Tech Article #3 - Adjusting Your Sheet Metal Brake

 There are four adjustments

• CLAMPING PRESSURE
• RADIUS/SET BACK
• END TO END CLAMP ALIGNMENT
• CENTER TRUSS ROD PRE-LOAD

The basic components of a brake are: Table – the base or major frame; Clamp – the top which holds against the material being formed; and Apron – the front plate which you swing up to form material.

Use test strips of metal, approximately 3 inches by 3 inches each, of the thickness you will be forming for the following adjustments.

Step 1
Check clamping pressure by clamping test strips in the brake approximately 3 or 4 inches away from each end of the brake. Set the clamping pressure so that it is enough to keep the material from slipping during a bend. It is not desirable to use excessive clamping pressure. To change clamping pressure, see the stem going from the bottom of the locking cam. There are two nuts on the stem. One end of the stem is reverse threaded. By loosening both nuts you can turn the stem and increase or decrease clamping pressure.

Step 2
Look at your brake from behind. Under the clamp and near each end of the table find a bolt going down through a slotted bracket and through the table. Loosening this bolt allows 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 apron. Move the clamp back from the apron at least 1 ½ times the thickness of material being formed when forming up to 18ga (.050), and at least 2 times the thickness of material being formed when forming 16ga (.0625) or more, re-check clamping pressure.

Step 3
Check end to end alignment by clamping two test strips in the brake, about 3 or 4 inches away from each end of the brake. Bend to about 90 degrees, and see if they appear to be bent to the same degree. Remove them 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, move the end of the clamp which that strip came from back slightly. Test again.

Step 4
Center truss rods are adjustable to make the center of the brake bend the same as the ends, or, to compensate for flexing during a bend. There is a large nut on each of the three struts which when turned can add pressure in the center of the clamp, apron, or table. Do the test using strips of material again, but add a third strip near the middle of the brake. See if the middle one matches the ends for degree and sharpness. If adjustment is needed, usually the strut under the table is the one to adjust first. A combination of the three struts may be adjusted. If two or three turns of the adjusting nuts do not produce the desired effect, back off all three and start again. Over tightening can distort brake permanently.

Step 5
When adjusted, a hand brake should form with the same sharpness the full length of the brake except for the last 2 or 3 inches at each end, which is normal and acceptable in hand brakes. Reasonably accurate is what we are going for here – you don’t need to get out your protractor and dial gage. It may be necessary to change adjustments when different material is formed.

Step 6
Oil the apron pins, the cams, and the vertical guides behind the clamp.