Chuck jaw help

Starting the new year by recomissioning my Harrison toolkmakers lathe which has patiently sat in the workshop for the last 15 months.

It has what I think is a Bison 3 jaw chuck. It is 6" dia.

The chuck jaws have bolt on jaws, which are badly worn.

Ideally I would like to get new jaws, but new soft/hard jaws would also be an option.

The bison jaws (not the bolt ons) are stamped "3500".

Does this mean any jaws stamped 3500 will fit - ie does this refer to the scroll teeth and other dimensions?

Some suppliers seem to sell 3500/3200 jaws. Are these the same?

Sorry for the daft questions, but I do hope someone can just reassure me.

Many thanks and Happy New Year

John

Try this company very helpful with lathe chucks etc. http://www.rotagriponline.com

Are you sure it's a 6" chuck not a 160mm?

The set on ebay listed as "Hard Jaws American Style to suit Bison 160mm Chuck" should be direct fitment for your chuck. Try sending the seller a message I have dealt with him and he was good at responding. He might even take an offer since they have been listed quite some time.

These people also sell various chuck jaws. Since they have dimensioned drawings for some of them this may help identify what you have.

Zoro Uk

Martin C

Thame Workholding actually make these type of jaws so they would definitely have an answer.

Tony

John,

If those jaws are hard ones then using the least worn of the 4 possible clamping faces and using a known pre turned round bar test how much run out the chuck has.

If they are soft jaws, which I hope they are, true them up and using a known pre turned round bar test how much run out the chuck has.

The chuck scroll may be bad as well.

How does truing up soft jaws tell you what the run out is? The point of truing up soft jaws is that it eliminates problems of run out.

Martin C

My little experience with new 3-Jaw chuck was I checked it with various round bars and found it differ in runout towards the centre holding options the most.
-If you grind the jaws it might be more out in other places because of the scroll.
-I decided to make the 3-Jaw chuck adjustable, now I can adjust it if I had turn around work or refit work to make it run true. I then leave it at the last diameter setting till needed again.
-I used split washers to create drag when loosing the 3x jaw bolts to spindle, so I just slightly loosen it, then screw te grub screws to true it up, this works great.

I bought a set of slot and tenon Toolmex jaws some years ago very cheaply which did not fit the chuck I had thought they would. If you post the dimensions of your worn ones and they match, I will send them to you FOC.

Only at the truing point, as the jaws move further out to where there might be less wear will they not go out of true?

Once you have machined soft jaws at one point moving them to any other position tells you only one thing, they were not machined at that point and there is some runout that may be due to the jaws or may be due to the scroll or may be due to the chuck. In other words it tells you nothing of use.

Martin C

With respect, it would tell me not to spend money on it if it went say 10thou out.

Maybe not an answer to the OP but just my experience and information imparted during my abandoned apprenticeship training, circa 1968, is that no 3-jaw chuck will ever provide repeatable concentricity once the work-piece has been removed. Therefore, as many diameters as possible are turned at one setting and if the work-piece has to be removed for another operation and then returned to the lathe, either you resort to the 4-jaw or grip-true and clock it with a TDI, you use a collet chuck or you turn it between centres if at all possible from the start and continue the work after replacing it between the centres. Self-centring chucks are obviously useful and some are quite accurate at various diameters but they will never reset precisely once the work-piece has been removed which always has to be borne in mind.

It is indeed 'good practice' to machine as much as possible in one setting.

Tony

This page refers to Indexa 3500 jaws. Zoro chuck jaws

In May 2020 I offered a set of these jaws free to anyone who needed them (as opposed to just wanting them) Outside jaws for Indexa chuck 

If they will fit your chuck you can have them for the price of the post and packaging. The dimensions are shown apart from the pitch of the scroll which is 7mm. They are for the 125mm chuck but, from the given dimensions, if the scroll pitch is the same they should fit.

Martin C

Edited By Martin Connelly on 02/01/2022 11:25:09