Feet 'n Inches
Out of the rat-race at last
- Messages
- 544
- Location
- Devon, GB
Hopefully no one will think I am trying to teach their grandmothers to suck eggs but may find it of some use; especially those who are new to the trade or new hobbyists. I first learned this method back in the late 60s and have used it ever since. Here I'm thinking of the equipment I personally have used: either a ring roller (manual or powered) or a set of horizontal pyramid rolls (again manual or powered).
Every cylinder or tube has three diameters: the outside diameter, the inside diameter and the mean diameter. The latter is the one that will produce a pretty accurate finished product. It is half the thickness of either side of the material being rolled, as the illustration shows.
To calculate a circumference where the inside diameter is the critical dimension, add two 1/2 thicknesses (or one thickness) to that diameter. Where the outside dimension is the critical dimension, subtract two 1/2 thicknesses (or one thickness).
For example, if calculating the circumference for rolling a cylinder of 5mm thick material, with an inside diameter of 600mm add 5mm to the calculation so, Pi (I use 3.142) x D (mean diameter) will be 3.142 x 605 = 1900.91 or rounded up, 1901. Conversely if the outside diameter is 600mm then the mean will be 595mm so, 3.142 x 595 = 1869.45 or rounded up, 1869.5.
Every cylinder or tube has three diameters: the outside diameter, the inside diameter and the mean diameter. The latter is the one that will produce a pretty accurate finished product. It is half the thickness of either side of the material being rolled, as the illustration shows.
To calculate a circumference where the inside diameter is the critical dimension, add two 1/2 thicknesses (or one thickness) to that diameter. Where the outside dimension is the critical dimension, subtract two 1/2 thicknesses (or one thickness).
For example, if calculating the circumference for rolling a cylinder of 5mm thick material, with an inside diameter of 600mm add 5mm to the calculation so, Pi (I use 3.142) x D (mean diameter) will be 3.142 x 605 = 1900.91 or rounded up, 1901. Conversely if the outside diameter is 600mm then the mean will be 595mm so, 3.142 x 595 = 1869.45 or rounded up, 1869.5.