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Posted by GeoLane at PTD dot NET on February 16, 2008, 10:58 pm
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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
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Posted by James on February 17, 2008, 9:18 am
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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.
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Posted by Jim Wilkins on February 17, 2008, 12:40 pm
Please log in for more thread options On Feb 16, 10:58=A0pm, 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? =A0The 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. =A0[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] =A0Any 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
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Posted by Mechanical Magic on February 17, 2008, 1:18 pm
Please log in for more thread options 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
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Posted by GeoLane at PTD dot NET on February 17, 2008, 9:04 pm
Please log in for more thread options
>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?
>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
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