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Re: [BKARTS] metal shear = board shear?



On 28 Nov 2003 at 0:00, Automatic digest processor wrote:

The question is asked:-

" I know that a metal shear is not equal to a board shear, but when I use
a
...............................................................................................................
which could do dual duty since I'd like to also be able to cut metal.

Is there anyone out there that can tell me finer points about differences
in the blade angles, use or any other potential booby traps? Are there
good reasons not to do this? "

The board shear that I have just restored is 10mm thick on both blades.
As my other hobby is amateur radio I occasionally want to use the shear
for cutting thin aluminium sheet say 20/22 SWG.  These shear blades will
do this without too much of a problem.  Probably the purist will blanch at
this, but providing care is taken the stress is within the blade metal's
capability.  The blade length is 36", but I would not try to cut a sheet
of this dimension as the leverage is reducing all the time as the cutting
point approaches the handle.   I have tried cutting half-hard, aluminium
alloy, 16SWG, and  about 10" wide.  This was just possible without
excessive effort.   I can see no discernible effect on the blade edge.

The cutting action takes place at the "point of contact" of the two
blades - not as in a normal machine shop, hydraulic  metal cutting
machine which generally cuts in one go across the width of the sheet (or
for that matter a paper guillotine cutting through many sheets at once).

You will need to make quite sure the clamp is working properly and
holding the metal sheet firmly.    Putting a thin coat of lubricant on the
blade face or along the cut line would also be sensible - remembering to clean
the blades afterwards.  I don't know what the carbon content is of my
board shears, but "Machinery's Handbook" suggest 0.75-0.85% carbon for
shear knives, punches and chisels.    I would also suggest inspecting the
edges on both blades after a session of metal cutting to ensure that any
"blunting" is smoothed off with an oilstone.

Rodney Fry
England

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