What are these inserts?

Does anyone know what these insets are, I have enough to make it worthwhile either buying or making a tool.

Length across edge is 14.2mm

Thanks!

Edited By Chris Denton on 12/07/2015 11:45:55

Edited By Chris Denton on 12/07/2015 11:46:53

Hi Chris,

Not exactly sure of what you have but similar to the inserts which I use on my milling cutters. Lots of tools available that use these inserts at a reasonable price. (Take them with you to a local machinery tool store and confirm if they fit their cutters. Easier than making a special holder). Paul.

ISO TPMN 160308, Grade PR1255

t =3.18mm, I =16.5mm, d =9.925mm, R =0.8mm

The radius of the tips is quite large so maybe not so useful on a small hobby lathe? At least that's what I've found and certainly inserts aimed at the hobbyist tend to have a more modest radius. Well worth a try though if you can knock up a holder for them. They look to be double sided so six cutting edges per insert is very nice if you can get them to work for you.

They look to be " negative " inserts TPMG style, if thats the case, then they will be double sided the the clearance angle is provided by the toolholder. TCMT are the positive rake inserts {amongst other variations of the "T" type.

Positive rake inserts are the best suited for small lathes.

I suspect you'd have a pretty miserable time trying to use these. As Raymond says, they are negative inserts, so you'd end up with negative top rake and the tip radius is massive by our standards as Vic points out.

As Raymond suggests, you'd be better off trying a TCMT (triangular) or CCMT (rhombic) positive rake insert. There are also versions for aluminium with ground finish, different (no) coating and higher rake which give excellent results (TCGT and CCGT).

Note that as well as the basic shapes and dimensions of the inserts, there are many different cutting edges to choose from.

Murray

Thinking about it a bit more one of my milling cutters takes two inserts like the ones you've pictured.

Do you have a milling machine you could use them on instead?

Look closely at the first photo. The triangular faces are flat and parallel and the axial faces are perpendicular. This means that the only way you can present them to the cutting surface is with negative top rake. That would be OK for copper or lead but suboptimal for steel and light alloys. The upside is that you get 6 identical cutting corners. Doesn't really matter if you are turning or milling, the process is essentially the same.

In contrast, Paul's illustration shows a zero or positive top rake insert. It isn't double sided so only has 3 cutting corners but you can present it with positive rake with a suitable holder.

Are you convinced that your milling cutters are like the photo, rather than the illustration? The common or garden indexable milling cutters from Glanze (Chronos) have positive top rake inserts.

On an amusing note, I see that the photographs published on the Glanze Chronos website show all the inserts mounted backwards. I hope they don't ship them like that...

Merry

Hi Guys
They look like inserts for an high flow milling cutter.
Nobby

I use similar ones on the vertical milling machine, mine are 16 mm per side, I also use them in the lathe.

Ian S C

I have the little hogger set from Chronos. One has round inserts, one square and the other triangular and all the inserts are double sided. I checked the website but the pictures aren't clear.

**LINK**

I only usually use the face mill but it works really well on my mill and as said it's quite cheap to run as you get six edges per insert before it needs replacing and only two inserts in the cutter.

Not the best of pictures but you can just see the inserts are double sided.

Found a better picture.

Thanks, yes they are negative rake, probably not worth the bother then.

I already use CCGT inserts.

Thanks.

You could try making a flycutter type holder for them for use on a mill?

vic, if you want some top rake, you could make a tool holder with a few degrees of rake on it, the one in my photo is flat topped. I also have another one for the same size tool with left hand at one end, and right hand at the other. I'v got a hand full of other sizes that I got for $NZ5 (about 2 pounds) that I must make holders for. With the bridge type holder you can even hold tips that are normally brazed on.

My milling tool is a 2" three tipped face cutter.  A single tip fly cutter would be a very useful tool, scale it's size to suit your mill.

Ian S C

Edited By Ian S C on 16/07/2015 10:57:18

I'm happy with the hobby inserts and holders I use on my 8 x 14 lathe. If I had a few boxes of inserts like the OP though I'd try to find a way to use them, probably on the mill!

.

Ian,

Forgive me if I have missed a trick; but ... If you mount this insert to give positive rake, then surely there would be negative front clearance and no cutting.

MichaelG. .

As the tip has front clearance when mounted flat, the tip could be raised about 5* to vertical, this still gives clearance. Some tips are made with a 90* front clearance, and can be turned over, and the other side used, giving 6 cutting edges on a triangular tip of that type. On the photo of my tool holder the angle of the tip can be clearly seen.

Ian S C

Sorry, Ian ... I'm confused

If the tip can be turned over to give six cutting edges; how can they have front clearance unless tilted downwards ?

... am I being dim ?

MichaelG.

Ian is talking about 2 different things here:

His toolholder shows an insert with zero top rake. It's not "double sided", so has only 3 corners. Ian's point is that if the front clearance is anything like the 11 degrees shown in Paul Lousick's picture, you could actually mount the insert at 5 degrees or so to the horizontal and thus generate some positive top rake should you wish, while still retaining a degree of front clearance.

His second sentence simply observes that there are (other) inserts that are symmetrical and can be turned over, giving 6 corners. Obviously you can't pull the same trick with those and they wouldn't be very suitable for internal (boring) operations either, as you would be seeing negative top rake no matter what you do.

Both of these comments relate to making use of inserts that come with zero top rake. Obviously if you were buying new inserts you would want to buy proper positive rake examples to begin with.

Murray