Parting-off Tools for Small Lathe

[Howard LewisParticipant @howardlewis46836]

My starting point would be a piece of steel the same width , or as close as possible, to the width of the Cross Slide.

Brick mausoleums and all that! But a big lump will improve the rigidity of the Cross Slide, making chatter a bit less likely, for other operations, if there is room to leave it in place.

Howard.

[James AlfordParticipant @jamesalford67616]

Thank you, again, for the suggestions. Reading through all of the replies, and thinking about the way I have been trying to part-off, I can see areas where I can make changes, which is good.

Michael: yes, that is my lathe.

The suggestions about a rear tool holder and ensuring that it is sturdy make sense and, again, I can see where my holder may not be helping. It works perfectly for turning, but I can see how it could be less effective now for parting.

I shall post a sketch of the cross-slide this evening and would welcome any suggestions.

This is the tool which I have, which was a present RDG Tiny Parting Off Tool. I am wondering about replacing it with one of these, depending upon which will fit Chronos Parting Tool or Another Chronos Parting Tool.

Regards,

James.

[David George 1Participant @davidgeorge1]

I made a rear toolpost last year and it is excellent. I can part off at least 50mm bar without thinking about it and i can just loosen the top bolt slide the blade to required length and tighten still on center height. I am still using the same tip I fitted last year which hasn't worn amazing.

David

[JasonBModerator @jasonb]

James, the style of adjustable toolpost you look to be using will be very unstable for parting off as you really only have the slender column supporting the tool so I would look at that before a rear mounted one.

I also would not expect your lathe to part off particularly large diameters, maybe 20mm in steel would be as much a sit could handle assuming wear over the years

[Michael GilliganParticipant @michaelgilligan61133]

Posted by James Alford on 16/12/2020 07:44:18:

[…]

I shall post a sketch of the cross-slide this evening and would welcome any suggestions.

[…]

Another Chronos Parting Tool.

.

Something along those lines should be easy to build into a rear post like David’s

MichaelG.

[Mick B1Participant @mickb1]

Posted by James Alford on 16/12/2020 07:44:18:

…

This is the tool which I have, which was a present RDG Tiny Parting Off Tool. I am wondering about replacing it with one of these, depending upon which will fit Chronos Parting Tool or Another Chronos Parting Tool.

Regards,

James.

Oh Gor blimey, I never realised RDG sold anything like your 'tiny' one, with only that ickle clamp to stop it nosediving. The one I've used for ages, and have found adequate for most purposes in a lathe that would accommodate it, looks pretty much identical to your 'Chronos Parting Tool' – though I reckon I bought it from RDG.

I've never bothered with making RTPs, though I'd use 'em if I found 'em when I was working as a turner – but then I'm always reluctant to embark on tooling projects unless I have to.

[JasonBModerator @jasonb]

Not found an issue with the RDG one" nosediving" myself, worked OK doing the cooling fins on this bit of 40mm dia steel in a standard front toolpost.

[egaParticipant @ega]

I like the idea of a narrow parting tool. So far as I can tell from their website, the RDG blade is 1.4mm thick.

I assumed that the RDG clamp would have to project from the toolpost but Jason seems to have minimum stick-out?

[JasonBModerator @jasonb]

This shot shows the stickout better

I tend to use this on material upto about 20mmdia as being a 1.5 x 6mm blade if you have much more out of the holder it can start to wander off sideways quite easily. I also have the ARC version of "another Chronos parting tool" which is similar width and 8mm deep, main advantage of this type is the tool is clamped firmly as I did find the single clamp type can let the tool slide back into the holder.

My preferred thin parting tool is the Nik-Cole Minithin with the 1mm wide insert but that will only do 12mm dia, it can also go right upto a shoulder unlike the single clamp type.

Bigger stuff gets done with a GTN2 insert tool

[Mick B1Participant @mickb1]

Posted by JasonB on 16/12/2020 10:54:00:

Not found an issue with the RDG one" nosediving" myself, worked OK doing the cooling fins on this bit of 40mm dia steel in a standard front toolpost.

…

Well, your photo seems to show a retaining cleat or suchlike at the rear end, stopping it from rising, but I can only see a small clamp at the front of the holder on James' link…

[JasonBModerator @jasonb]

Mine is the same as James' link. There is a short 25mm or so ledge that the bottom of the tool sits on and then just the upside down "L" shaped clamp to hold it there, nothing at the other end to stop the blade lifting. Just like these Warco ones but I would not use them with so much blade sticking out

[egaParticipant @ega]

JasonB:

Thanks for the Minithin tip; Santa will have to be in a very generous mood!

A more economical solution with the 1.4mm HSS blade would be a shop-made holder for minimum stick-out and rear support.

[Gary WoodingParticipant @garywooding25363]

I use This Chronos Parting Tool in preference to the tipped type that I used to use. It has a groove along the top and works really well.

[James AlfordParticipant @jamesalford67616]

Thank you for all of the suggestions and feedback on the different types of cutter and holder.

No sketch, but the slide on the Flexispeed is a whopping 2" wide, 4" long, with a 3/8" slot down the middle.

Decision:

• Buy one of these: Chronos Parting-Off Tool
• Try it in my current tool post, purely for comparison with the current parting off tool
• Make a sturdier tool post if, or when, the current one proves to be too unstable
• Try a rear tool post if the front tool post proves to be ineffective

Regards,

James.

Edited By James Alford on 17/12/2020 08:05:37

[Gary WoodingParticipant @garywooding25363]

James,

In my opinion, the Chipbreaker blade, as in my previous post, is superior to the usual flat topped blade.

[Michael GilliganParticipant @michaelgilligan61133]

Good decision, James

MichaelG.

[Howard LewisParticipant @howardlewis46836]

Parting blades or tips, with a central groove reduce the risk of swarf jamming in the slot, because the swarf is now two streams, each much narrower than the slot being cut.

As a plug for rear toolposts, where possible; for a long time I ground the tool at an angle so that any "pip" was on the raw material rather than the work. This results in swarf that is wider than the slot, and has the additional disadvantage of tending to force the blade sideways. With the tool set with zero top rake, and light lubrication with soluble oil, a dig in was pretty rare event.

With the tool ground square, and zero rake, I am now brave enough to use a fine power cross feed for parting off.

No doubt this is pride coming before a big fall!

Howard

[James AlfordParticipant @jamesalford67616]

I chose the flat-topped blade and holder because it was smaller than the v topped blade and holder. After ordering it I realised that the v topped chipbreaker type comes in different sizes.

Hey, ho.

James

[Mick B1Participant @mickb1]

My own view is that parting under power is a bit of circus trick. You can get excellent feel for how fast you can advance the tool doing it by hand, and there are often conditions where it may be practical to vary the feed rate as you plunge in – especially going extra slow as you near the cutoff point in order to minimise the pip or ring. I can't see that you'd reliably save time with power feed in most situations outside a repetition shop.

[not done it yetParticipant @notdoneityet]

My own view is that parting under power is a bit of circus trick.

I nearly always part off with power feed. Likely takes a little longer than hand-feeding, but leaves me with one hand for lube/cutting oil and the other ready to trip the power feed before it falls off, if It is a large lump, or to catch the part rather than losing a small part. I’m not working at piecework rate!

[Anonymous]

Posted by Mick B1 on 17/12/2020 17:42:03:

…..reliably save time with power feed in most situations outside a repetition shop.

I tend to part off under power on the manual lathe and by hand on the repetition lathe.

Andrew

[Author]

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