30 Questions
What assists the power of the Flywheel?
Hydraulic power
What is the main advantage of Throatless Shears?
They can cut metal of any length and shape
What is the primary function of Scroll Shears?
To make irregular cuts on the inside of a sheet
What must be considered when manufacturing a sheet metal item?
The overall dimension and bend allowance
What is the cutting action of Throatless Shears similar to?
A pair of scissors
What is the principle of operation of Scroll Shears?
Similar to a can opener
What is the range of standard capacities for mild steel sheet in a cornice brake?
12 to 22 gauge
What is the purpose of the clamping nose bar in a cornice brake?
To hold the job in place and facilitate different thicknesses of material
What happens when the bending leaf is raised higher in a cornice brake?
The bending angle increases
Why is it necessary to bend metal past the desired angle in a cornice brake?
To allow for spring-back
What is the purpose of a radius bar in a cornice brake?
To allow for greater bending angles
What is the primary use of a bar folder?
To bend edges of light material
What is the purpose of cutting or notching waste material in step 4?
To create a snug fit between sides
How are the lengths of sides C and E determined?
By measuring the outside of the box
What is the rule of thumb for the size of relief holes?
Diameter = 2BR
Where should the centre of a relief hole be located?
At the intersection of the inner BTLs
What determines the BTL from which the sight line is measured?
The side that is placed under the folder
What is the purpose of determining the bending sequence in step 6?
To determine which BTLs the sight lines will be measured from
What is the primary use of shears in an aircraft workshop?
Notching out corner material to facilitate folding
What is another name for a treadle guillotine?
Squaring shear
What is the purpose of the clamp in squaring shears?
To hold the job tight
What should be kept clear of the clamp and blade in squaring shears?
Fingers
What type of guillotine is used to cut wider and thicker flat sheet metal stock?
Power guillotine
What type of snips are colour-coded?
Aviation snips
What is the purpose of the K-value in the setback formula?
To apply an additional multiplier to the setback formula
What is the K-value for a 90° bend?
1
How can you find the K-value if a K chart is not available?
By using the tangent of half of the bend angle
What is the formula for calculating the setback?
SB = K(BR + MT)
What is the purpose of the setback calculation?
To calculate the distance from the neutral axis
What is the value of K for a 60° bend?
0.5773
Study Notes
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.
This quiz covers the basics of press brake dies, including cornice brakes and their capabilities in bending metal sheets of varying thicknesses.
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