When do you choose between a 2 or 4 flute end mill?

I almost always use 4 flutes for steel, and 2 flutes for aluminum or plastic. 2 flutes evacuate the chip better, but 4 flutes are stronger.

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======================= Everybody "ruins" tooling during the learning process. This is only a problem when you keep doing it....

One of the least expensive sources for end mills I have found is wholesale tool. see

and for end mill sets see More flutes means less chip load per tooth for a given feed/speed, thus more teeth is generally better for harder material. Unless you are into production you can use 4 flute for everything although it won't be quite as fast for aluminum.

A three flute end mill works well for slotting as you avoid the cogging action when the teeth engage and release on both sides of the cut at the same time.

As you are just starting out, the M2 end mills will be your better choice as these are cheaper and you will break several in the learning process.

For roughing mills it depends on exactly what you mean. For cleaning up sandy, scaley or rusty material the 1/2 shank, 5/8 diameter carbide insert mini mils are hard to beat. C. 10$ for the holder and c. 1$ for the insert [TPU no-name] with three corners. See other current thread for information on this.

You should also invest in a fly cutter, possibly a set. This will allow you to use a M2 square lathe tool you can resharpen your self with just a belt sander or shop grinder. see

There are many other discount suppliers with the same types of tooling, I just happen to use WT.

For hints, tips and general how to you may want to buy "Turret Mill Operation" (Paperback) by John G. Edwards This will more than pay for itself by limiting tool/machine damage. While written for the Bridgeport style mill, the information applies to all milling machines.

see (new)

?tag2=amd-google-20and Unka George (George McDuffee) ............................. I sincerely believe . . . banking establishments are more dangerous than standing armies, and that the principle of spending money to be paid by posterity, under the name of funding, is but swindling futurity on a large scale. Thomas Jefferson (1743?1826), U.S. president. Letter, 28 May 1816, to political philosopher and Senator John Taylor

I have a few fly cutters but haven't gotten around to replacing the poor quality allen setscrews yet and I'm still not good at grinding the plain square HSS cutter stock so I haven't used them yet.

The roughing mill (I guess that's the right term) looks like a 4 flute mill with serrated edges all the way up the flutes, I'm thinking these are for hogging off material.

One thing though, I've already paid for my mill in doing small shaft repairs on the lathe and fabricating special shafting for projects.

Thanks for the very helpful post, I'll buy that book.

A useful hint here is to use a endmill that is slightly under the desired width and cut to full depth right down the center of the slot and the come back and side-mill each side of the slot to produce the exact width you need. Metric size endmills with 3/8 shanks can be useful for slotting as these are frequently "just under" the desired inch slot widths.

The surface finish will be much better, and you can control the width. For example, either because of run-out or size, a quarter-inch end mill will almost never cut a slot that is exactly 0.2500 wide.

I have found three flute endmills to be better for slotting in both steel and aluminum.

Because you are using a home shop or hobby type mill, limit your feeds/speeds and per tooth chip load. You can't go too low as the end mill will start to burnish/rub rather than cut and wear rapidly, but the suggested feeds/speeds are for commercial machines in a production environment, where higher tool consumption/shorter tool life is offset by the higher production rate.

Unka George (George McDuffee) ............................. I sincerely believe . . . banking establishments are more dangerous than standing armies, and that the principle of spending money to be paid by posterity, under the name of funding, is but swindling futurity on a large scale. Thomas Jefferson (1743?1826), U.S. president. Letter, 28 May 1816, to political philosopher and Senator John Taylor

The forward/reverse hi/low functions of a bridgeport has killed a lot of tooling.

Wes S

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your are correct, however...

While I am sure that some home shop / hobby machinists use and swear by these cutters, they are really useful only in a production shop where maximum material removal rates are desired and where the chips/swarf disposal is a problem. The geometry of these cutters produces smaller flake type chips that are more easily flushed away by the **high pressure/volume coolant flow.** The coolant pump motor on one of these production machines is in all likelihood bigger than your spindle motor. In commercial application, such as high speed cnc machining, typically the coolant flow looks like a fire hose, and it is impossible to see the part/cutter. The machining area is also enclosed in what is operationally a water tight box.

Unless you are having problems with the volume of chips/swarf generated, such as bad surface finish and excessive power loss due to recutting of the chips in the cut, you will gain little to nothing.

High feed rates and chip loads [i.e., rigidity, power and spindle RPM] are required for effective application that are generally far beyond the capabilities of the typical home shop mill.

Unka George (George McDuffee) ............................. I sincerely believe . . . banking establishments are more dangerous than standing armies, and that the principle of spending money to be paid by posterity, under the name of funding, is but swindling futurity on a large scale. Thomas Jefferson (1743?1826), U.S. president. Letter, 28 May 1816, to political philosopher and Senator John Taylor

I swear in them. I don't do production runs. But they cut soooo much smoother and quicker and last longer that I _highly_ recommend them if you have to remove lots a mass. Chips are no problem because they are much smaller. They just flow out like butter.

The ones I use are called SilentCut. And they are. Great stuff, try it!

Nick

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Be sure and take your fly cutters with you when you go to buy the replacement setscrews. There are some strange [at least in the US] threads being used that are neither standard inch or standard metric.

The only way to "get good" at grinding HSS lathe tools is to grind a bunch of them.

A tip is that the consistency of tool grinding is more important that the actual numerical rake/relief degree values. If possible rig some sort of jig or fixture so that you can duplicate, and

*slightly* increase or decrease the rake/relief angles. for an example see: While these show a "baldor" style carbide grinder, something similar can be rigged for a belt sander.

It can also be helpful if you invest in a machinists' protractor or use the protractor head with your machinists' square set to measure/record which angles work for you, on your machines and with your materials. Also be sure to keep a notebook of this and similar information.

A tip -- to "hone" the edges of the freshly ground tool use an abrasive bristle nylon brush in your drill press. (c. 5-10$ at most hardware stores) a few seconds will remove the wire edges. Also the nose radius can be important. A sharp corner will make a surface that looks like a phonograph record, but too big a nose radius will cause chatter. Think Goldylocks -- not too big, not too little, but just right.

Note that when you use a lathe too in a fly cutter you will need to be sure that the "corner" on the backside of the tool is relieved. This is not necessary in lathe use, but frequently causes problems for the beginning machinist in a fly cutter.

Unka George (George McDuffee) ............................. I sincerely believe . . . banking establishments are more dangerous than standing armies, and that the principle of spending money to be paid by posterity, under the name of funding, is but swindling futurity on a large scale. Thomas Jefferson (1743?1826), U.S. president. Letter, 28 May 1816, to political philosopher and Senator John Taylor

Oddly enough, roughing cutters can be useful when you are working at the limit of the machinery. For example, I've had acceptable results with a 5/8" roughing cutter (free/acquired from work) in a Myford lathe with cast iron. It doesn't stand a cat's chance in hell of coping with a 5/8" conventional cutter, even cutting butter.

Mark Rand RTFM

I'd have to agree with Nick. Roughing cutters work really well in non-production settings - lower chip load, less deflection and generally easier on the mill and feed system.

Do some identical cuts with a conventional end mill and a roughing cutter.

Or on proper location.

Harold

The main reason is economics of time- adding flutes is like hiring extra help. Other explanations you will hear are that 4 flutes are stiffer than two flutes, due to a thicker cross-section. In my experience, this isn't as big a gain since four-flutes naturally chatter more in deep, full-width cuts, despite the cross-section gain. I therefore use four flutes mainly after roughing, and then, only for the economic benefit in a production shop. For a home shop, IMHO, two flutes will do everything you need, provided you don't mind waiting a little longer. Roughing mills are a different story- most have four or more flutes and are not subject to chatter- bury them as deep as is safe, keeping in mind that deep cuts create proportional forces on your workpiece. Brent.

According to Modat22 :

4-flute removes more metal when side cutting. A given size of endmill is rated to remove a certain depth of cut per tooth, so more teeth, more metal removed. 2-flute makes a more accurate slot if that is what you are trying to cut. With a four-flute, the leading flute (the one directly in the path of the cut) is applying force to offset the endmill at the very time that the two side flutes are cutting the width of the slot.

So -- you need both in your collection. The two-flute for cutting slots of a precise width, and the four-flute for more serious metal removal (and a 6-flute for the larger sizes is even better.)

Enjoy, DoN.

Or any other mill...blush.....

Gunner

"A prudent man foresees the difficulties ahead and prepares for them; the simpleton goes blindly on and suffers the consequences."

- Proverbs 22:3

No one has made more than passing mention of this, but...

You need to use a two flute in aluminum or other soft metals, especially in the smaller sizes. The chips don't clear out of a four flute very well. This isn't a problem in steel, where the chips tend to be small and hard. But the large, soft aluminum chips pack in, then the whole mess semi-melts. At this point, the tool quits cutting and you get to say choice words while you take a pick of some sort and dig the remains out from between the flutes.

Obviously, if you don't have some sort of cooling system on your mill, the problem gets much worse. I use a mist cooler on my Bridgeport, but, even so, I've had aluminum wad up in quarter inch four flute cutters when cutting slots as little as a quarter inch deep.

Jerry

Also keep in mind that hog mills have a nasty habit of pulling out of your tool holder in a heavy cut. Make sure you got a good grip on it.