I have done it loads of times - perhaps I have just been lucky!
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Rescued it. Looks like the chuck survived, in the pics I had already straightened out the top finger adjuster. I parted the end close to the inch diameter I'd bored using the tailstock and live centre, then removed the tailstock to finish the part. It ended up slightly shorter, by 250 thou or thereabouts, still long enough for the bronze bearing it sits in.
Should have used a 4 jaw for extra grip but L1s aren't exactly light and easy to change!
Hindsight is also a wonderful thing.
If you had broken the chuck remember you know someone with spares
Yes, changing the chuck is not something I do lightly. Thanks for the offer, hopefully not needed. I did find one other potential issue that may have contributed whilst removing the fixed steady - the clamp nut wasn't very tight - don't know whether the bolt had stretched in the crash, or maybe it settled after I tightened it??
Lesson learned anyway, don't be a cocky parting fool....
Lesson learned anyway, don't be a cocky parting fool....
Mr Hindsight would have trued up the chuck end and then shoved it hard into the chuck face so you get max jaw engagement on something more reliable than heavy rust and an invitation to bell mouth the jaws.
This Mr Hindsight would have parted till it sounded unhappy then sawed it off and faced the part in the chuck.
This Mr Hindsight would have parted till it sounded unhappy then sawed it off and faced the part in the chuck.
Screwdriver
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Just looking at the dynamics of that set up, there is a lot of scope for toque to build up as the part is spun up at one end, twist and flex in the bed and steady etc.
What that means is that if there is a tiny bit of "grab", all of those pent up forces which had been in equilibrium with the cut, suddenly have nowhere to go except into the cutting tip - which had just grabbed onto/into the workpiece.
I hate parting off with a passion and will often take a light pass before grabbing a hacksaw or taking it off to the bandsaw. But with a firmly held part ideally close to the chuck, I find that making a few passes to open up the slot helps tremendously. If any flex allows the side of the parting tool to dig into the cut, it's game over.
What that means is that if there is a tiny bit of "grab", all of those pent up forces which had been in equilibrium with the cut, suddenly have nowhere to go except into the cutting tip - which had just grabbed onto/into the workpiece.
I hate parting off with a passion and will often take a light pass before grabbing a hacksaw or taking it off to the bandsaw. But with a firmly held part ideally close to the chuck, I find that making a few passes to open up the slot helps tremendously. If any flex allows the side of the parting tool to dig into the cut, it's game over.
That would reall have f***ed up the chuck. The job of the chuck was to hold it sufficiently to turn it. The job didn't fail at the chuck. Never sounded unhappy either, until it went bang.Mr Hindsight would have trued up the chuck end and then shoved it hard into the chuck face so you get max jaw engagement on something more reliable than heavy rust and an invitation to bell mouth the jaws.
This Mr Hindsight would have parted till it sounded unhappy then sawed it off and faced the part in the chuck.
The need to part it in place was twofold - I don't have a bandsaw, and once cut off I would then have to accurately re-true it so that the end was perfectly perpendicular with the diameter of the piece, otherwise it would pull when tightened on the arbor, distorting it.
No twist or flex in the part or the bed, this is not ml7 stuff..
agree about widening the cut, it may have made all the difference (assuming it was swarf buildup that caused the jam).
Screwdriver
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Of course there is. More than most people imagine. The workpiece will also twist and deflect a lot more than you might think. Not easily detected on a human scale but once you get down to thousandths of an inch, there is appreciable movement.
So if a tool jams even slightly in a cut, there is no more flex to be had and somethings got to give. Usually that involves chatter where those forces build up and release rhythmically but parting off tools have a habit of digging in.
If on the other hand, you still don't believe in twist and flex, how do you account for a "spring pass"? Where do you suppose that cut is coming from?
Screwdriver
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Indeed, mostly yes but the spring pass is typically after a light finish cut. When you're hogging off material and especially when parting, there is a lot more deflection. A lot of that will still be in the tool and toolpost but also twist and deflection in all of the parts between the cutting tip and the headstock bearing. That is why you always want to keep those two points as close as physically possible.
Funnily enough there is no spring at all on my Holbrook H20. That might be due to the fact it weighs 5000kg
E T
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I have them touching, but just. I adjust the fingers until I feel them rubbing slightly on the part. Works fine for normal turning.
No way that has the same grip on a part as good and tight chuck jaws.
But up to now I haven't had the need yet for parting off next to the steady rest. I will give it a try and see how it goes.
Close to the chuck my small South Bend has no problem with parting off. Normal rpm and power cross feed.
E T
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I will give it a little test this weekend. Might even film it.
Fingers crossed I don't need a change of underwear after.
pressbrake1
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E T
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Don't worry, I've seen what you're up to. Your input is very much appreciated.I’m a experienced turner so hopefully my tips even though ignored on here are valid
When parting off from a steady start with the parting tool slightly high so it’s less inclined to climb and pull
Never ignored @pressbrake1 , ridiculed sometimes, but never ignored...I’m a experienced turner so hopefully my tips even though ignored on here are valid
When parting off from a steady start with the parting tool slightly high so it’s less inclined to climb and pull
E T
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So, I did a little test and my underwear is still clean(ish).
No drama at all actually. 460rpm and powerfeed as usual, but I kept the feed a bit slower just in case.
Thanks @pressbrake1 for giving me the confidence.
