1214 Turning Pitfalls

[Anorak Bob]

Bruce tells me that I'm not an orphan when it comes to turning mishaps with this stuff. My current interim* project is the tailstock micrometer feed. I have been machining a threaded boss 38mm dia. x 25mm long from 1214 to replace the original cast iron affair used by Hercus to retain the Acme threaded screw and handwheel. The thread is 1.100" x 16 tpi.

Boss no.1 was pulled out of the chuck by an overzealous depth of cut when the boss was held gingerly by the threaded section. The threads were damaged enough to embark on Boss no.2. I had not proceeded to the threading stage before it was torn free of the chuck. The stuff cuts easily encouraging heavy cuts but heavy cuts without tailstock support even with a stubby workpiece and working close to the chuck can turn bad quickly. Boss no.3 was successful but I have moved onto a new revised design with version 4. The turning of this requires holding the finished machined surfaces in the chuck while drilling and boring a through hole. Jaw pressure high enough to discourage displacement results in marking 1214.

I guess a 6 jaw chuck might be an improvement over a 4 jaw and I have no ER collets larger than an inch.

How do you blokes get on machining this stuff without denting or marking?

BT

[pipeclay]

I try and steer clear of that as much as possable,more so because its fiddly and I prefer 4140.
Have you tried copper as a protective barrier or aluminium.
I would not use shim material or material less than 3mm thick.

[Ueee]

Hi BT
I have a piece of old copper facia that I cut bits out of for protecting things either in the lathe or (and especially) sword blanks whilst held in various jigs on the mill. Works a treat and I have never had anything come loose.

[morrisman]

At the TAFE they used aluminium drink cans , cut to appropriate size , between the jaws and workpiece.. worked well MIKE

[Crossfeed]

Am I missing something?
Using a bit of 1214 a foot or so long, turn to final major diameter
turn the step for the thread with the undercut, thread, Drill through hole blind at this stage and over depth, bore, part off.

1214 is a bit sticky aluminium soft jaws grip steel well if you need to grip the part on the threads.

[Anorak Bob]

Am I missing something?
Using a bit of 1214 a foot or so long, turn to final major diameter
turn the step for the thread with the undercut, thread, Drill through hole blind at this stage and over depth, bore, part off.

1214 is a bit sticky aluminium soft jaws grip steel well if you need to grip the part on the threads.

I'm obviously the one missing something.

I don't have a lathe that would enable me to confidently drill out the end of bar a foot long supported only by the chuck. I'd have to do it with a fixed steady supporting the outboard end. The piece of steel I'm working on is about 40 mm long and about 45 mm in diameter. My question was about preventing the marking of the steel while still holding it with sufficient tension to prevent its loosening. I have turning to do on both ends of this short piece of bar. I do not own any aluminium jaws.

I know why I have dislodged the bosses that I have damaged.:doh:

BT

[Abratool]

I'm obviously the one missing something.

I don't have a lathe that would enable me to confidently drill out the end of bar a foot long supported only by the chuck. I'd have to do it with a fixed steady supporting the outboard end. The piece of steel I'm working on is about 40 mm long and about 45 mm in diameter. My question was about preventing the marking of the steel while still holding it with sufficient tension to prevent its loosening. I have turning to do on both ends of this short piece of bar. I do not own any aluminium jaws.

I know why I have dislodged the bosses that I have damaged.:doh:

BT

Bob
I reckon Pipeclay had the answer.
You need thick aluminium...... 3mm or 1/8th" thick individual pieces 3 pieces for a 3 jaw chuck.
The thick alum will bite into the threaded section of the workpiece & get an impression
from the threaded piece without damaging it. It will then hold the piece firmly while you work on it. :2tsup:
Still requires light cuts so the tool does not grab, maybe its those carbide thingoes you use. :oo:
I was machining 1214 this afternoon with HSS toolbits & all went well.
All sent to test us :rolleyes:
regards
Bruce

[PDW]

The turning of this requires holding the finished machined surfaces in the chuck while drilling and boring a through hole.

Why don't you drill & bore the hole first in some oversize stock, then mount it in a mandrel between centres and do the OD turning?

That's how I'd tackle it.

FWIW a mandrel turned just undersize (push fit) and with a flat machined across it will hold very firmly by placing a bit of small round stock on the flat and twisting the workpiece so the little roller acts as a wedge. Turning the workpiece the other way releases it. I've done this a number of times over the years so I can assure you that it does work.

PDW

[Crossfeed]

I'm obviously the one missing something.

I don't have a lathe that would enable me to confidently drill out the end of bar a foot long supported only by the chuck. I'd have to do it with a fixed steady supporting the outboard end. The piece of steel I'm working on is about 40 mm long and about 45 mm in diameter. My question was about preventing the marking of the steel while still holding it with sufficient tension to prevent its loosening. I have turning to do on both ends of this short piece of bar. I do not own any aluminium jaws.

I know why I have dislodged the bosses that I have damaged.:doh:

BT

I meant have the bar back inside the spindle bore so only enough material for the boss + parting allowance and clearance is protruding from the chuck. The reason why I mentioned one foot is to allow you to comfortably make all 3 parts while still having some stock to grip the full length of the chuck jaws on the last part.
If your spindle bore is smaller than 45mm then you can only have enough material to slide inside the the chuck bore, if your chuck bore is less than 45mm then I see your problem. That is where the aluminium comes in, cut a few short strips of 2 or 3mm thick aluminium sheet and place them between the chuck jaws and the thread, the thread will bite into the soft aluminium. hope that makes more sense. I missed the part about turning on both ends, I thought it was a boss stepped on one end with the minor diameter threaded and a through hole which may have been threaded

[Anorak Bob]

Now the picture is clear. The Hercus has a bore of 19mm.

[Abratool]

Now the picture is clear. The Hercus has a bore of 19mm.
Bob
That damaged workpiece took my breath away, & made me feel crook in the stomach.
I think it would have been worse for you.
Just hope the chuck has not been strained.:rolleyes:
regards
Bruce