[zephyr9900]

Asking a question of the community at large--is this the type of situation where a 3-flute cutter would be any advantage? I know that in aluminum with "slotting" like this 3-flutes help because they're not getting wedged in the cut, so to speak. I'm a newbie myself in that regard.

I'll echo the sentiment for stub-length mills--using a mill that has the minimum flute length for the cut has been the biggest single advancement for my milling--more than adjusting speeds and feeds and DOC...

Randy

[pete from TN]

That is something I never thought about really. I always think of a three flute or any other type of cutter in terms of the number of cuts per rev for my speeds and feeds but you are correct in that the cutter on a two or four flute will cut from both sides in a full width or plunge cut causing more pressure and friction on the cutter whereas a three flute will only be cutting one edge at a time. I do not have any three flutes bit I am thinking a centercutting three flute is in my future for sure. If I remember correctly the IH videos show some impressive performance from a specialized aluminum cutter and I think it was a three flute but I could be mistaken. I often slot steel manually on my knee mill and it is always a difficult cut especially in tubing which I have to sometimes file for a decent finish, I wonder if this will be a solution. Peace

[300sniper]

am am new to this but from what i understand, a 2 flute would be better for full cutter width grooving than a 4 flute because there is more room for the chips to evacuate. at the same time, you loose rigidity of the cutter and feed rate. a 3 flute is a compromise between the two.

i have not tried a 3 flute in steel. i have been using some 3 flute carbide endmills designed for aluminum with great results.

[StephanWenger]

Hi all,

first posting here in this forum, so bear with me. While I have not cut any stainless yet on my PCNC, I have had some experience with this great material a while ago--20 years or so. At the time we played around with a large Traub VMC (40 HP spindle or so) with 4 or 6 flute HSS cutters, 1" or more. When we chipped a cutter or a drill bit, we had to re-grind it---manually, and to the satisfaction of the (German) machinist master. Not fun... Deciphering my notes from the time, what the master told us then:

-work hardening is a serious issue, and basically unavoidable. The trick is to keep the exposure of cutters to work-hardened areas minimal
-keep the feed up; rubbing will not help against hardening, it will make things worse
-remove as much material as you can through drilling. Helps to bring down the chip load, creates spaces for the chips (at least initially), and is generally the fast way to remove metal anyway. Also, sharpen a drill bit is way easier than sharpening an endmill.
-drill with a diameter slightly smaller than the mill bit you plan to use. Again, work hardening is unavoidable even when drilling, but by using a smaller diameter drill bit you can minimize the area.

I have followed these tips with good results in all materials I work with. Even considering the tool changes, chances are such a program would actually run faster on a PCNC, as the feed rates (especially in hard stuff) are rather limited due to lack of rigidity and spindle horsepower, and, accordingly, one has also to go down with spindle RPM.

I'm not sure that chip removal is the key problem here. My guess is, it's not.

Cooling is, of course, particularly critical on work-hardening materials. You may wish to consider a specialized, high viscosity coolant.

Regards,
Stephan

[68rustang]

Today I had some success. The carbide mill I picked up yesterday was a 3-flute bull nose end mill and it worked much better. I had a little hiccup when it initially cut through the discolored area. It tried to pull the TTS tool holder out of the collet but I was right there and stopped it. reset it and all was ok today. I will post the numbers and calculations on Monday of what I ended up running.

[levelzero]

I curse every time I have to cut stainless. I'm found that using a rougher followed by a full depth finishing pass with a 4 flute cutter works best for me.