Parting tool recommendation

[Sonic EscapeParticipant @sonicescape38234]

I'm looking for a good parting tool, preferably with a HSS blade. Something like this:

It should cut to a depth of at least 10mm. My tool post can hold tools up to 23mm tall. So I would avoid those 10mm tools that seems to be so common.

Anybody tried this kind of parting tools? I don't see how that insert can stay there …

Edited By Sonic Escape on 03/08/2023 15:24:10

[Sonic EscapeParticipant @sonicescape38234]

[bernard towersParticipant @bernardtowers37738]

the insert stays put because its in a taper and the forces acting on it push it further into that taper. the holder and the inserts also have matching V gloves top and bottom giving sideways integrity.

[Gary WoodingParticipant @garywooding25363]

Although I've got, and use the insert-tip tool, I usually end up using the blade type with a groove along the top of the blade, like ***THIS***

[Sonic EscapeParticipant @sonicescape38234]

That is interesting! I suppose it cuts more efficient than a plain blade.

[Sonic EscapeParticipant @sonicescape38234]

I had a look on other parting tools on that site, Chronos, and I found this model:

It is not a HSS blade type but unlike other models it doesn't hang outside the tool post. Maybe this helps.

Edited By Sonic Escape on 03/08/2023 16:27:56

[KWILParticipant @kwil]

I use the insert type almost to the total exclusion of the plain type, works every time for me, even when used for quiye large diameters. If set correctly they are fine, but being an insert you have to make them work hard.

Edited By KWIL on 03/08/2023 16:30:46

[bernard towersParticipant @bernardtowers37738]

the parting discussion goes on and on but as KWIL says you have to make them work , most parting problems seem to occur with users being too tentative its one of those jobs where you have to grow a pair of !!!!!!!!. Once mastered its a joy.

Edited By bernard towers on 03/08/2023 17:09:07

[SamsarandaParticipant @samsaranda]

I have both types of tool but must admit not had much success with the insert type, probably because you need to run at speed to be successful and having had some fearful lockups when using speed I am afraid to use its full potential. I now use the HSS blade type and find it very successful, you do need to make sure that there is the minimum amount of slack in your setup, not always easy on model makers lathes but from your posts it appears that you have probably got a commercial lathe. Dave W

[old martParticipant @oldmart]

We use both types of carbide inserted cutoffs at the museum. I prefer the blade type as they are double ended and if you crash the other, it might be scrap in one easy go. I have holders for 26 and 32mm blades, mostly Kennametal and Kyocera, but recently have got a couple of the second type illustrated by Sonic Escape together with a box of ten inserts which are very good value in 2mm width. For smaller lathes there are blades less than 26mm deep on the market. I have an HSS type at home for my 7×12 lathe that works very well.

Edited By old mart on 03/08/2023 18:09:26

[Harry WilkesParticipant @harrywilkes58467]

Success with parting off came when I purchased one like your first pic and mounted it on a rear tool post never looked back since to the point Ive got the insert type but never use it

H

[Howard LewisParticipant @howardlewis46836]

Having had bad experiences with parting tools munted in the front toolpost, Many years ago, I made a rear toolpost forn the ML7, and for its replacement.

I tried an inserted tool in the front post, on the new lathe and had dig ins which eventually distorted the holder so that the tips would no stay in place.

The tool used is a very old 3/32" HSS with no top rake.

At the risk of asking for trouble, dig ins are rare.

Howard

[old martParticipant @oldmart]

As Harry Wilkes mentiond, a rear toolpost mounted directly to the cross slide has great advantages. They are much stiffer and the swarf removal is helped by gravity. The top half to the one I made on a mill can be turned round for the 26 and 32mm blades which we use in 1.6, 2 and 3mm tips. Being able to lock the saddle front and rear also helps.

Edited By old mart on 03/08/2023 18:33:30

[DMBParticipant @dmb]

Sonic Escape, hi,

I recommend that you view website of RDG Tools. I am just a satisfied customer, having used one of their parting tools for sometime now. The holder fits my QCTP and a wedge clamp on the holder, securely holds a 3/32" thick blade. I chose the thick blade as thinner ones bend, creating concave and convex ends.

John

[Andy StopfordParticipant @andystopford50521]

I use the insert type 95% of the time – they're good, but resist the temptation to use cheapo inserts from ebay (other sources of dodgy inserts are available). I bought some and they mostly worked fine, but sometimes would shatter for no apparent reason. They'd probably still be an OK deal compared with more durable but expensive, quality ones, but the break up often left a fragment of carbide embedded in the cut, ready to destroy the next insert or HSS blade you tried.

[VicParticipant @vic]

I found insert types have their uses but aren’t particularly cheap to run. I mostly use the T shape HSS ones now. Much more wallet friendly and can be used on many different materials including plastics etc.

T shape parting blade

They are a available in a range of sizes.

[Chris CrewParticipant @chriscrew66644]

I am afraid I am a bit behind the times when it comes to this new-fangled tooling and a little too long in the tooth to change now. I use the good old-fashioned J&S type parting tool holders with the Eclipse type blade mounted upside down in a very rigid rear tool-post. On the odd occasion when I have 'pinged' the blade it's a two-minute job on the grinder to put the edge back on. With lots of suds pumped on it all works for me.

[Howard LewisParticipant @howardlewis46836]

A supply of lubricant, either by drip fed soluble oil, or even brush applied lubricating oil, is an enormous help.

Howard

[Mick B1Participant @mickb1]

I've used these things for about 20 years now:-

https://www.rdgtools.co.uk/acatalog/PARTING-SYSTEMS-FOR-SMALL-LATHES-1728.html

…in my Warco WM250V and Myford Speed 10 before that.

Every so often I decide they get so worn and chewed up that I buy a new one. I recently started using my third.

I won't say they always provide the user with the slickest and smoothest partoff experience, especially on grumbly steels – but they do actually work, often well, and they're cheap.

Edited By Mick B1 on 04/08/2023 11:23:36

[Martin Johnson 1Participant @martinjohnson1]

My experince with an RDG offering as in photo 1 of the OP was that the holder was fine, but the blade was not great in terms of grinding – the first 5mm or so was tapered the wrong way. After grinding that off, mounting it upside down at the back it has done some decent work, but the blade soon loses its edge.

The ceramic insert style (phot 2 in OP) have a habit of running under the pip and then shattering, each occurence costing about 7 GBP. That was with coventional toolpost. I gave up when the wallet couldn't stand the strain.

That is my experience.

Martin

[Bob Unitt 1Participant @bobunitt1]

Posted by KWIL on 03/08/2023 16:30:17:

I use the insert type almost to the total exclusion of the plain type, works every time for me, even when used for quiye large diameters. If set correctly they are fine, but being an insert you have to make them work hard.

I agree absolutely. I always used to have trouble parting-off, even with a rear toolpost. Since I changed to the insert type a good few years ago I've had much better results.

[Sonic EscapeParticipant @sonicescape38234]

Thank you for all replies. They were very useful. I didn't knew about RDG tools, there are a lot of interesting stuff there. I think I'll try a T shaped HSS blade. For parting I don't like to make deep cuts required for carbide tools.

On my lathe I can't use a rear tool post. But I can reverse the motor direction. So if I mount the tool upside down it should be the same thing.

I remembered that I have this tool (20x20mm). Does it worth the effort to try to make a parting tool from it? This would mean to decrease the width of the top part to 2-3mm. A lot of grinding.

Edited By Sonic Escape on 04/08/2023 15:51:45

[old martParticipant @oldmart]

Running in reverse is completely safe if you do not have a screw on spindle. You do need to still get the inverted tool tip on the centre line and if the saddle can be locked it will be a bonus in stiffness. That tool you illustrated would be much too much bother to get thinned down to a usable 3mm or less width for parting. If you can use a blade for carbide inserts or a tapered section HSS tool in a holder it would be better. I would recommend getting 2 or 3mm wide tooling for most sizes of lathes for best results.

That tool could be used for grooving or be made into a general turning tool. Possibly right and left handed at the same time provided you could get it shimmed to centre line both ways round.

Edited By old mart on 04/08/2023 17:27:38

Edited By old mart on 04/08/2023 17:29:07

Edited By old mart on 04/08/2023 17:31:13

[VicParticipant @vic]

Posted by Sonic Escape on 04/08/2023 15:38:39:

I think I'll try a T shaped HSS blade.

You won’t regret it, the blades are far more rigid than the plain tapered type. Several places sell them if you do a Google.

[SillyOldDufferModerator @sillyoldduffer]

I find blades in a rear-tool post work best for me, but it's not really the cutter that makes the difference. Which tool is the wrong question, should be 'What's the best way to part-off?'

First secret is rigidity. Parting-off applies more force to the cutter, job, and lathe than most operations. They are all likely to bend, causing chatter and dig-ins. When a dig-in occurs, the forces involved make it likely be violent.

Second is the need for a steady feed at the right rate. Steady is vital, and most humans are wobbly. The tool has to cut continuously, not too deep or too shallow.

Third is making sure the cutter is aligned correctly, going straight in, not applying side-pressure because it's at a slight angle.

Fourth is making sure swarf doesn't collect in the slot and jamb the cutter. Cutting fluid in applied in quantity helps.

Example likely to fail:

• A small lathe, these are light and bendy
• protruding job, sticking out of the chuck, also bendy
• a long slim cutter in a towering tool post perched on the top-slide, perched on a cross-slide, perched on the saddle, gibs loose or unlocked. The whole arrangement is bendy, plus all the slides can twist
• Operator mounts the tool at a slight angle, causing heavy side pressure. Maybe gets the height wrong too – parting off is fussy!
• Operator moves the tool by hand. He is unsteady, and him varying the feed-rate causes the cutter to bounce. It often collides violently with the job rather than peeling metal off at a sensible rate
• Operator is low to lubricate and stop swarf jambing the cutter

Counter example likely to succeed:

• Heavy lathe – big lathes are far more rigid than small ones
• Job protrusion minimised
• Short deep cutter able to resist pressure, protruding just enough to make the cut.
• Cutter mounted on a hefty rear tool-post bolted directly to the saddle.
• Ideally run lathe in reverse. This pushes the rear toolpost and saddle down, rather than lifting them.
• Operator selects correct RPM and feed-rate and engages automatic feed. Automatic feed maintains a constant cutting force, and eliminates human error.
• Operator pays close attention to clearing swarf

Only real men can part-off on a mini-lathe. They're light and don't have a rear tool-post or automatic feed. The tools are small and bendy.

Myford size machines are much less challenging, They have more weight and probably have a rear tool-post and automatic drive. Parting off from the front is do-able, but more likely to go wrong. A rear tool-post is generally reliable.

Parting off on bigger than Myford is almost trivial. Lots more weight, and even the front tool-post is impressively rigid. Automatic drive etc available. With a rear tool-post, parting off is trivial.

My lathe is a WM280, rather heavier than a Super 7, but not massive.

I can part-off by hand using the front tool-post if I'm really careful, but failure is always an option Front-tool post with automatic feed is almost 100% reliable – mostly works, occasional grief. Rear tool-post is 100% reliable unless I do something stupid.

Dave

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