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chatter with form tool at low speed

Because I feel lazy, it's friday and I am avoiding work, went and looked a little because these things are not well-known. They were for high-volume production and for example would make a trailer ball hitch thingy in two minutes, all in one infeed with a single form tool. Yes, we're not talking a little 1/4" radius :)

Anyway, here's a 6" one and you can see it's pretty beefy for a little 6" lathe.

f70f65c98ba8587c61ee9db32031a2ab.jpg

I remember the sales lit had examples, which could give some hints on what works with form tools, but wasn't able to find much. As I remember it was pretty common to set the tools a bit below center tho, so even normally they'd be sort-of along the lines of skiving tools.
 
Probably why people make those dinky little radius cutting attachment using reduction gearboxes.
 
So you have tried lots of different things to try and improve the cutting performance, that if I read correctly had no positive results.
All efforts were aimed at most of the machines elements with one exception.
Did not read about any attempt to change or improve the work holding.

Try ditching that 3 jaw in favor of a good collet setup.
Or, set it up with a good 4 jaw ( jaws with full length contact)
Or, fit that 3 jaw with a set of soft jaws bored for the material size being run.
Wide jaws giving almost a full wrap on the stock)

Cheers Ross
 
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Case closed. @swarfless gets a gold medal for bringing up chuck overhang and @AlfaGTA gets honorable mention for putting collets into the mix.

The chatter is caused by the overhang of the chuck. Here's how I know:

I walked over to another part of the building and had a buddy take an R.25 cut on a 1" bar in a collet on his little Schaublin 102-VM. There was audible chatter and it took some "dialing in" as folks here said, but got excellent finish. Dwelling was no problem, unlike on my engine lathe where the cut starts screaming.

The bed on the Schaublin is about the size of the cross slide on my engine lathe. How could it be that a much lighter machine performs better?

That got me thinking about the overhang, so I switched from this:
chuck.jpg

To this:
collet.jpg

The 5C collet adapter is a shop-made hunk of junk that doesn't fit the spindle taper correctly. But, I can't make this setup chatter even if I try. The finish is perfect:
collet_finish.jpg
 
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Well thanks for the kudos pcd but, c'mon you can't put me on a podium with Ross, I can barely see his boots.
I did cut a bit of 1" dia 1020 or 1030 yesterday, chucked it in the Myford (worst case scenario?) & repeated the expt @ 400 rpm the 'correct' speed for mild steel vs HSS, & again @ 600, 50% overspeed. No chatter. It 'wanted' to @ 400 but feeding with the apron handwheel gives you the ability to instantly increase/decrease feed & chatter was averted. There was no inclination to chatter @ 600. Finish is just as shithouse even tho' I touched up the tool with a Dremel style grinder. It's the tool not the lathe. 0.25r 400a.jpg0.25r400.jpg0.25r600.jpgThis time I managed to take some snaps, #1 & 2 for 400rpm, # 3 for 600. I realise it's a done deal but pics aid credibility esp. for the Myford knockers. Be nice, this was my first lathe I bought 2nd hand unused, 61 years ago, it's been a good little workhorse. Its stand is a bed-length piece of 8" x 3" channel boxed at the ends with welded legs 'A'-frame style 2 x 2 x 1/4 angle bolted to 5" fibre steel concrete floor. 1 hp 3 phase 415 V motor. I've only had the Chipmaster about 22 years, so the Myford still tends to be favourite.
 








 
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