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Why aren't there solid cermet/ceramic endmills for general use?

Machinery_E

Titanium
Joined
Aug 19, 2004
Location
Ohio, USA
I'm getting into running cermet lathe inserts, and I'm amazed at the performance of cermet compared to carbide. I go for long tool life, and stable machining as most of the time its barfeed work and I'm working on something else while its running. For example I was just hogging these parts out of 4150R prehard in the Rockwell "C" 30 range. About .300" DOC, spindle load at about 80%. Ran about 70 parts. With one of the better grades of carbide I've found, the insert would be getting tired near the end of the run, finish would start to suffer, so would rotate it. Cermet still powering along just fine.

I've been thinking, why aren't there "solid" endmills made out of this stuff "commonly available" for general use? I do alot of milling with 3/8" endmills, and something that is so tough and wear resitant like the cermet in the lathe, would be a dream come true. I'm thinking it may be a matter of the cermet material not being "strong" enough? As a lathe tool has a constant load on, but an endmill has a sort of "pounding" action to it as each tooth engages/disengages with the material.

It does look like there are some solid cermet endmills, but they seem like a pretty specialized thing and not for general shop use as they have very short flute lengths. For example, on the 3/8" the flute length is 9/32", I'd need about 7/8".
 
I recall seeing them advertised several years ago. I often wondered how they would stand up. But without ever having one to try, I'd think they would be as brittle as glass and would fail easily due to the shock of milling. A lathe insert is well supported in comparison.
 
Carbide is brittle enough I couldn't imagine how quickly one could snap off a solid ceramic endmill. Ceramic is like glass it has no give to it.
 
My assumption would be that the material is strong in compression not shear so something like a lathe or a milling cutter with a backing for the insert is acceptable while a long lever like an endmill would snap like a dry stick. The 3/8" inch one you mention has a WxØ ratio that lets it not break under milling forces but would explain by you cannot find any in a longer LoC.
 
Sandvik and Kennametal both have solid ceramic endmills in most sizes and configurations. I ran some tests for Kennametal about 6 months ago. I ran 3/8" and 1/2" endmills in Inconel. I don't quite remember the exact parameters, I would have to look it up. I think SFM was up around 800 SFM. Tool life (minutes)was about the same as carbide at carbide speed but metal removal rates were obviously much higher.

Paul
 
It seems I was way off on my recollections. We only had an 8000 RPM so were running at about 1000 SFM. Our rep wanted 15K and said the endmills would have been much happier in that range. DOC was about .500" and WOC was .080 per side.

Paul
 
There was an article in one of the trade mag's just a cpl months ago (or less?) about ceramic endmills.
They were using in nickle I think.
The case they made was pretty compelling.
Perishable cost per cubic inch removed may have been about the same to a bit more IIRC, but the machine time was fractional. Maybe cut by 2/3 possibly? I don't recall for sure. Also don't recall which trade. Prolly Cutting Tool Engineering would be my guess.

???


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Think Snow Eh!
Ox
 
most likely the cost of the end mill is limiting factor.
.
in bigger sizes 1" dia carbide end mill can be $300 to $400
.
sure little 3/8" one would cost less in cermet or ceramic. but many try buying long length end mills and put in long length tool holders. i would think tool life would vary considerably considering how tool is used. like one person getting 100 minutes tool life and another getting 1 minute tool life
 
if you use set screw holder on cermet end mill will it crush and break just from the set screw being tightened ?? or possibly they do not even come with a weldon flat
 
Kennametal, Mitsubishi, and possibly even Kyocera have ceramic endmills. They're most often used in Inconles & other super alloys. I'm not aware of anyone making endmills from Cermets...

FYI - From what I understand anyway, cermets are Titanium-Carbide particles bonded in cobalt, instead of the more traditional tungsten-carbides. The particles are harder, and therefore more wear-resistant, but you trade-off heat resistance. I would suspect that's why cermets are typically recommended for "slower speeds" when compared to tungsten-carbide grades.

Member Oldwrench has a lot of experience with cermets, and he would be a good resource on the subject - I'm hoping he'll chime in here...
 
Cermet are used for stainless steel. They work great for stainless. For high temp alloys you can use ceramic for roughing. You can not use for finish. High temps lead to part deformation in high temp alloys. Ceramics for rough good: Ceramics for finish bad.
 
Cermet are used for stainless steel. They work great for stainless. For high temp alloys you can use ceramic for roughing. You can not use for finish. High temps lead to part deformation in high temp alloys. Ceramics for rough good: Ceramics for finish bad.


Now that you say that, I believe that was in the article.
They were using for rough only.

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Think Snow Eh!
Ox
 








 
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