I bought one of those enco fixtures,
http://www.use-enco.com/CGI/INSRIT?P...&PARTPG=INLMK3

Tonight I gave it a try using a surface grinder and a normal wheel. The end
mill was a 1/2" HSS 4 flute that I'd done something stupid with and broke
about 0.100" of the edges a year or so ago.

I tried to estimate where the cutting edge would be when I got down 0.100"
to remove the damage. Since you are removing material perpendicular to a
helix the cutting edges are receding CW for this em.

Right there I should have just slapped that end mill into an abrasive saw
and cut away the damaged section or used a grinding vise to grind the end
parallel to the table. The sharpening fixture isn't the tool to use for
that. I'm learning I hope.

I used some dykem to make showing where I was grinding a bit easier and
finally got the primary relief right after having to reorient the bit in
the fixture. If I'd just cut it off or ground it flat it would have been
easier.

Then I tipped the thing over to the 30 degree or so angle, blued it up again
and worked the secondary relief until the margin on the primary looked good
as in like the factory end on the other side.

I've lost most of what I think is called gnashing. How do I do that? The
end mill cut okay. I milled a 1.5 x 1.75" crs block to make a 94 degree
rest for using a diamond wheel to sharpen my scrapers. End mill worked fine
for me but I have to think that gnashing has a purpose.

The enco 'economy' item uses a thumbscrew and a ball. I think the other
higher priced one uses a spring loaded pin. If you pull the 5C holder out
of the economy model, be prepared to loose the ball bearing. Just a tip.

Thanks,

Wes

On Dec 9, 9:22 am, Wes wrote:
I bought one of those enco fixtures,http://www.use-enco.com/CGI/INSRIT?P...O=949927&PARTP...
....
Wes

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As you noted, chipped end mills need to be ground flat first. I use a
pedestal grinder and also rough-grind the 30 degree relief.

You may not have noted that the cutting flutes slant inward very
slightly toward the center on a factory-ground endmill, which is why
that fixture tilts sideways as well as lengthwise. Any amount of
inward slant seems to work.

Since the fixture doesn't sharpen the side edges that do the actual
side cutting you have to shorten the mill to remove the dull section.
I've modified the endmills that I resharpen by grinding a bevel
instead of a sharp point at the ends of the flutes, using the 30
degree tilt, and limiting depth of cut to the beveled edge.

It's hard to resharpen a center-cutting end mill so that it will
plunge cut. I mill a pocket with them by either drilling a starting
hole or cranking the table back and forth while slowly advancing down.

Jim Wilkins

I've lost most of what I think is called gnashing. How do I do that? The
end mill cut okay. I milled a 1.5 x 1.75" crs block to make a 94 degree
rest for using a diamond wheel to sharpen my scrapers. End mill worked
fine
for me but I have to think that gnashing has a purpose.

I've managed to do this with a die grinder and cutoff wheel. Not the right
tool for the job, but it will work if you're careful. Like you're learning,
try to do the bulk of the material removal in the pedestal grinder freehand.
Putting a proper wheel in this grinder will help a bunch. With practice,
you'll have less than 10 thou to remove on the secondary relief. it won't
hurt a thing if the back part of the relief still shows free hand grind.
Then just do the cutting edge.

For me, the ticket is to have a sharpening day once a year. Then do a bunch.
You can get dull end mills almost free on eBay etc. I now have several
hundred that I've sharpened.

Karl

On Sun, 9 Dec 2007 09:46:47 -0600, "Karl Townsend"
wrote:



I've managed to do this with a die grinder and cutoff wheel. Not the right
tool for the job, but it will work if you're careful. Like you're learning,
try to do the bulk of the material removal in the pedestal grinder freehand.
Putting a proper wheel in this grinder will help a bunch. With practice,
you'll have less than 10 thou to remove on the secondary relief. it won't
hurt a thing if the back part of the relief still shows free hand grind.
Then just do the cutting edge.

Might I suggest that if one has spare arbours for the surface grinder, a
cutoff wheel on the surface grinder might be the quickest solution.

Haven't done it yet myself, but it's on the to-do list for when the mill is up
and running.


For me, the ticket is to have a sharpening day once a year. Then do a bunch.
You can get dull end mills almost free on eBay etc. I now have several
hundred that I've sharpened.

Got to do that with the drill collection...



Karl






Mark Rand
RTFM