When I join two pieces together using the Kreg pocket hole the mating part with the screw clearance is pulled toward the side of the board with the clearance hole and thus a less than 90 degree joint. I have tried to "fixture" it up but it is a crap shoot if it comes out at 90 degrees. I now put screws in from both sides to "even it up" Any suggestions?
I'm sorry to hear that you are having problems with your application. Could you please provide me with some pictures to better understand the situation? You can either put them in this post, or you can send them to me through a personal message.
Bill I'm shooting in the dark but normally the things that cause the angle of two cut pieces to end up at different angles than what is intended is the accuracy of the miters that are cut, Not only do the angles have to be cut at the precise angle that you are seeking but they must also be at an exact 90 degrees to the surface. A saw that cuts the angle a little off of the 90 degree to the surface results in a joint that is often a tight miter but not a straight flat miter to surface. I hope this makes sense as it is hard to explain.
Another reason is the accuracy of the bore and insertion of the screw. If the bore is not exact it will pull the miter tighter on one side and smashed the end grain tighter that the opposite side of the miter. Sometimes this leave a miter that is tight on one side and open on the other side. The two pieces will try to "horseshoe" or bow upward at the extreme ends of the piece.
It is best to use the clamp with the large dia metal round disk and place the large disk on the side opposite of the screw inserting . This keeps the miter flat and because of the surface area of the large disk area, tight. Often times it requires that the piece be clamped down on a flat surface is there is any bow or twist in material . It is also a factor in cases were the materials are different in thickness as the clamp does not hold the miter pieces together and allows one or the other to slip.
If the miter is open at either the heel and tight at the toe or vice versa it is also caused by the same as above. A screw that is tighten too much and the pressure is great enough to crush the wood fibers you will sometimes have one that will tighten the miter unevenly and cause it to open on the end that is the furthest from head of the screw. These are the main causes that I have experienced in my work with the pocket hole jig.
Think of a miter as being a framing square. One that is not true can be corrected by moving the tongue away from the body, By using a center punch lay it on a flat hard surface. If the square Is open (further that a 90 degree ) place the punch at the outer corner and tap the center punch, That little amount of force will move the tongue inward (closing it) . If the opposite is the condition then place the center punch in the corner of the inside of the square and do as above. So see it takes very little pressure to move the steel square so the same is to be expected in the miter of two pieces of wood. That means that the difference in the pressure in the screw of a miter can and will result in an inaccurate miter.
Agree with Jay's comments. I've found there are 3 keys to getting square joints;
1. Make sure that your cuts are square; take some time setting up your saw to ensure that it's right on.
2. Make sure your wood pieces are tight when screwing then together. I use the Kreg right angle clamp wherever I can, and when I can't I use bar clamps. If the wood pieces aren't tight together then the screw can move around.
3. Don't over-torque the screws. Turn the clutch way back on your drill. You want the screws tight but not over-tight, especially in softer wood.