Which is the best parting tool ?

[Speedy Builder5Participant @speedybuilder5]

More to the point, what top and front rake should we use with HSS tooling on perhaps the most common materials.

Viz: Steel, S.Steel,Cast Iron,brass,copper and Aluminium.

Should the front of the tool be parallel to the axis of the lathe, or part left or right.

What speed should we use to minimise chatter (assuming that we have reduced tool overhang, tightened slideways etc). I frequently start off in back gear and then revert to normal as the diameter reduces (Oh for variable speed etc).

I guess this has all been answered before, but is there a wall chart or something we could print off ?

[Brian JohnParticipant @brianjohn93961]

Yes, I agree. Some sort of table or chart would be an excellent idea. I have bought a few books on how to use a lathe and so far NONE of them have given me this information. The writers always seem to assume that the reader knows how to use a lathe. We don't…that is why we bought their bloody book !

[JasonBModerator @jasonb]

Brian if you go for the holder in the second link you won't need to worry about top rake as like quite a few others the tool holder incorporates a few degrees of positive rake so the top of the tool does not need grinding.

This will give you a general purpose tool that will work on all the common ME materials, if you are going to be doing a mass of work in one particular material you could consider grinding a tool to suit but most of the time this one angle will do and saves having to have 3 or 4 different profile tools or regrinding the one tool every time you work a different material.

As for speed, as fast as the machine will allow without complaint eg chatter. Just like one tool is not the best, one set of speed tables will not cover every machine, tool width, angle, material and work dia ( which is constantly changing anyway) Get used to using the machine and you will soon get a feel for what works in your own situation.

J

Edited By JasonB on 25/06/2014 18:24:32

[Neil WyattModerator @neilwyatt]

+1 for what Jason says. My HSS blade has a few degrees top rake from the holder, I grind clearance on the end then polish on diamond wheel. Works fine in all the materials you list + bronzes. Just doesn't like being forced in high carbon steels

Neil

[Bob Brown 1Participant @bobbrown1]

With HSS I usually run about 5 degrees front rake with a slight angle in the front rake left to right looking down and similar angle on the back rake. Back rake is not always needed but some tools have a profile on the top edge so those will need ground. The angle on the back rake helps to provide a small amount of side clearance to the tool, more relevant on larger diameters.

Not that critical, near enough is fine but rigidity is the key and tool must sharp, be on centre height and square to the work piece.

Do not be frightened of it as less feed can cause chatter, but for some of the smaller machines do not try to use a tool that is too wide.

Largest diameter I've done to date is around 9" 6082 aluminium that was some tool overhang and did cut a slightly curved shape as the tool was pushed off line. I was not too worried as I was only trying to save material.

Bob

[NJHParticipant @njh]

The best parting tool ? – the one that works for you! The best advice is to be not too tentative in your approach. I guess you need to practice and get the feel of things.

If all else fails there is always the two handed tool in the frame! ( but that might be considered by some as cheating. I put up my hand and admit that I've gone that way on occasion )

Norman

[Neil WyattModerator @neilwyatt]

I don't angle the front on tools below 3/32" wide, as they flex too easily.

Neil

[Nigel McBurney 1Participant @nigelmcburney1]

HSS parting tools ,about 7 degrees top rake, speed I was taught use about half normal turning speed, on centre lathes though on capstan lathes higher speeds could be used as they were designed to part off as they nearly were all used on bar work. The front angle was set so there was no pip left on the finished part,

[Chris TriceParticipant @christrice43267]

I’ve always used 50% of normal cutting speed for parting off too.

[Brian JohnParticipant @brianjohn93961]

This might be an even better parting tool as it has three nuts to secure the blade :

**LINK**

[Bob Brown 1Participant @bobbrown1]

As your lathe is small that should work quite well for smallish diameter around 1" as the blade is quite thin at 1.5mm.

I have used something similar for 12mm dia 304 stainless with no problems.

[Stuart BridgerParticipant @stuartbridger82290]

I use a Glanze indexable parting tool from Chronos. Works a dream. I have also used HSS with no issues.

I would recommend flood coolant. I must admit I have never really worried too much about speed. I have a VFD and tend to ramp up the speed as the cutting diameter reduces, which just "feels" better.

[Michael GilliganParticipant @michaelgilligan61133]

Brian,

I'm going to answer your original question literally …

In my limited experience: The best parting-off tool I have used was one of these.

… Coolant fed, with a chip-breaker insert.

It's an unsuitable tool for your lathe but; study the features and you will look at some of the others with clearer vision.

MichaelG.

[MuzzerParticipant @muzzer]

Apart from figuring out the speeds and feeds to avoid judder, the biggest problem with parting tools seems to be when the swarf gets snagged in the groove and you get that awful dull cracking noise as the HSS tip shears off. Since I bought my Korloy 3mm Sawman parting tool (very similar to MichaelG's but without the nice coolant channel – and stocked in the UK by Cutwel), I've had a few moments when the swarf has tried to jam but the tool has prevailed – the blade is significantly more rigid than the HSS tools and is presumably also a lot less brittle than hardened HSS. I always part with power feed now, as I find it is actually easier to get a consistent feed rate and I expect that is better in terms of reducing the risk of breakage. There are some pictures of the parting tool and swarf in my albums. I bought the blade and made the holder myself

I also bought a Korloy MGT 2mm grooving and parting tool which can part up to about 2" dia but is also capable of turning (axial cutting) which is dead handy. The aluminium cutting tips are worth getting (I got mine from APS in Glasgow) as this further reduces the likelihood of snagging the tool when cutting light alloys. They have more top rake and are differently coated.

Unless you have a snazzy CNC machining centre which maintains constant surface speeds (which I currently don't!), the cutting conditions at the tip will vary throughout the cut and the swarf formation will change as you progress. That sudden change of swarf generation seems to be what causes the snagging and breakage that I learned to dread with HSS. With the indexable parting and grooving tools I have yet to suffer any breakages. They just power on through.

Murray

Edited By Muzzer on 27/06/2014 03:34:58

[Michael GilliganParticipant @michaelgilligan61133]

Posted by Muzzer on 27/06/2014 03:27:26:

… the biggest problem with parting tools seems to be when the swarf gets snagged in the groove and you get that awful dull cracking noise as the HSS tip shears off.

.

Murray,

Exactly !! … Been, there, done that < etc. >

The real beauty of that Sandvik Coromant tool is that the chip-breaker shaping also curves the swarf slightly, across its width, so that the swarf becomes narrower than the groove: Being in short pieces, it's then easily washed away by the coolant. … Very, very, clever.

MichaelG.

.

Edit: corrected typo.

Edited By Michael Gilligan on 27/06/2014 07:07:47

[IanTParticipant @iant]

I'm afraid I don't use that much coolant Michael – just the odd brush dipped in the cutting-oil jam jar.

What I am guilty of (on some of the 'scarier' cuts/tougher material) is winding back, stepping over a smidge and machining myself a bit of clearance before stepping back to the original cut and going in deeper. To get a better finish on the "parted off' bit I either do a very light "skim-in" (as part of the final parting cut) or lightly face the item after parting off.

This is a habit I gained before I discovered inserted tip parting tools and my tips do have the shaped top surface that you describe, so I guess swarf jamming in the groove may be not be so much of an issue now anyway.

But sometimes a bit of belt and braces does help to calm the old nerves!

Regards,

IanT

[Bob Brown 1Participant @bobbrown1]

There seems to be a large difference in techniques all of which work, about the only thing that is common is sharp tool and square.

The technique that suits one machine may not suit another even ones of a similar make due to variances in rigidity amongst others, even the material will effect the operation. I think at the end of the day it is a case of horses for courses, a bit of trial and error and practice usually results in a technique that suits the individual machine/person.

As the parting operation is normally one of the last operations I prefer just to turn the tool post or fit the tool (3 way Dickson tool post) and part the job off. Messing about is not for me if I'm making 2 + parts just like to get in to a rhythm and not had any problems to date.

[Brian JohnParticipant @brianjohn93961]

I like this one a lot but the seller does not have spare blades :

**LINK**

Who makes spare blades to fit this parting tool : 1.5 X 10 X 80mm ? The three nuts should hold the blade very firmly.

[BazyleParticipant @bazyle]

A feature if the link above is that the holder thickness is overcome for small lathes by having the mounting bar on the side. It was mentioned that the initial post link 3 would be too thick for mounting in a small lathe. However I have one of these on my Hobbymat with a bar screwed to the side.

[Neil WyattModerator @neilwyatt]

> so that the swarf becomes narrower than the groove

GHT (and others) recommended a v-groove ground along the top of an HSS parting tool for this purpose. Not easy to do well.

Another tip (as per LBSC) is an HSS tool with the tip shaped like the tail of a fish, possibly with the corners slightly rounded as well. This is not for parting off, but for turning crankpins etc. to a good finish. The tool can be worked from side to side as well as fed in and is less liable to chatter. I have tried this and it works well.

Neil

[Michael GilliganParticipant @michaelgilligan61133]

Posted by Michael Gilligan on 26/06/2014 21:42:25:

It's an unsuitable tool for your lathe but; study the features and you will look at some of the others with clearer vision.

.

Neil,

Nice to see we're getting there

MichaelG.

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