Something Jim Rozen posted prompted me to post this. He uses a ball
end mill in the lathe tool post to cut thread reliefs. Well, router
bits can also be used for this. Carbide router bits are now fairly
inexpensive and come in a huge variety of shapes. So both convex and
concave radii can be cut along with many other contours. Since these
tools are made for wood they seem to leave a worse finish that cutters
made for metal. But the carbide router bits will even cut stainless
steel. So for the home shop, where money is often less plentiful than
time, the extra time it takes to sand the part to a better finish is
OK. Even though 1/4" shanks will work, the 1/2" shanks are really much
better.
Good luck!
Eric R Snow,
E T Precision Machine

Eric R Snow wrote:

Carbide router bits are now fairly
inexpensive and come in a huge variety of shapes. So both convex and
concave radii can be cut along with many other contours. Since these
tools are made for wood they seem to leave a worse finish that cutters
made for metal.

Good idea!
I think it can be made even better if you de-solder the tips from the
body and braze them on some square stock. Take some time to hone them to
produce better surface.
Will try this, thanks.


Nick
--
Motor Modelle // Engine Models
http://www.motor-manufaktur.de
DIY-DRO - YADRO - Eigenbau-Digitalanzeige

On Fri, 20 Jan 2006 17:30:12 +0100, (Nick Müller)
wrote:

Eric R Snow wrote:

Carbide router bits are now fairly
inexpensive and come in a huge variety of shapes. So both convex and
concave radii can be cut along with many other contours. Since these
tools are made for wood they seem to leave a worse finish that cutters
made for metal.

Good idea!
I think it can be made even better if you de-solder the tips from the
body and braze them on some square stock. Take some time to hone them to
produce better surface.
Will try this, thanks.


Nick
You are most welcome. Maybe it would be better to either make a square
holder with a hole to accept the cutter shank or use the boring bar
holder with an Aloris type tool post. This way the cutters can still
be used in the mill. As to lapping, my method is to turn a brass bar
to the desired radius and then charge the brass rod with diamond
lapping compound. Then the lap is used with kerosene, water, or
soluble oil. Solvent, with a little oil added works OK but I like
kerosene best and then water soluble oil mixed 5% with water as a
second choice. Whenever I grind a high speed steel (HSS) tool bit with
a concave radius I finish the radius with a brass lap turned just for
the tool. Diamond or silicon carbide abrasive will both work with HSS.
Charging the lap with diamond will make the lap suitable for carbide
whereas the silicon carbide abrasive won't. The lap can be charged in
the lathe without removing it from the chuck after you have just
turned it. This method works: Use a piece of flat, hard steel, ( like
a square HSS tool bit), with the abrasive spread on it. With the
spindle turning very slow press the steel against the lap using a lot
of pressure. Make sure the steel moves with the spinning lap, as if
were two gears running together. Do not let steel stop moving. Do this
a few times and the abrasive will be forced into the surface of the
lap.
ERS

Eric R Snow wrote:

Maybe it would be better to either make a square
holder with a hole to accept the cutter shank or use the boring bar
holder with an Aloris type tool post.

They might get in the way. YMMV.
And it doesn't look that much like a good tool. 8-/


As to lapping, my method is to turn a brass bar
to the desired radius and then charge the brass rod with diamond
lapping compound.

[snipp]
Great! Thanks for a lot of good procedures (I partialy knew :-), but not
the neat little tricks)


Nick
--
Motor Modelle // Engine Models
http://www.motor-manufaktur.de
DIY-DRO - YADRO - Eigenbau-Digitalanzeige

In article , Eric R Snow says...

... So both convex and
concave radii can be cut ...

Ball nose end mill for concave radii, and corner
rounding end mills for convex ones.

Jim


--
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JRR(zero) at pkmfgvm4 (dot) vnet (dot) ibm (dot) com
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On 21 Jan 2006 14:47:48 -0800, jim rozen
wrote:

In article , Eric R Snow says...

... So both convex and
concave radii can be cut ...

Ball nose end mill for concave radii, and corner
rounding end mills for convex ones.

Jim
Jim,
I do the same thing. But I make my livelyhood with my tools and so
sometimes the extra cost is worth it. For the cheap hobbiest the
router bits may be the best deal. I know that if I wasn't a machinist
by trade I'd be that cheap hobbiest.
ERS