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Re: [BKARTS] board shear adjustment



Lesha wrote:
> Should those adjustments be made with the counterweight on or off?

ON!!

I ship the shears with the counterweight on. If the counterweight is off
when you get a board shears, I advise putting it on and securing it with
the pin or bolt at the end of the shaft (so it can't slide off) BEFORE
mounting it to the cutting table. If there is no pin or bolt, drill a hole
through the shaft and add one.  If the counterweight loosens during use
from the vibration and slides off the shaft when it is up it can de deadly.

To minimize vibration, I adjust it so the blade balances almost exactly
when raised and left at any position, with maybe a very slight, slow upward
motion.  There should be a steel stop under the counterweight shaft just in
front of the weight. If that is missing replace it immediately. It limits
the height that the blade rises to.  If it crashes up too fast or doesn't
stop, there will be too hard a vibration, not only creating a situation
that might loosen the weight, but that will throw the blade out of
alignment.

Remember when adjusting the pivot bolts to loosen one and then tighten the
other an equal amount until the moving blade is parallel to the fixed
(table) blade.

When adjusting the blade gap (moving the curved blade in and out from the
table blade), loosen the bolt that is in the direction you want to move,
then tighten the other one.  When tightening the second bolt, feel the
blade and make sure it just has free movement, does not stick anywhere, but
does make contact all along the blade. Most shears have a second lock-nut
on this adjustment.

If there are spots that are not making contact, you can shim the curved
(moving) blade to straighten it by loosening the screws that hold the blade
to the blade arm near the point of no contact, inserting paper or playing
cards between the blade and the arm, and tightening the screws. This should
not be necessary with blades that were properly maintained, but
occasionally you get an abused machine, such as one where someone pulled
the moving blade in toward the fixed blade, wearing it unevenly. Sometimes
the blade has been reground poorly, or is too thin to take another
grinding. And these blades ain't cheap!

The fixed (table) blade may need to be adjusted to be level with the table,
using the adjustment bolts below the blade.  This needs to be done every
time that blade is ground.

As far as sharpening goes, I haven't sent a blade out to be ground in
decades. I don't let anyone pull or push the blade in my shop, so it just
gets slightly dull from cutting heavy boards and sheet metal (such as for
pressing tins--mostly old aluminum offset plates).  When that happens I
don't get a perfect cut on a sheet of thin paper the length of the blade,
or a board doesnt have a sharp edge when cut.  My test is to cut a sheet of
tissue without holding the blade (just giving it a downward push and
letting go).

If there is a problem area and the blade is properly aligned, I feel the
edge at that point with my thumbnail. If it's dull, the thumbnail slides
across it.  Then I sharpen the blade with a regular fine oilstone, holding
it first on the bevel and then the flat. I do the same with the fixed
blade. Generally it doesn't require realignment after that, as the amount
of metal taken off in fine sharpening is very slight. But after a few times
it might.

After sharpening and adjusting your blades, if your cutter has an embedded
ruler, check your first cut against an engraved ruler. If it's not exactly
right, adjust the table ruler or blade. If you send the table blade out to
be ground, the measurement will decrease by the amount that was ground off
the blade. If the ruler doesn't have an adjustment, you can shim the table
blade out to compensate for the grinding.  Cut two adjacent sides of a
board and check it with a steel square. If your guide isn't square, adjust
it. If you can't adjust the guide and have to shim the table blade, be
careful that you adjust the moving blade pivot to the same angle and
recheck the gap before cutting again, so the blades don't cut each other.

Also remember when cutting to pencil marks on boards to sight straight down
the table blade before clamping the board. If your eye is to the left or
right of the blade edge you will get a parallax error.

When you get perfect sharp cuts from your properly set up board shears your
work goes much faster and is more fun.

--
 Richard
 http://minsky.com
 http://www.centerforbookarts.org

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Edelpappband / "Millimeter" Binding Bind-O-Rama, Entry Deadline - October 1, 2005

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