Miniature End Mills

EmilioG

EmilioG

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I was thinking that maybe a screw slot could be finished square, without the radius, by following a slot saw cut with a miniature end mill.
The tiny end mills look fragile, so I'm looking at reduced shank/stub length. .078" and .052" slots. Depth: .040"
Has anyone here used these tiny end mills with any luck? I suspect they would need high RPM's.
The other alternative is to use expensive screw slot files. $40 each! or can I just live with the small radius from a slot saw cut?
 
Use short working length EM. High RPM and low runout are required for small diameter carbide. The tips will snap by looking at them cross-eyed. I use end mills as small as .023" in materials like copper and stainless. I have also used them for boring holes in hardened caliper frames. I wouldn't take deep cuts with them to avoid grabbing. I run them at 10K rpm.
 
i have not successfully used mini endmills on anything! :bang head:
but i have tried!
my machines don't have the high enough spindle speeds to effectively use the smaller tooling.
had to test the theory though before i came to the conclusion.
i broke half a dozen before the idiot light came on - you ain't gotta hit me in the head with a brick :grin big:
 
EmilioG said:
I was thinking that maybe a screw slot could be finished square, without the radius, by following a slot saw cut with a miniature end mill.
The tiny end mills look fragile, so I'm looking at reduced shank/stub length. .078" and .052" slots. Depth: .040"
Has anyone here used these tiny end mills with any luck? I suspect they would need high RPM's.
The other alternative is to use expensive screw slot files. $40 each! or can I just live with the small radius from a slot saw cut?
Click to expand...

I use tiny end mills all the time. I've got drawers full of them. Short reach short flute are stronger and will produce a more accurate slot. I prefer not to use a reduced shank. I order all my micro end mills 1/8 shank, and as short of a reach as is practical. (I am currently finishing a 4140HT 3D embossing die with a 1/64 (.0156") ball nose mill. Well actually I have 12 dies yet to finish that way. Nine hours machine time for the smallest one. LOL.

Following a saw cut will create unequal and unpredictable cutting loads. Possibly beaking your end mill. If you have CNC you might consider doing the entire cut with an end mill. If not you might be able to manually mill it, but I have found I have a hard time not getting impatient and breaking small mills when I machine manually. I think the saw cut and slot file might be a better option for you if you do not have CNC. Sometimes hand work is the best option. I do a mix of CNC and manual machining in my shop nearly every day, and fairly often I just do stuff free hand to get the job done.
I don't worry to much about break end mills myself. I tend to buy multiples of every size I buy, and every time I break one I analyze in my mind why I broke it and try to learn something so I can better price a job like that in the future. But, there is the gist of it. I do 1st run and prototyping for the most part and I get paid for it. I figure a certain amount of broken and worn out end mills as part of the overhead cost of my home shop.
 
Heck just looking at them in their protective tubes with the ends covered and they break...

What about just using a slitting saw? Is it quality of finish or are the slot not clear across?
 
I have successfully used micro endmills in my machine, but I use a ~50,000 RPM air pencil grinder as a spindle. As said above, a tiny carbide end mill will break if you look at it too hard, but I have had good luck with tapered HSS down to 0.005 tip size
 
I use jewelers slotting saw blades for things like that, and have never noticed a radius at the bottom. They do make screw slotting saw blades, but again not sure of the profile.

David
 
I, like Bob, have and use a lot of miniature and micro endmills. However, I use them on a CNC mill with a high-speed (30,000 rpm), minimal run-out spindle. Depth of cut is very shallow and depends on the material, like 0.018" @ 10 ipm in aluminum with a 0.015 endmill.
I think Bob about said it all.
 
RJ: What are you using at 10K RPM, CNC mill? It would be great to have a machine capable of 10K rpm,

Harvey Tool: mini endmills SFM 150 for tool steel, annealed. About 6k RPM. Still, that's high speed, and of course, minimal run out is mandatory.
Slot saw and file for me.
 
Don't use a chuck, only a collet will do as you need no runout. I use .012" and .020" end mills in stubby/short reach just about every day. 60K rpm spindle in a CNC otherwise snap!
 
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