It is very easy to make perfect face frames with a KREG jig, in fact it is almost fool proof, if you follow the system and make careful preparations.
This the completed face frame for the upper section of my new tool cupboard. The corners are square and strong and it was easy to build with a table saw and a Kreg Jig.
My frame began as an 8/4 by six inch piece of rough poplar. First I jointed one face and one edge. Then I ripped off three strips that were a fat 3/4 by 2 by 60 inches.
After I cut off the three pieces I ran them through my planner so they would be smooth and exactly the same thickness. Then I stood the pieces on edge and put them through the planner so they would be exactly the same width.
The next step is to cut the pieces to length. After careful measurement I cut one edge off each board at my mitre saw and checked it for square. I had all ready checked the sides of the boards to see that they were exactly square.
When you are going to make face frames check the set up of your machines. Make sure the table saw is 90 degrees and make sure your jointer is exactly 90 degrees too. When you cut the end off your board you now have a perfect end from which to measure.
I measured the length for my long sides and cut both pieces at once, that way I wouldn't be out even the width of a pencil line. I did the same thing with the three short pieces too. Now the butt joints will fit perfectly because all the surfaces are 90 degrees and the wood is identical lengths.
I worked for KREG in Canada for five years. I drilled thousands of holes and made tonnes of butt joints in demonstrations. I still mark where every pocket hole is going to be drilled. I examine the wood, decide which face in out and which face is hidden and then I mark every pocket hole that will be drilled. Marking the wood reduces the chance of getting the pieces flipped over and the piece being ruined.
I screwed my jig to a board so that I can clamp it to my bench when in use. You can see I have my shop-vac connected to the jig too. The vacuum clears away the wood chips and makes drilling the hole easier and keeps the bit cooler. When I have many holes to drill or I want them to be perfect I use a corded drill because the faster drilling speed means smoother holes.
If your material is not accurately prepared your face frame will not turn out well. The pocket hole screws will pull your joint together tight, and crooked, if your cuts are off by even a little bit.
Before using pocket holes and screws to make a face frame it is worth double checking your saw blades and jointer for square. A little bit out of square can be ignored or clamped into shape with some forms of joinery but not pocket holes.
I am working on the sections that will be inserted in the frame, actually part of it is drying as I type. You'll see it at the end of the week.