Grinding flats on endmills

[Justin Beebe at Folsom Tool]

We mainly use carbide endmills .250 diameter up to 1.00 diameter. We hold them in 40 and 50 taper Parlec or similar brand solid tool holders with set screws. When we machine aluminum we don't grind a flat on the endmill. We run our machines up to 12000 RPM. In two years I have never had an endmill spin, push up, or pull out while machining aluminum. However, today the great debate started over grinding a flat. I was just wondering what everyone elses opinion is on this topic. I should also mention that we always use flats for roughing endmills, or any endmill that is machininmg steel or hard material.

 

I would appreciate everyones opinion.

[Gary]

I grind flats if set screwed in. If the shank is to spin on the screw and gull they are a pain to get out and not wreck the holder

[Justin Beebe at Folsom Tool]

Good point Gary

[BernieT]

Carbide end mills should be held in collets, not end mill holders with set screws.

 

However, if you have not had any problems in the last 2 years you are probably fine.

[connormac]

We were also told to run in collets. The amount of tool runout effects the tool life. Solid tool holders can push tool off center.

[Justin Beebe at Folsom Tool]

BernieT,

 

I grew up in Ventura CA, but moved to Pennsylvania three years ago. How long have you been there?

 

Also why do you prefer collets and what type of collets do you prefer?

 

We buy a lot of carbide endmills for steel that come with a flat already on them from the manufacturer. These are mainly four flute variable helix endmills such as Niagra Stabilizers. I beleive Hanita Varimills also come with a flat.

 

For aluminum we use three flute Vipers by Destiny Tool or three flute Acuccpro high performance endmills and they don't come with a flat. The company I work for now is the first place I have worked for that does not use flats for cutting aluminum but it seems to work and saves time.

[Justin Beebe at Folsom Tool]

Connormac,

 

What kind of collets do you use. We have ER16, ER20, ER32, and TG collets but we do most of our milling in solid holders. I heard the compression type collet holders are good for milling.

[connormac]

Iscar holders and collets. If we are doing work where there is alot of cutting pressure we use exact size collets. We were taught to clean them out every time and use alcohol to clean them before putting them together. We use ER 16 and 32. For real heavy cutting we use Iscar low boy holders.( I'm not sure what ther are called) The whole collet is inside of the holder. Use a 1 7/16 box end wrench and get it as tight as we can. We have snapped one off but never has one pulled out of the holder.

[BernieT]

quote:

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I grew up in Ventura CA, but moved to Pennsylvania three years ago. How long have you been there?

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Over 20 years - great place to live. 3 of our 5 offspring live here also. Also spent about 10 years in Ojai/Oakview

 

 

The collet advise came from end mill reps, I always tried to use collets, but I've done it both ways with no adverse effects.

[robk]

Using collets for milling is an accident waiting to happen. Use a precission milling chuck or a shrink fit holder. Weldon holders work good, but IMO not @ 12,000 RPM. If you're using hydraulic holders do not stick cutters with flats into them. Use the right tool for the application and you'll sleep better @ night.

 

quote:

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Use a 1 7/16 box end wrench and get it as tight as we can.

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[Guest]

I agree with RobK, milling chucks are really the best way to setup end mills.

 

Side lockers if that is what you HAVE to use and yeah, I'll grind a flat along the shank.

[Joe788]

Using an ER32 collet for anything larger than .375 is really rolling the dice. The steep taper just doesn't have the holding power of other methods. This all depends on how aggressive you get though.

 

I've found endmill holders to actually be the BETTER than milling chucks or shrink fit, when using larger endmills on a 40 taper machine. Why? Because you can get .625, .750, and 1.0 endmill holders with a .750 gage length. This short gage length makes a HUGE difference in rigidity, when you consider the contact circle of a CAT40 holder is only 1.75 at it's largest point. (Unless you have Big Plus).

 

The shortest TG100 holders I've seen are about 3 inch gage length. The shortest milling chucks and shrink fit holders I've seen are closer to 3.5-4.0.

[MotorCityMinion]

Choices in order for me:

Heat shrink, mill chuck, side lock, er 32 as a last resort.

 

ER typically runs truer than the side locks as there's always a few guys in a shop who tend to put pipes on the wrench and then stretch the holder out of round.

 

Ever see a noob put a e-mill in a drill chuck?

[Programinator]

Alum cutters with the correct feeds and speeds normally do not need flats on the shanks IMO. Saves me lots of time on setups.

[Superman]

quote:

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Ever see a noob put a e-mill in a drill chuck?

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Yep

Told the guy not to come near me if again or to ask me why all the drills don't run true

 

I even laughed when the tool fell out when the spindle stopped.

[pip]

12000 with an unbalanced tool, cant be doing the spindle bearing the world of good.

Shrink fit tools all the way here.

[Justin Beebe at Folsom Tool]

pip,

 

12,000 RPM is pretty rare for us, but we do have spindles that go up that high. We normally keep it under 10,000. I have heard that anything under 10,000 doesn't need balanced holders. Am I correct about this?

 

Thanks for the input.

[Guest]

Justin,

 

I believe that number to be 15,000.

 

Anything over that is recommended to be balanced.

[Dave.L]

We always grind flats for setscrews when using Endmill holders, sometimes with a grinder and sometimes by hand. It’s too much risk to simply rely on the setscrew since this is purely frictional force. You really run the risk of a minor movement in length and not catching it until you have a bucket of scrap.

 

We use both ER & endmill holders and we really don’t find any difference in run out which effects tool life. Last year we tried some milling chucks for a steel project that we had good data. The tools in the milling chuck did not last any longer than those in ER and endmill holders. I was disappointed since in theory it makes total sense. However, at $500 a crack for milling chucks, I was not too disappointed.

 

In the future I would like to try shrink fit for common tools.

 

Does anyone have good success with hydraulic holders, and if so, what brand?

[Chris Rizzo]

quote:

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Using an ER32 collet for anything larger than .375 is really rolling the dice. The steep taper just doesn't have the holding power of other methods. This all depends on how aggressive you get though.

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ESP. in aluminum with high helix cutters. If you're not pulling .500 endmills out of an er-32 holder, then your not cutting fast enough.

[TK-32™]

I was taught in school to make the flats a little bit angled. This helps the E.M. from pulling

[Dave.L]

That's called a whistle notch and it's most commonly used for locating pins. It works better when there is a shoulder that you are pulling against since the angle cams the shoulder against the mating surface. For whistle notches, the angle is most common 7 degress. (20 years of machine design.....)

 

-Dave

[MLS]

quote:

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Heat shrink, mill chuck, side lock, er 32 as a last resort.

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+1 Motor City Minion

 

We use heat shrinks exclusively for any of our 10,000 and higher RPM machines, but the mill chucks I have used for a 10,000 machine in the past and they worked very well.

 

I wouldn't want to run a side lock over about 8,000 personally. They may not have to be balanced, but with collet type holders at least it isn't extremely off balance.

 

I have seen them in a side lock without a flat and I have seen them pull out in aluminum. It drove me crazy to see a flat ground on a carbide EM for aluminum, but I guess if you can't afford the holders it was better than pulling out and doing some scrappage.

[pip]

Angles should only be ground when you are using whistle notch holders.

Your fastening screw will not fully engage on the tools flat, so weakening the holding pressure.

 

[ 04-06-2009, 07:37 AM: Message edited by: pip ]

[Jmick]

We have been using er32 holders up to 5/8 on mostly high carbon steels (4140,1040,and a2,d2 tool steels) and have had no problems.