MetalworkingFun Forum

On the weekend I had the 4 jaw chuck mounted for the first time since getting my current lathe.
Its a Rohm brand - around 14" (350mm) diameter, and as I've found out its a "heavy duty" model. The gripping face of the jaws is about 12mm wide and it can't grip anything smaller than about 30mm across.
The 3-jaw (also Rohm) is  approx 10" and closes up pretty tightly so no such problem with that.


So I'm looking at options for smaller size 4-jaw work.

Firstly, I guess I've got the option of re-grinding the 45deg face on the jaws so they close tighter, but I'm wondering if I'll regret that down the track.
Next option would be to get a small 4 jaw (perhaps a 4 or 5"?) and just chuck it in the larger one.
Lastly, I could just buy another medium size 4-jaw ( 8 or 10") which would probably cover most of my work, and be lighter and easier to handle than the current one. Would mean sorting out a D1-6 backing plate to mount it which would be a bit of extra work/cost.
Pity I didn't realise about this chuck before I sold my old Hercus lathe, or I would have kept the 6" Bernerd chuck that went with that

Anyone care to throw other thoughts into the mix?

Steve

I've seen smaller chucks gripped in the big chuck, seems like a reasonable solution to me- also the small chuck can be 3-jaw, make sure you get a chuck with your dividing head
My 4-jaw chuck will only close down to about 20mm, I use a straight-shank ER32 collet chuck for small work.
Another option might be to attach some soft jaws with a smaller face.

Thanks Pete.
I guess its mainly the ability to be able to dial in an already round part that I'm after, so even though I was thinking small 4-jaw a 3-jaw would work - dialing it in using the outer 4-jaw as required.

I've already got a few ER32 collets for the mill and was planning to work out some form of collet chuck to mount on the backplate or or in the internal spindle taper, but I guess a collet block that I could chuck in the 4-jaw would be handy. Would cover that small size range up to 20mm.
Would still need something to handle between 20mm and ~30mm though...

Good thought about attaching some jaws with a smaller face - I'll think more along those lines too. If I could make some up that located over the main jaws well enough that they weren't a PITA to use it could work well. Even if it only handled that missing size range between ER32 collets and the main jaws.

Steve

Get the smaller 8 to 10 inch 4 jaw so you can also use it with the dividing head and a rotary table. That's what I've done and also have a 6 or 8 inch 3 jaw used on the lathe, dividing head & RT. Making/machining the adapter plates should not be that big of a job.