Why Buttweld Reducer Has 1" Seam in Its Collars

[jaysomlam]

Somehow reducers (CID#162) that have buttweld seam have 1" seam allowance in their collars.  There should not have any seam allowance because our Buttweld seam has zero male and female allowance.  This happens if a reducer has Buttweld seam or "None", or if it has "Raw" connector or "None".

We can see that a reducer with 32" diameter should have 100.53096" circumference.  The length (X-Size) of its collars should be the same as its circumference because it has zero seam allowance.  Unfortunately, the length of the collars has 1" seam allowance added to it.  No idea where the 1" seam allowance comes from.

Please let me know if you know where the 1" seam allowance comes from or a way to remove the unnecessary seam allowance.  Thanks.

Jaysam

Admin Edit:
Excessively large attachments removed.

[jaysomlam]

OK, I figure out where that extra 1" seam comes from.  It is from our specification for round duct that has a 1" Lap for collars as shown in the attached picture.

Now, I will have to figure out how to work around this problem for buttweld round duct that has collar.

Jaysom

Admin Edit:
Excessively large attachment removed.

[jaysomlam]

I believe the solution is as simple as asking our people to use our "Buttweld" specification.  Our specifications all have a "Buttweld" spec in each group of specifications.

Jaysom