(not) reusing endmills for different materials?

I stumbled upon the same advice several times in a couple of days, which is to dedicate a given endmill to cutting one type of material only, e.g. to not reuse an endmill that has been used for cutting aluminium to cut plastics.

It sounds like a sensible (albeit expensive) tip, I was wondering how many of you actually follow that rule ?

I’m halfway there without thinking about it since I dedicate my ZrN coated endmills to cutting aluminium anyway, but I have been using my other endmills liberally to cut wood or plastics or MDF, and now that I think about it it makes sense that I should keep a few endmills dedicated to plastics, they should stay sharp much longer.


I might have said it somewhere, although I didn’t explain in depth. It’s a matter of specificity. The endmills I buy to mill aluminum have helix angles and geometry that work well for aluminum. The ones I buy for plastic are single flute endmills that have too high of helix angles for aluminum. The endmills I buy for wood are general purpose endmills.

This leads me to segregating my endmills based on geometric intent rather than merely because one cut wood I won’t use it for aluminum or vise versa.


I’m not that fussy - but as the previous point, a lot of my end mills are purpose designed (or material designed).

That said, I was having trouble cutting some 5083 Al - it was gumming up my fancy designed for aluminium bits, so I stuck in a single flute cutter intended for MDF. I was truly amazed at the end result! I cut through a 8mm thick plate in one pass (with trochoidal cutting), then did a quick skim as a finish cut for an unbelievable surface.


Yeah it makes sense. I was asking because this guy insisted (at some point in the video below, I can’t find when exactly) that one should not use an endmill that has cut plastic, to cut aluminum, and vice versa.

And then I saw a similar advice in this CNC beginners’s guide, page 3-17:

“Never use tools that have been used to machine metal to cut plastic. The sharp edge of the tool will be compromised and cutting performance and finish will suffer. A good practice is to keep two sets of tools: one for plastic and one for metal.”

Now you need to tell us more about your cut settings ! :slight_smile:
RPM / feed / optimal load / coolant

Also, I had never heard of single flute recommended specifically for MDF, can you share what tool this is ?

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@Julien - I use Estlcam a lot to generate my gcode. If you’re not aware of it just go www.estlcam.de or look at this video:

It seems a bit scary to plow through at full depth rather than taking little passes. Once you do it and see that it works - it just becomes the norm.

His setup procedures aren’t quite as specific as others mandate. I run my spindle at max (24K), no coolant, no misting etc. Usually I use the 50% width as he suggests, and the engagement of 8% (between 5-10% depending on material). Feed rate - as fast as you can go before the machine shakes too much - I think I do 2000-2500 mm/min.

Again, not really as tightly controlled as other methods dictate. But it works so I use it. I like to keep things simple, why worry about optimal loading when you don’t need to!

Regarding the bit. It looks like any other single flute. It was marketed as specifically for MDF, but I suspect that is more marketing than anything else. I use the same one in solid hardwood, plastics, MDF and now aluminium. I buy them from China.

Yeah I’m a big fan of long chips / large depth of cut myself, and use adaptive clearing (== trochoidal milling) whenever I can especially since I have no productivity constraints, and it’s fun to watch too. Now that I’m invested (time/effort wise) in Fusion360 I won’t go the Estlcam way, but I had seen this video before. And this guy developing a CAM tool by himself and selling it cheap too, is a commendable thing.

80ipm, 24K @ 1 flute, and 5 to 10% engagement is around 0.0013" chipload after chip thinning, sounds like a very typical value to cut aluminium (just checking every single usecase I hear about, I’m kind of chipload-obsessed)

Thank you for sharing


I just saw on a YT channel a guy milling stainless steel and he made a remark that you should not use an abrasive tool (grinding and sanding) that is not new because the small impurities from other materials will get into the SS and destroy its properties. Maybe this does not apply to endmills but the principle is there for certain applications, an even lightly gummed-up aluminum bit would leave particles in other materials for example.


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