4-jaw for rotary table

[Marty Feldman]

Picked up, for under a hundred, a nice Bison 4-jaw, minus backing plate, for mounting on my rotary table. The only mounting modification needed is extending the length of each of the 4 t-slots in the top of the RT table by about 1/4" to allow the 4 t-nuts to slide inward enough to engage the through-studs in the chuck body, a straightforward milling operation.
-Marty-

[SteveHGraham]

Nice work. I put an 8" 4-jaw on my 8" table by making special T-nuts.

[SteveM]

Nice that you could find a chuck where the mounting plate bolts come in from the front instead of the rear.

Steve

[BadDog]

Coming from the front is very typical for "plain back" 4 jaw chucks. I've got an 8" Cushman 4 jaw that I use on my larger rotary table, and 6" Pratt Burnard 4 jaw that I use on my 6" indexer. Both are plain back and mount the same way, as do the plain backs I use on my lathe, but in that case they register and bolt onto a D1-6 adapter. Some are also actually "A" chucks, which always bolt from the front. My 12" Buck is actually an "A" mount chuck where I just turned the required "A" spindle nose on the front of the D1-6 adapter. Bolting from the back is common when dealing with scroll chucks (2, 3, 4, or 6 jaw) to avoid the scroll plate.

[SteveM]

All my 3-jaws mount from the rear and all my 4 jaws mount from the front.

Steve

[dgoddard]

Nice that you could find a chuck where the mounting plate bolts come in from the front instead of the rear.

I did that and posted it a few years ago. I had to make some special T-nuts too. The were a small metric size and Ihad to make them with round ends on one side as I used them in a different setup as well and in that case I had to get them all the way into the center. The 8 inch chuck I used was not as thin as the one Marty had. so by the time I had the chuck on the rotary table it was pretty heavy to lift both of them. I made a "pilot piece that plugs into the back of the chuck and into the top of the table to align them. To get it on and off the mill, Ihave a shelf where I store it and a cart the same height as the shelf So I can slide it off of one on to the other. I can raise or lower the mill table to match the cart so lifting is minimized. I also bent a piece of rod into an eye bolt that threads into the pilot piece. It makes a nice handle especially if the chuck and rotary table are oily. Grizzly had (has?) a whole line of such front to back bolted 4 jaw chucks.