Before learning to tap threads in wood, I thought it would be helpful to review other types of mechanical fasteners and why they might not be as good as a bolt in a threaded hole.

Nails

Nails are pretty much a brute-force way of holding things together. The nail is driven into the wood, splitting and compressing fibers the whole way. Over time, natural forces cause the wood around the nail to compress even further eventually leading to joint failure.

Screws

A step up from a nail is the screw. When you rotate the screw into the wood, it pulls itself in and threads itself into the fibers. The good thing about screws is they are removable, but over the course of years the cut threads become wider and wider and the screw will eventually loosen up.

Threaded Bolts

This is the star of our show today. Once the threads are cut into the wood, you can pretty much remove and replace the bolt as many times as you want and it really doesn’t do any damage to the wood. This is because the bolts threads are sized perfectly to fit into the threads that are cut into the wood. So this is perfect for applications where you may need to loosen and tighten components on a routine basis.

Tapping Threads

All you need to make a threaded hole is a drill bit and a tap. The drill has to be a very specific size and and you can typically find drills and taps in matched sets such as this one. If you need help matching up your bolt, drill, and tap, refer to the handy charts on this page.

Here’s how the system works. The drill bit is used to create the perfect size hole. The tap is then driven into the hole cutting the threads on its way down. You have to be very careful not to strip the threads during this part of the process but in a dense hardwood like maple, you should have no trouble at all. While you might be tempted to use a traditional T-handled wrench for this, I found it much easier to use a power drill at a very slow speed.

Tee Nuts

One alternative that we can’t forget to mention here is the Tee Nut. These little threaded inserts accomplish the same thing as the threaded bolt technique only instead of actually cutting threads, we simply insert a threaded insert into a hole. They are very easy to use but unfortunately, the way they connect to a workpiece leaves a little to be desired. Over time, the small teeth that go into the wood fibers can break or the wood itself can compress, causing the Tee Nut to lose its grip. So while they can get the job done, I don’t really see them as a good long-term solution.

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.

The Gear

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.

A crucial component of any pocket screw kit is the step drill bit. This bit drills a square-bottomed hole for the screw head to bear against and a shank hole for the screw body to pass through.

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.

The Process

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.

While at first it may seem like “shortcut joinery”, pocket screws are quickly becoming the norm in many commercial shops. If you look hard enough on many high end custom cabinet jobs, you?ll probably see evidence of pocket screw construction.

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.

Examples

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.

Have experience with pocket screws? Share your story (good or bad) with us in the comments!

This article was written by Tom Iovino, Managing Editor of TomsWorkBench.com and columnist for Wood Magazine. Editing and photos by Marc Spagnuolo.

I’m just getting started in woodworking. I don’t have many tools, and the ones I do have are Ryobi (fairly cheap) but I like them. Anyway, I saw a video on youtube of this very nice oak chest, but the craftsman used mostly biscuits to join almost everything, I wouldn’t think that biscuits would be strong enough to last a lifetime. Am I wrong? If I wanted to join two boards together, would a tongue and groove be more solid in the long run? What do you think?

And my response:

Hi David. I would agree with your gut on this one. Biscuits don’t really have much to offer in the way of strength. Here’s why:

- Biscuits slots can be a little tight or a little loose, depending on your machine and how steady your hand is.
- The biscuit doesn’t penetrate very far into the joining workpieces: a #20 biscuit will penetrate less than 1/2″.
- The grain of the biscuits runs on a 45 degree angle. Ideally, the grain would run perpendicular to the joint.

Despite their shortcomings, biscuits are still very handy for alignment, especially when doing big tabletop glueups. And I honestly don’t think they are a bad option for light-duty pieces either. But in most cases where biscuits are being used, its the glue that’s doing all the holding. Lets look at the two most common areas where you could use a biscuit, with respect to the grain direction of the adjoining pieces.

First, there’s long-grain to long-grain (a tabletop glueup is a good example of this). Some folks (including me) may use biscuits for alignment or “reinforcement”, but the truth is they do very little to strengthen the joint. In this long-grain situation, its really the glue that’s doing all the work. As you have heard me and others say many times, the glue joint is stronger than the wood itself. So adding a series of shallow biscuits isn’t really going to make the joint much stronger. But if they help you align the boards, I see no harm in using them.

Now the second situation is end-grain to long-grain. Think of a rail meeting a stile or an apron joining a table leg. Whenever end-grain is involved, the joint will be inherently weak using glue alone. So we absolutely need some form of reinforcement. Traditionally, this is the territory of the King of Woodworking Joints: the mortise and tenon. The real magic of the mortise and tenon joint is that it takes this end grain to long-grain union and converts it to long-grain to long-grain, simply by inserting one piece into the other. As a result, the joint has a great deal of glue surface and strength. Make no mistake about it: the biscuit joint is no substitute for the mortise and tenon, or its little brother, Prince Tongue and Groove! All three of the biscuits weaknesses listed above are the reasons for this.

So in case you couldn’t already tell, I would never use biscuits as a primary form of joinery, especially when there are end-grain to long-grain joints involved. But I do suppose for light-duty pieces, they would be acceptable. If the maker of that oak chest used biscuits in a bunch of long-grain joints, it would probably be a reasonably sturdy piece. But if the biscuits were used for end-grain joinery, I wouldn’t recommend moving that chest around too much. If I were you, I would definitely opt for tongue and groove or mortise and tenon joints. Good luck!

Oddly enough, as I wrote this, I noticed Tom Iovino from Tom’s Workbench put up a similary-themed blog post in the community. Check it out!

Hey Marc, I love your show. I watch it religiously and have learned so many good techniques. I wanted to know, what is your position on pocket hole joinery in relation to coffee table assembly. I built my first coffee table using a Kreg pocket hole jig to join the apron and legs together. Kreg states in their owner’s manual that a pocket hole is mechanically stronger than a mortise and tenon joint. Do you think pocket hole joinery is cheap sign of craftsmanship? I would like your feedback on what you think of my coffee table design? I have attached a picture of my coffee table.

And here was my reply:
Hi Chris. First off, let me compliment you on your design and craftsmanship. What a beautiful piece. No matter what the underlying joinery is, that is a fantastic design with great execution. Now, concerning pocket hole screws. Remember, joinery can be just as much about taste and opinion as it is about strength and utility. If you are happy with the final product and you enjoy using pocket screws, all the power to you! Screw away my friend!

Now for my opinion. I have used pocket screws in the past when I could get away with it. The only time I really use them is if they will never be seen. And even then, they are usually the last option I think of. Perhaps its a bit elitist, but I do feel that pocket screws “cheapen” a piece. I would certainly expect Kreg to defend its product and their strength claim may be valid (Im not convinced). But is strength really the only concern to us as woodworkers? If that’s the case, we might want to start using metal to build furniture instead of wood. :) Cant get much stronger than that!

Seriously though, I take pride in the fact that my best work contains little to no metal. But that’s just me. We all have to decide for ourselves where to draw the line. Some folks cant imagine using power tools on their projects. They take pride in the fact that their work is crafted the old-fashioned way. Some folks just want to get ‘er done!

Just remember that we all woodwork for different reasons Heck, some of us do it just so we can collect tools. And still others do it simply because its such a sharp contrast to what we do at the office all day behind our computer screens in the confines of our cubicles. Whatever your reason is, keep it fun. If pocket screws make it fun for you, then keep using them. Your work certainly is not suffering for it. Good luck.

Want to learn a little more about pocket screw joinery? Check out the Pocket Screw Primer!

“Do you have any opinions on the use of glue-joint bits for the use of making thick table tops? I am talking about gluing boards at least 1-1/8 inch thick for a project I am working on. I hate biscuits and want the extra strength that glue-joints offer. Other than self-aligning properties. Is it really needed?”

The short answer, in my opinion, is no. The long grain glue bond in a panel glue-up (such as a table top) is said to be stronger than the wood itself, and no further reinforcement is needed. If the joint is going to fail, it will usually fail in the wood fibers adjacent to the joint. You can actually test this yourself with scraps. Just edge joint two pieces of stock and glue them together. After an overnight dry time, try to break the joint apart. In most cases, you’ll find the glue joint remains intact while the wood splits along its weakest point in the grain. So in most cases, a simple panel butt joint requires no reinforcement at all.

You mentioned biscuits and while I don’t hate them, I do agree with your lack of trust in their strength properties. In my shop, biscuits are used for alignment purposes only.

As for the glue-line bit, I don’t even own one. Given what we know about the simple long grain butt joint, I just never thought something like a glue-line bit was necessary in my shop. So for full disclosure, I can only speculate on its usefulness. Clearly the bit would be quite handy for alignment purposes. And we know it creates extra glue surfaces by cutting interlocking mating profiles on both work pieces. More surface area is generally considered a good thing for a wood joint as the long-grain to long-grain contact is at the heart of the joint’s strength. So on the surface, our instincts tell us this would be stronger than a simple butt joint, even if that extra strength is overkill. But here’s the rub: some people believe the mating profiles actually decrease the strength of the joint. I wish I could remember the exact magazine article I read on this topic, but here’s the gist. Since the glue joint is stronger than the wood itself, if breakage occurs it will usually take place just adjacent to the rigid glue line. The profile that is cut into the wood essentially things the wood out in those areas thereby creating several weak spots. Those weak spots are now even weaker than the adjacent wood grain.

Again, I am only speculating here and more testing would need to be done to prove or disprove this theory. But to be safe, I recommend going with a good old butt joint. If you want some alignment help, go ahead and use biscuites, Dominos, dowels, or a spline. Or simply use a set of cauls positioned over the joint itself.

Want some more information on Glue Line Router Bits? Check out this NewWoodworker.com article!