My comments are buried in the reply text.
Look there for them :-)

--- In multimachine@yahoogroups.com, "Gus Rodriguez" <gusrod1948@...> wrote:
>
> Hi Keith,
>
> I use a lapidary wheel (a jeweler's wheel) made of a very fine grade of
carborundum (silicon carbide) to grind my carbide bits but it takes a lot of
work to grind them to shape. It also takes a lot of quenching, unless I leave
them mounted on the tool holder, 'cause they get too hot to hold very quickly.

That's a darn fine idea for grinding carbide bits!
On the plus side, almost every single lapidary wheel is DESIGNED for wet
grinding. A water bottle, some rubber tubing, and hotglue/epoxy, will net you a
very nice, slow drip watering system.
Not only will the drip do some quenching, but the wet stone will run cooler also
(limiting heat buildup in the bit).
All the lapidary machines I have ever cut stone on have plumbing for
water/coolant. just an fyi.



> Most of my turning is done with HSS 10% cobalt bits and I just use coarse and
medium grade silicon carbide wheels to grind those ('cause that's all I have),
but I've been told that you could grind them with regular aluminum oxide wheels
too. The real advantage to 10% cobalt is that it makes the HSS able to withstand
higher temperatures, so you can take deeper cuts without overheating and
destroying your tool bits. I think I paid $3 each, also from Enco, but I think
they were on sale at the time. Not sure what the regular price is. Last time I
bought a bunch of them so they would last me a while and so far, they've lasted
a lot longer than regular HSS. I think I'de bought a dozen.
>

If you happen to know a school or machine shop local, I've often gotten entire
stocks of old HSS bits that way. Once a shop switches over to carbide inserts...
the HSS blanks just sit on a shelf. The M42 cobalt steel bits I have, I sharpen
with a diamond wheel. Sure, It was expensive for the person who bought
it(replacments are around $70 us) but, since it came attached to the $15 motor,
I'll just keep using it. :-)



> I use a quick change tool post from CDCO and 3/8" tools are the largest I can
use on my lathe. I can't use 1/2 inch because I can't center them properly.
>


Is that the #29461 Quick change tool post?
If so, and you don't mind doing the job, the tool holders are thick enough to
allow you to shave off 1/8th" from the bottom of the bit rest.A hacksaw, and
file will accomplish the task in about 5 min.
If you do HEAVY cutting... you could also make your own holder. they are
actually quite simple, as you know. You can angle the bit slot down, to get the
clearance you need for proper centering while retaining enough 'meat' in the
tool holder to eliminate flex. It would involve re-grinding the larger bits to a
new geometry, but once the extra work was done, it would only need normal
sharpening.


> On thinking about leaf springs some more, I don't think I would ever try it.
Although they are made of high carbon steel, it's not the same as HSS and I
don't think they would work very well for turning steel. I think they would be
great for woodworking though - or soft metals, if someone wanted to take the
time to cut off and grind the tools. I regularly cut up to 5/8" plate steel with
an abrasive cutoff wheel mounted on a radial saw or a chop saw and even use the
chop saw to cutoff up to 4" diameter bar stock, but it's LOUD and makes a LOT of
sparks! LOL. I'm sure that would work well on a leaf spring.
>

Yep, that was my point earlier :-)
To be fair, you can also cut leaf spring with a good quality cold chisel. To be
fair though, If I'm forced to use leaf spring for a tool... I'll usually use a
4" cutoff wheel in the dremel.



> Today is payday for me (pension check from Dept of Veteran's Affairs) and I
thought I would have a "wild hog" day, going hog wild on a shopping spree at the
local tools stores, but the wife just called from work to tell me her car
overheated and now she has a $3000 car repair bill to contend with (damn!). I
hope you have better luck than I do!
>

Ouch! For that price, I could buy 2-3 more whole Geo metros! Or one REALLY NICE
one(red convertible and 5-speed. gotta love 40+mpg when gas climbs over $3)


> I recommend getting a silicon carbide wheel to grind the tool bits. If you
can't grind them with what you're using now, that should do the trick.
>
> ... Gus

Ceramic aluminum oxide wheels are what you're after I think. It's hard, strong,
and specifically designed for "grinding of tough steels and alloys". Silicon
carbide will work, but will wear quite a bit faster, and clog more readily. I
hate dressing wheels more often than I have to :-(
Straight aluminum oxide wheels SHOULD work on MOST tool steels.. but those
cobalt bits are a bit of a pain :-(