|Sheet Metal Brake Adjustment Information
Basic components of a sheet metal brake.
BED/TABLE--base, major frame
BEAM/CLAMP--movable top which clamps the material being formed to base
APRON--front plate that is lifted to form material
CAM--is used to adjust clamp pressure against table
Adjusting Your Brake
There are 4 adjustments and these MUST be adjusted in the following order.
Use test strips of the material you will be working with of approximately 2" X 3"
of the same material and thickness you will be forming. You will also need several
full length or near full length pieces by about 4" wide of the material you are
setting up for.
CHECK CLAMPING PRESSURE-- by placing test strips in
the brake about 3 or 4 inches away from each end of the brake.
Adjust the clamping pressure so that it is at most only enough to
keep the material from slipping. It is not desirable to use more
clamping pressure. More pressure can "pre-load" the brake in a way
which will force a distortion. Your best results may be with zero
clamping pressure. To change clamping pressure see the nuts at the
bottom of the cam assembly stem.
RADIUS- SET BACK--refers to the distance
between the leading edge of the clamp and the inside edge of the
apron. Look at your brake from behind. Loosen the bolts allowing you to
move the clamp forward or back on the table. Now from the front,
look at the distance between the leading edge of the clamp and the
inside edge of the apron. Move the clamp back from the apron at
least 1.5 times the thickness of the material being formed when
forming up to 18ga (.050), and AT LEAST 2 or 3 times material
thickness when forming 16ga (.062) or heavier. Be sure to move the
clamp back a little too far and then move it forward to take out
any slack. Recheck clamping pressure. Be sure clamping pressure is
very little or none.
CHECK END TO END CLAMP ALIGNMENT--by
placing a test strip about 3 or 4 inches from each end of the brake,
and bend to approximately 90 degrees. See if they appear to be bent
to the same degree. Remove the test strips from the brake and stack
one inside the other. Compare the sharpness of the radius. If one
test strip is over bent or has a sharper radius, increase the radius
set back on the 'tight end' slightly and test again. Here too, you
want to be sure to move the clamp back a little extra and then bring
it forward to take out any slack.
TRUSS ROD--are adjustable to
help make the center of the brake bend the same as the ends. Use
truss rods to stiffen the clamp.
CAUTION - OVER
TIGHTENING TRUSS RODS WILL CAUSE PERMANENT DISTORTION
For 6-10 ft brakes and 4' 12ga models, bolt the brake to the floor.
On models with 2 truss rods on the clamp, you can stiffen the clamp
to some degree by "pushing" with the larger truss and then "pulling
back" with the smaller one.
On models with 2 truss rods on the apron, the larger truss can raise
the center of the apron to level it or give it a slight crown. Then
the smaller truss can pull the center of the apron in snug against
There is a large nut on each of the truss rods which can add
pressure in the center of the clamp, table, or apron. If adjustment
is needed, usually the clamp is the place to start. A combination of
adjusting the clamp, apron and table truss rods may be needed. After
making a change, use the 2" x 3" test strips near the ends of the
brake to re-check clamp pressure and end to end alignment, then use
a full length strip to see if the middle is forming the same as the
ends. CAUTION: OVER TIGHTENING TRUSS RODS CAN CAUSE PERMANENT
DISTORTION. If, after several tries, you do not get the desired
effect, back off pressure on all truss rods and try again with a
different sequence. Sometimes a slight upward crown to the table and
apron is desirable. When the test strips look right, use the brake
normally. If it then changes after using the brake for awhile,
you'll need to re-adjust. But first see if the set back or end to
end alignment has changed by using 2" x 3" test strips near each end.
After a break-in period, truss adjustment is rarely needed. But you
do need to adjust clamp pressure and radius set back for varying
gauges. Most distortions are due to too much clamping pressure and/ or
not enough radius set back.
When adjusted, a hand brake should form consistently the full length
of the brake. Reasonable accuracy is what we are going for here -
you don't need to get out your protractor and dial gauge. And
remember, it is necessary to change adjustments when heavier or
lighter material is formed. At least, adjust your brake for the
heaviest material you use and leave it there for the lighter
SET CLAMPING PRESSURE TO ZERO OR ALMOST NONE, AND RADIUS SET BACK TO
AT LEAST 1.5 TIMES MATERIAL THICKNESS WHEN FORMING 18GA, AND 2-3
TIMES FOR 16GA OR HEAVIER.
OIL APRON PINS, CLAMPING CAMS, & VERTICAL GUIDES BEHIND THE CLAMP
Vertical guide pins on all
models are designed to be rotated when the develop noticeable flat
spots. This will be evident by front to back play in the clamp when in
the closed position but without "cam over" pressure. There is a set
screw in a collar that you loosen to allow the pin to be rotated. You
can also remove the pin and reinsert the other end first to continue
using it. Regular oiling will prevent most users from ever having to
replace this part.
The vertical guide plate or bracket
should outlast the pin and therefore you probably will never replace it.
However, it is replaceable and the part number is provided.
Apron bushings are
replaceable and part numbers are provided. Kept oiled they will wear
The cam assembly does
wear and can be rebuilt. Keeping it oiled and adjusted so that there is just a
little movement between the inner disc and the outer ring, and no
binding through it's range of movement, will make it last longest.
Either excessive tightness or looseness will cause faster wear, as would
lack of lubrication.
There is a block at the bottom of the cam
stem where you adjust clamping pressure with the nuts above and below
the block. After you adjust clamping pressure, the nuts above the block
should be locked against each other so that there is a gap between
the block and the nut above the black of about 1/32" to 1/8" (or about
.030 to .125) This will allow some movement of the anchor pin/block
assembly, which is necessary when only one end of the clamp is opened.
Having way too much gap, say 1/4" or more, will cause wear on some cam
assembly parts and on the anchor pin. Having no gap can cause some cam
assembly or vertical guide parts to bind and wear faster. In real life,
at least set it up for the thickest material you normally form with a
1/8" gap above the block. That will leave you room to adjust the nut
under the block for some thinner materials without having to adjust the
nuts above the block too.
During the break in period, clamping
pressure is an adjustment that will change with use. Keep in mind that
it is important to use the correct clamping pressure and minimize the
gap above the block at the bottom of the cam stem. It is also very
important to avoid having too much clamping pressure. Clamping pressure
and set back are the two adjustments that do need your attention
whenever you change the gauge of the material you are forming.
"HOW MUCH CLAMPING PRESSURE?"
Clamping pressure, or
cam-over pressure, is adjustable. Having a lot of it is often thought to
be a good thing. But try this when the middle is not bending the same as
the ends; instead of adding more clamping pressure, reduce it. Consider
the possibility that any brake is naturally stiffer near the ends than
the middle. When cam pressure is added more than a very light touch, the
material being formed has more pressure applied to it on the ends than
the center before the bend is even started (because the brake will flex
slightly more in the center than it will at the ends). So both the
material and the brake are in a distorted condition from the get go.
Adding more clamping pressure makes it worse. You may have noticed a
wavy condition to the material hanging out of the back of the brake when
clamped. Try reducing truss pre-load, and reduce clamp pressure. See if
you get a better bend, and if it is much easier to pull the cam over.
Try zero clamping pressure next. With little or zero clamp pressure, you
will see the entire clamp or head assembly of the brake lift at the
start of a bend, but that is okay since it is all lifting evenly.
RADIUS SET BACK OR BEAM ADJUSTMENT
When you are forming light material, set
your clamp back from the edge of the table at least 1.5 times the
thickness of the material being formed. When forming maximum rated
material use at least 2 times, and better to try 3 times material
thickness for your set back. Set back allows a radius. Up to a point,
more radius results in needing less pressure to make the bend. Less
pressure means everything is distorting less and you get more consistent
USING A "BOOT" TO INCREASE INSIDE BEND RADIUS
When forming some materials,
such as aluminum, it is desirable to bend against an edge that is not so
sharp as the standard edge of the clamp or fingers. This will decrease
the tendency of aluminum to stress crack, or fracture when forming it.
You can make a "boot" from about any light gauge material, say about 4"
wide by the length of your brake. Something like 22ga - 24ga mild steel
is good. Put the material in the brake so that you are bending a 2"
flange, but bend it all the way over until it lays against the top of
the brake. Now you can tape it or use other means to keep that piece in
place. With this "boot" in place, you will increase the inside radius of
the bends you make. An additional "boot" will increase the inside radus
of bends even more. Note that as you add one or more "boots", you must
also adjust the clamp set back, so to maintain the 1.5-3 times material
thickness as your minimum radius set back, also called beam set back.
And, clamping pressure will need to be adjusted. Remember, less pressure
is usually better than too much pressure.
BOX AND PAN BENDING
Detachable fingers on your brake allows the bending of third and fourth
sides of boxes by passing the first sides thru spaces between the fingers as the bends are made. Fingers are in
2", 3", and 4" widths. They may be grouped for even inch combinations, or spaced out for fractional dimensions.
With all fingers in place, the Box and Pan Brake operates as a plain brake. The fingers are
machined accurately and clamp to machined surfaces on the edge of the beam. While special fingers are
not available, it is possible to alter standard fingers for special jobs. Replacement fingers are available
for most brakes.
OIL ALL MOVING PARTS
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YOUR EQUIPMENT FOR FUTURE REFERENCE