Thread: Replaceable shorter jaws ? Available ?

Hey guys,
Me again.
I've started making a pitkin donut for my lathe, which helps support the compound. I started with a 4inch diameter piece of aluminum. I had to max out the jaws all the way to get it to fit on the inside teeth, i tried using the outside teeth but they hit the center of the chuck before it closed in on the material.
I had to actually remove my safety shield because the jaws protruded slightly out of the chuck and was fouling. It also limited how much adjustment i could make to get the work centered, which i managed to do, but was difficult.


By looking at the jaws, it would have really benefited if there was a tooth in between the teeth to hold this size item. is there somewhere i can buy some shorter teeth that will give me more or less travel, or is the solution to buy a new medium sized chuck.

I'll be making a ball turner soon and will be working with the same size diameter stock.


Cheers

ps. I know you guys like pics. I always try and include one.


IMG20140617022854.jpg

Go and buy a better type of 4 jaw.

Originally Posted by oohsam

Hey guys,
Me again.
I've started making a pitkin donut for my lathe, which helps support the compound. I started with a 4inch diameter piece of aluminum. I had to max out the jaws all the way to get it to fit on the inside teeth, i tried using the outside teeth but they hit the center of the chuck before it closed in on the material.
I had to actually remove my safety shield because the jaws protruded slightly out of the chuck and was fouling. It also limited how much adjustment i could make to get the work centered, which i managed to do, but was difficult.


By looking at the jaws, it would have really benefited if there was a tooth in between the teeth to hold this size item. is there somewhere i can buy some shorter teeth that will give me more or less travel, or is the solution to buy a new medium sized chuck.

I'll be making a ball turner soon and will be working with the same size diameter stock.


Cheers

ps. I know you guys like pics. I always try and include one.


IMG20140617022854.jpg

Hi

I dont know what a pitkin donut is but you might be better of drilling a hole through that stock and then push it onto a mandrel and machine it with your tailstock holding the mandrel steady . Mike

How big is the chuck? Maybe a used PB 6" 4 jaw from Mal might be the go? http://australianmetalworkinghobbyis...&product_id=77
You would need to make a new back plate if you could nor swap it for the back plate on the chuck you have.

Ew

You could turn up a ring that fits between the sizes of your chuck's steps - and then cut a few degrees out of it to use it as a 'spring collet' with a limited range. You would position the gap halfway between two jaws so that the accuracy is maintained (as each jaw is using an identical 'packer').
You could make 'sets' of collets to suit your 'stock'.

I do like the idea of a good 4 jaw chuck.

I am very hesitent to make a backing plate however. I dont feel that I have enough skill, nor the precision to complete such a task.

The other issue is the spindle on my lathe is a screwed spindle, with some weird M39x4 thread.

I have found a place in australia (minitech) that may have them ready to go with a 4 jaw chuck. Not cheap but may be better than stuffing one up if I decide to make it.

could you please tell me what those dark round circles are just inside the outer steps on your chuck? I'm wondering if they are some kind of plug covering a threaded hole to bolt on soft jaws to make the step in between...

That is a threaded bolt that has a nut on the other side, it allows me to flip the jaws around.

Sent from my X9006 using Tapatalk

That is the clue we needed!
You should make some replaceable soft jaws to fit there instead of the removable hard jaws - and turn them to suit whichever diameter you need at the time. That also ensures definite concentricity for that diameter! Perfect solution.
Would you mind taking one of the jaws off and show us the way it is keyed to it's base, please?

Does this help.


Jet_4-jaw_OEM_chuck_4.jpg Jet_4-jaw_OEM_chuck_5.jpg

Sorry mate it reeks of peanut oil just looking at it

There is no support for the Jaw and the locking method for the jaw will lead to hours of frustration truing something if you need accuracy

Even a cheap 100 mm job off ebay etc bolted to the front of that thing will be better in the long run

Bruce

hahaha
Yes, It is no good, I have managed to get it to work and I am able to true things up in it within 1thou of a inch, but it is frustrating.

Looks like my issue of finding a back plate is getting harder. I cannot find anyone with any M39x4

Surely someone sells these..

What I did with mine was get a couple of M39x4 nuts via the local bolt shop and modify them to fit the lathe spindle correctly. Get a suitable piece of steel and weld the nut to it, mount it on the lathe and turn it to the dimensions to fit my 4 jaw chuck. Takes time but works fine.

Roger

Originally Posted by rogerbaker

What I did with mine was get a couple of M39x4 nuts via the local bolt shop and modify them to fit the lathe spindle correctly. Get a suitable piece of steel and weld the nut to it, mount it on the lathe and turn it to the dimensions to fit my 4 jaw chuck. Takes time but works fine.

Roger

Thats a good idea roger.
I don't have as much of an issue doing that, its more about drilling the holes precisely enough to mount it to the chuck.

This is what worries me.
Maybe I need to watch more videos on how to do this process.

What size plate do you need?