Big work, little chuck?

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ttabbal

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So, my lathe, when it gets here, has a 11" swing. The chuck is 6", the clamping range is not listed, I assume for the 3 or 4 jaw that it's less than 6". What if I want to turn a chunk of 8" 6061 round stock?

The obvious solution is "buy a bigger chuck". Are the others? It seems like I could bolt it to a faceplate, turn the OD and face the exposed side. Then bore a smaller area for the chuck to grab using the ID. Then get the other side done. That could work for some parts. Drill the center and turn between centers, with a small hole for a lathe dog? That also mars the work, though it might not matter for some things. I saw one guy run a bolt through the center and use that as a mandrel. It ended up causing him some trouble later.

It came up thinking about making a drive wheel for a belt grinder. I'm thinking I'll buy wheels for that for now, but it seemed like a decent question to use to learn more about setting up work on a lathe.
 
Using od jaws you should be able to chuck a larger piece in a 6" chuck. How much depends on the chuck.
 
You can also add provisions to the 8" OD chunk of aluminum to aid in holding it in the lathe. I've used four socket head cap screws mounted on the face of the material. Requires drilling and tapping four holes at 90 degrees from each other on a bolt circle that the outside jaws will grab by chucking on the side of the head of the socket head cap screws.
 
Thanks. I hadn't thought of using the heads of cap screws to grip on.

The PM1127 lists both chucks at 6". An 8" would be nice, but I don't see myself wanting to run stuff that big very often. Of course, now that I've said that... :)
 
With a 6" independent 4-jaw, you should be able to flip/invert the jaws and extend them. One additional inch is probably a reasonable amount of extension. You always what to have 75% jaw engagement in the threads on the backside of the jaws. Like Savarin said, watch your clearance.


Ray
 
ttabbal said:
So, my lathe, when it gets here, has a 11" swing. The chuck is 6", the clamping range is not listed, I assume for the 3 or 4 jaw that it's less than 6". What if I want to turn a chunk of 8" 6061 round stock?
Click to expand...

If the chucks have two-part jaws (rather than solid), you can fashion outboard jaws for exterior holding.
... soft jaws for such chucks are very useful generally
Or, you can turn the blank (gently) by pressing it with a blunt bearing center against
the chuck/faceplate. Like:<
>
Or, weld a small block to the blank, and grab it by the block. Solder, maybe even glue,
might sometimes serve.
 
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