Sorta.....
If you V the back *and* the front jaw--contrary to my spec of V'ing *only*
the back jaw.

I have found that additionally V'ing the front jaw to be 1. somewhat
superfluous ito of pure holding power, 2. possibly a hindrance, as the front
jaw is loose anyway, or may even be misaligned w/ the rigid back jaw, and 3.
as you've noted, V'ing both jaws just about *doubles* the minimum size that
can be held w/ that size V slot.

Back and front V slots are, in fact, a circumscribed square around a circle,
and the problem can be solved in that manner as well.
Note, however, the diff. between using the depth of a slot and it's edge in
this calculation--altho the edge (sqrt 2 times the depth) is perhaps more
obvious geometrically, the depth is what we more easily measure in
machining--just Z.

There is indeed no upper limit on the size of the rod held, *if* you don't
care *how* it's being held!
Ie,
Past the limits I described you lose stability, because then the front
*edge* of the V is "holding" the rod, and *not* the 90 degree sides, tangent
on the circumference--in fact a condition in these calcs..
Note that as long as you are in contact w/ the sides, there is no advantage
of being deeper in the slot/using a bigger slot--the stability/holding power
is the same.
Or so I think....

And, holding larger rods on the cusp of a V slot can damage both.

Some may point out, Sheeeeit, no wonder this cadcamless muhfugguh is
slower'n'**** machining his stuff, Look at how he fritters away his goddamm
time....

Well, ackshooly, in making a super pair of jaws (w/ max. bang fer my
machining buck), I sorta needed to do this. And, in ball detent-type
scenarios and geometries, you have similar calculations.
----------------------------
Mr. P.V.'d
formerly Droll Troll
"Cliff" wrote in message
...
On Tue, 6 Dec 2005 01:32:46 -0500, "Proctologically Violated©®"
wrote:

The Q is:
For a given 90 deg. V slot (eg, one V-slot in the back vise jaw), what is
the smallest rod that can be held in a V-slot (ie, too small a rod will
rattle), AND, what is largest rod that can be held by that same V slot
(ie,
where the V slot walls will indeed hold the rod tangently and therefore
stable-ly, and not on the cusp of the V)?

If I've read that correctly the max diameter would equal the
length of one leg of the V (just a tad less, actually -- that's the
limit for perfect contact with no load).

Reasoning: The Vs make a square when fully closed. The
length of one edge of the square is the same as the
diameter of an inscribed circle in the square.
Oops .. that's the smallest that can be held .. no upper limit on
the largest G.
--
Cliff