The first number you need to find when calculating a rolling offset is the true offset which is found using pythagoras theorem.
Calculating a rolling offset in sheet metal.
This simply means that the offset squared plus the rise squared will equal the true offset squared.
The length of the material will then be 11 75 x pi or 36 9137 inches.
It allows you to determine either the size of raw material needed or the number of gore sections to fit on your available material.
Cells on the right will output the desired values.
Air bending one of the three types of bending for sheet metal where the outside mold line is not pressed against the die.
In the example the square root of 208 14 42 inches.
You need to calculate the circumference of the mean diameter of the ring you are rolling.
0 059 0 097 in.
Step 2 finding the setback and diagonal.
Rolling offsets are used in the piping and sheet metal duct work trades a rolling offset changes the elevation and locaton of the piping or duct usually by using two fittings to offset around.
Say you need to form an offset specified as 0 156 inch in 0 059 in thick material.
Calculate the square root of the number to find the rolling offset.
If you are rolling a ring with a 12 inch od out of 25 inch thick material the mean diameter of the ring will be 11 75 inches.
This page also includes a link to a on line sheet metal bend allowance calculator.
With this free online tool we quickly get the sheet metal bend deduction and therefore the sheet metal blank initial flat length from the finished part measurements.
This is used to calculate the back stop location when working off of a flat pattern.
Rolling offsets run the rolling offset run function computes the run length a rolling offset based on the offsets and fittings.
Air bend force chart a chart used to calculate the tonnage required for a bend based on thickness tooling and length.
Sheet metal calculator bend allowance equations and calculator.
The following illustration shows the equation calculation for determining the bend allowance when forming sheet metal.
Here you would subtract the material thickness from the specified offset.
You only have to insert interior angle flange lengths k factor inside radius and material thickness.
You then need to take the square root of the result to get the true offset.
