"Bob La Londe" wrote in message news:tlu0dn$1ept$1@gioia.aioe.org...
Actually a STUB length carbide 1/2 in end mill.
I have a couple small high speed milling machines. They are not ever
going to be able to handle a heavy cut with a 1/2 inch end mill, but
being able to use one for some jobs pushing the work envelope of the
machine would be very useful. "Stub" length are still 2-1/2 inches long which means they are heavy. I won't being using much of the flutes. No more than 0.015-0.020 DOC. A tool with a 1/4 inch flute and a total
length of 1-1/2 to 2 would be more ideally suited to the application.
Just long enough to fully engage the ER20 collet and leave 1/2 inch
(+/-) stickout would be ideal. I've been looking and just not found anything.
Custom made is to expensive (for me) I think.
Cutting down the shank is possible. I have a diamond cut off wheel for
my TC grinder, but these are high RPM machines. Typically I spin 24,000 rpm. For this operation I'm looking at testing at 8,000 to 10,000 rpm.
I'll need to see where my spindle still has enough power to make the
cut. Anyway, that's still pretty darn fast. I'm concerned about
balance if I just shorten one.
----------------------
If the cut is square the balance shouldn't change. Can you rotate the
endmill while cutting it, or afterwards, to square the end?
"Bob La Londe" wrote in message news:tlu0dn$1ept$1@gioia.aioe.org...
Jim Wilkins wrote:
If the cut is square the balance shouldn't change. Can you rotate the
endmill while cutting it, or afterwards, to square the end?
"Bob La Londe" wrote in message news:tlu81r$1fp2i$1@dont-email.me...
On 11/26/2022 2:47 PM, Jim Wilkins wrote:
"Bob La Londe" wrote in message news:tlu0dn$1ept$1@gioia.aioe.org...
Jim Wilkins wrote:
If the cut is square the balance shouldn't change. Can you rotate the
endmill while cutting it, or afterwards, to square the end?
Oh, yeah. I would spin it in the 5C tool holder on the TC grinder and
just slowly advance into the diamond wheel. I would probably grind a
small chamfer on it as well the same way, but at a different angle. I
just wasn't sure how good I could do it. At high RPMs even a small imbalance can be an issue. More so on a larger diameter tool. Most
days I don't run anything larger than 1/4 inch in those spindles.
I have cut the chowdered tips off end mills before so I could still use
them for side milling. It works decently, but I'm topping those out
usually at 3000-5000 RPM. I can run a fly cutter at 3000 RPM, but the faster you spin the more affect there is from an imbalance.
Most of the tools I have made on the TC grinder are pretty simple single
lip cutters run at modest RPM.
A lot of times I just try things like this and see, but these little
quick change ISO20 spindles are a little more expensive than your
average Chinese import high speed spindle. Worth it for the time they
save me, but not super cheap.
Bob La Londe
CNC Molds N Stuff
---------------------------------
You could measure the squareness of the end after cutting, and maybe
correct any runout.
I recently squared the spindle flange seating surface of a cast iron
chuck backplate according to Tony Griffith's procedure on LATHES.CO.UK,
using the tailstock, centers and a mandrel to remove any axial play in
the spindle while taking the very light final cut. http://www.lathes.co.uk/latheparts/page7.html
That could let you grind the outer portion of the end true, then true
what's left in the center by running the endmill reversed in the mill
against a diamond lap.
I came up with a different procedure to locate the mounting bolt holes.
I removed the top jaws and extended the lower jaws beyond the chuck body
to provide clamping surfaces. A tap screwed into one lathe chuck
mounting hole centered it under the mill's drill chuck, then table
clamps on the extended jaws locked the lathe chuck in position. Each backplate hole was drilled with minimum clearance (M8 cap screw, 5/16"
stub drill) at that location, then bolted at another hole. Then the
holes were counterbored for the heads the same way. I didn't have to
increase the hole clearance.
Since the drill bit stopped short of the chuck body a little flash was
left at the end of the holes, but a hand held drill bit and countersink easily removed it. On other jobs I've used a step drill as a piloted countersink.
jsw
"Bob La Londe" wrote in message news:tm0aph$1ncej$1@dont-email.me...
I admit I am probably over thinking it.
-----------------
What matters is if you can detect an imbalance without suffering damage,
and easily correct it.
On 11/27/2022 4:05 PM, Jim Wilkins wrote:
"Bob La Londe" wrote in message news:tm0aph$1ncej$1@dont-email.me...
I admit I am probably over thinking it.
-----------------
What matters is if you can detect an imbalance without suffering
damage, and easily correct it.
Well, when I accidentally spun a Sharpie marker up to 24,000 rpm I knew
there was a problem seconds before it exploded, but I still wasn't able
to hit the e-stop button until after I felt bits of ink and marker hit
me in the face.
"Bob La Londe" wrote in message news:tmlumu$1mbt$1@dont-email.me...
Ok, I have an approximation of one lower speed power limit now for the spindles. I tested the 1/2 inch 2 flute mill at 10600 RPM and was able
to slot almost as fast as I could turn the pendant knob. Around 100-120 IPM. At .05 inches deep it ripped through like it was nothing in 6061-T6511. At .13 it bogged down. This gives me a feel now of
available horsepower at lower RPMs with these high speed 2 pole motors.
I've always been afraid of running these spindles at the lower end of
their RPM range. That's either 8000 or 6000 depending on which reseller
you believe.
If I have the math right that tells me I still have safely over half horsepower available down as low as 10K. That's a lot more than I
expected.
These are 1.8KW (nominally about 2.25-2.4 HP depending on which
guesstimate you use) spindles, but I only ever figured they could
produce it at RPMs where I couldn't use it anyway. I do spin them at
1500 RPM with edge finders, but that is virtually zero horsepower to
spin a wiggler.
To test I ran it with the doors open and no coolant so I could see and
hear the cut. These chips come off fast and hot. Pretty darn hot for aluminum anyway.
I'd still like to find a mill that's a half inch shorter with a half
inch shorter flutes, but I'm comfortable running these now for the job
they are intended.
The nice thing about aluminum is if you run coolant you can get away
with all kinds of less than perfect speeds and feeds so this is as good
as I need to dial it in for now. (Actually you can get away with a lot
with some steels too, if you run a quality end mill with a quality
coating, and an air blast.)
Bob La Londe
CNC Molds N Stuff
------------------------
We are exploring nearly the same question under very different
conditions. After regrinding the HSS bit I worked up to 0.100" depth of
cut at ~0.2 IPM manual feed (axially) in a cast iron backplate for a 5" chuck. Might as well get all the CI projects done before thoroughly
cleaning the lathe.
https://shane.engineer/blog/measuring-mill-power-speed-and-torque
I like the Wattmeter idea, not so much the brake. The $16 PZEM-061
Wattmeter with a 100A current transformer can be added to the line side
of a power supply to show instantaneous and totaled power consumption. 1
HP = 0.7457 KW.
jsw
...
1 HP = 0.7457 KW.
jsw
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