I was doing this last night and I found a way not to do it. I held the scales together with a scrap of material and then fastened them in a vice, after marking with a pencil where the hole should go. Then I proceded to drill through both scales. Because they weren't actually taped together at the top, once the drill bit went through the firs scale it bent the second before the drill bit could start the hole. The result was pin holes that were dramatically off center and at an angle.

Amazingly, after pinning, the blade closed straight. (But this blade is only about three inches long from toe to tail).