How do I use a pocket hole jig?

A pocket hole is a shallow angled bore that lets a screw run from inside one piece into the end or the face of another, so the joint needs no clamps while it sets and comes apart again with a screwdriver. It is the fastest joint in woodworking and the one most often used where it does not belong. The mechanics are simple; the setup errors are what cause almost every failure.

What you'll need

• A pocket hole jig with its stepped drill bit
• Pocket hole screws in coarse and fine thread
• A face clamp or a bench clamp
• A driver with a long square-drive bit
• Wood glue (optional)

Step by step

1. Measure the actual thickness of the piece being drilled.Not the nominal size. Both settings on the jig follow from this one number, and 18 mm ply that is really 17.2 mm will put the screw in the wrong place if you set it to 18.
2. Set the drill guide to that thickness.The guide slides up and down so the pocket exits in the middle of the mating piece's thickness. Too high and the screw breaks out of the face; too low and it exits the bottom edge.
3. Set the stop collar on the bit to the same thickness.This controls how deep the pocket goes and therefore how much screw is left to enter the second piece. Most failed joints are a collar set at the wrong depth.
4. Clamp the workpiece in the jig and drill each pocket in one go.Run the drill at full speed and withdraw a couple of times to clear chips. The stepped bit cuts a flat-bottomed pocket and a pilot hole in one operation.
5. Choose the screw by material and thickness.Coarse thread for softwood, plywood, MDF and chipboard; fine thread for hardwood, which coarse threads can split. Length follows the material thickness — the jig maker's chart is on the jig itself and is worth following exactly.
6. Clamp the joint before driving anything.This is the step people skip. As the screw pulls up, the angled thrust slides the joint sideways. A face clamp across the joint holds the alignment; without it the parts step out of line by a millimetre or two every time.
7. Add glue to the joint face.Where the joint is face to face or edge to face, glue does most of the work and the screws hold it while it cures. Where the joint is into end grain, glue contributes little and the screws are the joint.
8. Drive to firm, then stop.Set the driver clutch low and increase it until the screw just pulls the joint tight. Over-driving strips the pilot hole in softwood and chipboard, and the joint then has nothing holding it.
9. Plug the holes if they will show.Matching wood plugs glued in and pared flush, or moulded plastic plugs. On a hidden face, leave them.

Tips

• Drill the pockets in the piece that will be hidden. Deciding this before you drill saves plugging holes on a show face.
• In thin material, a pocket hole is on the edge of what is possible — under about 15 mm the pocket has very little wood around it and the joint is weak.
• For outdoor work use screws rated for exterior use and remember the pocket collects water. Angle the joint so water can drain, or fill the pocket with sealant.

Common mistakes

• Not clamping the joint while driving — The screw enters at an angle and pushes the pieces apart sideways as it tightens. The joint ends up stepped, and it cannot be corrected without taking it apart.
• Setting the collar and the guide to different numbers — The pocket then exits in the wrong place, and the screw either breaks out through the show face or has too little thread in the second piece to hold.
• Using coarse-thread screws in hardwood — The aggressive thread acts like a wedge in dense timber and splits it along the grain, usually at the moment the joint pulls up tight.

If it doesn't work

Questions people ask