Which Carbide Lathe Tools?

[MarkSParticipant @idriver]

Hi Guy’s,

I now have my new lathe (DB10VS) and mill (Seig SX3.5) setup. The lathe came with a set of HSS cutting tools and I added some carbide tip boring tools. During my first few test pieces I really liked the ease with which the boring tools cut the metal and have decided that I want to go down the route of using carbide tipped tools for general turning on the lathe which will take 12mm tooling once I fit the QCTP.

What a bewildering array of tools and tips there are though!

Is there a recommended general make or type of tip I should start with for some standard turning and facing of mild steel?

Thanks.

[JasonBModerator @jasonb]

I have tried to standardise on the CCMT and CCGT inserts as these can be used in boring bars as well as turning tools. A right handed holder for these will do both turning along teh length as well as facing when the holder is mounted at right angles to the lathe axis and would be my suggestion for trying them out.

I have used mostly the Glanze brand sold by Chronos for the last 15yrs and they seem perfectly adequate. Sods law they are not listing a 12mm one which probably indicate sout of stock but this is the 10mm one, I would suggest even at 12 mm that you use the 06 size inserts as it keeps the cost down, my preference is a CCGT 060202 which is the bright polished (sharper) insert with a small 0.2mm tip radius and they will work on ALL metals we are likely to use.

Add other holders such as left hand and ones that use the obtuse two “spare” corners of the inserts if you get on OK with the righthand one.

Inserts from APT, they do them in two’s for hobby use or boxes of ten once you have decided what you like to use

[John HaineParticipant @johnhaine32865]

12mm seems large for a smallish lathe. Id suggest standardising on 10mm.

[Nigel Graham 2Participant @nigelgraham2]

The bewildering variety of inserts is due to they being made for high-rate machining of all sorts of shapes in all sorts of metals. The intention in industry is that you use the right tip for the material as well as the form being cut, and the tips’ commercial lives are often quoted by their own manufacturers in a few tens of minutes!

Although I am not convinced by the arguments that carbide tips have to be used at high speeds on our modest machine-tools because they can be to meet commercial production rates.

The arcane mix of letters and numbers encodes the tip shape, size, material and profile.

 

I do use both HSS and carbide – almost all bought from J.B. Cutting Tools – but mainly carbide tips for screw-cutting only because the angles are fully correct. Sometimes it is easier to obtain a better finsih on steel with a properly-ground HSS turning tool than with carbide, but it depends a lot on the material, depth of cut and feed. And is a lot cheaper – carbide costs brass!

 

Thread-cutting using insert tooling:

The standard screw-cutting tips do not normally give the true, rounded roots and crests; so if you go in to the “book” depth for the tip’s apex the result will be shallow. So I normally cut to that depth and finish the thread to size and shape with a die; sometimes turning a little “book” root-diameter spigot on the end as a guide.

(Studs are sometimes left with that little spigot anyway, as thread-protector and assembly aid.)

 

[Nigel Graham 2]

On Nigel Graham 2 Said:

 

 

Thread-cutting using insert tooling:

 

The standard screw-cutting tips do not normally give the true, rounded roots and crests; so if you go in to the “book” depth for the tip’s apex the result will be shallow. So I normally cut to that depth and finish the thread to size and shape with a die; sometimes turning a little “book” root-diameter spigot on the end as a guide.

(Studs are sometimes left with that little spigot anyway, as thread-protector and assembly aid.)

 

The standard is generally a “full Form” insert which has all the correct radii and wil “top” the thread. It is the “partial form” inserts that cover a range of pitches that won’t form the correct radii and need the depth adjusting.

Just down to the user what they buy but as many model engineers have deep pockets they don’t tend to use full form as much preferring one insert that may come close to what several full forms would do.

[Julie AnnParticipant @julieann]

I prefer to use full form inserts. Saves faffing about; starting with nominal diameter material one just cuts to the theorectical thread depth, give or take a thou, and job done. The roots and, more importantly, the crests are fully formed. So no need to mess about deburring the crests. When the crest is ‘just’ beginning to get cut that is a good indication that the thread depth is correct.

Be aware that external and internal threading inserts have different profiles as per thread specifications.

Julie

[old martParticipant @oldmart]

For 12mm square tooling, I would recommend starting with CCMT 06 for steel, CCGT 06 finishing steel and non ferrous, they use the same holder. And DCMT 07 for steel and DCGT 07 for finishing steel and non ferrous which also share a holder. There are several sizes of boring bar which also use these inserts.

If you want to try small quantities of inserts rather than buying a whole box which turn out to be unsuitable, then APT will sell them to hobbyists at a slightly greater unit price which allows experimentation. APT also sell threading inserts singly. I can recommend buying from them.

The cheap Chinese inserts made today are better quality that they used to be.

[BazyleParticipant @bazyle]

“general turning on the lathe which will take 12mm tooling once I fit the QCTP.”

As JH implied it is not about shoving in the biggest you possibly can. For a 5in centre height lathe 1/4″ is enough and 3/8″ when you need long reach. Big tools just get in the way.

[VicParticipant @vic]

I’ve only got one 12mm Toolholder, this type, it works well. This is a pretty good deal at the moment, Tool Holder + 10 inserts. You can get replacement inserts on eBay and Amazon for around £10 for a box of ten. Even cheaper if you don’t mind waiting a week or so for delivery from abroad.

[old martParticipant @oldmart]

I didn’t expect to see a 12mm square toolholder made for DCMT 11 size inserts, they are more at home in 16mm and larger fittings. DCMT 11 and DCGT 11 are our favourites in 20mm toolholders.

The Smart & Brown model A toolroom lathes are only 9 X 20, so the working radius is only 4 1/2″, but they were originally intended to take 3/4″ square tooling.

[JasonB]

On JasonB Said:

I have tried to standardise on the CCMT and CCGT inserts as these can be used in boring bars as well as turning tools. A right handed holder for these will do both turning along teh length as well as facing when the holder is mounted at right angles to the lathe axis and would be my suggestion for trying them out.

I have used mostly the Glanze brand sold by Chronos for the last 15yrs and they seem perfectly adequate. Sods law they are not listing a 12mm one which probably indicate sout of stock but this is the 10mm one, I would suggest even at 12 mm that you use the 06 size inserts as it keeps the cost down, my preference is a CCGT 060202 which is the bright polished (sharper) insert with a small 0.2mm tip radius and they will work on ALL metals we are likely to use.

Add other holders such as left hand and ones that use the obtuse two “spare” corners of the inserts if you get on OK with the righthand one.

Inserts from APT, they do them in two’s for hobby use or boxes of ten once you have decided what you like to use

Thank you for the great reply. That gives me a lot to go on moving forward.

[Howard LewisParticipant @howardlewis46836]

One of the advantages of using a 8 or 10 mm tool shank is that the CCMT0604 inserts are common with 6 and 8 mm boring tools reducing the cost and space of tip stock holding.

Howard

 

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