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I have been mounting bindings for many years. If you've done this, you know a common problem is the ski topsheet puckering up when you tighten the binding screws down, which prevents the binding from sitting flat on the ski. One way to get around this is to use a binding bit with a shoulder that countersinks the topsheet, or use a countersink after drilling with a regular bit. This takes off a little of the topsheet to offset the pucker effect. I have always been a bit wary of this, especially on skis without a metal layer -- to me the more topsheet material for the screws to bite into, the better.

While mounting a pair of RailFlex II plates on some Karmas today, I decided to use a #12AB tap to pre-thread the topsheet. My thinking was that by cutting threads, the pucker effect would be minimized. This was true for the most part -- I was only left with a thin burr around the hole that was easy to shave off with a 1/2" wood chisel. When putting screws in, I gave each screw a light counter-clockwise twist until I could feel the threads engage, and then tightened down the screw (still went in nice and snug -- not like loose machine threads).

So I have to give a thumbs up for the #12AB tap. Normally you'd only use one on skis with metal layers, in order to prevent delamination when tightening screws (this is not a hard and fast rule, just a good idea), but I like the idea of using the tap to cut threads in the topsheet and avoid puckers. Good deal.

BTW, I got the tap at Tognar, it's a Wintersteiger part with a T-handle. I find this kind of tap to be a little more compact and easier to handle on skis than a traditional tap handle and tap bit.

EDIT: one other thing I though was good was that the screws went in smoothly, and it was easy to identify when they were snug up to the whoa point, where I stop and add a final 10-20 deg (or so) of twist before walking away from the screw. If you've ever wrestled binding screws in a plain untapped hole, you know they go in tight and sometimes it's hard to know when to stop. In those cases, it's easy to over-tighten and strip, especially if you're also fighting a top sheet pucker.