Don't you hate it when you've invested $$ on pocket screw technology and you STILL have to sand things flush and flat? I do. My most recent purchase was this tool, the Kreg Foreman air driven pocket screw cutter. It cuts fine, but it is a little different from my old Porter Cable 550 - a router based pocket screw cutter.
<img src="http://burchwoodusa.com/miscpix/pockethole_machine.jpg" alt="Kreg Foreman Air Driven Pocket Hole Cutter.">
My old PC 550 cut a much flatter pathway (a much longer hole too), so the screw entered the butt joint at about 2°. It was fairly consistent at staying put when the screw was driven, as there was a full pilot hole made as part of the drilling operation (albeit a second, manual step with a hand drill, long thin drill bit through a bushing, into the end grain and existing into the router-created swath).
This new (much quieter) Kreg is a lot faster than the Porter Cable, but with that came new techniques to learn to produce flush joints. At first, many of my joints were pulled offset by the action of the operation. Since there was not a clean exit hole for the screw, debris would be pushed out by the screw between the pieces.
<img src="http://burchwoodusa.com/miscpix/pockethole_debris.jpg" alt="Wood debris created by the screw">
Since the pieces were now further apart, and the screw is heading down at a 7° angle, the screw would enter the mating (target) piece lower. When it was pulled tight, it would be pulled up, thus creeping upwards, producing a non flush, somewhat offset joint.
So, I've come up with two things that can be done, short of investing in complicated or expensive machinery or building a universal clamping jig.
First, I pre-drive the pocket hole screw (sometimes called face frame screws) to make a clean hole. Any debris that will come out does. Along with this, I make sure there are no proud chips still sticking out of the hole that might cause the two pieces to not meet flush.
<img src="http://burchwoodusa.com/miscpix/pockethole_pilothole.jpg" alt="No thru-hole produced my the Kreg">
Second, I shim the piece that the screw starts in, and apply downward pressure to the target piece.
<img src="http://burchwoodusa.com/miscpix/pockethole_someshimming.jpg" alt="Shimming the source piece, not the target piece">
For the picture below, shown on the left, no pilot hole was made and no shimming was used, and I held the joint as best I could with one hand while power driving the screw with the other. In the middle example, I made a pilot hole and used a piece of printer paper, folded once, as a shim. On the right, again, I made the pilot hole and I used the same paper, folded twice as a shim. This last example is quite acceptable.
<img src="http://burchwoodusa.com/miscpix/pockethole_endresult.jpg" alt="End result, showing all three examples">
Here are some face frames that I did this afternoon, using my "old" method and using the "new" method just figured out. The frame in back will eat my lunch in time spent sanding the joint flush. The frame in front will merely get the obligatory final sanding.
<img src="http://burchwoodusa.com/miscpix/pockethole_realworld.jpg" alt="Real World example - saving money by not spending as much time sanding">
Even if you have the portable Kreg pocket hole system, or another brand, perhaps you can use either or both of these tips to help produce a better face frame joint.
Todd
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