If you are using Old bolting then what you are getting for item 12 is a standard bolt (item 13) plus 38mm for the blind + 3mm (i assume this is gasket thickness).
For item 14 you get a standard bolt (item 15) plus 18mm for the blind + 3mm
My instinct to get the exact bolt length you are looking for is to change the blind thicknesses in the catalogue by 1mm.
In the overall scheme of things, 1mm will not make a significant difference. Especially when you take manufacturing tolerances into account.
If you are using Old bolting then what you are getting for item 12 is a standard bolt (item 13) plus 38mm for the blind + 3mm (i assume this is gasket thickness).
For item 14 you get a standard bolt (item 15) plus 18mm for the blind + 3mm
My instinct to get the exact bolt length you are looking for is to change the blind thicknesses in the catalogue by 1mm.
In the overall scheme of things, 1mm will not make a significant difference. Especially when you take manufacturing tolerances into account.
