Pan & Box Brake Vs. Sheet Metal Brake
Hand brakes are used to make tight straight bends of varying degrees in sheet metal. There are two common hand brakes used to produce bends in sheet metal fabrication. They are a sheet metal brake and a box and pan brake. Although both bend sheet metal and contain similar parts, they are vastly different in the types and amount of bends that they are able to perform.
Parts of a Hand Brake
Hand brakes consist of a clamping leaf, bending leaf, counterweighted bending handles, clamp leaf handles and a bed.
Supporting the sheet metal is the job of the bed. Hand brake beds are 12 to 24 inches deep and are set level with the leading edge of the bending leaf. The clamping leaf or top die holds the sheet metal in place as the bending leaf is rotated to make the bend. As the bending leaf rotates on the pivot pins, the sheet metal is forced upward. The higher the bending leaf is lifted, the greater the angle of the bend.
Sheet Metal Hand Brake
A sheet metal brake is the most commonly used hand brake in the sheet metal industry when one or two bends are required. At times the sheet metal brake can be used for a third bend, but rarely.
Sheet metal brakes are designated by their length capacity. The clamping leaf and the bed are the same length and therefore an eight-foot brake has a clamping leaf that is eight feet long and has an eight-foot capacity.
Sheet metal brakes have one major downfall. A sheet metal brake is limited to the type of bends that it can make by the length and angle of the clamping die.
Bends a Sheet Metal Hand Brake Can't Make
There are many times that multiple bends are required during sheet metal fabrication and this is where the sheet metal brake begins to fail. A bend on sheet metal that has a flange greater than one inch is another example of the limitations of a sheet metal brake.
Box and Pan Brake
Where the sheet metal brake fails, the box and pan brake shines. As its name states, the box and pan brake used to bend sheet metal boxes and pans. Unlike a sheet metal brake, the box and pan brake's clamping die is removed and replaced with fingers. The clamping fingers are different sizes and are easily added or removed.
This allows you to adjust the size of the top die to the width needed to make multiple bends on a piece of sheet metal.
When clamping fingers are removed and added often, the locking bolts on top of the fingers wear down. This can result in loose fingers that shift or improperly align. When this happens, bends in sheet metal will have uneven areas.
Hand Brake Routine Maintenance
Hand brakes are rugged and capable pieces of equipment, but as with any equipment that has moving parts, they are prone to wear. The clamping die, pivot pins and bending leaf are the most common items that wear and cause problems during use.
Regularly greasing the pivot pins of the clamping leaf and bending leaf will ensure that the pins will not become loose due to friction wear. Another important procedure is to check all bolts and tension springs for proper tightness. This will keep the hand brake moving freely and sheet metal bends tight.