Parting off query

Not the usual query as haven't turned anything yet! Served my apprenticeship 30 years ago in the machine shop and my brain must be failing me earlier than I thought it would. All my work was done on big machines so I don't recall any of the jamming/breaking problems that seem to be the main concern on smaller machines, which may be the case when I finally start parting off with my myford. My question really though is I cannot for the life of me remember if you just let the parted off piece fall away (and risk damage) or do you try to catch it in a tub or something underneath? Sure my mentors would have had kittens if we put our hands near a revolving chuck??? Thanks John

Hi John

Don't know what you intend parting, although I've never put catcher tubs under part offs, mine tend to stay between the parting tool and the tail stock centre at the point of break, but then I go steady when the cutting tone drops just prior to break off.

Don't forget you may not be able to wind your cuts in as vigorously as you did with the larger machines.

enjoy

Thanks guys, will take it easy when it comes to it, have loads of bits and bobs to make so will keep updating as these happen.

For hollow washers or bushings etc being part off, a piece of small diameter rod held in the tailstock chuck slid up inside the piece to be parted will catch it.

For washers and other hollow objects I do as advised above, for solid parts I put a piece of cardboard with a slight U shape underneath to catch the parted off part.

Thor

Oa tougher materials like alloy steels and titanium when I get towards the breaking off point rather than risk chipping the tool or the part falling off i use a hacksaw to do the last 2-3 mm because indexable parting inserts are not cheap.

The nastiest experience I have had parting off is the item jamming between a chuck jaw and a way of the bed. Biggish bang and a sudden stop.

Since then I have always tried to find a way of catching the part when it separates. However using a hand or centre in tail stock is out of the question (hand and lathe too valuable). A hacksaw has been used for the final separation when convenient with a wood block beneath to stop the saw blade from hitting the bed.

JA

I'm surprised anyone parts off fully with the centre in. The clearance between the tool and work is very very low when the tool is cutting. When the part does part off - oh dear, the work tilts and as result reduces the clearance. A good way of getting a mangled end. It's best to let parts fall away unhindered really.

Afraid I use my hand if needed but best to remember that parts can be very hot so sometimes use something to catch it on the bed. It's usually the smaller bits that get hot.

On Myford 7 series lathes people often seem to find that a rear parting off tool works best. It depends on the particular lathe to some extent. I managed without on an ML7 I had but had to be rather careful about the feed rate. Too slow and lots of chatter and once it started the only way to get rid of it was a short sharp increase in feed rate and then back to something faster than I was using.

John

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Edited By Ajohnw on 14/01/2016 12:34:10

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My parting off has been totally transformed from a regular disaster to total success since I changed to a decent tool holder.

I must have the world record of broken parting tools and ruined parts being parted off. - All this changed overnight.!

I tend now not to 'pussy-foot' about with the feed when parting but use lots of lubricant when doing so.

The new tool holder goes to prove that one of the main requirements for parting off is "Ridgidity, ridgitity, ridgidity.!

Nick

Cheers guys for all the info, will try and keep my fingers intact when I start parting off and use bits of wire etc instead, John

Thats Three main requirements Nick !!

Ridgidity that is the reason why I am making a new cross slide for my lathe. This will incorporate provision for the rear mounted tool holder, along with a new lead screw and nuts should improve parting off woes.

Since my apprenticeship days ,we always used to catch hold of longer rods as they were parted off,it was shop practice,and as we were making instrument parts and damage to the part was frowned on as it meant more polishing,later on ,damage to the employee was not thought about,small parts were caught in a tobacco tin which had a few holes in the bottom to drain the slurry. Fifty years later I still do it on long parts,small parts with holes are caught on a screwdriver or land on the swarf between the bed ways which acts as a cushion.Parting off in those days was all high speed toolbits laboriously ground to shape but they worked better as they had more side clearance,speed was usually half normal turning speed, All apprentices did their 6 month turn on the Ward capstan, sometimes parting off a couple of thousand parts a week,for the first hour or so in winter the slurry was freezing cold,and it rotted our shoes,One thing do not hold hexagon bar when parting off ,if your hand is near the tool post it really hurts.Keep the tool blade as short as possible,non working slides locked,speed lower,on the capstan parting tools were usually on the front and form tools to the rear,and don't break the blade when the turret is fed forward,On the Boxford parting off was done from the front (no rear tool post) and with four way tool post,which is better for holding tools rigid but nowadays prefer the Dixon tool holders as it makes turning so much easier, particularly on one offs ,at work batches were up to 200 hundred so the time to shim up the tools in the four way was lost. One other comment is if the job is to be sawed off after parting most of the way then remove the rod from the lathe and saw it off in the vice.

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The only other people I have met who would pick up on that is ex girlfriends.!

Are you one of them pretending to be a machiney type guy still stalking me.?

Nick

Seems like everyone has their own particular method but all along the same lines, thanks guys. Am sure it will come back to me when I start but it shows what we do forget in 30 years! John

The one thing I do not do is part off with a centre supporting the right hand end, maybe you can start off that way, but when you are getting near to the stage when the metal can flex you risk the groove closing on the tool, if the free end is unsupported it will fall away, and the groove open out. That's my excuse anyway.

Ian S C