newb talk, 2 flute vs 4 flute cutters

[DerHammer]

Could anybody also give me some advice on the differences between the 2 and 4 flute cutters. I bought a center cutting end mill kit which has both types, two flute and four flute.

Currently, I'm under the impression that a two flute end mill will allow the user to IPM around quicker but leave a poor finish behind, which is where the four flute mills come into play for the finish pass right? Now assuming that this is indeed the case, Could a guy instead just start with the four flute mill and just go a little slower in order to avoid a tool change? What strategy will minimize the number of tool changes for a guy who doesn't have an ATC mill but still leave a nice finish behind on aluminum?

[sp1nm0nkey]

Two flute gives more chip clearance for aluminum. It doesn't matter thaaat much. I usually just grab whatever is on hand. You'll find machinists that'll tell you that it matters and machinists that tell you that it doesn't.

And yes, if you run a 2-flute end mill on steel at 600 rpm then you'll have to go slower to get a real nice surface finish, but on aluminum running a 2-flute at 3k-6k it just doesn't matter that much.

[philbert]

Those two-flute cutters may well be slot drills (I bought a Chinese set that has five sizes of matching slot drills and end mills). Slot drills can plunge cut (driven straight down into the work like a drill bit) whereas four-flute end mills will not, as they are not centre cutting. Four-flute end mills generally give a better finish , and can cut faster as they have twice the number of cutting facets.

[bookwurm99]

look for the thread in this area that talks about 2 vs 4 flute. more info than you would ever need to know. can't remember what its called. should be only a few pages back.

bookwurm99

[DerHammer]

Interesting point Philbert, Mine is 20 piece Chinese set all center cutting. I choose these because some of my parts require inner pocketing. So if I'm understanding this correctly, on aluminum the finish different between 2 and 4 flute is negligible and the biggest difference is actually chip load up, which of course effects the feed speed you can run?

My machine is an older one, so I can IPM around at mach speeds anyways. Maybe 150 IPM at most. Since this is the case, Should I just switch to the four flutes altogether since I imagine my feed capabilities are not that fast compared to some? What happens if you chip over load a cutter anyways? finish gets crappy?

[philbert]

I'm no expert, and I steer clear of aluminium (or 'aluminum', mate ). Finish is mainly about the about the amount of work each tooth is doing. Because the cutting speed of aluminium is so high (about 600fpm as opposed to steel at 100 or so), you can run a cutter very fast, and provided your feed rate is low compared to your spindle speed, then a two flute cutter can give a good finish.

Chip build-up will always mar a good finish because it rubs, and can force the tool out of alignment (digging in, etc). If you get too much chip build up, you could break the cutter. Aluminium is particularly nasty because it likes to bind to the cutting edges. The best cure is coolant to flush the chips away (and keep temperatures in check!) I believe you can also get compressed air setups to blow the chips away (in a safe direction I hope!) in situations where you're not using coolant.

[CarbideBob]

General rules of thumb (very general)
2 flute for aluminum, 4 flute for steel.
Use of WD-40 while cutting aluminum gives much better finishes.
Always climb mill aluminum.
Aluminum likes lots of rpm.

[fpworks]

Originally Posted by DerHammer ... Currently, I'm under the impression that a two flute end mill will allow the user to IPM around quicker but leave a poor finish behind, which is where the four flute mills come into play for the finish pass right?

Nope! A two flute will allow you to rough faster AND get a better finish than a four flute. Four flute tools do not have clearance to get rid of chips, so your finish will suffer.

Generally speaking, in aluminum, I see the best roughing performance with two flute tools and the best finishing with three flute tools. There are some exceptions...for instance, in many instances (but not all), Data Flute ALDH three flute tools can rough faster than most two flute tools. They also have a five and seven flute aluminum specific finishing tool that works very well.

[DerHammer]

1st off I want to say that I love this site and as a new machinist I really appreciate what this community does for each other. Very cool to see.

so back to business. Ill stick with the 2 flute cutter and keep it lubed even if I haft to feed at a slower speed. I'm not a production shop and my part runs are relatively small so it doesn't hurt my feelings to move slower as long as good parts are coming out in which require less sanding later. The final product requires polishing and the better the finish=hours saved .

I found some feed and speed calculation software on "the zone" which recommends higher feed speeds when using 4 flute cutters, which confuses me because it seems counter intuitive to whats being suggested by other users. I'm assuming this is the case because the software probably does not take chip load into account most likely? So putting this back in order then, If 4 flute mills chip load bad on aluminum and you can get a decent finish with a 2 flute cutter... Do my 4 flute mills serve any purpose when cutting aluminum over a 2 flute? If we take an example, I'm going to be using a 1/2 cutter and 1/4 cutter, both HSS for my stuff. I have both versions in 2 and 4 flute. At what IPM and RPM is a good starting place to get the best cut? I also have 5hp spindle if thats a factor also.

[fpworks]

Originally Posted by DerHammer Do my 4 flute mills serve any purpose when cutting aluminum over a 2 flute?

No. Four flute endmills are way inferior to a two flute in aluminum. A two flute endmill will cut any geometry MUCH faster and with a better finish until you start getting into large tools that have a lot of clearance between flutes. Even with a 0.75" endmill, a two flute absolutely destroys a four flute.

The difference is significant...expect to feed a two flute at least 3-4 times faster than a four flute in aluminum (same rpm)

Originally Posted by DerHammer At what IPM and RPM is a good starting place to get the best cut? I also have 5hp spindle if thats a factor also.

More importantly, how much rpm do you have available, and what kind of feed rates can your machine and control handle? What is your spindle's taper size?

[dertsap]

Originally Posted by DerHammer recommends higher feed speeds when using 4 flute cutters, which confuses me because it seems counter intuitive to whats being suggested by other users. ..

4 flt has more flts which means more material removal/ rev



.

Originally Posted by DerHammer Do my 4 flute mills serve any purpose when cutting aluminum over a 2 flute? .

rigidity is far greater with a 4 flt which gives less chatter and less deflection especially with hss tooling

lots of times the right tool for the job depends on personal preference and experience ,i would by far use a 4 flt above a 2 flt for finish and roughing ops , as long as the chip evacuation is there ,at which most times it is there , go for it , it just takes a little forsight

i firmly beleave that as far as plunging tools goes ,if it can be avoided then avoid it ,add a drill at the plunge point to remove material and give some clearance for the cutter , this will save time and will deter any deflection issues of plunging an hss endmill ,hss can walk away and oversize quite easily, even carbide can deflect a fair bit before the tool will break which leaves a potential of overcutting when you can t afford to have it happen

[fpworks]

dertsap,
Respectfully, No! No! No!

Originally Posted by dertsap 4 flt has more flts which means more material removal/ rev

That doesn't apply with aluminum. With superior chip evacution of a two flute tool, you can make a much bigger chip and get it out of the way.

Originally Posted by dertsap rigidity is far greater with a 4 flt which gives less chatter and less deflection especially with hss tooling

True, but in this case, a three flute wins. A four flute just cannot move chips, especially with a deep cut, where you would be most concerned about rigidity. Carbide, two/three flutes, shortest flute length is king. Here is one of my parts running a 0.375" two flute endmill, 12000 rpm, 210-460 ipm. I changed tooling suppliers and now I'm running the same part at 250-500 ipm. Don't try this with a four flute endmill.

(save to your computer first)

http://www.foreprecisionworks.com/video/MVI_2165.AVI