Pocket Screw Primer
Article - January 4, 2011
Wouldn’t it be great if you could build a project without using clamps or waiting for glue to dry? How about assembling strong joints in a fraction of the time it takes to cut tenons and mortises?
That’s what you get when you use pocket screws, and if you haven’t given them a chance yet, you might want to try.
The joinery process involves two parts. First, a shallow-angled hole is drilled into one board to create the “pocket”, usually by using a special jig. The workpiece is then butted against the adjoining piece and joined using special pan-head self-tapping screws. The joints take a minimal amount of time to prepare, and the results are more than strong enough for many applications.
What do you need to get started? Well, of course, you need to start with a pocket hole jig. The jig not only guides the drill bit but also holds the workpiece in place while you drill a perfect shallow-angled hole. CMT, General, and others make excellent jigs, but you can’t say “pocket screw” without immediately thinking of Kreg Tool Company. Kreg produces a number of kits and jigs to suit any budget or shop setup, ranging from a small pocket-sized mini to more elaborate kits with built-in toggle clamps and dust collection.
Many of the tools you already have in your shop will also be pressed into service, such as a drill. If you are drilling a lot of pocket holes, you might consider dusting off the old corded drill since battery life won’t be an issue. A cordless drill with a clutch is ideal for screw driving and will help avoid driving the screws too far. Obviously your project boards need to be cut to proper dimension, so whatever means you use to get them there is up to you. Just as with any other type of joinery, pocket screws work best with clean, square, tearout-free project parts.
The screws themselves are of the pan head self-tapping variety. They come in various lengths for different-sized parts as well as coarse and fine threads for different materials. Generally-speaking, I use fine threads for hardwoods and coarse threads for softwoods, plywood, and composites.
First, your parts should be cut to proper length and width. This brings up an important benefit to the pocket screw system: you don’t have to account for joinery. No more mental gymnastics when trying to calculate tenon lengths! When you’re ready to join your pieces, simply mount the workpiece onto the jig and drill the holes.
When you set up to drive the screw into place, its a good idea to use one of the manufacturer?s face clamps. These specialized clamps work very much like vise grips, but the wide faces help keep the surfaces flush as you drive the screws home. Many times, I will employ an additional clamp (F-style or parallel) across the joint just to help ensure everything is held as tightly as possible.
Once the screws are set, you can remove the clamps and move on to the next step, even if glue is involved. This may sound like a minor point, but when you think about the complexity of some projects, this can help keep you sane and negate the need for a wall full of clamps. Furthermore, you’ll save yourself a great deal of time! Take a face frame for example. If you cut classic joinery on the frame members and then glue them together, you’ll lose at least an hour just waiting for the glue to dry. Then, of course, you have to glue that face frame to the casework. That’s another hour. With the pocket screws, you can go from step to step without missing a beat.
When To Use Them
Without a doubt, pocket screws shine when it comes to cabinetry! As I mentioned, I use these screws exclusively when working with face frames. There’s nothing easier for the task, and it saves a great deal of time. I use them not only to join together the solid wood face frames, but also to attach solid wood reinforcing edging for plywood shelves and the plywood boxes as well. Pocket screws also work very well for attaching table tops, flat mitred items like picture frames, legs on occasional tables, and repairing broken pieces of furniture. Many folks use them as an exclusive joinery system for all types of projects.
When Not To Use Them
Let’s face it: the pocket hole itself stands out like a sore thumb! When designing a project, take your time to lay out the joints where the hole will be in an inconspicuous area. Putting them toward the inside or back of a project is always a good idea. If you can?t hide the hole, manufacturers also make special plugs that you can insert into the hole and sand or plane flush. They are made out of many common wood species and you can find one to match or you can use a contrasting species to make a statement.
Remember also that the screw and wood are dissimilar materials. While they hold well for static loads, when you use them in projects that deal with a lot of shifting loads and racking forces, specifically chairs, you definitely want to lean toward more traditional, beefier joinery methods.
Pocket screw joinery is fast and strong. While I don’t use them on every project that leaves my shop, I do find them incredibly useful and my Kreg Jig was a solid investment.
Here are some great examples of projects made using pocket screws from the Wood Whisperer community! From left to right: Dyami Plotke, Mike D’Alfonso, Dean Jackson, and Roger Turnbough.
This article was written by Tom Iovino, Managing Editor of TomsWorkBench.com and columnist for Wood Magazine. Editing and photos by Marc Spagnuolo.