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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.

  1. 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.

  2. 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.

  3. 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.

  4. 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 the table.

    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 material too.

    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 FREQUENTLY.

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 very slowly.

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 bends.

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

KEEP  A COPY OF THIS PAGE WITH YOUR EQUIPMENT FOR FUTURE REFERENCE

 

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Last Updated: 03/27/2014