CASA Part 66: Press Brake Dies

Cornice Brake

• A cornice brake is used to bend large sheets of metal and can accommodate metal thicknesses from 12 to 22 gauge (0.110 in to 0.032 in) and 3 to 12 ft wide.
• It has a sharp nose bar, a bed with a clamping nose bar, and a bending leaf that forms the material around the nose bar/radius block.
• The clamping nose bar is adjustable to facilitate different material thicknesses and is actioned by a handle to clamp.
• The bending leaf is adjustable to facilitate different radii and is counterweighted to aid the operator in bending.

Bar Folder

• A bar folder is used to bend edges of light material.

Calculating Lengths of Flats

• To calculate the lengths of flats, consider which two sides will fit inside the other two.
• Cut or notch waste material, and decide which sides will fit inside the other two.
• The length of C and E should be the same as the outside of the box, while D and F should be the length of the box minus 2MTs.

Maintenance Practices

• Use relief holes to prevent cracks emanating from the corners of bends.
• The centre of a hole must be at the intersection of the inner BTLs.
• Determine the bending sequence and mark sight lines.
• Think about the bending sequence and how it will affect which BTLs your sight lines will be measured from.

Sheet Metal Cutting Tools

• Hand shears include aviation snips and tin snips, used for notching out corner material to facilitate folding.
• A treadle guillotine is used to cut flat sheet metal stock and has a foot-operated blade.
• Squaring shears have side fences as guides to enable a square cut and incorporate a clamp to hold the job tight.
• A power guillotine is a foot-operated, power-assisted tool used to cut wider and thicker flat sheet metal stock.
• Throatless shears are a hand-operated tool that allows more mobility in cutting and can cut metal of any length and any shape.
• Scroll shears are used to make irregular cuts on the inside of a sheet without cutting through the edge.

Sheet Metal Working

• To manufacture a sheet metal item accurately, consider the physical changes that occur inside the metal when bending.
• Calculate the bend allowance and add it to the overall dimension to finish with the correct size component after bending.
• The neutral axis is the point where the metal does not change length during bending.

Setback

• For bends greater or less than 90°, the setback (SB) will be different, and an additional multiplier (K-value) is applied to the SB formulae.
• The SB formulae becomes: SB = K (BR + MT).
• For a 90° bend, the K-value is 1.
• Use K charts or the formula K = Tangent of half of the Bend Angle to determine the K value for given angles.
• Example: For a 60° bend, the K-value is K60° = tan 30° = 0.5773.