Chuck question...

[AdeV]

I've finally decided to splash out on a brand new 3-jaw chuck for my lathe; I've picked up 3 2nd-hand 3-jaws at various times; and, frankly, they're all rubbish; chucking a bar, then re-chucking it, and I get anything up to 0.010" TIR. Not good. I've been getting along with a 4-jaw independent, but there's wear in that too & I have to shim one of the jaws to prevent it holding the workpiece at an angle.

So, anyway, new chuck.... I'm aware I will have to make a backplate; my question is, should I get the 200mm chuck, or the 250mm for an extra £30? The next size down (160mm) doesn't have any soft jaws available, which rules it out IMHO; and the next smallest is smaller than my spindle nose. The biggest bar stock I tend to use is ~2", although I do have some plans to turn a piece around 9.5-10" diameter (but I can always use the 4-jaw for that, if I have to). The lathe spindle will only pass ~45mm stock, so the size of the hole in the centre of the chuck isn't really a consideration.

Is this  a case of bigger basically being better? Or should I save the 30 quid by going for the smaller one?

[lordedmond]

well if you don't you will wish you had

get the bigger one its only 12 pints

but do get one that has soft jaws tho

seriously if you get a smaller one then need a bigger one you will not have saved the £30 but you will have spent the cost of the chuck twice ( not sure that reads right )

anyway spend the extra now else you will have to fork out for another one later

BY eek I am tying myself up in knots

just my 2 cents worth of rambling

Stuart

[DaveH]

AdeV,
If you are happy (and your lathe is) about the 250 chuck, then a larger chuck is always useful to have.

On the odd occasion you really need that 250mm it will be well worth the extra.

However, asking your lathe to do something it was never designed to do will in the end just cause you trouble.

That’s my 2 p’s worth.
 

DaveH

 

[krv3000]

well i wood say the big one to

[AdeV]

Cheers chaps, the big one it is then.

Dave - my lathe is quite large, and cheerfully spins a 10" 4-jaw chuck, so I figure the 10" 3-jaw should present no problems for it. I'd wondered about the 12" 3-jaw, but it's starting to get quite pricey, and I'm sure I won't need anything THAT big.

[Davo J]

Just keep an eye on the minimum diameter the jaws will hold, because as they get bigger so does there minimum griping diameter.
For me a 200mm 3 jaw is plenty big enough to lift on and off. I have a 250mm 4 jaw and I use the crane to get it on and off.

Dave

[PekkaNF]

This might be a silly comment to any veteran, but I'll take my chances and would also check these:

* Clearance between the cross silde and the chuck. If you intend to turn next to chuck,  jaws might come close to cross slide. Espesially if the chuck jaws gets a little out and you happen to have that kind of lathe that there is some considerable distance from the extreme left side from the slide edege to the toolholder. Something to consider on my lathe.
* Then there is always consideration of safe rpm chuck can take. Most lathes are slow, then there is no problem. I have one clunker that could spin 5200 rpm and you don't want do that to all of the chucks.

I have heard quite often a view that 4 jaw selfcentering is best choice to use with soft jaws. I'm going to buy one later this year, this is one consideration.

Pekka