On Sat, 5 Jan 2008 16:20:35 -0800 (PST), "Robin S."
wrote:

On Jan 4, 9:40*pm, Don Foreman wrote:

HSS is tough, hard, and you don't have to heat-treat it. I'd likely
grind a chamfer so that the bits can be welded into the die shoe. I'd
also grind some shear ("V" ideally so it won't push your material to
one side) into the toolbit which comes in contact with the scrap (if
there is any scrap) as this will reduce your tonnage requirements (as
well as snap-through) drastically.

I don't understand this part about the V.

Well, if the entire length of both blades contacts the sheet metal at
the same time, you will require the highest tonnage to complete the
cut.

To reduce the tonnage, you can grind one of the blades at an angle
such that one end contacts the sheet metal first. As the blades
continue to cut, the actual cut line moves along the blades. Because
you've only got a limited length of the blades inside the material at
one time, your tonnage is reduced significantly. It's like using
regular scissors or shears. You're making the cut progressively as you
squeeze the scissors.

Making one blade angled is pretty easy on a grinder. The problem is
that this causes an imbalanced load. The moving members within the die
are stressed unequally, which causes uneven wear (not good). Also,
this tends to force the sheet metal to one side.

If you grind the blade as a "V" instead, you have a balanced load, and
the sheet metal is not forced to one side. The problem is that it's
more work to grind the V, and it will likely deform the cut-off
section such that it cannot be straightened.

Just something to keep in mind.

Regards,

Robin

Gottit. Thanks! I think there are several other viable options for
this project, but I've little doubt that I will use your ideas
somewhere eventually.