Chip per tooth for end mill
 

A continuation of my query regarding slot milling with a 1/8" end
mill.

The peripheral feed per tooth recommended was 0.0005" for a 1/8" end
mill.

What's the feed per tooth for 3/16 to 1/2" end mills? Is there any
rule of thumb?

Second question. With a center cutting end mill, what's the down feed
rate? BTW, I've got to do this by raising my table - my old BP head
has no downfeed.

RWL

Chip per tooth for end mill
 

GeoLane at PTD dot NET wrote:
A continuation of my query regarding slot milling with a 1/8" end
mill.

The peripheral feed per tooth recommended was 0.0005" for a 1/8" end
mill.

What's the feed per tooth for 3/16 to 1/2" end mills? Is there any
rule of thumb?

The info on my McDonnell Douglas speed & feed calculator (slide
rule sort of thing) says for end mills under 1", multiply chip
load value by cutter dia. So, for aluminum, they recommend
..010" feed per tooth at 1", so for a .125" diameter cutter, that
should be .00125 (I'd be conservative, especially with HSS, you
can watch the cutter bend under load.) So, 1/2" should be real
safe at .005" feed per tooth.
Second question. With a center cutting end mill, what's the down feed
rate? BTW, I've got to do this by raising my table - my old BP head
has no downfeed.
I use something like 1/4 to one half of the feed rate you'd use
for side cutting. When this is a straight plunge into solid
material, there's no side force, but the chips tend to pile up.
It may be better to make short stabs at it and then come up to
clear the chips and apply coolant. Especially with aluminum,
heating of the workpiece softens the aluminum, and then it
sticks to the cutter, and you have a mess. So, you may have to
allow cooling between cuts, use plenty of coolant, or other
strategy. With a little experience you learn the kind of things
that lead to the heat buildup. In some cases racing along with
several cuts much shallower than rigidity dictates helps to keep
the heat buildup from causing those messes. Also, knowing the
alloys is important. 2024-T6 and 6061-T6 cuts like a dream, and
you have to work at it to run into these troubles, like using a
dull tool. But, 2024-T1 will drive you nuts, it is so soft it
tears rather than cuts cleanly, and then the tool gets hot.


Jon

Chip per tooth for end mill
 

What Jon said,
BUT, with more emphasis on chip loading of the tool.
Peck .05" in Al, if it packs up you have a problem.

No recs on downfeed rate, it's too dependant on the grind of the end
mill, some brands/sizes downfeed great, sometimes a lemon. To me
center cutting end mills are a mystery. If you find a good
combination stay with it. Another black art.
Dave

On Feb 18, 8:02 pm, GeoLane at PTD dot NET GeoLane at PTD dot NET
wrote:
A continuation of my query regarding slot milling with a 1/8" end
mill.

The peripheral feed per tooth recommended was 0.0005" for a 1/8" end
mill.

What's the feed per tooth for 3/16 to 1/2" end mills? Is there any
rule of thumb?

Second question. With a center cutting end mill, what's the down feed
rate? BTW, I've got to do this by raising my table - my old BP head
has no downfeed.

RWL

Chip per tooth for end mill
 

Mechanical Magic wrote:
What Jon said,
BUT, with more emphasis on chip loading of the tool.
Peck .05" in Al, if it packs up you have a problem.

No recs on downfeed rate, it's too dependant on the grind of the end
mill, some brands/sizes downfeed great, sometimes a lemon. To me
center cutting end mills are a mystery. If you find a good
combination stay with it. Another black art.
Yes, it really is a black art. The problem is no tool really
cuts all the way to the center, as the center isn't turning.
So, it has to mash the center out of the way and/or twist it
to crumbs. The sharpness of the grinding work makes some
difference, as it makes the area that doesn't cut smaller
towards the infinitesimal. Take a look at some center-cutting
end mills with a strong magnifier, and you will probably see
differences, even from the same batch.

Jon

Chip per tooth for end mill
 

On Feb 18, 11:02*pm, GeoLane at PTD dot NET GeoLane at PTD dot NET
wrote:
A continuation of my query regarding slot milling with a 1/8" end
mill.

The peripheral feed per tooth recommended was 0.0005" for a 1/8" end
mill.

What's the feed per tooth for 3/16 *to 1/2" end mills? *Is there any
rule of thumb?

Second question. *With a center cutting end mill, what's the down feed
rate? *BTW, I've got to do this by raising my table - my old BP head
has no downfeed.

RWL

With larger endmills I push it until the machine starts to slow down
or vibrate a little (not hard to do on a Clausing), then back off. I
burned and dulled the first end mill while learning on a Bridgeport,
then I knew when to lighten up. I've never broken an end mill but
other prople have in company shops I ran. The corners chipped off,
good reason to wear eye protection, but in these cases they weren't
injured. I ground the end square past the break, added back relief
almost to the edge, carefully reground the cutting edges (by hand &
eye), and they were back milling again, though not nearly as fast.

The endmill downfeed rate is a lot higher if you drill a starting hole
first. Or you can zig-zag down if the endmill isn't centercutting.

Jim Wilkins

Chip per tooth for end mill
 

Thanks to all who replied

RWL