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End Mills stoning the sharp tip of end mills

Mecheng47

Plastic
Joined
Apr 7, 2019
a friend is fairly adamant that the sharp cutting tips should be stoned back to a small radius to improve life. I have not heard of this before.

Does any one have a definitive answer

regards gill
 
IME it does as your mate says, and usually leaves a better finish, ………FWIW I only leave the factory sharp corner when the job calls for it.
 
Its true they will last longer depending on how you use them. but, It’s better to buy end mills with bull noses rather then stone the edge just because you’ll never hand stone two edges equally or create the same cutter geometry behind them.
 
Its true they will last longer depending on how you use them. but, It’s better to buy end mills with bull noses rather then stone the edge just because you’ll never hand stone two edges equally or create the same cutter geometry behind them.

The big snag there is that corner radiused EMs have a restricted range (IME, virtually un-obtainable in HSS) and are usuallyconsiderably more expensive.

As for cutter geometry? .if you're after the max number of parts at the optimum output etc etc etc, then you have appoint and you should get them factory ground, ...but for general run of the mill machining, don't get too anal, stoning - with the help of an 8 or 10X eyeglass, will be more than adequate.

Don't believe me, find yourself a full or chipped HSS EM, stone and glass, and have a practice at honing followed by a test cut.
 
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Also it helps the first few inches or minutes of drilling or milling to run the cutter with a little less feed. If convenient after changing the tool I will stick around and when that tool ( end mill or drill) is machining I reduce the feedrate to 50 or 60% for a few seconds or a minute max.

Tools wear or chip the most during the beginning of its life and then the end of its life. My 2 cents.
 
a friend is fairly adamant that the sharp cutting tips should be stoned back to a small radius to improve life. I have not heard of this before.

Does any one have a definitive answer

regards gill

end mill corners come with different radius or chamfer sizes. a finisher might have a .008" radius or have a sharp corner needed to finish mill a corner with a tighter radius.
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roughing mills often have bigger radius corners .020" or bigger is common. you can buy end mills with .030 or .060" radius edges or corners on a end mill. usually you order what you need or works best for the application
 
end mill corners come with different radius or chamfer sizes. a finisher might have a .008" radius or have a sharp corner needed to finish mill a corner with a tighter radius.
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roughing mills often have bigger radius corners .020" or bigger is common. you can buy end mills with .030 or .060" radius edges or corners on a end mill. usually you order what you need or works best for the application

Exactly. We stock a whole bunch of finishers with different radiuses and even 45 deg corner chamfers. The corner chamfer is nice because many times it can save a tool position. You can finish a feature and then deburr and chamfer all surfaces.

3 Flute Carbide High Helix Corner Chamfer End Mill Finishers - Made in USA - MariTool

3 Flute High Helix Corner Radius End Mills - MariTool

4 Flute Square Carbide Single End Corner Chamfer TiAlN End Mills - MariTool

4 Flute Carbide Corner Radius End Mills TiAlN Coated - MariTool

and many more. We are also starting to get demands for our variable flute endmills with different radiuses.
 
Doing that with a fine hone for HSS and a fine diamond hone perhaps 200 or finer grit and at about the same primary clearance can aid cutter life.
A good way is to eyeball a 45* angle and give the same number if swipes to each flute.

Some times one can flat hone the end mill end on a fine stone to get a better surface finish but this can shorten tool life a tad.
 
Depends on what the friend means by stoning. If it is just rounding over the cutting edge to make the end dull it is now a dull tool. I break the edges on all the cutters I run by honing a 45 WITH clearance at least .001 wide. It will still cut a sharp corner for most purposes but last longer.
When I am done I want to see a line about .001 from the edge following the ground clearance of the new cutter.
 
To be more clear on this I am suggesting a corner 45*made with a fine hone stone.

Re Post: #8: Doing that with a fine hone for HSS and a fine diamond or jus an abrasive hone perhaps 200 or finer grit and at about the same primary clearance can aid cutter life.
A good way is to eyeball a 45* angle and give the same number if swipes to each flute.

Some times one can flat hone the end mill end on a fine stone to get a better surface finish but this can shorten tool life a tad.
 
Thanks very much I tend to put my faith in the manufacturer
Then maybe it would ease your soul to know that manufacturers of milling cutters, and major makers of milling machines, both endorsed the practice well over 100 years ago. And as the laws of physics have not changed, the same mechanical principles apply today.

Use a sharp cornered endmill if you need the sharp interior corner in the cut. But that's frequently a bad mechanical feature, being a stress raiser in the part. Use an endmill with a small chamfer or minute radius on the corners when part tolerances allow for longer tool life.
 
I see quite a few new square end carbide endmills actually have the rake face inside the flute ground flat and parallel to the tool axis for a short distance. This removes the hyper-sharp and weak corner of the tool, and it will still cut a square corner if needed.

I tend to hand chamfer the endmill after it has gotten slightly damaged. I do this on a diamond wheel. This might mean the endmill has become a rougher, but it can still do a lot more cutting like that. BTW, I'm well past the stage where I think all 4 flutes have to exactly match one another to remove metal. I've amazed myself lately with how dull an endmill can be, how dissimilar the flutes can be and still remove material :D
 
Depends on what the friend means by stoning. If it is just rounding over the cutting edge to make the end dull it is now a dull tool. I break the edges on all the cutters I run by honing a 45 WITH clearance at least .001 wide. It will still cut a sharp corner for most purposes but last longer.
When I am done I want to see a line about .001 from the edge following the ground clearance of the new cutter.

Not endmills, but this can/does apply to drills depending on material. I was taught to do this when drilling copper (and maybe alum bronze)...
 
Small radius in what orientation?
One is a edge prep, the other is a corner geometry modification.
Both help if done right and matching the application.
Does not normally come on your catalog endmills or drills because it cost money to do it and you would have to stock al kinds of flavors.
Production drills and end mills a different story. where users buy high enough volumes to get tailor made at the same price as commodity stuff.
Bob
 








 
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