Calculating A Rolling Offset In Sheet Metal

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.

Step 2 finding the setback and diagonal. This page also includes a link to a on line sheet metal bend allowance calculator. This simply means that the offset squared plus the rise squared will equal the true offset squared. Say you need to form an offset specified as 0 156 inch in 0 059 in thick material.

You then need to take the square root of the result to get the true offset. The length of the material will then be 11 75 x pi or 36 9137 inches. 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 is used to calculate the back stop location when working off of a flat pattern.

In the example the square root of 208 14 42 inches. 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. 0 059 0 097 in. Air bending one of the three types of bending for sheet metal where the outside mold line is not pressed against the die.

Air bend force chart a chart used to calculate the tonnage required for a bend based on thickness tooling and length. Most sheet metal materials will conform to the calculations. You need to calculate the circumference of the mean diameter of the ring you are rolling. You only have to insert interior angle flange lengths k factor inside radius and material thickness.

The resulting number is the offset depth as measured from the material surface. It allows you to determine either the size of raw material needed or the number of gore sections to fit on your available material. Rolling offsets run the rolling offset run function computes the run length a rolling offset based on the offsets and fittings. Here you would subtract the material thickness from the specified offset.

Calculate the square root of the number to find the rolling offset. 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. Cells on the right will output the desired values.