Carbide Insert Designations & Suppliers

[Dr_GMJNParticipant @dr_gmjn]

All,

Many years ago I was given some Sandvik 8mm carbide tool holders and inserts. I'm now pretty much out of inserts, and initially wanted Sandvik again. The prices are daft, so I sourced some from Chronos.

The original Sandvik inserts were DCMT 07 02 04 PF.

Having de-coded this, I think they were suitable for fine work on model engineering type work, however, today I've been turning some small top-hat bushes and shims for a rc model car. It occurred to me that the nose radius of the inserts was a bit big for this type of job, where I wanted a sharp internal corner on the inside of the bush overhang. I believe it is 0.4mm. Normally I'd have chamfered the mating part external corner to 0.5mm x 45 or something, but I couldn't get access in this case.

Question: The Chronos product code for their inserts was DCMT070204. There was no option to choose other options, so I'm guessing it's a 0.4mm nose radius again. Where can I get reasonably priced DCMT inserts and specify the nose radius? Or, as ever, any other comments on what I'm doing and how I'm doing it are welcome.

Thanks.

 

ETA: For scale,  the larger OD of the top hats was 7mm.

Edited By Dr_GMJN on 09/05/2020 21:30:33

[Dr_GMJNParticipant @dr_gmjn]

[KWILParticipant @kwil]

Cutwel tools £4.36 + vat. buy a whole box get a box free.

JB tools also a good source.

[HollowpointParticipant @hollowpoint]

The last two digits are the radius so just google DCMT070202 and you will find plenty of suppliers.

[Ian McVickersParticipant @ianmcvickers56553]

Check out Shop-apt. Always had good service from them.

[Dr_GMJNParticipant @dr_gmjn]

Thanks all.

what is a good radius for an insert used in a fly cutter – presumably reasonably large?

[jimmy bParticipant @jimmyb]

good starting point for info!

Jim

[Thor 🇳🇴Participant @thor]

Here are a couple of links explaining what the insert codes mean:

***Link***

***Link***

You can get DCMT 07 02 04 here, if the ALU versions fit your holder they have inserts with 0.2mm nose radius. Seems you can get DCMT 070202 here.

Thor

Edited By Thor on 10/05/2020 06:10:45

[JasonBModerator @jasonb]

For the non ferrous and even ferrous and fine work I would get DCGT 070202, APT mentioned above sell them in twos if you don't want to get a whole box.

I've not tried such a pointed shape insert in a flycutter, most then to use the rhombic CCGT or round RCGT. But if you are going to use the DTMT then try 0.8 tip radius

J

PS are those arms off a Rough Rider or Sand Scorcher

[magpieParticipant @magpie]

My fly cutter. I get a really great finish with this one.

[Dr_GMJNParticipant @dr_gmjn]

Thanks very much everyone – I think that answers my questions.

[Dr_GMJNParticipant @dr_gmjn]

Posted by JasonB on 10/05/2020 07:02:54:

PS are those arms off a Rough Rider or Sand Scorcher

They are actually off my 1984 Frog that I’m mildly upgrading to play around in the garden during lockdown.

IIRC they are the same basic arms as the Sand Scorcher and Rough Rider, but those versions had ball joints screwed into them instead of the shoulder screws I’ve got. Even when new it had around 1/2mm of play in the assembly (up and down and side to side), and combined with play elsewhere (and wear) I could move the wheels several degrees by hand. I did restore a Rough Rider in the past – far more robust in this area, but heavier too.

Cheers.

[Michael GilliganParticipant @michaelgilligan61133]

Posted by magpie on 10/05/2020 10:04:40:

My fly cutter. I get a really great finish with this one.

.

… How do you get it to give that straight-line finish ?

MichaelG.

[Dr_GMJNParticipant @dr_gmjn]

Posted by Michael Gilligan on 10/05/2020 10:21:14:

Posted by magpie on 10/05/2020 10:04:40:

My fly cutter. I get a really great finish with this one.

.

… How do you get it to give that straight-line finish ?

MichaelG.

That's awesome work, but I was going to ask the same question.

[Dr_GMJNParticipant @dr_gmjn]

Posted by JasonB on 10/05/2020 07:02:54:

For the non ferrous and even ferrous and fine work I would get DCGT 070202, APT mentioned above sell them in twos if you don't want to get a whole box.

So G seems to be a tighter tolerance on insert dimensions in 'plan'?

How does this affect cutting performance (assuming the actual cutting geometry is the same as an M designation)?

[Michael GilliganParticipant @michaelgilligan61133]

Posted by Dr_GMJN on 10/05/2020 11:13:42:

So G seems to be a tighter tolerance on insert dimensions in 'plan'?

How does this affect cutting performance (assuming the actual cutting geometry is the same as an M designation)?

.

I’m sure Jason will explain in detail, but

G = Ground

M = Moulded

MichaelG.

[Dr_GMJNParticipant @dr_gmjn]

Posted by Michael Gilligan on 10/05/2020 11:17:41:

Posted by Dr_GMJN on 10/05/2020 11:13:42:

So G seems to be a tighter tolerance on insert dimensions in 'plan'?

How does this affect cutting performance (assuming the actual cutting geometry is the same as an M designation)?

.

I’m sure Jason will explain in detail, but

G = Ground

M = Moulded

MichaelG.

OK, thanks.

So in practical terms…the entire cutting geometry in three dimensions is a tighter tolerance, or just the overall dimensions in one plane? The Sandvik chart doesn't make it very clear:

**LINK**

[Anonymous]

Posted by Dr_GMJN on 10/05/2020 11:13:42:

How does this affect cutting performance (assuming the actual cutting geometry is the same as an M designation)?

That's a wrong assumption, the cutting geometries are different. The ground insert generally has a better defined edge and a higher rake angle. Since it is ground the surface finish is better and thus swarf is less likely to stick to the insert. That's important when turning materials like aluminium. Moulded insert on the left, ground on the right:

Ground inserts are intended for non-ferrous materials, although of course they will work with ferrous. I don't use them for ferrous as the edges are a bit delicate.

Off topic – given your sobriquet are you a real doctor or a medic?

Andrew

Andrew

Edited By Andrew Johnston on 10/05/2020 11:40:06

[JasonBModerator @jasonb]

What Andrew says, **GT tend to have a crisper edge so are happier taking very fine depths of cut and also less likely to deflect long slender parts. The polished finish helps stop aluminium building up on the tip and they have a higher top rake angle which although not teh usually suggested geomerty for brass works very well and can actually reduce that shower of chips that a zero top rake tool tends to produce.

This shows a 0.2mm tip on the left of the DCGT type and a 0.4mm DCMT on the left.

Same DCGT taking a 1 thou cut off EN8, probably easier to see the swarf as it pile sup on teh cross slide than coming off the tool.

Different types of swarf

[Dr_GMJNParticipant @dr_gmjn]

OK thanks all.

Yes, I was getting a spray of fine chips when I was making the bushes. I cut very nicely though, and surface finish was OK. I think I'll get a few different types and try them.

[Jon LawesParticipant @jonlawes51698]

This thread has been a real education. Maybe this sort of thing should be a Model Engineering Magazine article if it hasn't been already.

[VicParticipant @vic]

Posted by Michael Gilligan on 10/05/2020 10:21:14:

.

… How do you get it to give that straight-line finish ?

MichaelG.

On the assumption that you’re being serious. You hold the part on some fine abrasive and hold it down tightly and push it along carefully in one direction. It gives a “brushed” effect. The only problem is that it’s quite easy to round the extreme edges of the part, this looks to be the case on one of the edges in the picture. I finished some parts like this a few weeks back.

[ChrisBParticipant @chrisb35596]

Look like you did not get the gist of Michael's post Vic

That's supposed to be a flycut finish, but as you say its a brushed finish…

[Dr_GMJNParticipant @dr_gmjn]

Posted by Jon Lawes on 10/05/2020 18:36:09:

This thread has been a real education. Maybe this sort of thing should be a Model Engineering Magazine article if it hasn't been already.

TBH I imagined most beginners would want to know this kind of thing, but I couldn't find anything in a search. Maybe I used the wrong terms, I don't know.

[JasonBModerator @jasonb]

Posted by Michael Gilligan on 10/05/2020 10:21:14:

Posted by magpie on 10/05/2020 10:04:40:

My fly cutter. I get a really great finish with this one.

.

… How do you get it to give that straight-line finish ?

MichaelG.

1000s of passes with a very small step over

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