Thread: Setting up in a 4 jaw independant

What is it you are setting up?

Is it a casting,or a piece of stock,has it already been machined?

Is it an OD or ID your setting up?

Is it a short piece of stock or is it long?

Are you using a surface gauge,pointer or indicator to set up?

Is it a casting,or a piece of stock,has it already been machined?

Round brass (machined 65mm round)

Is it an OD or ID your setting up?

OD

Is it a short piece of stock or is it long?

300mm supported

Are you using a surface gauge,pointer or indicator to set up?

Tried pointer and an indicator


I get it right and when I tighten down, it goes out of whack.

Use two chuck keys

Originally Posted by Stustoys

Use two chuck keys

Well I must admit, that thought never crossed my mind.

When you say supported are you using a centre at the tailstock or cat head or using a steady.

You will need to get chuck end running eye true 1st then give the outboard end a tap to get it running eye true.

Is the OD to be machined?

Using the 2 chuck keys is ok depending on the size of lathe you have or are using.

This was a big help to me FOUR JAW FUN - YouTube

The 2 key method works a treat, as does having an indicator solidly mounted and not in the way.

Ew

Originally Posted by pipeclay

When you say supported are you using a centre at the tailstock or cat head or using a steady.

You will need to get chuck end running eye true 1st then give the outboard end a tap to get it running eye true.

Is the OD to be machined?

Using the 2 chuck keys is ok depending on the size of lathe you have or are using.

I'm using a steady.

I'm boring into the bar.

Its a small (hobby size) AL60 lathe.

Probably best for you to describe the way you went about setting it up.

Was the outside pre machined prior to using the steady?

I use 2 chuck keys and a DTI and don't have any trouble setting things up in the 4 jaw chuck. If you are using a steady, get the job true in the chuck first, then set up the steady. Maybe getting it right quickly takes a bit of practice, I'm always amazed how easy a good tradesman can make a job look, and when I try it, it seems nearly impossible.

I've tried using 2 keys, I usually do it with one. Very much a practice thing, so the more you do it the better you will be.
Concentrate on doing 2 opposite jaws at a time. you will need to set those up, do the other pair and then do a little bit of minor adjustment to the first pair. Use the concentric lines on the chuck face for your rough positioning - that's what they are there for. Your indicator needs to be rigidly mounted so it can't be knocked. I prefer a DI to a DTI for this as it has greater range but use a DTI for internals. If you have a QCTP, make up a bracket to clamp in a holder so you can mount the DI on the toolpost quickly.
Once you have the chuck set then worry about the steady. Set that by putting it next to the chuck and adjusting the fingers then move it to the final position.

Michael

Hi there,

Plenty of advice already given so all I will add is that I too have had problems setting up a 4 jaw. It takes lots of practice with lots of different sizes and shapes to get good at it. When I say good I mean doing it quick, most people will get there in the end to the required run out, the more skilled people will just do it a lot quicker.

If I'm using a steady, I usually indicate off the steady as well once the 4 jaw is set, that way I know I have not forced the part off centre ever so slightly with the steady. Not sure if this is the done thing.

Simon

Looks like I just need to practice practice and keep at it till I work out a system.

I should add, some days I nail the 4 jaw and get it spot on (no indicator movement) even if to the nearest 0.1mm is good enough. Then other days I may be working on something that requires tighter tolerances and be buggered if I can do it within 30 minutes and not chase my tail!

I figure as long as each jaw adjustment reduces the run out then I'm always heading in the right direction, even if it is a slow process. Practice makes perfect & thank god I'm not trying to do it for a living!

Simon

Do you find when you tighten up though, things can go out of whack