traveling steady, turning 1/2 bar down over 10".

[Reg]

Graffian,

God loves a tryer!

What is the spindle for?
Can you post a back-of -a-fag-packet sketch of it?
How dimensionally accurate does it have to be & what sort of finish do you need?
What sort of tool were you using?
What depth of cut?
What feed rate?
What spindle RPM?
Does it really have to be made of EN24?

Hopefully, if armed with the above info someone will be able to help

Reg

[graffian]

Spindles are for girder forks, 3/8 seems to skinny!
I was hoping for 1/2 thou over and I would set about them with an external hone then polish them, I did wonder about hard chrome or some sort of coating? They are running in PB102 bushes, two bushes 1.5 long 6 inches apart, the previous ones were extremly worn[.01 lips] and the holes they run in were .05 oval, so a few thou clearance is probably fine, finish wants to be good.
I am using a triangular insert, it's about as much as I can remember about the insert. Not quite. It's probably .4mm nose and they are probably 7º sides. They are from a box of gold mitsubishi inserts from drill services £1 for the hospice box;-). They leave a lovely surface on EN24.
I was cutting to depth, so either .0625 or .125[3/8 or 7/16 spindles], feeding between 2 -3.5 thou. Keeping the speed right down to 3xxrpm, I am running to slow because of the steady.
I have just carefully set the centres and steady each time I moved the bar, or tailstock.
I was setting everything and then had multiple goes on the same setting.

Each part has been usable, .4367-.4385 across 10" and the middle 6 inches, which is the bearing, is less than a thou of variation.
After getting enough usable stock for the 7/16" spindles, I upped the speed to a thousand rpm and feed to 7.5 thou, finish is better and I have the 3/8" diameter spindles with 1/2 thou variation across 8.75" inches.
I have the ends the same size with a huge great 1/2 thou bulge in the centre;-)
I think an old carbide insert brazed to the stud in my steady wouldn't be a bad idea, I had to move the bronze stud several times as it was wearing. I also changed the oil for the steady from a way oil to a motor oil, the surface of the bat where the steady was rubbing wasn't damaged.
But I wouldn't want to have to make some of these for someone. I clearly need more practice with a steady.

[Reg]

It sounds like you have got there eventually which is the main thing.
It was probably the initial heavy cuts that caused a few issues. These inserts like a lighter cut, a higher speed and a faster feed. A good reference guide can de found at :
Cutting Data

Rather than turn down long lengths of material you can obtain ground imperial silver steel if you think it suitable here:
Silver Steel Imperial including: Stubs R004AK & Stubs R006AK

I hope this helps in some way,

Reg