:U Geez, Paul, ya must've been truly desperate to enlist the other half's help! First, you have to be prepared for the smug superiority when they find it (which they nearly always do, the term 'having a boy look' didn't come from nowhere), then the implied obligation that you will now have to do something like spend a morning shopping together, in return..... :oo:
In future, just call me & place an order for a spare! I might've tried a few lines like 'absent-minded old git' or similar, but I think you'd have quickly detected a lack of sincerity, since I'm still smarting over that brand new 4.5mm brad-point bit I managed to lose a couple of weeks back, the very first time I went to use it. :C
Getting the recesses for the bolt heads & nuts at the right depth can certainly be a challenge. Having done one or two handles, I've gotten pretty slick at judging it by eye, but I sometimes have to go back & drill a fraction more out, which I do with great care. The bolt hole in the centre removes the resistance caused by the centre point & incomplete cutters of the Forstner bit & it will bite in & take out a thick shaving with virtually no pressure at all. I've wrecked more than one handle before by not paying enough attention. Next time, we'll taper the heads & nuts more so that the counter-sinks don't need to be such a precise size to match. Live & learn! :U
Fitting the spine is the very last job I do on assembly. As you've discovered independently, you need to be able to take it on & off the blade several times during the process of fitting everything together. I find it easier to tooth, set & sharpen the bare blade, too.
Cheers,