket to center the chuck. Put the ext into the rotary table, the tighten the chuck to the outside of the socket, then tighten the mounting bolts into the t-nuts. Then checked with a dial indicator, work perfectly.

[Paul Alciatore]

Dickie,

I did something similar. I have a 10" table and wanted to mount my 6" four jaw on it. I drilled 3/8" holes clean through the outer wall of the chuck and use long bolts to hold it down. My table uses 3/8" tee nuts so I just use three from the hold down set I purchased.

As for centering, it's a four jaw so centering is not critical. I wrote down the measurement from the outside of the table to the centered chuck and I use a caliper to set an adjustable square to that length. Then, when the chuck is loosly fastened, I simply push it toward center with that square. from all sides, till it stops moving. Then I tighten the bolts. Only takes a few seconds. You don't have to be too picky, because the work still needs to be centered anyway.

[oldtiffie]

Mounting chuck on Rotab

Awright then...I received my (early) Father's Day present Grizzly 150 mm. rotab and it looks very nice; better than I expected for the price. http://www.grizzly.com/products/h7527

It looks like it's a good match for the X-3 and mounts up great. Question: I want to mount my 160 mm 4 jaw chuck on it and am at a loss as to how to do that efficiently.

(1) The pics show one way I came up with ie: take the lathe adaptor plate off the chuck and just drill 4 - 8mm holes right through the chuck and bolt it down on the rotab using the t-slots in the table and long 8 mm bolts. 4 square keys bolted to the back of the chuck would prevent it slipping under load. Prolly be a be-otch to get 4 keys precisely machined and mounted so that the chuck drops in without a bunch of slop. I reckon 2 keys would be easier now that I think about it.

(2) Machine the keys deep enough to reach down into the slots and make them expandable with a tapered bolt of some sort so that it could lock down firmly without drilling holes in my chuck.

(3) Any other ideas; what say ye-all?

First of all - that was a very thoughtful gesture from your family - you are a lucky man indeed.

I recall the discussion of this topic on another thread.

I have the exact same 6" Rotab and can say that it will do all that you want it to do - with the usual caveats of course.

Just a couple of comments.

I am highly cautious about drilling through chucks, but have both seen it done and advised on this and other HSM threads that it not only can be done but that it is successful, I defer to this advice.

Drills by their nature can and do "wander" to the the extent that the "exit" can be considerably "off' the intended point of exit - not always but enough to give cause for concern or caution. To cancel that problem out, I'd drill from the back face (ie the back or bottom of the chuck) as the holes there will be accurate and if the holes do "wander" it will only be a the "exit" on the top face which while unfortunate will only be a "cosmetic" problem that any sma**ar*e that comes in will never notice and won't be aware of it unless you tell them.

I am also sure that your family will be thrilled to bits to see that you appreciate their gift and the thought and resources that they put into it and that you have and will use it with enjoyment for a very long time.

Well done.

[motomoron]

Here's an 8" square of Teflon on my weedy little Atlas/Craftsman 8" rotary table. I threaded 2 3/8" holes near the ends of a 12" length of flat stock and slid it through the through the T-slot...

[DICKEYBIRD]

Ahhh, purty clever...I'll have to remember that one. Actually, It'd probably work fine too to use 4 shorter pieces tapped on one end so the work would be clamped down even better/flatter.

[DICKEYBIRD]

Why is it when you get new tools, you always have to make new stuff to get to where you can actually use them?

I had to make up a DTI mount to dial in the 4-jaw chuck back plate so I could drill the holes needed to utilize El Stevo's (Sir John's) patented mounting system. I made the mount from from inkjet printer rod, some 1/2" square CRS and a wingnut. Works pretty good and seems to be adjustable enough to dial in future projects on the rotab.


Then I made up the 4 tee-nuts and drilled the backplate per the El Stevo method but I hit a wall when it came time to mark & drill them and cut the taper on the screws. An hour or so of CAD work playing around with angles and hole sizes and I finally ended up doing almost exactly what Sir John described. The length of the bolt and it's diameter at the small end are pretty critical. With careful CAD work and measuring of the parts I somehow got it right on the 1st try! When I tested the 1st one, the witness mark on the screw was right in the middle of the taper. A blind hog gets an acorn once in a while!


You can hardly tell how it's mounted...very clean Sir John! Plus it'll pop back off easily and switch back to the lathe quickly.


Last pic shows that my other worry was unfounded...the headroom left after a rotab, chuck and adapter is bolted down on the X-3 table. Seems to be sufficient for my work. I will have to take it easy 'cuz that column just has to be a little springy with the head up that high.


I am concerned with this method about the wear between the tapered screws and the edge of the tee nuts. I'll use moly grease and take it easy on the torque and hope for the best.

Oh yeah, the rotab w/chuck is HEAVY!