Two Piece Jaws

[Jammer Six]

Why are two piece jaws a CNC thing? It seems to me they'd help us, too...

[Bented]

They are not strictly for cnc machines, there is no reason one can not install such a chuck on a 100 year old lathe.

Many modern lathes employ hydraulic chucks which often have limited jaw travel, serrated top jaws may be moved in small increments to accommodate part size.

[eKretz]

I have them at home, and several of the shops I've worked in have two piece jaws on every manual lathe. Very handy indeed. Soft jaws machined to size make for very precise chucking - akin to a supersized collet chuck. This is especially useful for high precision on multiple piece runs or securely holding irregularly shaped parts.

[MrWhoopee]

There are several advantages to 2-piece jaws. One of the biggest is that the chuck and jaws rarely get separated from each other when sold by the family of the deceased. There are lots of chucks floating around with only one set of 1-piece jaws.

[old mart]

The common type of two piece jaws used on manual chucks are slot and tenon. They will have a minimum of 2 screws, normally SHCS type per jaw. The advantage I would take advantage of if I had that type of chuck, is with a mill, you can make soft tops in steel, aluminium or even plastic. I would think they take about the same time to change round as taking one piece jaws out and changing them. I do have a manual chuck with serrated jaws, an early type used before power chucks became the norm for cnc lathes. It is primarily intended for soft jaws. The other difference between otherwise identical size chucks is that two piece jaws overhang the front of the chuck body about 50% more than one piece ones.

[Paul Alciatore]

Well, YES! I have a SB-9 and have a chuck with two piece jaws on it. It works great.

I never even thought to question it's use on a manual lathe.

Why are two piece jaws a CNC thing? It seems to me they'd help us, too...

[RSG]

No reason not to! I have three chucks with two-piece jaws, all dedicated to soft jaws for my home shop.

[Jammer Six]

If I'm shopping for just the jaws, where would I look? I only see two piece jaws with chucks out there, but I'm sure that's because I don't know where to look.

[oxford]

If I'm shopping for just the jaws, where would I look? I only see two piece jaws with chucks out there, but I'm sure that's because I don't know where to look.

I guessing you are asking about 2 piece jaws for your current chuck? If so, I don’t think you are going to find it. At least I never seen it offered. I have seen replacement top jaws but that’s it.

[Jammer Six]

I see. So one buys a chuck to get the jaws? Or at least one pays attention to the jaws when one buys a chuck?

[old mart]

I have bought numerous sets of used soft jaws for chucks with one piece jaws, and some are well used up. These can be milled down and threaded to hold soft top halves. The ones I have done this to have larger tops which can be bored to hold delicate items.
Buying any sets of extra chuck jaws is difficult due to the sellers often not knowing how to measure them properly and also just quoting the serial numbers which are only useful to match a set. The chuck makers often only make proprietry jaws which only fit a particular model. An example of strange practice is the lightweight 6" four jaw independent that Pratt Burnerd used to make, the jaws had either ACME or square thread forms.

[Doozer]

Just search Ebay for "Chuck Soft Jaws" or "Chuck Top Jaws".
Ajax sells Abbott jaws.

-D

[djc]

If I'm shopping for just the jaws, where would I look?

Are you in USA? Maybe MSC. Do you have Zoro there?

The relevant standards are ASME B5.8-2001 (you can find a pdf of it online) and IS 15248:2002 (Indian Standard, available at the internet archive. It is a direct parallel of ISO 3442:1991). Bonus points for anyone who compares the dimensions in the ASME (inch) and ISO (metric) standards.

[Lee Cordochorea]

Machinists have been using two-jaw chucks for at least 200 years. According to the old books, they were the go-to choice for many operations in brass.

[jimsehr]

If you are looking for chuck jaws check out US shop tools. Lots of info there.