On 2009-07-23, Michael Koblic wrote:
I got a small parting blade in Vancouver last week: It has a 'V'
cross-section with the top 0.057" and the bottom 0.048". It is 5/16" wide.
The question is: How do you hold it to work? I assume that the 'V' should be
vertical to provide clearance on both sides but to mount it like that
requires some tricky arrangements. I tried to look for a holder that would
do that but could not find one.

I can see how having the 'V' tilted so that one side of the 'V' is vertical
would be easier to do but would it work right? I understand now why the 'T'
shaped tools are easier to deal with.

The slot into which it mounts should have a tilted side equal to
half the included angle of the blade.

Without that -- you can put a thin strip of shim stock ((0.057 -
0.048)/2) or 0.0045" thick near the bottom to set the angle. Make the
width of the stock less than 1/4 the height of the blade, and round off
to the nearest lower thousandth, so go for 0.004" shim stock. 5/16
divided by 4 is 0.0781", so aim for about 1/16" wide by at least as long
as the slot in the holder. A bit longer will let you fold the ends over
to keep it from sliding as you slide the blade to adjust stick-out.

I would like to use the blade in a rear tool post on the Taig which brings
up another issue: If you try to grind a top rake on the blade and clip the
point even slightly the point is going to be *above* the center and I cannot
see how this can be corrected by shims as in a front tool post.

Since the Taig does not have a reverse switch, and it has a
rather small threaded spindle to make running in reverse somewhat
dangerous, you want to run forward and cut on the bottom side of the
blade, not the top, so I guess that it is a bottom rake. :-)

Make the holder to provide an automatic rake without having to
grind, just as the quick-change holders for the Aloris toolposts and
clones have. Ideally, you want to make a way to slide the holder up and
down the post to set the tip height for different degrees of blade
extension and then lock it firmly. A dovetail on the post and a gib on
the holder might work well.

None of the literature available to me nor the web searches have helped so
far.

Does the above help any? Not everything is on the web. :-) Get
in the habit of thinking of ways to overcome your problems and you will
have to ask fewer questions over time -- and will be able to answer some
of the questions of others.

Good Luck,
DoN.

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