XPost: alt.machines.cnc, alt.home.repair
"Bob La Londe" wrote in message news:t4poo7$1q0$
1@dont-email.me...
On 5/2/2022 1:11 PM, Jim Wilkins wrote:
The top one sharpens the end flutes of end mills nicely. https://www.kbctools.com/catsearch/146/end-mill-grinding-fixtures
The lowest one does side flutes but it's fussy to adjust and difficult to use, and of course they become undersized, better for roughing than finishing.
For my low-budget hobby use I sharpen only the end flutes and rough out
steel by plunging down, which doesn't dull the sides. The horizontal feed between plunges is less than the radius so I don't have to keep them center-cutting.
I guess I could say I don't really have the skills to sharpen end mills.
I expect if I setup a finger tracer for the Tool and Cutter grinder I
could sharpen the flutes of some end mills. Maybe the ends on 2 flute
and maybe some four flute. I do mostly CNC work where I am running by
dead reckoning and I have to count on the machine to be close enough. I
have measured and setup jobs using regrinds, but only for one off
special jobs where I needed an angle or a corner radius that was an
oddball and the only one that I found that was cost effective was a
regrind. Mostly for efficient time management I use new end mills and
when specs fail it goes in the bucket.
When I first got the T&C grinder I bought a diamond cutoff wheel for it.
This might be right up your alley for being frugal. Most of the time
when an end mill fails its just the tips/corners. I can cut that off
while turning the mill and approaching the wheel at a slight angle.
This gives me a nearly new side mill with a shorter flute, and there is
a slight hollow grind on the end to eliminate drag. You can't plunge
with it, but you can get some more life out of a mill (its no longer an
end mill) that would otherwise just go in the scrap carbide bucket.
When I chowder that I save what's left to make a D-bit cutter of some
kind.
----------------------------
I do have diamond grinding wheels, and if my machines were tight and rigid enough to not chip carbide I'd use them.
Surface-grinding the end flutes is really very simple, the fixture sets the relief angles and indexes in 15 degree steps (360/24) between flutes,
there's no finger stop. The base can be squared by eye on the mag chuck, the back rake isn't very sensitive to slight misalignment. You do have to
carefully adjust a 4-flute endmill's angular position in the collet and the fixture's on the mag chuck so you can grind arbitrarily close to center
without hitting the next flute. They are easier if you grind away two
opposite flutes near the center and center-cut with only the other two. A
pilot hole lets an imperfect center grind plunge cut and advancing less than the radius lets it nibble.
My mill advances 0.100" per turn so with a half inch end mill I advance two turns and downfeed with the drilling handle. This saves the side flutes for light finishing.
I made a collet closer nut with a half inch center hole to sharpen stub
length S&D bits with it, using the 30 degree back clearance setting to give
a point angle of 120 degrees.
The 30 degree setting can grind a sharp beveled cutting edge on the dull
tips of end mills. I use it for trial skim cuts on surfaces that might be hardened such as cast iron or chrome plated rod, since I do a lot of salvage and repair of old metal instead of production with new stock like you.
I've bought very cheap high quality dull used endmills in a variety of diameters and lengths and sharpen them as needed if a common size won't do.
I can't easily trade time for money like you because I'm in a residential instead of rural zone, but instead I can save by spending 5~10% of the new
cost on used equipment I need, like a snow blower, and fixing it. I used my time to minimize living expenses, to $0 for heat and $40 a month for electricity, and invested in the high-paying areas the Left totally depends
on but loves to hate. Practice what you preach.
We were discussing that life choice in auto shop class last night. Some
former students repair and sell free broken lawnmowers etc. I tried that
with motorcycles but I'm too much of a perfectionist to make money at it. Learned a lot, though. The freedom, lack of stress, self-reliance and treasure-hunting fun of it can be attractive and satisfying.
To me creating advanced electronics was too. I would have worked on the
space projects for free. Machining was necessary at microwave frequencies
where the enclosure is not only shielding but part of the circuit's ground plane or a resonant cavity. We were dealing with the speed of light over fractions of an inch.
--- SoupGate-Win32 v1.05
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