Parting off - upside down, right way up, front, back

Having had a few parting-off disasters I've been doing some searching around for ideas; now it's time to consult the experts ...

Is it better to run forwards with the tool in the normal position, forwards with the tool inverted in a rear toolpost, reversed with the tool inverted in the front tool post or reversed with the tool in a rear toolpost (all assuming a camlock chuck mount)?

What speed? With power feed or manually? With or without coolant? How should the parting tool be ground? Does it help to use a spring or bungey to take out any play in the cross slide? What are the other secrets (other than squareness and rigidity)?

Dave

Reply to
NoSpam
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No secrets Dave Get yourself a Kennametal-Hertel parting off tool holder with inserts from J&L Industrial.

They sometimes do a special deal, ten inserts and the tool at a discounted price.

I tried their a cheapo from J & L first , had to send it back because the thing kept flicking its inserts out then, split open on me.

So insist on Hertel.

The holder for the tool was quite expensive so I made my own .

Shown here next to a fixed steady adaptor I made.

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...never a problem .

after that .

after over 100 parting offs ...I've just changed the insert for the first time.

I do squirt coolant onto it as I'm the parting off though.

ALL THE BEST.......MARK

Reply to
mark

Dave, I'm no expert but after many years of trying and failing I solved my parting problems a couple of years ago when I bought a "Q-cut" type tool. I assume that you have a reasonable sized and rigid lathe as you mentioned a camlock chuck mount. I have had success with this type of tool on lathes from Myford Speed 10 to Warco BH600. Have a look here

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Similar in concept to the one that Mark has shown. There are many about and most are very good. I have seen a couple of very cheap copies that did not hold the insert firmly, when it has been used you will certainly need the removal tool if it is working correctly. Have a read of this thread and my experience is similar to Nigel's. I have the pile of thin discs in the scrap box to prove it. When you have struggled for years success is adictive.

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I bought mine from Jenny at JB Cutting Tools and although I bought an extra insert I haven't needed to use it yet. I use the tool regularly on all my lathes from the front with every success. I have used power crossfeed but normally prefer to hand feed as you can then feel what the tool is doing. I always use lubricant and use a medium/slow speed but not dead slow. I use a steady confident pressure as most problems are caused by underconfident "pecking" at the material. The cross slide play shouldn't be a factor if you keep that constant pressure - confidence is everything. Oh and did I mention coolant/lubricant.

Before I found this type of tool I had most success with a tool mounted upside down on a rear toolpost running the machine forward. Again I used a steady pressure and plenty of coolant. It worked when the wind was in the right direction and the "parting off gods" were pleased (not often) and never really gave me any real confidence. Having invested in a good blade type tool with a good insert you will never, as Mark says, look back. These tools are one modern development that make years and years of "trade secrets" redundant.

Having said all of that, machine rigidity and squareness need to be "a given" if the spindle is going to lift or the saddle/cross slide is loose then mounting it upside down at the back is the only way to get the physics working for you instead of against you. Good luck.

Best regards

Keith

Reply to
jontom_1uk

On or around Wed, 18 Oct 2006 20:57:26 +0100, NoSpam enlightened us thusly:

hehe.

got a tool with a replaceable blade which came with the current lathe...

some trial and error and a question like yours to alt.metalworking or whatever it's called, and I can now part things fairly successfully.

The gist was that you need to get the tool set right and ground right. Mine is now ground not far short of 90 degrees. I set the tool so the top of it is about level with the centre of the work. The more obtuse you grind it, the less the tool can dig in - this was where my problems came from, mostly

- tool point was too acute so it could dig deep into the metal and then break or do other nasty things.

It takes a steady, quite firm feed and definitely works better with cutting fluid. slow power crossfeed and quite fast spindle speed seems to be the most reliable, but it can be done by hand too, if you don't have power crossfeed.

The blade on this tool is about 3mm wide at the top and about 20mm deep. I had a titchy tool with a thin blade, but it was a waste of space.

Reply to
Austin Shackles

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Hello All,

Regds. Jim Lugsden

Reply to
James Lugsden

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Thanks Jim, I can see the appeal of having the swarf tending to fall out but don't understand why the tool would tend to dig-in less just because it's upside down. By moving from front erect to rear inverted you've only moved it 180 degrees around the job, why would this change the tendency to dig-in?

Dave

Reply to
NoSpam

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Thanks Mark, what depth of cut can you get? My latest disaster happened when I was trying to part something about 75mm diameter (although that was unusually big).

I see you've got a multifix toolpost, have you ever found a use for the circular scale on the top?

Dave

Reply to
NoSpam

Dave, have a look at the following pic:

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On the front mounted parting tool: If you take a line from the mounting point to the tip of the tool, the natural movement is into the work as it deflects downwards.

On the right hand side is the rear post, and the arc of deflection is away from the work as it moves upwards.

Regards,

Duncan Munro

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Reply to
Duncan Munro

Aha! Thanks Duncan, a picture saves a thousand words.

Dave

Reply to
NoSpam

On or around Fri, 27 Oct 2006 11:16:31 +0100, Duncan Munro enlightened us thusly:

This was the point about grinding the tool with a more obtuse angle - having done that, mine is now better behaved - the more obtuse relief angle on the tool controls the speed at which it can be driven into the work.

Reply to
Austin Shackles

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Done 100 mm with no problems and unsupported by the tail-stock.

And I have a heavily constructed lathe Smart-and-Brown 1024 ...that must help.

I don't worry about parting off with my tool ........I just do it ...and that's it ...that's how good this tool is ...honest.

Circular scale has not come into use with me yet ..spose it's meant for repeating jobs with the same set-up if you are doing production work.

Got about five tool holders for it so far ...think I need another

5...there is never enough !

Guys are selling new Chinese ones on ebay ...but want too much for the things.

Managed to get 4 new German made ones from a guy on German ebay, cheaper and inc postage, ex-rate about a year ago.

All the best.mark

Reply to
mark

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