How to mount a chuck to the same diameter rotary table.

[Spajo]

I am asking whether the problem I describe here has a known solution. I clearly made a newbie mistake. I bought a 4" (100mm) rotary table with the intention of using my 4 inch 3-jaw and 4-jaw lathe chucks on the table. I did not think through how to mount the chucks. In my situation, the chuck covers the whole rotary table and that prohibits the use of T nuts, even with a plate adapter. My little rotary table has four mounting slots in a cross pattern.

I have searched for a solution on this site, but did not find it.

I have one possibility. The table is attached to its base with a screw from the bottom. I drilled the hole all the way through the table and then tapped the hole - I think it is 3/8". The hole comes through where the T-slots meet in the center of the table. I can bolt a plate to the chick and then open the jaws and bolt the adapter to the table. Clearly it could unscrew when rotated the wrong way.

I'm hoping there is a better solution.

Spajo

 

[RJSakowski]

I had essentially done what you describe on my 12" RT. My 4" chuck had a backplate threaded for 1-8" tpi to fit my Alas 6 x 18 lathe. I made an adapter threaded for 1-8 tpi with a 3/8-16 tpi female thread. I used a stud from my threaded into a bushing at the bottom of the RT to screw the chuck and adapter to the RT. Yes, you do have to be careful not to unscrew the assembly but I have only had that happen once in thirty years.

In my case, I could have made a backplate to fit the chuck and utilized the tee slots but it would have to be removed each time I wanted to use the chuck on the lathe.

In your case, you could make a latger diameter backplate that fastened outboard of the RT table with an elongated tee nut that fit almost to the center. Not ideal but you should be able to fix backplate securely. Anither way would be to make an internediate plate about 5.5 -6" in diameter and fasten it to the RT. Tap holes outboard of the RT table and use a similar sized backplate to mount the chuck to the table.

 

[davidpbest]

I am asking whether the problem I describe here has a known solution. I clearly made a newbie mistake. I bought a 4" (100mm) rotary table with the intention of using my 4 inch 3-jaw and 4-jaw lathe chucks on the table. I did not think through how to mount the chucks. In my situation, the chuck covers the whole rotary table and that prohibits the use of T nuts, even with a plate adapter. My little rotary table has four mounting slots in a cross pattern.

I have searched for a solution on this site, but did not find it.

I have one possibility. The table is attached to its base with a screw from the bottom. I drilled the hole all the way through the table and then tapped the hole - I think it is 3/8". The hole comes through where the T-slots meet in the center of the table. I can bolt a plate to the chick and then open the jaws and bolt the adapter to the table. Clearly it could unscrew when rotated the wrong way.

I'm hoping there is a better solution.

Spajo

Not exactly your situation, but this might trigger some ideas. I like the suggestion above about over-length T-nuts, or some kind of strap clamping mechanism that goes into the rotary table t-slots and cinches down on a blackplate that's oversized.

https://flic.kr/p/2fj7oCv

 

[Spajo]

I had essentially done what you describe on my 12" RT. My 4" chuck had a backplate threaded for 1-8" tpi to fit my Alas 6 x 18 lathe. I made an adapter threaded for 1-8 tpi with a 3/8-16 tpi female thread. I used a stud from my threaded into a bushing at the bottom of the RT to screw the chuck and adapter to the RT. Yes, you do have to be careful not to unscrew the assembly but I have only had that happen once in thirty years.

In my case, I could have made a backplate to fit the chuck and utilized the tee slots but it would have to be removed each time I wanted to use the chuck on the lathe.

In your case, you could make a latger diameter backplate that fastened outboard of the RT table with an elongated tee nut that fit almost to the center. Not ideal but you should be able to fix backplate securely. Anither way would be to make an internediate plate about 5.5 -6" in diameter and fasten it to the RT. Tap holes outboard of the RT table and use a similar sized backplate to mount the chuck to the table.

I get the extended T slot idea. Thanks. Your success with the center stud is encouraging too. I could see that both ways could be useful.

 

[Weldingrod1]

Radial bolts and straps with two angled surfaces? Use 3 or more. You would need to machine mating features into both parts.

Sent from my SM-G715A using Tapatalk

 

[Spajo]

Not exactly your situation, but this might trigger some ideas. I like the suggestion above about over-length T-nuts, or some kind of strap clamping mechanism that goes into the rotary table t-slots and cinches down on a blackplate that's oversized.

https://flic.kr/p/2fj7oCv

Yes, thanks for sharing! My cheap table doesn't have a tapered hole, but I can see where being able to mount a concentric pin would be very useful and save a lot of time during a setup. A friend gave me some tools and I think there is a MT #2 or MT #3 cutter/reamer in the box. I've decided it would be worth the risk to try and modify the RT. Worst case, I buy a 6" RT and just say lesson learned!

 

[Spajo]

Radial bolts and straps with two angled surfaces? Use 3 or more. You would need to machine mating features into both parts.

Sent from my SM-G715A using Tapatalk

I get the general idea, and I can see right away that there might be several ways to arrange this type of clamping system. The trick is the radial bolt gives you access to the bolt head. Another plus for me is that the parts can fit under the chuck, keeping things small.

 

[f350ca]

With careful placement I managed to sneak 4 holes through an 8 inch Chinese 3 jaw to mount on my 8 inch rotary table.



Greg

 

[mickri]

You are part way to an easy solution. Make a backing plate that screws onto the chuck. Either machine or attach tabs to the bottom of the backing plate that fit into the slots on the RT. Bolt the chuck and adapter plate to the RT as you described in your first post with a threaded washer that fits the inside of the chuck. Thread the bolt to the washer. Then thread the bolt/washer into the RT. The different TPI on the chuck and the 3/8 bolt will work against each other preventing the chuck from unscrewing.

I made a similar thing for my lathe to keep chucks from unscrewing when running the lathe in reverse. I call it a "chuck keeper." I welded the washer to a 1/2" rod that runs through the spindle.

 

[Just for fun]

How about something like this? You would lose some Z height though.