Round shell flat pattern

[SLG2007]

When creating a flat pattern I am using the following formula for all of our material from 3/16" up.

[ID + (.8 (1material thickness))](Pi)

Then on our sheet material we are using the following formula.
[ID + (1 material thickness)] (Pi)

My questions is. Am I using the correct formulas for determining the flat pattern?

Please advise.

 

[SnTMan]

SLG2007, most schemes are based on the mean diameter with either some or none allowance added for shrinkage of a long seam.

Your second formula is mean diameter, no allowance.

You have to kind of see what works for whatever shop is doing the work. Early input might be a good idea. Otherwise add a drawing note stating no allowances are provided, fabricator is responsible.

Regards,

Mike