Yes, I find that can also happen because some of the cheaper tips seem to need a bit of pressure to keep them cutting – I try and ease-off a bit when I know it’s very close to the middle, and let it just ‘shave’ the last bit for a few turns, any residue left should be foil-thin and can be scraped off, much as Nealeb says.

‘Sharper’ inserts can help, also, as said, making sure that c/height and alignment are as good as you can get them.

The ARC ones are Neutral inserts hence the N in the code, just the image shows the “ideal”. Right and left bias are available but can have the cut wandering off if the setup is not rigid.

MGGM200 inserts are available and sharper so will  put less pressure on the material and not cause the unsuported part and bit at the bottom of the cut to break off so soon but you are still likely to get a foil thin piece attached but flick it off with a finger nail or pull with pliers and then deburr the hole.

You could happily double or treble your speed with brass of that sort of diameter

Nealeb’s comment is what I’ve found. The effect can be somewhat reduced by grinding only a slight angle. I very rarely use inserts for parting since I tried the T shape HSS blades. They work great in all but the hardest materials and can be used on plastics and softer materials as well. They work fine on brass.

On 30 August 2025 at 11:35 Andy Brocklehurst Said:

On 30 August 2025 at 11:31 roy entwistle Said:

Don’t use cutting oil on brass. Is your tool too high? and slow down a bit.

Roy

Ok thanks, I’ll try and get the tool a bit lower.

As you are learning to use your lathe, try to establish the basics, such as making sure the cutting edge or point of the tool is exactly on the centre of the work.

This is one way

or

Most industrial parting I’ve watched videos of are using at least medium to high pressure flood coolant, enclosed machines, wider and very rigid carbide parting tips, tool & tip holders, and extremely rigid lathes as well. When there tail stock weighs more than my whole lathe, the results are going to be a bit different. 🙂 And many are using the slightly angled parting tip so there’s nothing left on the finished part. The usual parting tool blade deflection with our usually delicate parting tools may not be acceptable to some. All that contributes to usually acceptable surface finishes. Were still trying to do the exact same thing as they are, but there’s huge differences in how it’s being done. A second operation clean up cut to improve the parts surface finish where it’s been parted off or to remove any pip would be highly undesirable in an industrial environment due to time and extra cost.

Few of us are using anything like that. Sometimes I can get a nice clean parted surface without any minor grooving from the parted swarf, but it’s not predictable. For myself I’ll usually part off slightly too long and accept that need for a second operation clean up cut to the parts finished length. If that surface finish is unimportant and there is any pip or torn material left as Samuel already mentioned, that few swipes with a file or a rub on some emery paper will remove it. What industrial part production considers easy and normal, most of us can’t even dream of doing. And for those high volumes of part production, they also spend a lot of time and expense to optimize every single cutting tool, carbide grade down to the brand and coating type, rpm etc until they can get exactly what there looking for in the absolute shortest time possible for every part. That’s something rarely even mentioned. Even when parting, the most basic of cnc lathes today are going to have constant surface speed (CSS). So the surface cutting speed remains constant until it’s parted off. Many here may not have or for there own reasons, may not want to use power cross feed while parting off, so that’s another variable.