Figuring out the straight length of a flatbar after its been rolled into a circle

[hommeacier]

Flats are easily removed by backrolling using the common power or hand crank slip roll.

[hommeacier]

My mistake. you are correct Broccoli. I was referring to DGM's reply just before yours.

[machinisttx]

Ummmm...

Why not just wrap a tape measure around it?

Because a standard tape measure is made to be used flat. You'd need to use a pi tape to get a correct measurement.

[NTXsixseven67]

Same here. I have a few years in a fab shop and I'm just now starting out on my own. I still have my day job as a jr Project Manager but I plan on starting my own company in a few years. I just turned 20 Friday.

[Lay out mechanic]

The same you figure the flat pattern for any round tube or pipe .
.
Outside diameter then minus 1 material thickness times 3.14 / Below chart does not account for weld shrink !
.
Then add 1 material thickness for weld shrink /this is only a Typical factor number / weld joint design and welding technique can make a difference also.
.
Any measuring tool going around the outside diameter is not going to be accurate. unless its a "Pi Tape''
better off measuring across 6 equal places and then take average dim' provided it's pretty round .
.
For your example:
Measure outside diameter then minus 1 material thickness times 3.14
Then Add' 1 material thickness
.
So ...... Lets say there is a 1" X 1/4" flat bar that has been rolled and has a diameter of 20".
Assuming the 1/4" is the thickness, Right ?
.
20" (outside dia') minus .250 (1 material thickness) = 19.75 then times Pi (3.14) = 62.046 then plus .250 (1 material thickness) = 62.296