My rotary table wants a chuck

[RandyWilson]

I have been thinking out my options on installing a chuck on my rotary table. It's an antique Excel 12" table with 1/;2" T-slots and a 1" center pilot. Looking around it seems the standard way is to make a backing plate that bolts to the table, then you bolt a chuck to the plate. This requires a chuck that mounts from the face side with through-bolts. I have spied on some suppliers and it seems that most offer only tiny chucks to fit their tiny rotary tables. A 3" vise on a 12" table seems a bit silly. To get into anything of decent size will take a fair chunk of bitcoin.. I'm a certified cheapskate. So....

I do have a pile of chucks. One has a 1-3/4-6 mount. It's from the dividing head. The rest are 2-3/8-6 from the lathe. There are four of those from 5" to 12", basicly small and large in 3 and 4 jaw. I also have a 3" long chunk of 5" round in 1045. S I'm thinking of making an adapter with a 1" dowel for center, slots for four T-nut mounts, and a 2-3/8-6 spigot to mimic the South Bend spindle nose. The down side is that is several joints, each with a potential accuracy loss. Table to adapter, adapter to back plate, back plate to chuck, chuck to ...... The upside is I could move work in the chuck from the mill to the lathe and back.


The questions: Is the 1045 a good choice for the adapter? I don't want to heat treat it and risk warpage, so it would be annealed 1045. And the more important question. Am I missing an easier way to do this that doesn't require cubic dollars?

 

[silverhawk]

You simply want material that is solid enough and rigid enough, so 1045 should be fine.

One thing to remember is that spun-on chucks on a rotary table have a tendency to son off of the table depending on the direction/position of the mill cutter. If you do a chuck adapter to an existing backplate, you will always need to make sure and be aware of the cutter direction potentially loosening the chuck and losing reference to the part.

To get around this, you would need a way to lock the chuck/backplate to the adapter to prevent spin unless you are changing chucks out.

joe

 

[JRaut]

I just did something quite similar to what you're describing.

I've got a 12" rotary table with a MT4 center hole.

My lathe is an old Logan with a 1 1/2"-8 spindle nose.

So I made up an adapter, allowing me to bring my chuck directly from the lathe over to the rotary table.

The adapter would, of course, be pulled right out of the MT4 hole once the chuck is seated against the face of the rotary table, so I tapped a 1/2"-13 hole in the back side of the MT4 taper end and use a draw bolt to hold everything in place. No photo of that, but I think you'll get the idea.

I used 4140 prehard. I'm sure 1045 would work too

 

[silverhawk]

I just did something quite similar to what you're describing.

I've got a 12" rotary table with a MT4 center hole.

My lathe is an old Logan with a 1 1/2"-8 spindle nose.

So I made up an adapter, allowing me to bring my chuck directly from the lathe over to the rotary table.

The adapter would, of course, be pulled right out of the MT4 hole once the chuck is seated against the face of the rotary table, so I tapped a 1/2"-13 hole in the back side of the MT4 taper end and use a draw bolt to hold everything in place. No photo of that, but I think you'll get the idea.

I used 4140 prehard. I'm sure 1045 would work too

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Does your chuck backplate offer a way to keep it from spinning? I see the flats on your back plate, does something press against that surface when milling?

joe

 

[JRaut]

Not yet....

I've only used it for light work so far, but you brought up an excellent point re: the chuck potentially spinning.

I'll add that to my to-do list...

 

[RandyWilson]

I hadn't considered that, thanks. I have a few preliminary thoughts on using grub screws in a non-critical area of the backing plate. Or I could just buy a gaggle of left-handed end mills. I'll have to study the four backplates and see what scheme pops into my coffee addled brain.

 

[Janderso]

I'm getting ready to do the same thing. (mount the chuck to the pallet) , I'm just wondering how you hold position once you center the Chuck on the pallet. I can see how to center it, use transfer screws to mark center drill positions, drill and counter bore from the backside.
I hope that would be accurate.

 

[Janderso]

I'm getting ready to do the same thing. That was my plan, I made the pallet, I'm just wondering how you hold position once you center the Chuck on the pallet. I can see how to center it, use transfer screws to mark center drill positions, drill and counter bore from the backside.
I hope that would be accurate.

 

[GL]

Depending on how often you need it, or how many chucks are moving around between machines, using clamps to locate a chuck on a rotary table works fine. Not as quick to locate as adapted chucks, but don’t lose any Z, it won’t back off a threaded spindle, and it’s cheap.

 

[projectnut]

A while ago I purchased a 10" chuck to use between my 8" Eron rotary table and my 12" Index table. I chose a chuck that has through holes to mount the backing plate to the chuck. Rather than make a new backing plate I just removed the original backing plate and use the through holes in the chuck with T nuts in the slots on the tables. It takes a few minutes to center the chuck on the table, but once in place I haven't had problems with it walking to one side. So far I've only used the combination a few times, and only for smaller parts. I haven't tried any heavy duty hogging.

Here's the style chuck I chose:

6" CUSHMAN 4 JAW LATHE CHUCK, FLAT BACK | eBay

Find many great new & used options and get the best deals for 6" CUSHMAN 4 JAW LATHE CHUCK, FLAT BACK at the best online prices at eBay! Free shipping for many products!

www.ebay.com

This one is a Cushman. Mine is a Skinner. I purchased it at a local used equipment dealer for less then $100.00

Here's a similar 8" rotary table:

Palmgren Machinist Milling Drill Press 8" 2 Axis Slide Rotary Table Nice Cond. | eBay

<p dir="ltr">Palmgren Machinist Milling Drill Press 8" 2 Axis Slide Rotary Table Nice Cond.. Condition is Used. Missing one handle. Shipped with USPS Priority Mail.</p>

www.ebay.com

This one is a Palmgren. Mine is an Eron. They're identical except for the hand wheels.

Here's a picture of my Index brand 12" rotary table before it was cleaned and put into service. Note I can only use 2 T nuts to hold the chuck to the table due to the slot configuration: