# Adapting a D1-3 4Jaw chuck to D1-4



## dbur (Mar 28, 2013)

Tell me if I'm crazy.  I have a D1-3 4 jaw chuck but my lathe is D1-4.  There's plenty of meat in the chuck to locate the D1-4 pins and screws, but the cut for the new taper will break into the old D1-3 pin holes.  I do not want anything that will harm my lathe spindle.  I think I have 5 options:

1. let the break out occur and assume there is still plenty of meat around the taper to support the chuck
2. fill in the old holes with machinable titanium epoxy ($100 for about 1/2 cup of this stuff, but I already have some)
3. weld in the old holes.  I don't like this since I don't think it would be a great idea to put that much heat on the chuck body.
4. get a D1-4 plate and mount the 4J chuck to that.  I would remove the pins and through bolt it, but I'd just as soon not stick it out an extra inch to do this.
5. forget this idea.

What do you think?

On another note, the 4J chuck taper seems to be closer to 2" dia rather than the 2.125" standard for a D1-3 mount.  What's with that?

Thanks.


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## British Steel (Apr 5, 2013)

4 would be easiest and quickest, really - would losing an inch cause much of a problem?

Filling the holes and recutting the taper could work, best to fill with a like material, loctite or shrink fit? The critical operation is cutting the taper, as this is where D1 chucks get their accuracy, you'll need to make a dummy spindle nose to use as a gauge, with a flange to set the pull-in distance - the few thou" clearance between chuck back face and spindle that's taken up by tightening the cams. Ideally, the taper should be ground, but a good finish cut will do!

Either way, good luck with it!

Dave H. (the other one)


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## Ray C (Apr 5, 2013)

I've looked at this a couple times and I'm confused.  Could your summarize your goal?  I can't tell if you have a basic 4J chuck already mounted on a D1-3 or, if you have a 4J chuck with integral D1-3 provision.

Sounds to me, you just need to get a D1-4 backplate and mount it on the chuck.


Ray



dbur said:


> Tell me if I'm crazy. I have a D1-3 4 jaw chuck but my lathe is D1-4. There's plenty of meat in the chuck to locate the D1-4 pins and screws, but the cut for the new taper will break into the old D1-3 pin holes. I do not want anything that will harm my lathe spindle. I think I have 5 options:
> 
> 1. let the break out occur and assume there is still plenty of meat around the taper to support the chuck
> 2. fill in the old holes with machinable titanium epoxy ($100 for about 1/2 cup of this stuff, but I already have some)
> ...


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## darkzero (Apr 5, 2013)

Sounds to me like he has a direct mount D1-3 chuck. Unless it's an expensive chuck, sounds like too much trouble than it's worth. Adapting a D1-4 adapter to the chuck sounds easier than converting a direct mount D1-3 chuck to direct mount D1-4 (if it's possible)


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## dbur (Apr 6, 2013)

Just to clarify, my lathe spindle is D1-4.  The 4J chuck is D1-3, except as mentioned I think the D1-3 taper should be about 2-1/8" dia, but this chuck is closer to 2" dia at the taper.

I think I agree that #4 would be the easiest and give the best result.

I think I could plug the holes with some cast iron custom fit pieces glued with titanium machinable epoxy, but that is probably more work.

Seems like 3 D1-4 pins cost almost as much as a D1-4 adapter plate with the pins included as well.  $94 for a D1-4 backplate, or about $65-70 for 3 D1-4 loose pins, unless they can be had cheaper somewhere I haven't found.

Thanks for the comments.


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