Three slot Rotary table direct to 3 hole 6" chuck?

I have a Vertex 8" table with 3 slots. I've been looking to see if anyone made a bolt thru chuck (6" 4 jaw independent) that had 3 holes to save a bunch of work and an inch of Z axis (Rockwell knee mill).

The chuck just needs to work hold mostly alum and delrin so I don't need much. I found an asian POS chuck with the right 3 hole config made of "semi steel" a term I have to google...
8" D1-4 4 Jaw Independent Lathe Chuck

but the chuck I found is not a thru hole just an internal socket on the bottom side.

So I had a couple ideas

First just remove platter from rotab and bolt thru to the underside of chuck and reinstall platter or
the other idea- pick up the holes they have and blow thru to use T nuts.

Just wondered if I'm missing anything basic before diving in. I'm self taught and what I don't know is impressive.

You should be able to drill just about any chuck to mount that way. O use the T-slots to hold it. Or a thin backing plate.

Generally 4 jaws have 4 mounting holes.

And also generally, chucks that can be bolted on from the face are 3X as
much as ones that are mounted from the rear, especially 3 jaws.
Same damn POS chuck, just a couple extra holes.

The answer is that "in general", and in my experience. You can drill
and counter bore your own face mount holes. Its actually a lot easier
on a 4jaw since there is no scroll in the middle. You can pretty
much drill anywhere you want.

That is exactly what I did to mount a 6", 4 jaw on my RT which has six radial slots. I purchased a new, import four jaw without any back plate. I did do a little planning on the hole locations but basically they are about 3/4" from the outer edge and at 120 degree spacing. It really was easy.

When it is mounted on the RT the bolt heads are on the front surface of the chuck but this has never been a problem - at least not yet.

Bobw said:

Generally 4 jaws have 4 mounting holes.

And also generally, chucks that can be bolted on from the face are 3X as
much as ones that are mounted from the rear, especially 3 jaws.
Same damn POS chuck, just a couple extra holes.

The answer is that "in general", and in my experience. You can drill
and counter bore your own face mount holes. Its actually a lot easier
on a 4jaw since there is no scroll in the middle. You can pretty
much drill anywhere you want.

Click to expand...

Bob that is incredibly useful info thanks for filling me in on the state of play with these things.

EPA, when you say "that is exactly what you did" you mean drilled the chuck out by boring holes to fit or blowing out the sockets that were provided?

And thanks for the genius attack, duh using a regular bolt upside down might prove easier that removing the table platter!

I'm seeing an old Cushman heavily built 4 jaw for the same amount as a new Sh@@rs, I don;t see that I need the bulk and reduced clearance with the older chuck- thinking for this the POS might be the right choice.

Bobw said:

Generally 4 jaws have 4 mounting holes.

And also generally, chucks that can be bolted on from the face are 3X as
much as ones that are mounted from the rear, especially 3 jaws.
Same damn POS chuck, just a couple extra holes.

The answer is that "in general", and in my experience. You can drill
and counter bore your own face mount holes. Its actually a lot easier
on a 4jaw since there is no scroll in the middle. You can pretty
much drill anywhere you want.

Click to expand...

Yep, did this with a Chinese 3 jaw to mount on my RT. The holes from the back went almost all the way through so I finished the job then countersunk them for the bolts.

Worked out fine.

PDW

Perhaps these adapter plates might work for you. I have a Phase II 8 inch with the adapter plate and a 3-jaw, it just all bolts up with no problem. Fairly thin, doesn't add much to the table height. https://www.mscdirect.com/industrialtools/phase-ii-chuck-rotary-table-accessories.html

I did not use the locations of the existing, threaded holes in the chuck. I wanted to be able to add a back plate at a later time so it could also be used on my lathe. With no back plate installed on the chuck, I drilled new holes from the front face at locations where it would not interfere with the four slots for the jaws and where the amount of CI was at a minimum. This worked out OK for my particular chuck but I do not think that other brands would be very different.

The back of the chuck sits directly on the RT with the long bolts being inserted from the front of the chuck. This is a very solid way to mount a chuck on the RT. And the centering does not need to be super precise because the part is centered in the normal manner using the chuck's jaws and a DI. I normally use an adjustable square set to a known distance that I have recorded to quickly push the chuck from all sides to the center and then tighten the bolts. Really fast.

I do not know exactly where that chuck is at the present time, but if I can find it, I will take and post some photos.

helmbelly said:

Bob that is incredibly useful info thanks for filling me in on the state of play with these things.

EPA, when you say "that is exactly what you did" you mean drilled the chuck out by boring holes to fit or blowing out the sockets that were provided?

And thanks for the genius attack, duh using a regular bolt upside down might prove easier that removing the table platter!

I'm seeing an old Cushman heavily built 4 jaw for the same amount as a new Sh@@rs, I don;t see that I need the bulk and reduced clearance with the older chuck- thinking for this the POS might be the right choice.

Click to expand...

Thanks for the link Video man, only prob is how parsimonious I am (cheap). The price is more than the chuck, shipped!

Cool enough, interesting to use an adjustable square for setting up. I use my regular square when I first set it down on the mill table and square up by eye on both sides of vise and it's very close. Avoids chasing indicator. I plan to get an MT3 arbor with a machinable head and turn it to .75 to to mate with an R8 - like Tom's Techniques describes on youtube. After that I'll indicate the chuck on the table, set it and forget it.

The chuck Ive found has no holes in front and since I need 3 holes I'll attach chuck to RoTab initially with tie downs, drill at 0, 120, and 240. I'm guessing there is enough slack with 3 bolts to get several thou for dialing in.
Appreciate your info

EPAIII said:

I did not use the locations of the existing, threaded holes in the chuck. I wanted to be able to add a back plate at a later time so it could also be used on my lathe. With no back plate installed on the chuck, I drilled new holes from the front face at locations where it would not interfere with the four slots for the jaws and where the amount of CI was at a minimum. This worked out OK for my particular chuck but I do not think that other brands would be very different.

The back of the chuck sits directly on the RT with the long bolts being inserted from the front of the chuck. This is a very solid way to mount a chuck on the RT. And the centering does not need to be super precise because the part is centered in the normal manner using the chuck's jaws and a DI. I normally use an adjustable square set to a known distance that I have recorded to quickly push the chuck from all sides to the center and then tighten the bolts. Really fast.

I do not know exactly where that chuck is at the present time, but if I can find it, I will take and post some photos.

Click to expand...