"Robin S." wrote in message
.. .

"Tom Gardner" wrote in message
m...
Take a look: http://www.metalworking.com/DropBox/wire_cutter.jpg

Tom,

Neat gadget. Have you already decided on the inserts, or are you open to
suggestions? You can buy inserts with holes for a securing screw. The
screws aren't cheap, but they're not crazy and that would be a quick way
to index them.

Screws would mean complete dissassembly to change.

It would probably be a good idea to have the inserts nested in the block.
When we build our dies with steel punches and trim steels, we go to great
lengths to have solid steel/cast iron support (shoulders or keys) in every
steel in order to keep them from moving. Carbide would be significantly
more susceptable to failure due to a sloppy fit.

I have the inserts shown floating out of their pockets for clairity, imagine
they are seated and clamped.

I would not have the carbide inserts sliding against each other, if you
can avoid it. This rubbing will cause premature failure, as well as
excessive stress on the arm and base block. While rubbing will give you
the advantage of nearly zero burr, your insert life will be shorter.

I have a similar cutter with the wire passing through a hole in in 1/2"
round carbides. They have to be but-tight to each other or the hard steel
wire forces them apart and destroys the carbides and leaves a bad burr.

I'm not sure what an ideal clearance between your inserts would be.
Typically, 10% of material thickness is used in many punching operations,
but you may find that this much clearance will create a massive burr,
deform the end of your wire, and smear metal on your inserts (causing
premature failure and nasty cuts). Ideally, you could make some shims and
try out different clearances.

As your clearance increases, the required force should decrease, which
should increase the lifetime of the wear components within your tool
(bearings, inserts, wear surface on arm, cam, motor, etc.)

All the wear should be on the carbides. My target is anything better than
125,000 cuts or a week.


Finally, I would take care to make sure there is no slop in your tool at
all. Again, if things don't fit correctly this will cause premature
failure (which can be fun when it's burried inside some monster machine).

Just the flex in the arm is enough to demand a pre-load.

Just my $0.02 worth.

Regards,

Robin