How many flutes should I use?

[Swiss]

Hi all.

OK, so you can buy end mills with 1, 2, 3, 4, 6, 8, .. n flutes. How do I go about choosing? As far as I'm aware, more flutes means faster feed rates. So why do people make 1 or 2 or 3 flute tools? How do I decide how many flutes I need for a job?

Many thanks

hugo

[SRT Mike]

Depends on what you are cutting. For example, on aluminum, if you are slotting, you get big gummy chips. A 4-flute mill tends to not have enough space between the flutes to let the chips evacuate, so they gum up. In this case, a 2-flute endmill would be better.

Usually single flute mills means there is only one cutting surface contacting the workpiece at a time, which often seems to help with vibration. We were using a single fluted mill when we cut thin copper sheet and we tried one (without success) in acrylic sheet.

A 4 (or more) flute endmill is going to have more cutting surfaces hitting the part with every rotation, so it would produce a finer finish at the same RPM as a 2-flute mill would, or it would allow a higher feed if the machine has the HP and feed for it, and the material supports it.

I think in general you usually would want the highest number of flutes you can get - but really 2 and 4 flute mills are the common ones. 5, 6, and more flutes generally are special purpose (meaning they are expensive!) and used for specific applications. For example, we used a 6-flute 1/2" endmill to take a very light finish cut on a part we made in aluminum. We were RPM limited (4k rpm spindle) so that mill gave a nice finish - maybe like a 4-flute mill would on a 5500rpm machine with the same feed.

Hope it helps

[Ken_Shea]

Hugo,
To add a bit to Mike's post, using 4 flute on aluminum while profiling works well but I agree for other material removing in aluminum use the very common 2 flute.
That said on the 2 flute, I use them at last resort since I discovered 3 flute carbide cutters designed for aluminum.

These work very well, I do not have enough experience with other cutters to say they are the best but they are clearly superior to the standard 2 flute.

http://www.lakeshorecarbide.com/inde...TS&Category=35


Ken

[Geof]

You have to visualize a Ven diagram with the overlapping circles labelled metal removal rate, power requirement, surface finish, material strength, chip clearance, metal cutting characteristics and probably others.

As Ken says if you are cutting aluminum, which is low strength and can make big chips when cut at fast feed, you may need two flutes for chip clearance.

On steel which is stronger and which has to be cut at a slower feed you can go to four, five, six flutes to increase metal removal rate.

If you want an ultrasmooth finish on a profile on any material you go as many flutes as possible because the cut depth is going to be very small so chip clearance is not important.

I think if you are using a smallish mill which is limited to less than 5000rpm and does not have a big motor it is not necessary to go beyond using a two or three flute standard end mill for aluminum and standard four flute mills for steel.

[dertsap]

for a general mill , 3 flt high helix can t be beat in hogging and typical finishes in aluminum ,6 or 8 flt work excellent on parts where a near or ground surface finish needs to be accomplished (if done on a decent machine),
also 6 and 8 flt high helix are great on steals such as 4140 when a beefy cutter is needed to avoid chatter and such , it s especially so when the use of a long series is necessary
then you get stuff like the hanita varimill that in steel will hog full dia depth and slot at high speeds and feed rates ,beautiful cutters

the varieties , types and uses go on

most times the type of endmill needed boils down to the application it will be cutting and personal preference

if your planning on just doing general milling i'd suggest having some run of the mill type cutters such as 2 flt 4 flt endmills and a couple 2 flt high helix

[Swiss]

Thanks guys for all your responses,

Let me see it I've understood. Am I right in thinking that more flutes are generally better (since you can remove material faster) except that they have less space for the chips to fly out? So you choose the most number of flutes that seems to de-chip properly.

We have a 4-flute, 45 degree helix end mill designed specifically for Aluminium, from Garant. And it seems to cut perfectly, though I haven't tried deep slotting. I suppose that if you're pocketing, with an 80% step over, the chips are just going to wash out easily.

hugo