What depth of cut is safe to take with a HSS end mill of 1/8" dia, and
how fast can you feed in mild stee without breaking or quickly dulling
the end milll? The ROT of that I'd read in a book years ago was 1/8th
of the end mill diameter as the depth of cut (0.015 for an 1/8" mill)

I don't have power feed, and have never had coolant, except flood
coolant (what a mess) the few times I ran the horizontal part of the
mill. [1940s vintage Hardinge Universal horizontal mill with a
Bridgeport C head in the overarm hole for vertical milling - not very
rigid, but it's what I have] Any technique to use to do hand feeding
of the table?

Thanks

RWL

GeoLane at PTD dot NET wrote:
What depth of cut is safe to take with a HSS end mill of 1/8" dia, and how fast
can you feed in mild stee without breaking or quickly dulling the end milll? The
ROT of that I'd read in a book years ago was 1/8th of the end mill diameter as the
depth of cut (0.015 for an 1/8" mill)

I don't have power feed, and have never had coolant, except flood coolant (what a
mess) the few times I ran the horizontal part of the mill. [1940s vintage
Hardinge Universal horizontal mill with a Bridgeport C head in the overarm hole
for vertical milling - not very rigid, but it's what I have] Any technique to use
to do hand feeding of the table?

Thanks

RWL

Without some sort of auto feed the task you have at hand is near imposable.

You might control the feed speed steady enough for some short period but being human
sooner or later your hand will involuntarily "jerk" and while it might not seem like
much, the "jerk" could easily quadruple the feed speed for an instant and in tough
material that's enough to hear the fat lady sing.


A thought did occur to me while writing the above and that is if you geared down your
feed enough, manual hand feed irregularities would not translate into such violent

(violent for a 1/8 th end mill)

bed movements. Thing is, if you go to all that trouble you might as well have a motor of
some kind drive it.

On Feb 16, 10:58*pm, GeoLane at PTD dot NET GeoLane at PTD dot NET
wrote:
What depth of cut is safe to take with a HSS end mill of 1/8" dia, and
how fast can you feed in mild stee without breaking or quickly dulling
the end milll? *The ROT of that I'd read in a book years ago was 1/8th
of the end mill diameter as the depth of cut (0.015 for an 1/8" mill)

I don't have power feed, and have never had coolant, except flood
coolant (what a mess) the few times I ran the horizontal part of the
mill. *[1940s vintage Hardinge Universal horizontal mill with a
Bridgeport C head in the overarm hole for vertical milling - not very
rigid, but it's what I have] *Any technique to use to do hand feeding
of the table?

Thanks

RWL

I can get away with 0.050 depth but prefer 0.025 for such a fragile
tool. The manual feed on my well-worn Clausing 8525 is sensitive
enough to feel the cutting resistance and I control it with light
finger pressure rather than trying to hold a speed. The inertia of the
dial evens out the impulses from each flute cutting.

Once I have the feel for the cut, I speed up the mill and use the same
pressure.

Jim Wilkins

Speed for mild steel no faster than 120 ft/min, but since you will
probably be using a squirt of cutting oil, maybe 60 ft/min. A 1/8"
endmill is .033 of a foot in circumfrance. 60/.033 = ~1800 RPM.

DOC 1/4 of diam = .032"

Feed .0005" per tooth, two flute cutter = .001"/rev. At 1800 rpm =
1.5" per minute, that works out to one turn every eight seconds.

When I hand feed, I use a two handed motion, (grabbing on the dial),
one hand rotates about 20 degrees, then other hand 20 degrees,
repeat. By making the changes often, it seems to even out the motion
for me Easier if you have round wheels instead of a crank.

That's where I would expect to run.
Dave

On Feb 16, 7:58 pm, GeoLane at PTD dot NET GeoLane at PTD dot NET
wrote:
What depth of cut is safe to take with a HSS end mill of 1/8" dia, and
how fast can you feed in mild stee without breaking or quickly dulling
the end milll? The ROT of that I'd read in a book years ago was 1/8th
of the end mill diameter as the depth of cut (0.015 for an 1/8" mill)

I don't have power feed, and have never had coolant, except flood
coolant (what a mess) the few times I ran the horizontal part of the
mill. [1940s vintage Hardinge Universal horizontal mill with a
Bridgeport C head in the overarm hole for vertical milling - not very
rigid, but it's what I have] Any technique to use to do hand feeding
of the table?

Thanks

RWL

On Feb 16, 10:58*pm, GeoLane at PTD dot NET GeoLane at PTD dot NET
wrote:
What depth of cut is safe to take with a HSS end mill of 1/8" dia, and
how fast can you feed in mild stee without breaking or quickly dulling
the end milll? *The ROT of that I'd read in a book years ago was 1/8th
of the end mill diameter as the depth of cut (0.015 for an 1/8" mill)

I don't have power feed, and have never had coolant, except flood
coolant (what a mess) the few times I ran the horizontal part of the
mill. *[1940s vintage Hardinge Universal horizontal mill with a
Bridgeport C head in the overarm hole for vertical milling - not very
rigid, but it's what I have] *Any technique to use to do hand feeding
of the table?


Most of the info already given is quite sound.

Some further thoughts...

If you're making a full-width slot with the cutter, use coolant to
remove chips. You need to remove those chips. If you don't get the
chips away from the cutter, you'll likely break the tool from the
chips jaming in the flutes of the cutter. Use a 2-flute endmill!

Make sure the machine is pretty tight (this is *always* important!).
If you can't tell, use an indicator on the table, and give the table a
good tug. If you can see more than perhaps a thou or two of play, you
should consider adjusting your gibs. If the machine isn't tight and
you change your grip or something, you run significant risk of
breaking the cutter. I typically snug the table lock until just before
the table won't move.

Always make sure to lock all the axes which aren't moving! You must
*always* do this! If you don't lock your axes, the cutting forces can
drag the axes enough to break the cutter (or at least start cutting
where you don't want to cut).

What you're attempting is pretty standard stuff and you really
shouldn't have trouble. Machining isn't magic, but it's also not very
tolerant of sloppiness either. If you don't follow standard
proceedures (like outlined above), you're never going to get
consistantly good results.

Good luck.

Regards,

Robin

On Feb 16, 7:58 pm, GeoLane at PTD dot NET GeoLane at PTD dot NET
wrote:
What depth of cut is safe to take with a HSS end mill of 1/8" dia, and
how fast can you feed in mild stee without breaking or quickly dulling
the end milll?



On Sun, 17 Feb Mechanical Magic wrote:

Speed for mild steel no faster than 120 ft/min, but since you will
probably be using a squirt of cutting oil, maybe 60 ft/min. A 1/8"
endmill is .033 of a foot in circumfrance. 60/.033 = ~1800 RPM.

DOC 1/4 of diam = .032"

Feed .0005" per tooth, two flute cutter = .001"/rev. At 1800 rpm =
1.5" per minute, that works out to one turn every eight seconds.

When I hand feed, I use a two handed motion, (grabbing on the dial),
one hand rotates about 20 degrees, then other hand 20 degrees,
repeat. By making the changes often, it seems to even out the motion
for me Easier if you have round wheels instead of a crank.

That's where I would expect to run.
Dave

Excellent. Thanks Dave. That's the kind of detailed advice /
experience I was hoping to get. Thanks also to the others who
replied.

RWL