Just bought some blank bits for a small boring bar. Says 5% Cobalt on
the side, 1/8"
What do I need to sharpen this - will my regular gray grinding wheels do
it? Also have a small diamond wheel that might fit a Dremel.

--
- -
Rex Burkheimer
WM Automotive
Fort Worth TX

Rex B wrote:

Just bought some blank bits for a small boring bar. Says 5% Cobalt on
the side, 1/8"
What do I need to sharpen this - will my regular gray grinding wheels do
it? Also have a small diamond wheel that might fit a Dremel.


A gray grinding wheel is really too hard for grinding HSS, but you don't have
much to remove with bits so small. Make sure your wheel isn't glazed (use a
dressing stone or a star wheel but don't tell Harold) and don't let it load up
on ya. Watch your temperature. 1/8" bits are easy, only take a few seconds.

GWE

In article , Rex B "" wrote:
Just bought some blank bits for a small boring bar. Says 5% Cobalt on
the side, 1/8"
What do I need to sharpen this - will my regular gray grinding wheels do
it?

They should -- I've done so -- though some others might be better.

Also have a small diamond wheel that might fit a Dremel.

Proably not that good an idea. Cobalt HSS has steel, and steel
absorbs carbon from the diamonds so you will burn up the wheel working
on this. Diamond is good for sharpening carbides, but not so for
steels, including cobalt HSS.

Enjoy,
DoN.
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Email: | Voice (all times): (703) 938-4564
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In article , Grant Erwin says...

... Make sure your wheel isn't glazed (use a
dressing stone or a star wheel but don't tell Harold) ...

:^)

:^)

:^)

Jim


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please reply to:
JRR(zero) at pkmfgvm4 (dot) vnet (dot) ibm (dot) com
==================================================

DoN. Nichols wrote:
Also have a small diamond wheel that might fit a Dremel.


Proably not that good an idea. Cobalt HSS has steel, and steel
absorbs carbon from the diamonds so you will burn up the wheel working
on this. Diamond is good for sharpening carbides, but not so for
steels, including cobalt HSS.

Did not know that, thanks

At grinding wheel speeds the diamond will heat and react with the
iron and the diamond evaporates. Lapping and stoning with diamond tools
is alright, it doesn't raise tempatures high enough to affect the diamond.
The best wheels for grinding HSS or HSC bits are white al oxide or
the blue SG type wheels. Keep the bits cool with water and try not to
discolor them.
You can use a grey wheel but they are usually fairly coarse and will
not give you a very good finish for your tool bits. You may have to lap
or stone them afterward.

Rex B wrote:

DoN. Nichols wrote:

Also have a small diamond wheel that might fit a Dremel.



Proably not that good an idea. Cobalt HSS has steel, and steel
absorbs carbon from the diamonds so you will burn up the wheel working
on this. Diamond is good for sharpening carbides, but not so for
steels, including cobalt HSS.


Did not know that, thanks

On Fri, 24 Jun 2005 15:15:12 -0500, Rex B wrote:
Just bought some blank bits for a small boring bar. Says 5% Cobalt on
the side, 1/8"
What do I need to sharpen this - will my regular gray grinding wheels do
it? Also have a small diamond wheel that might fit a Dremel.
We sharpen 10% cobalt lathes tools from 1/8 sq through 3/8 square
from time to time using the regular AlOx [white] wheel with no
problems. We seem to get better results from the fine grit wheel

Be sure the face of the wheel is dressed/clean, take your time,
and avoid overheating the tool. You can dip to tool in water
while you are grinding to cool it off as long as it dosent get
too hot. If the tool is real hot, and makes a hiss when you put
it in the water you run the risk of thermal cracking and early
failure.

We have found that if you will recycle a windex type spray bottle
and mist the wheel you can keep the tool much cooler while
grinding. Also, avoid breathing any of the dust. Cobalt dust is
listed as a hazardous material [do a google search on cobalt
grinding msds for more info]

We have found that if you will recycle a windex type spray bottle
and mist the wheel you can keep the tool much cooler while
grinding.

I like! Another neat trick filed away for future reference!

While a little OT, I use the same spray bottles with alcohol for aluminium
samples (for chemical testing) turned on a lathe as a coolant. This prevents
the tip "welding" itself to the job and it's surprising how little is needed
from a spray bottle to produce a really clean cut on a wide range of
aluminium alloys. Between the coolant and the flash triangular lathe tips
that can be interchanged and turned three times, you can get an almost
mirror finish with slow feed and fine cuts.

Hope this helps,
Peter

p.s. Don't try this at home with your smoke hanging out the side of your
mouth!