4 jaw or between centres?

[smashweld]

the part is basic but any comments/advice will be helpful....for this stub axle starting out as square stock, how would you tackle the job? test piece at the back

think the easiest way would be to start with stock large enough to complete it without removing it from the chuck but lets assume starting with just enough to face off either end and now much diameter to play with

cheers

 

[roofman]

you can clock a 4 jaw much more accurately than a 3 jaw plug and play if there is nothing to take off.

 

[brightspark]

if it can be done all in one go a 3 jaw if you have take it out and re clock it up and has to be done in the 4 jaw .

 

[not done it yet]

If I could be sure of achieving the full diameter (may not need to clean up 100%, perhaps, anyway?) between centres every time.

 

[iNf]

Is there a reason for starting with square stock?
Turn the long section 1st with tailstock support.
Turn around leaving enough of the just turned section sticking out that you can get an indicator on it, clock in and turn the rest.
( same if starting with round stock as well)

 

[not done it yet]

Actually, as just a stub axle concentricity may not be important.

It could also be made as a shaft with a collar attached (loctited in position, then further fixed with a couple of taper pins)? Entirely depends on the application, I suppose.

 

[smashweld]

cheers

starting with square because that's what I have...well, have been given!
I think the original in the pic is actually a collar attached, bit hard to tell because of the paint

 

[Wedg1e]

Looks like it might be a bit precision; I'd want to be certain of my lathe's tailstock alignment as the slightest amount of taper might well ruin that piece.
At least if you clock it in a 4J you've got taper out of the equation.

 

[DAPPH]

On most lathes with cheaper chucks .... face plate , driving dog and between centres , it will always be highly accurate if removed & reinstalled , so long as your tailstock will allow you to turn a parallel test piece the same length .

 

[not done it yet]

On most lathes with cheaper chucks .... face plate , driving dog and between centres , it will always be highly accurate if removed & reinstalled , so long as your tailstock will allow you to turn a parallel test piece the same length .

Yep. A centre turned in the three jaw is perfectly adequate - as long as it is trued up every time the centre is removed and replaced in the chuck.

Looks like it might be a bit precision

Somehow, if we knew the actual application, I think it may not need to be as precise as one might at first think. Could be a stub axle for a lawn mower, for instance

 

[smashweld]

It’s for a horse cart but let’s pretend it’s for a helicopter, or something else maybe

Seriously tho, if You can see the little groove in the test piece, the part up to the shoulder is 2 thou less than the side nearest the threads and the play in the bearings is noticeable

 

[Smallfry]

I suppose it depends on how much bigger your square stock is, than the largest diameter of the finished article, and if the square stock slide up the lathe spindle.

Can the chuck be easily changed for a 3 jaw ?

Is the stock the correct specification for aviation use, and do you have the appropriate certification ? It will also need to be X rayed on completion.

 

[Brad93]

your square stock, is it bright steel? If so then hopefully it's EN3B or something.

Wouldn't be trusting a bit of mild for a stub axle on something potentially carry passengers

 

[smashweld]

I don’t know exactly what it is tbh but it was bought about 20 years ago for making stub axles for carts/carriages, the person who did the machining and would know what it is isn’t here now
I don’t suppose there’s any way to tell or narrow it down?

 

[Wedg1e]

I don’t know exactly what it is tbh but it was bought about 20 years ago for making stub axles for carts/carriages, the person who did the machining and would know what it is isn’t here now
I don’t suppose there’s any way to tell or narrow it down?

You could PMI it, but even if it was just cooking mild steel (say 99% Fe and a bit of Mn) it wouldn't tell you any heat treatment state.