parting off tool

[some bloke]

you lathe guys, I keep busting part off tools and need a decent one that has a cutting height of 14mm in a holder with a 16mm shank - any ideas please? vendors seem to keep the cutter secret for some reason.

[Hilbily]

Cant help you with that size tooling as mine are larger. HSS or M42 steel, make sure to have vertical and side relief, slow speed, tool above center by a hair so it doesn't grab, feed in slow and use oil applied with a brush into the parting cut before the cutter.
Mike

[Gloop]

Yup feed in slowwwwwww. If you dig. In to much it will snap.

[PESCA]

My father-in-law uses big lads' lathes and parts off from the rear, with the tooling upside down.

George

[some bloke]

I think my lathe is an oddball size. I get great results with ally, it's just the copper that's giving me grief and blunting tools very quickly. The chips come of like pieces of grit, and yes it grabs, if I try it a tad high it binds.

I've asked two local machine shops for a quote to do one end of it and part them off so I can do the other end - they don't want to know even if I could take good quantities. Both indicate that copper is a bitch to machine.

Am I being reasonable to expect vendors of tools like this to state the tool cutter height, because it's not clear in the photo or description?: http://www.ebay.co.uk/itm/360592597324

[Hilbily]

I think my lathe is an oddball size. I get great results with ally, it's just the copper that's giving me grief and blunting tools very quickly. The chips come of like pieces of grit, and yes it grabs, if I try it a tad high it binds.

I've asked two local machine shops for a quote to do one end of it and part them off so I can do the other end - they don't want to know even if I could take good quantities. Both indicate that copper is a bitch to machine.

Am I being reasonable to expect vendors of tools like this to state the tool cutter height, because it's not clear in the photo or description?: http://www.ebay.co.uk/itm/360592597324

Last weekend I turned down some 1" soft copper bar to .550 and parted off 8 washers .080 thick to make connections for a 4 x AA battery box. What worked for me was a sharp cutter with plenty of relief and oil and I got ribbons and without the oil it was little crinkled chips. The surface finish was pretty good. There was some discussion of using butter or cream a while ago, I didn't try that I just used motor oil and it worked well. Lubrication is your friend parting off.
You may need more relief under the cutting edge of the parting tool if it won't go any above center. Binding could be not enough side relief or cutter position not exactly parallel with the crossfeed direction and/or perpendicular to the part you want to part off.

You might call them and they could measure it, but depending on your swing it could be too tall with out modifying the holder. The toolholders are generally sized for the swing of the lathe: 6"-7", 12"- 16" and so on.

[some bloke]

Cheers Hilbilly, looks like I need a 12 mm one and shim it or a 16mm one and have 2mm ground off the bottom of it.

[terry1001]

Parting off can be a real pain but you do need plenty of clearance on all 4 faces, without it you will get grabbing and tool breakage. It's also important to have the tool as rigid as possible so keep the overhang to a minimum. It also helps to lock the carriage so that it doesn't tend to creep along the bed. Getting the feed rate is a matter of trial and error, just trying to keep the tool cutting smoothly without going to fast and grabbing.

[some bloke]

Bought a beefier parting off tool now with replaceable bits, should be here this morning.

[PESCA]

So what did you end up buying, Dave, and in what size?

George