End Mills

M

Maplehead

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Hi All

So I purchased a 3/4” cutting width EM for my micro mill to “route” out a 1/8” deep by 2” long cavity in some 3/16” steel. Basically I am creating a 3/4” wide by 2” long by 1/8” deep rectangle with rounded ends. Not the point really.
My question is, any time I have used an end mill for its main purpose, (which I believe to be the use of its end cutting edges), the bit screems and fights as it plunge cuts into the metal. I am running around 3000 RPM and I go very slowly into the steel. (Standard Lowes steel.)
Why does it seems to have such difficulty plunge cutting from the end as opposed to the ease in which my end mills cut from the side?
Is it because using the whole bit plunge cutting a circle has the regular cut and climb cut sides fighting each other?
Any suggestions on how I can start cutting the ends of my 2” long cavity without the bit acting so angry?
And again, the ends are plunge cuts. I cannot come in from the side of the stock because I am creating a cavity with 1/8” side walls.

Without all the description above, I probably could have just asked, is plunge cutting with an end mill always so much more difficult than when feeding the stock into the side of an end mill?
 
Hi,

First I assume you are using a centre cutting EM.

My mill is a light set up and when I do this type of work I drill an under size starting hole so that the EM doesn't have all that much to remove. Also on my set up if I need to have an accurate 3/4" slot, I would start with a smaller diameter EM and then do step overs to finish to accurate width. My set up just isn't rigid enough.

David
 
David S said:
Hi,

First I assume you are using a centre cutting EM.

My mill is a light set up and when I do this type of work I drill an under size starting hole so that the EM doesn't have all that much to remove. Also on my set up if I need to have an accurate 3/4" slot, I would start with a smaller diameter EM and then do step overs to finish to accurate width. My set up just isn't rigid enough.

David
Click to expand...
This is the mill I ordered.
Niagara Cutter N52206 Cobalt Steel Square Nose End Mill, Inch, Weldon Shank, Uncoated (Bright) Finish, Finishing Cut, 30 Degree Helix, 4 Flutes, 3.625" Overall Length, 0.750" Cutting Diameter, 0.500" Shank Diameter
 
Well it is centre cutting. Sounds to me that your mill is perhaps not stiff enough for this size cutter. However I am a hobbyist, and only know how I have to work around my set up.

Hopefully the pros will be along soon to give more help.

David
 
For one thing, it seems that you are running the mill way to fast for steel, for a cutting speed of 80 to 100 SFM, the rpm should be 500 - 600 RPM; also it is a four flute mill, and you do not say if it is center cutting, if it were center cutting, two of the flutes on the end of the mill would be cleared to center, other styles are solid in the center and just relieved.
 
benmychree said:
For one thing, it seems that you are running the mill way to fast for steel, for a cutting speed of 80 to 100 SFM, the rpm should be 500 - 600 RPM; also it is a four flute mill, and you do not say if it is center cutting, if it were center cutting, two of the flutes on the end of the mill would be cleared to center, other styles are solid in the center and just relieved.
Click to expand...
As far as I can tell it is center cutting. I’ll try slowing the mill down.
51Rqp8NI6HL.jpg
 
Yes indeed, that is center cutting. Are you using a cutting oil?
 
What type of mill do you have? Make model?

David
 
Micro Mill and 3/4" end mill are not two words that go together in my humble opinion. For a tiny bench top machine I would stick to end mills of 3/8" or less. As others mentioned your speed is way to high for that size end mill and the machine is most likely not rigid enough to handle it cutting full width. Even machines that are massive its best to use less than full width of cutter in most situations. If you do any reading of the projects that the famous Rudy Kouhoupt made, he used small endmills using bench top machines and did marvelous work.
 
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