Originally Posted by keep it simple
Hi David, sorry, just back from band practice.
I don't understand your measurements. Did you measure from one lug to the next around the circumference? This is not a good guide to roundness. Some drift in the drilling is inevitable, & TBH, those measurements sound typical & not a cause for concern. You need to measure accurately diagonally across the shell from bearing edge peak to peak.
That said, the fact that your heads are showing uneven contact pretty much suggests your shells aren't round. The photo doesn't tell me much, other than the head is some considerable distance away from seating correctly. A wrap becomes part of the shell, & in many cases, acts as a stabilising element in the construction. It's removal can equate to warping & expansion. Unfortunately, I think your shells are suffering from both, although that's difficult to confirm without inspecting them myself.
OK, what to do. Your plan to gently force the head onto the shell is a good idea, but you should tension each screw evenly, not apply greater pressure to the pinch points. You're effectively trying to get the shell to follow the form of the head, so you don't want that to be uneven. Once tensioned evenly, place the shells in a warm place, preferably at a higher temperature than they've been used to. Although this seems counter intuitive (you expect things to shrink when chilled), it will help the shell to adjust. Hopefully, that will pull them into the round. Getting them round is critical, even if they're still over size. If you get them into round, but they're still too big, then I'm afraid you're into removing some thickness behind the head collar to allow the head to seat without hindrance. It may take some time for the shells to respond to gentle persuasion from the heads. Just overnight will likely not be enough.
I'm worried about this event David. If your photo is representative of just how far out the shell is, then this is quite unexpectedly excessive. Keep me updated before resorting to drastic measures. You'll be surprised by just how much wood can move.
no problem! I'm grateful for your help anyway!
Sorry for confusing - yes, I measured from the bearing edges, not from the lugs. I just used the lugs to get the right position.
I just put each screw to equal tension and placed them in my room in front of heater.. It should get pretty warm in here..
Damn I really hope that the damn wood will move back again.. It would be more than just a pitty if these shells wouldn't work.. :(
I'll keep you updated!!