Need Advice

Gary

SE Kansas
I'm in the process of purchasing End Mill(s) and I'm clueless. I need 1/4 and 3/8's End Mill but do I purchase 2 Flute, 3,4,ect?
Going to use the en
 

Brad

Benevolent Overlord and site owner
Staff member
It seems that 2 flute are more commonly used for Al and 4 flute for steel. The Al chips can clog the smaller flutes on higher flute end mills.

That is a broad generalization. I have used a 4 flute on Al with no problems. That was also a 3/4” end mill making smaller cuts. If I really wanted to hog material I would tend towards the 2 flute.
 

Pistolero

Well-Known Member
I'd like to hear from someone who knows more than I do on this topic, too. I have mostly
4 flute, never seem to have trouble. Brad's comments sound entirely reasonable.

Bill
 

KeithB

Resident Half Fast Machinist
I'll just share a few of my views here, but don't take anything I say as the final word on the subject, about the time I think I know something I find an exception, but here goes.

Four (or more) flute mills are stiffer and stronger than two flute mills and can generally cut at twice the feed rate, so for maximum material removal and minimal side deflection they work best. They also wear slower, you're cutting the same material with twice the teeth so each tooth wears less.

Two flute mills cut slots that are more accurately located. With a two flute mill, at one point the two teeth are cutting on each side of the slot, so there is no side thrust to cause the cutter to deflect sideways; with a four flute mill when two teeth are opposite each other across the width of the slot another tooth is cutting sideways into the thickest part of the cut and causing the mill to deflect sideways. Two flute mills are much better for most cutting of aluminum, especially if you don't use flood coolant to flush out the chips. The extra space between the flutes, especially in the smaller sizes, makes it easier for chips to clear out. One trick I use on the manual mill is to use compressed air instead of coolant to blow the chips clear when machining aluminum.

End mills come in center cutting and non-center cutting styles. I don't buy anything except center cutting mills if I can. Center cutting types allow you to "plunge" (drill) down into the piece as well as cut sideways. Even so, do not crowd an endmill down into the workpiece like you would a drill, the clearance angles on the end of the mill are not the same as a drill.

There are all sorts of materials used to make end mills - High Speed Steel (HSS), carbide, coated carbide, cobalt alloys (nonferrous material content), and ceramics. For harder steels carbide is probably best, but for mild steels, aluminum and brass just about any material works fine, especially for the hobby machinist. A lot of the development in ceramics and coatings is meant for high speed production machining and doesn't give too many advantages to the hobbyist.

If you machine a lot of aluminum having a few high-helix multiflute end mills around is handy, they tend to clear chips out nicely, but you can get along without them.

If you plan to machine soft material like copper do not rely on a friction collet to hold any end mill with a helix. Use a Weldon (setscrew) shank type so the end mill can't screw itself down into the workpiece.

Hope this helps. I suggest buying a a couple of each type and watch what happens when you use them.
 

smokeywolf

Well-Known Member
Can't add much to Keith's info and recommendations. Will say that for versatility, my favorite end mill is a TiAlN coated, high percentage cobalt HSS, 3 flute with a 37 degree helix. If you go with a faster helix the points of the flutes tend to chip off. If I can't get or use a 3 flute, I'll usually reach for a 4 flute.
I have dozens of 2 flute end mills and they work very well in softer materials where maximum chip clearance is needed. Don't forget that efficient chip evacuation also results in good evacuation of heat.
 

Pistolero

Well-Known Member
Hmmm. I am not sure I have ever seen a 3 flute. If I did, I didn't particularly notice it.
Will pay attention now, try to locate a few of them.

Thanks for the info.

Bill
 

KeithB

Resident Half Fast Machinist
I have used a lot of single and multi-flute carbide tipped straight helix router bits to mill wood and plastics, using my milling machine like a great big router. I have made all the switch/utility box covers in our house from the left over Brazilian Cherry flooring we had installed. Nice to have the covers match the floor. If you're used to using a handheld router or even a table router you won't believe how accurately you can make wood parts using a milling machine.

Bill, I've read that end mills with odd numbers of flutes (3 and 5) were developed for several reasons, one of which involves limiting harmonics at extremely high RPMs. And very large diameter mills can have even more teeth, I have several of them in the 1-1/4" to 1-1/2" range that have six flutes. At the slow RPMs you have to run these it would take forever and cause a lot of banging to only have two flutes.

If you looked at the power/load curve for a two flute mill you would see the load looks like rectified AC, i.e. the load is zero when the tooth engages the workpiece, rises to maximum approximately 90* later as the tooth cuts the full feed, and then drops to zero as it exits the cut, only to repeat the process when the opposite tooth engages the workpiece. The load curve for a multi-flute end mill is closer to that of three or multiphase AC, since at least one tooth is engaged in the cut at all times. The load is more even and never drops to zero. Since fatigue (the loss of strength due to cyclic stress) is more pronounced when the difference between the minimum and maximum load is the greatest, and fully reversed stresses are the worst case of that, two flute cutters under heavy loads at high RPMs will tend to have a shorter useful life. Factor in vibrations from harmonics that can cause edge chipping and you can see why most high speed milling is done with 3+ flute cutters.

If you're just getting started don't overthink things, just get several types of cutters and see how they work for you. There has been tons of research done on cutting tools - just like bullet molds, we are living in an age when there are better tools made from better materials than ever before, there is something out there to cut almost anything you can think of. But the plethora of choices can sometime be overwhelming.

When I got my first milling machine I bought a set of HSS end mills with two and four flute versions in four different sizes - I think they were 1/4", 5/16", 3/8" and 1/2". Came with a cheap little wooden block for storage, didn't cost much, and worked well enough for me to get started and make chips and parts while I watched how they cut. I learned from that what worked for me. I bet there is something similar on eBay for less than $50 right now.
 

KeithB

Resident Half Fast Machinist
I just searched eBay ("end mill sets") and found several 20 piece HSS coated 2 and 4 flute sets for about $60, and many sets with four to six cutters for less than $40. Unless I need 24 hour shipping I buy a lot of tooling from eBay nowadays.
 

Intheshop

Banned
Get a medium priced,"cheap set" as a starter.Some come in 2 and 4 flutes,per size.

You will quickly learn what NOT to do.... HAZ's,interupted cuts,work hardened materials,etc etc. Better to learn this with a cheap cutter.

As you find out your requirements,then start ordering higher $$ singles. Believe me,you'll not only take care of the "good stuff" but,you will grab a cheapie on occasion. Further,practice sharpening the cheap stuff before messing up the $$ stuff.
 

Gary

SE Kansas
So, I got some 4 flute pieces and some 2 flute pieces ordered AND I got a Palmgren 250 Milling Vise to hold the work pieces. Once I get everything setup (Palmgren on a angle plate) and the End Mill(s) located in the head stock I'm be ready to try and mill on the lathe.