Maximum Hardness Machinable by Carbide

[Smrtman5]

What is the maximum hardness Rc that an average carbide endmill or insert can machine?

and while im at it, can the more exotic inserts like PCD or ceramet cut harder material?

[Andre' B]

Tool steels up to 60 RC can be machined fairly well without getting into really high priced tooling and machines.

Yasda says they are machining stuff up to 90 RC but I do not know what they are using for tooling.

[mike sandvik]

I've turned hardened h13 ( 72 rc) with PCD but only .010 deep of cuts.
If your milling, try Tricordial milling .It works great even with 65+ rc. with a carbide endmill

[K&Y]

Originally Posted by Smrtman5 What is the maximum hardness Rc that an average carbide endmill or insert can machine? and while im at it, can the more exotic inserts like PCD or ceramet cut harder material?

I can tell you that CBN (Cubic Boron Nitride) can be used. CBN is used in the machining of "hardened" ferrous materials (Rc 45 and harder), and High temperature alloys (Rc 35 and harder). Here's a chart of where CBN can be used.

Hardened ferrous materials (45 Rc and harder):
Alloy Steels: 1055,4140,4340,8620,52100
Tool Steels: M-2, M-42, T-15, O-2, A-s, D-2, S-5
Chilled Cast Iron

High Temperature Alloys (35 Rc and harder):
Nickel-Based Alloys: Inconel, Rene, Monel, Incoloy, Waspaloy#
Cobalt-based Alloys: Stellite, Colmonoy, Wallex


You'd be surprised how inexpensive CBN is when you figure out your bottom line, due to the fact that it will outlast anything that carbide manufacturers have out there.


PCD is strictly for use in "Non-Ferrous" applications, such as the following:

-Aluminum Alloys
-Copper Alloys (including bronze)
-Sintered cemented tungsten carbide
-Fiberglass, plastic composites
-Carbon/Carbonfiber, and plastic composites
-High-alumina ceramics


If you have any more questions, I'd be happy to try and answer them for you.

[Smrtman5]

Thanks for the great info everyone

Andre- 90Rc?? That cant be a normal steel can it? that would be way to brittle, i didnt even think you could get most steel past 70Rc

What are the advantages of PCD? Longer life? I thought HSS was better than carbide for aluminum? i could certainly see an argument for lower cost for a hobbyist or small runs.

[Andre' B]

Did some looking around, found a story from 2002.
http://news.thomasnet.com/fullstory/9875
Cutting on carbide using some kind of diamond coated EM.

The HSS being better then carbide for aluminum is way out of date, there are carbide inserts available that have a very sharp edge.
PCD in aluminum gets you some very, very high cutting speeds like 10,000 SFPM.

[K&Y]

Originally Posted by Smrtman5 Thanks for the great info everyone Andre- 90Rc?? That cant be a normal steel can it? that would be way to brittle, i didnt even think you could get most steel past 70Rc What are the advantages of PCD? Longer life? I thought HSS was better than carbide for aluminum? i could certainly see an argument for lower cost for a hobbyist or small runs.

PCD is definitely the best when comparing to carbide for working on aluminum for the following reasons.

-Price (over the long term). Initially, PCD prices may seem steep, but considering PCD can outlast carbide 100+ times, it's fairly easy to see the cost advantages of machining aluminum with PCD as opposed to carbide. That, and taking into consideration that PCD tools can be re-lapped and if need be, shimmed and re-lapped, for a fraction of the cost of a new PCD tool, it's just another way you get longer tool life out of the PCD tool as opposed to a carbide tool.
-Speed. You can use the hardness of the PCD material to your advantage, and increase your speed and feed rates (bearing in mind your machine is rigid enough and your spindle is a very good one).
-Surface finish. If surface finish is an important factor, carbide can't compete with PCD.
-Down time. You have to factor in down time with carbide tools when formulating a job quotation; (it's costs, etc.) Machine down time related to replacing, re-indexing, worn or broken tooling, all has to be taken into consideration.


In the end, PCD tools may have a little bit more of a price tag attached to them, but after all is said and done, you always come out ahead if you go the PCD route.

[cinci5]

We run H13 all the time but I didn't think you could get up to 72Rc on H13. We use alot of Ceramic and WG 300 wisker grade greenleaf on our hard stuff

[mactec54]

Hi cinci15
Yes I agree H13 54to58Rc is about max hardness for it, 72Rc is not possible for this
material without coating like crome/nickel etc then you would not be turning it you have
to grind it if needed 72 Rc is in the HSS range

[mike sandvik]

I made a mistake. I used CBN NOT PCD to turn hard parts
Sorry

[K&Y]

Originally Posted by K&Y PCD is definitely the best when comparing to carbide for working on aluminum for the following reasons. -Price (over the long term). Initially, PCD prices may seem steep, but considering PCD can outlast carbide 100+ times, it's fairly easy to see the cost advantages of machining aluminum with PCD as opposed to carbide. That, and taking into consideration that PCD tools can be re-lapped and if need be, shimmed and re-lapped, for a fraction of the cost of a new PCD tool, it's just another way you get longer tool life out of the PCD tool as opposed to a carbide tool. -Speed. You can use the hardness of the PCD material to your advantage, and increase your speed and feed rates (bearing in mind your machine is rigid enough and your spindle is a very good one). -Surface finish. If surface finish is an important factor, carbide can't compete with PCD. -Down time. You have to factor in down time with carbide tools when formulating a job quotation; (it's costs, etc.) Machine down time related to replacing, re-indexing, worn or broken tooling, all has to be taken into consideration. In the end, PCD tools may have a little bit more of a price tag attached to them, but after all is said and done, you always come out ahead if you go the PCD route.

One very important factor that I forgot to mention, as far as PCD being an advantage over carbide, is the following:

-The ability to hold tighter tolerances for a longer period of time.