Grinding carbide inserts

[Steve PaveyParticipant @stevepavey65865]

in an attempt to get my Banggood face milling cutter to achieve something other than clatter and bang I decided to have a go at grinding the inserts – the problem being that they didn’t all make contact with the work. And it seemed to work – with some trial and error I managed to get all four inserts to more or less touch the workpiece and this resulted in a much smoother cutting action.

I have since had a go with a couple of used lathe tool inserts, also successfully.

Does anyone else reground their inserts?

[Steve PaveyParticipant @stevepavey65865]

[John HinkleyParticipant @johnhinkley26699]

I don't – or at least I haven't yet, but Stefan Gotteswinter on YouTube does. Here's a link to his video about it:

**LINK**

Good luck,

John

[David George 1Participant @davidgeorge1]

I regularly touch up inserts to change the radius or form and as I braze some to shanks to make tools I regrind them all the time.

David

[John OlsenParticipant @johnolsen79199]

I have the good fortune to have a Glendo Accu-finish machine which uses diamond wheels and can sharpen both HSS and carbide. The wheel turns quite slowly and is kept wet with a suds solution so they last well. Mine was originally purchased by my father during the eighties and the original wheels are still going strong. I have three grit sizes, 300, 600, and 1800. The latter leaves a mirror like polish on either HSS or carbide. This helps in giving a similarly good finish on the end job.

I haven't tried resharpening inserts that screw on. but I have used quite a lot of triangular inserts without holes and with plain faces. (no chip breaker edges) I braze these onto a square shank and then sharpen them. They work well in either the lathe or the shaper..

I see Glendo are still around, I would recommend them. I have no connection with them other than being a very satisfied user.

John

[Chris Evans 6Participant @chrisevans6]

I am a cheapskate and have been grinding inserts for years. I have a face mill cutter that should use a TPKN 16*** milling insert that costs twice the price of TPUN1608*** turning insert. I use the turning insert and with a touch up on the diamond wheel cuts well and gives a good finish. Changing corner radii is also a regular thing.

[GoCreateParticipant @gocreate]

Hi

I use a carbide insert parting tool. Initially I found it did not cut as well as expected and I didn't have much confidence using it . Recently, after very lightly grinding the front rake of the parting insert on a diamond wheel, I found it cut a great deal better and without any problems.

Nige

[Neil WyattModerator @neilwyatt]

Posted by tractionengine42 on 10/01/2018 10:42:20:

Hi

I use a carbide insert parting tool. Initially I found it did not cut as well as expected and I didn't have much confidence using it . Recently, after very lightly grinding the front rake of the parting insert on a diamond wheel, I found it cut a great deal better and without any problems.

If you don't have the confidence to use quite a positive feed with an inserted carbide parting tool it will wail, rub, and then may grab and break. You do need to 'go for it'.

Sharpening one will allow you to cut more gently but make the insert significantly more fragile.

Neil

[Mike PooleParticipant @mikepoole82104]

I suspect that insert tooling does not perform as expected because many tips are designed to perform in very defined conditions. Many amateurs me included tend to creep up on a finished size and many inserts do not work well in this scenario. Stefan demonstrated putting a very sharp edge on some tips and was able to take fine cuts with what looked to be a fine finish. I suspect that although he has made a very useful modification it will not perform anything like the tip he made it from, but that was the point I think. Part of the attraction of tipped tooling is that it relieves the user of the task of making and maintaining a HSS tool and the task of making or buying equipment to do the task. A basic bench grinder can do much with a practised operator but some tooling to reliably present the tool bits is well worth making or acquiring.

Mike

[MWParticipant @mw27036]

I don't think it's possible to rule out older cutting materials like HSS completely, even carbon steel tools have their uses. As been stated, harder tips tend to have a "blunter" edge because of how brittle it is at a fine point, So they only tend to perform very averagely in the finish department for softer materials, where a finer edge is desirable.

Having said that, the polished "aluminium" cutting tips tend to do better for this.

I have watched quite a few of Stefan's videos and his one piece of advice for carbide sharpening- "don't get the green grit wheels, get a decent diamond wheel instead".

Michael W

[Chris Evans 6Participant @chrisevans6]

Most tips are of the "MT" moulded tip design. Grinding them does help on our toy lathes, somewhere there is an old thread from Jason B about using "GT" ground tip inserts made for aluminium when cutting steels with light cuts. I have found them to work really well.

[Neil WyattModerator @neilwyatt]

Another trick is to use a diamond slip to put a tiny wiper flat on CCMT inserts. It seem to be hard to find ones smaller than CCMT09 with a wiper, but I've had a mirror finish on horrible steel using a CCMT0602 after using a few light strokes to create a wiper – you need to barely remove anything.

Neil

[paul raynerParticipant @paulrayner36054]

Neil

Whats a wiper flat?

Paul

[Neil LickfoldParticipant @neillickfold44316]

The wiper flat behaves like a burnishing tool. It will also enable higher feed rates on straight turned parts. But of no use to profile turning. When profile turning a better finish can be obtained with a different surface speed to the 1st pass and with 1/2 or 1/3 of feed rate. For regrinding the carbide inserts, the best is to use a diamond grinding wheel.

Neil

[paul raynerParticipant @paulrayner36054]

thanks for reply Neil. Never heard of it before. I will have to try that sometime

regards

Paul

[MuzzerParticipant @muzzer]

Posted by Neil Lickfold on 11/01/2018 03:38:42:

The wiper flat behaves like a burnishing tool.

Neil

That's misleading. "Burnishing" involves polishing (rubbing), whereas in fact a wiper geometry is about having a flat or larger radius that is parallel to the direction of travel. So instead of ending up with scallops with the radius of the tip, you get a larger radius / shallower scallop. If the wiper has a true flat, you can achieve an almost scallop-free finish. Instead of requiring larger forces (rubbing), it actually reduces them, as it still cuts in the same way but with a smoother profile and normal clearance angles.

Murray

Edited By Muzzer on 11/01/2018 22:14:43

[EmgeeParticipant @emgee]

Posted by Neil Wyatt on 10/01/2018 17:32:53:

Another trick is to use a diamond slip to put a tiny wiper flat on CCMT inserts.

Neil

Please add some info on which surface or edge the flat is applied to.

Emgee

[Neil LickfoldParticipant @neillickfold44316]

Muzzer it depends how you make them. Yes some is a radius that then has a small parallel section then has a relief. These are most of your commercial inserts. You can also make you own that has a very small section that does burnish the section. To burnish it can only be very small radial change, like 0.005mm is a lot. If you try to burnish like 0.01mm per side that is a whole lot and will make a galled up looking mess. Often the wiper flat is quite short and in general is equal in length to the radius on the insert.

So you have a radius, that instead of being a complete radius , it finishes at tangent to the work surface and stays parallel for about that radius in length, and then the tool has clearance from there.

Neil

[Neil WyattModerator @neilwyatt]

Posted by Emgee on 11/01/2018 22:25:43:

Posted by Neil Wyatt on 10/01/2018 17:32:53:

Another trick is to use a diamond slip to put a tiny wiper flat on CCMT inserts.

Neil

Please add some info on which surface or edge the flat is applied to.

Emgee

Parallel to the surface of the work.

[Author]

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