View Full Version : Interchangeable chuck jaws, top or full jaws

09-08-2006, 06:37 PM
I have another newbie question for you folks. What is the deal on interchangeability of chuck jaws? I have a P&B 6.25 3 jaw scroll with 2 piece jaws. it came with only a single set of blocky soft jaws, no good at all for anything smallish diameter. I also have an 8” P&B 4 jaw independent with 1 piece jaws and a Buck/Logan 2 piece 3 jaw that is fairly worn and the inside L00 taper is really pretty trashed from years of being installed on top of swarf, but may be of some use I suppose.

So, for the P&B, I would like a set of ID and OD hard top jaws as well as soft jaws. I can make the soft jaws, but I see some from time to time that are labeled specifically “Buck”, “Bison”, or whatever that are cheap enough to not be worth making. I expected the slot/groove was proprietary to each chuck, but now I’m told that “some” (whatever that means) top jaws interchange. I’m further told that within a “size” of chuck, say like any 6-1/4” 3 jaw, that the base jaws and hard jaws interchange. And that last is by the guy I bought my lathe from who included a set of actual “Buck” hard jaws that seem to fit, though with play. Is that because they don’t really “fit”, or simply because it is worn? Yet the original (?who knows?) bottom jaws seem to have very little play in the chuck.

As you can see, I ‘m fairly confused. Would one or more of you experienced folks care to lay this out for me? I’ve had little luck searching this out on my own, and what I have found seems somewhat contradictory...

09-08-2006, 09:34 PM
Measure the tongue and groove and see if they are standard, by looking in the soft jaw section of one of the catalogs. If they are standard then finding a set of hard tops should be petty easy, and I don't think it really makes any difference which manufacturer, just how much you want to pay.
I've got a couple of chucks that aren't standard dimensions on the tongue and groove, those jaws I have to make.

09-08-2006, 09:50 PM
99% sure the P-B's are "standard". But, hard top jaws usually have to be purchased through the chuck manufacturer, the machinable jaws which you have are sold as after-market because they're a consumable item. A single set of hard top jaws is all that's required, they flip end for end to be both inside and outside jaws.

Interesting to note that Buck chucks in the smaller size, 6" and such, do not use a standard type jaw, their's are unique to Buck.

09-09-2006, 01:45 AM
Ok, sounds like maybe I've maybe got a good thing going with the P&B 3 jaw, assuming I can find a catalog with dimensions. Seems like I saw one somewhere, just have to search a bit tomorrow. Once confirmed, I only need one set of hard top jaws for inner/outer duty, if I can find some on ebay or whatever. And hopefully I can also take advantage of the too cheap to make soft jaws once I find out about the standard-ness of the P&B base jaws.

And also sounds like the Logan/Buck is going to be more trouble than it's worth, given that it uses the proprietary jaws AND has the scared L00 taper. I'll probably use it for a grinding chuck, or maybe for low precision CI work, or some such nasty/bad work where I don't want to mess up my good chuck.

But nobody has commented on the one-piece or bottom jaw interchange. I've got my doubts, but the shop owner who sold me my lathe stated in no uncertain terms that they would interchange across chucks of the same size. Is he confused at some level?

Mark McGrath
09-09-2006, 02:18 AM
I have a lot of chucks and have not found much in common between different makers of chucks and their bottom jaws.It can be a bit of a pain but you have to look at manufacturers dimensions,collect catalogues and do a bit of measuring.Try and avoid chucks that use a cross tenon for locating top jaws as it severely limits the range of sizes you can handle with one set of jaws.There will be independent suppliers of jaws for the common makes of chucks the trick is finding them.Most of the European and Asian chuck manufacturers list all the jaw sizes on their websites.Hardinge would probably be a good place for you to start.It is worth gathering this information as it lets you see all the possibilities,saves you wasting money on jaws that don`t fit,and lets you buy jaws cheap on Ebay as you have the info on them and a lot of others don`t.And lastly don`t believe everything a machine seller tells you.


09-09-2006, 03:05 AM
And lastly don`t believe everything a machine seller tells you.

Oh, believe me, I don't. In fact, my first response is NOT to believe unless I can verify. If it can't be verified, I ignore it for purposes of any decision (such as price determination or go/no-go on purchase). And yet, if I have no reason not to believe, I will log it away for future investigation such as this. :D

In the final evaluation, that point on interchangeable jaws had no bearing on my purchase any more than including that sad excuse for a chuck did, though I had hoped it would prove in some way useful. Hmm, maybe I can adapt it to my Super Spacer or Rotab by machining off the L00 receiver? Hmmmm...

I've got a friend in the machine tool business who has what appears to be a library of most every catalog ever produced. I'll try to go down there tomorrow and do some investigation. Thanks for the info everyone...

09-09-2006, 03:34 AM
Try and avoid chucks that use a cross tenon for locating top jaws as it severely limits the range of sizes you can handle with one set of jaws.
BTW, what do you mean by avoiding chucks that use a "cross tenon". All the 2 piece jaws I've seen have both a longitudinal and cross key/slot to locate the top to the bottom jaws. And without the cross, I don’t see how it could be positively located, unless you’re talking about the jaws I've often seen on CNC chucks where they have teeth.

09-09-2006, 12:18 PM
When you get figured just what you've got, you may want to try these guys for jaws:


Some of the crowd on Practical Machinist feel their prices on vise jaws are among the best, and I see they also have a large selection of chuck jaws.



Mark McGrath
09-09-2006, 04:59 PM
Bad Dog,the chucks with long and cross slots are what I call cross tenon.We mainly have them on the big Warner Swasey`s.I think the serrated jaws were more of a European/Asian thing and the cross tenon was more common in the States although Pratt in the UK used to use them as well.The serrated ones are better as you have more leeway on the range of sizes you can grip and how much life you get out of them.For light second operation work you can hold them quite safely with one bolt.The problem with the serrated ones is that there is more info to collect as they come with a range of imperial and metric sizes as to the pitch of the teeth and the teeth themselves come with different angles.You will find that soft top jaws are cheaper than one piece soft jaws.You will still need hard jaws as well and they are expensive whether they are one piece or not.All our cnc`s run soft jaws unless they are on collet chucks but I use soft jaws a lot on manual lathes as well.Pratt Burnerd has a catalogue that covers the dimensions of all their chuck jaws but you have to ask them for it.Kitigawa,Rohm,Hardinge all have on line info and there will be others as well.