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 Question from ayman: i would like to know the radius of an arc , i do not know the angle , can u please explian it with an example , all i know , or i think i know is a draw line , the reason i asked yu guys this Q , is i am a boilermaker apprentice , sometimes i do deal with a bended pipes or flate plates of metal . when i try to do the same bend as these pipes , it is quite hard so for me to find out the radius of the pipe already bended & find out the angle i will be able to know the full length of the material thats all , thank you

Ayman,

You will have to measure something, so you might as well measure the radius directly, as curvature.

I have seen gauges in the form of metal arcs or discs that can be fitted to the inside of a curve to make such a measurement, but I have no idea where to buy them. You could make your own set (sheet aluminum? light plywood? plastic?) easily enough. 45 degree sectors at whatever radii you come across in your work would work well. For big radii (10cm or more) you could cut out "rainbow" shapes a couple cm in width.

My understanding is that bending jigs for pipe, etc. often come with interchangeable inserts so that one jig may make more than one radius of curve. If you are using such a jig you could try placing these inserts against the inner curve of the pipe and see which one comes closest.

Good Hunting!
RD

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