I have been putting off making some 3/8" and 7/16" spindles for ages, I bought a length of 1/2" EN24 in September 2011 to make them!
I have to be able to turn a 10" length. I tried a steel block in my rear tool post as a steady, I drilled a hole in it and ran the bar through it, then turned the bar behind it[tool following]. The block had a well in it full of oil, but it welded to the block. So that was no good. I had a tool holder with a tag brazed to it, that I have bolted a chuck of phosphor bronze to and used as a steady before, the steel bounced against it and it wasn't any good.
I dug out the traveling steady[it's a CVA] I have never used it before and it was like the steady bolted to the tool holder, the steel bounced[shopudl say rattled] against the hardened steel blocks, I tried varying tool height and I couldn't get it to work.
So I added a third rubbing block to the steady, I machined a flat on the steady body and bolted a block of aluminium with a phosphor bronze stud in it, to the steady. It works as steady. I have a piece of plastic over the bar, between the cutting tool and the steady rubbing blocks, so I can keep swarf/coolant away from the rubbing blacks and I have a tube full of oil[way oil] dripping on the bar.
I turned the first part, thou or so under size, but it tapered by a thou, it got smaller as it got nearer the chuck.
The steady is leading and the bar is on a centre.
Turned as many as I had bar left, they gradually got worse, the last has 3 thou taper and some ridges.
The bar surface is getting rough and the bar is eating into the bronze and pushing away from the hard steel rubbing blocks, so the turned diameter is smaller.
anyone any ideas?
I got another bar of EN24T today, haven't touched it yet;-)
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
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.
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 :
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,
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