Corner Rounding end mills

Douglas mc · Mar 6, 2008

hello this is my first time using a corner rounding end mill, I would like to know the RPM of the end mill in 1020 steel.
radius is 3/16
shank is 1/2
cutter diameter 3/4
end diameter 3/8
thank you Douglas

Joe Miranda · Mar 6, 2008

corner rounding endmill

Is the endmill HSS or carbide?

Joe

L Vanice · Mar 6, 2008

Go by the largest diameter of the cutter, which you said is 3/4. That is where they dull first. You can figure the RPM just as you would for a 3/4 endmill. Be careful with the speed, because they cost more and are harder to sharpen than an endmill.

Larry

Carl Darnell · Mar 6, 2008

Douglas, something don't sound right. The endmill is 3/4" dia. with a 3/16" radius can't have or cut a 3/8" dia.. The 3/4" endmill with a 3/16" radius will cut a flat on the bottom of a slot not a 3/8" dia.

I don't use charts to get the rpm and feed for endmills. I do it by how it cuts and the chips. I start at a low speed and feed and work it up. You need to use cutting oil or water based coolant with endmills. You don't want blue chips coming off the cuts. Even tan chips are border line. There is a fine line where speed and feed match with manual mills and you have to learn to feel it during the cut. The slower the spindle speed the more jerking the cutter will do. If you speed up to where the speed and feed gets a fairly smooth feel on the crank and nothing is shaking and jerking and the cutter is getting nice looking chips your there.

even a speed/feed surface inch per minute chart is only a guide.

L Vanice · Mar 6, 2008

Carl Darnell said:
Douglas, something don't sound right. ...

Douglas has a corner rounding endmill, not a ball ended endmill. The OD is 3/4 and there is a 3/16 sharp cutting radius on each side, leaving a 3/8 flat on the end.

Larry

toolmakerjim · Mar 6, 2008

Pi X .75 = 2.355

90 SFM X 12 = 1140

1140 / 2.355 = 484 RPM

Carl Darnell · Mar 6, 2008

Yep, that's what I said, a flat on the bottom not a full dia. as a ball endmill will do. It's his description I was taking issue with. A conflict of statement.

Bluejeep · Mar 6, 2008

The major dia. is probably 7/8, at least that what my 3/16 radius mill 1/2 shank, 3/8 bottom is.

jwatts · Mar 6, 2008

I don't think there is anything wrong with the description. Starting with 3/4 and subtracting 3/16'ths twice, once for each side of the mill gives you 3/8. 3/4-3/16-3/16=3/8 As far as the math is concerned it realy doesn't matter whether we are talking about a convex or concave radius.

Joe Miranda · Mar 6, 2008

corner rounding endmill

Toolmaker jim gave you the formula for HSS. That's why I asked the question as to whether the tool was HSS or carbide. If it is carbide, use the same formula that toolmaker jim gave you except substitute 200 for the 90 and it will get you a good starting parameter. From there you can adjust slightly if you want to in order to get the best surface finish and tool life.

Joe Miranda

Carl Darnell · Mar 6, 2008

jwatts, 3/16" raduis is half of 3/8" dia.. A 3/16" raduis on each side of a 3/4" shaft would have a 3/8" flat in the center.

Hense the reason I questioned his statement quote " end diameter 3/8" " quote. That can't happen with a 3/4" endmill with 3/16" radius on the side. However, an endmill with a 3/16" radius would be a 3/8" dia ball endmill.

As I and another said it would have a 3/8" flat in the center. A 3/4" dia. ball endmill would have a 3/8" raduis on the end.

I guess I am nit picking on terminology and description. If you put an incorrect statement or number in a question it could change the answer or make it unanserable.

Mud · Mar 6, 2008

Carl Darnell said:
Douglas, something don't sound right. The endmill is 3/4" dia. with a 3/16" radius can't have or cut a 3/8" dia.. The 3/4" endmill with a 3/16" radius will cut a flat on the bottom of a slot not a 3/8" dia.

He's asking about corner rounding endmills, you are describing a bull nose endmill. Corner rounding endmills don't cut slots.

Carl Darnell · Mar 6, 2008

I Know That, Read The Post I Just Made Above Yours Again.

toolmakerjim · Mar 6, 2008

Douglas;
are you there?
just wondering if you stood around all day waiting on this info?...jim

JST · Mar 6, 2008

Carl.........

EXTERNAL corner rounding.......... turn it inside out.......... radius is CONCAVE, kinda like the tool that would cut the inside shape of a trumpet bell. can cut a convex corner rounding on OD edges of a cube.

You seem to be thinking of a rounded corner endmill, i,e, one with a radius on the OD corner, so it cuts a curve on the bottom ID of a recess.

Mud · Mar 6, 2008

Carl Darnell said:
I Know That, Read The Post I Just Made Above Yours Again.

OK, I did. Again. As I did just before I posted.

Now how about you read this whole thread again and explain yourself more clearly?

Without the attitude.

Carl Darnell · Mar 6, 2008

I don't have to read the thread again, I have read and posted all day on it and I have said the same thing all day.

Attitude, yes and I am tired of having to explain a fact over and over.

Below is his statement in quote
"hello this is my first time using a corner rounding end mill, I would like to know the RPM of the end mill in 1020 steel.
radius is 3/16
shank is 1/2
cutter diameter 3/4
end diameter 3/8
thank you Douglas"

Now look at the second line from the bottom and read it. He is making a statement that would indicate it's a 3/8" ball endmill and the rest of the statement is about a 3/4" endmill.

That is what I have made several posts about. A rant, maybe, a question, yes, seeking a correction, yes.

Mud · Mar 6, 2008

Mud · Mar 6, 2008

Carl Darnell · Mar 6, 2008

So you think he is talking about a edge radius cutter and I am thinking he is talking about a endmill with a 3/16" radius on the outside edge as others have thought so to.

An edge radius endmill as you picture does not have a 3/8" radius on the end, but it does have a 3/16" radius cut into the periphery at the bottom edge. He did say 3/16" radius.

Funny thing is both of us could be right or wrong and the other funny thing is he has not replyed as to what he means.

Toolmakerjim answered his question of spindle speed while the rest of us has wrestled with semantics or description and correctness of the question.

Do you understand why I ask about the 3/8" end dia.?

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