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Shearing problem


#1

G’day; Although it has occurred to me that the shearing
problem mentioned in a couple of posts might be with revolving
shear-blades, I offer the following If the problem is with two
flat blades moving past each other something like scissors. With
such guillotines the usual problem is that the moving blade
pulls the metal between it and the static blade, so try pulling
the moveable blade hard against the static one during the stroke.

A point of interest is that I have a home-made guillotine used
mostly for paper up to A4, and the blades are of mild steel
3/4"x3/16". The edges used for cutting are square or at
right-angles to the width so there doesn’t appear to be a
cutting edge, but closer examination will show that there is.
When the blades get a bit blunt I put the blades separately in a
bench vice and draw-file the edges, being careful to keep exactly
at right-angles. On re-assembly they will cut from the finest
tissue paper up to 0.3mm sheet brass remarkably well - SO LONG
AS THE BLADE IS KEPT HARD AGAINST THE STATIC BLADE whilst
cutting and the cut is made with a swift movement. This
guillotine has been in almost daily use for around 15 years. It
only needs sharpening about every three months or so. Another
thing that might help is to clamp the metal firmly on the
guillotine table. However, with a pair of rotating blades one
can only suggest that the edges of these be ground so they are
sharp and true (they would be hardened, so filing wouldn’t be
easy) and are tightened as hard against each other as possible.
Cheers,

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At sunny Nelson NZ , Te Wai Pounamu (!)