Union 3 jaw chuck

[FordMustangKingCobra]

I recently received this Union tool Co three jaw Chuck for my metal lathe and I'm trying to determine the best way to go about adapting this to my lathe, currently the spindle on my lathe is a 1-8tpi thread, the chuck and it's current form uses a 2-1/8 5tpi thread, would it be better to make a spindle adapter or cut the welds off the flange to make a backplate?

 

[no704]

Make a backplate. No need for the extra complication or stick out.

 

[larry_g]

I'm not seeing any welds that need to be cut. It looks like someone welded a spindle nose protector to a disk of steel making a backing plate. With the screws removed from the front the current backing plate should separate from the chuck. Then make or purchase a new backing plate..

One example of what is available. Scroll to the bottom of the page.

3.93" Fully Machined Threaded Back Plate with 1 x 8 TPI For 3 or 4 Jaw Lathe Chucks

www.shars.com

There are other tool vendors who also sell similar backing plates.

lg
no neat sig line

 

[whateg01]

I'm not seeing any welds that need to be cut. It looks like someone welded a spindle nose protector to a disk of steel making a backing plate. With the screws removed from the front the current backing plate should separate from the chuck. Then make or purchase a new backing plate..

There are no screws in the front of the chuck.

 

[slowtwitch73]

You'd probably be better of getting a new import chuck.

 

[FordMustangKingCobra]

There are no screws in the front of the chuck.

Oh I took those screws out

 

[FordMustangKingCobra]

Also here's the temporary back plate I made for the chuck to me it looks pretty good run out wise but let me get a second pair of eyes

https://imgur.com/a/NFV2b2h

 

[whateg01]

I can't tell if that video is real time or not, but with a threaded back plate, it's generally not advisable to stop the truck spinning quickly because it can unthread itself

 

[FordMustangKingCobra]

I can't tell if that video is real time or not, but with a threaded back plate, it's generally not advisable to stop the truck spinning quickly because it can unthread itself

It is real time, its two different spindle speeds

 

[larry_g]

The only way to check runout is to put a test bar in the chuck and measure it there. What you see is not worth much. I have to assume that since you have a machine tool you also have an indicator to measure what your doing...

 

[FordMustangKingCobra]

The only way to check runout is to put a test bar in the chuck and measure it there. What you see is not worth much. I have to assume that since you have a machine tool you also have an indicator to measure what your doing...

I have both a dial indicator and a test indicator, although a test bar is on my list of things to make/buy.

 

[alfadan]

Before putting too much work into this, tighten something in the jaws tight and check for bell-mouthing. Those jaws look pretty worn.

 

[FordMustangKingCobra]

Here's the chuck disassembled, it's quite clean

Here's the back of the chuck, does anyone recognize the mount?

 

[FordMustangKingCobra]

The adapter mount that was welded

 

[FordMustangKingCobra]

Before putting too much work into this, tighten something in the jaws tight and check for bell-mouthing. Those jaws look pretty worn.

I can buy new jaws for it if needed, i just need to measure them

 

[MShaw]

Beyond new jaws the scroll could be worm as well as the fit between the scroll and the body. Also, the slots the jaws run in can wear. The first two will affect runout and the last will affect bellmouthing of the jaws. Check everything carefully before you start putting money into it,

 

[FordMustangKingCobra]

Beyond new jaws the scroll could be worm as well as the fit between the scroll and the body. Also, the slots the jaws run in can wear. The first two will affect runout and the last will affect bellmouthing of the jaws. Check everything carefully before you start putting money into it,

I'll look up how to check for wear

 

[slowtwitch73]

Get something straight.. preferably a test bar and chuck it up repeatedly keeping the bar in same location rotation wise and check readings.

Or chuck up some solid stock, take a cut and keep re chucking the piece keeping it in exact same location in jaws, take your readings.

You want a 3 jaw to be repeatable within reason.... that's the point.

As stated above, there's many places for wear... if it looks old and worn it most likely is.

4 jaws are a different story. Rough rule of thumb, used 4 jaws can be ok, old used 3 jaws not so much.. better to buy new.

 

[Provincial]

If the scroll and jaw slots are not worn past being serviceable, the removable top jaws can be reground to remove the bell-mouth. Do you have someone local that knows how to do that?

 

[MShaw]

The best way to regrind jaws is to drill a small (1/4") hole in the front face of each jaw. put a pin in each hole. Cut a slice of an appropriate sized pipe. Chuck the pipe by the three pins then grind reaching thru the pipe slice. This will true the jaws in the bellmouthed position.

 

[FordMustangKingCobra]

The best way to regrind jaws is to drill a small (1/4") hole in the front face of each jaw. put a pin in each hole. Cut a slice of an appropriate sized pipe. Chuck the pipe by the three pins then grind reaching thru the pipe slice. This will true the jaws in the bellmouthed position.

Could you like a video to show how it's done?

 

[alfadan]

All kinds of videos on jaw regrinding. Some use equal length spacers between the jaws, others use pipe on the outside of the jaws and use the scroll to put outward pressure on them, though I don't think that is the right way to do it. The idea is to load the jaws equally and grind the working surfaces straight again. At one particular diameter anyway, lol.

On my Logan, I tore apart the factory chuck and cleaned it, only to find it bellmouthed due to slop in the slots rendering it practically scrap.

 

[paulsomlo]

I can buy new jaws for it if needed, i just need to measure them

Other than the used market, I don't know that you'll find jaws for that. That's a small spindle - is the lathe an Atlas/Craftsman?

 

[FordMustangKingCobra]

Other than the used market, I don't know that you'll find jaws for that. That's a small spindle - is the lathe an Atlas/Craftsman?

It's a Craftsman 101 with a 1-8tpi spindle.

 

[slowtwitch73]

I would do the test I detailed above before buying anything or grinding the jaws so you don't get into a bad money after good situation.

If the scroll is worn, new jaws/grinding wont do you any good.

For the most part regrinding helps get the jaws contacting the work their full length.

 

[FordMustangKingCobra]

I would do the test I detailed above before buying anything or grinding the jaws so you don't get into a bad money after good situation.

If the scroll is worn, new jaws/grinding wont do you any good.

For the most part regrinding helps get the jaws contacting the work their full length.

Alright, I'll check it when i get home