When to NOT use pocket screws... and when you SHOULD! | Evening Woodworker

Tonight we're talking about when to use pocket hole joinery and when not to

if you want to know when to use pocket holes and when not to you first need to understand something

about wood expansion and contraction. A piece of wood is basically a bunch of straws that are used

to bring the water from the roots of the tree up into the branches. A good way to show this is if

you take a piece of wood that has very large pores like oak and you put soap on one end and then you

blow air through the other end you'll actually see bubbles form because you're blowing through

a bunch of straws. These straws will expand and contract based on the relative humidity in the

room or the area where you are and the dryness of the wood. So when it comes to the expansion and

contraction of the wood you have to assume that the straws are going to get larger and smaller

based on whatever is happening, whatever season it is, and wherever you live. So in my shop I

have a little ten dollar temperature and humidity sensor and what this does is shows me kind of the

range of where my shop fluctuates in terms of the humidity and I've seen it go from about 65%

down to probably 25%. In the area where I live I'm on the coast and so the temperature and humidity

swings are not too extreme. I've still noticed that the wood will expand and contract in that

humidity range from 65 to 25 percent. So if you want a quick rule of thumb, just assume that a 12

inch wide board will expand or contract about an eighth of an inch in either direction depending on

the season and the humidity. If you factor that into your designs you won't run into problems

later when the wood expands and contracts. Now the hardwoods typically will expand and contract

a little bit more than soft woods will but if you stick to that rule of thumb you should be fine.

So the expansion you'll see in a board will go across the grain this way. It's going to get wider

and narrower; it's not going to get longer because the straws are cut at a certain length so that's

typically not something you have to worry about. The thickness may be affected slightly if it's a

very thick piece but typically that's thin enough that it's negligible, so it's your width that

you've got to be concerned about. Now what about a piece of plywood when you have something that

could potentially be two, three, four feet wide? Fortunately the way they build plywood is they run

the grain perpendicular on each ply so the first ply will be like this, the next ply will be like

this, and it'll just go back and forth until it gets to the final position. What this does

is it makes it really stable so the expansion in plywood is pretty much negligible as well because

those cross grains are counteracting any expansion and contraction that happens. So now the question

comes what are the things I can use pocket screws on and what are the things that I can't? If I'm

putting pocket hole screws into a board like this, I put a screw here and I put a screw here,

I should be fine because this board is not going to change in length, but if I put a screw here

and I put a screw here, I'm across the grain and that will expand and contract over time

and that may cause buckling, that may cause things to split or crack or separate.

So this is bad. This is good.

As I mentioned before anything with plywood is going to be very stable and so you can use

pocket screws pretty much anywhere in plywood which is why they're commonly used in cabinet

carcasses. I use them a lot when I'm building my shop cabinets or any cabinets of that sort

they're also great for attaching face frames onto your cabinet box.

Let's say I'm going to attach these two boards at a 90 degree angle like this. This is a great

application for a pocket hole joint because I'm going to put two screws in like this

and I'm putting them right into the side of this board. Now as we said wood is not going to expand

in length, it's going to expand in width; so those two screws are not going to separate or

pull apart or anything. Another good application of pocket screws is if you're making a tabletop

or like a dresser top or something like that. If the bottom of your tabletop is going to be hidden

and let's say you don't have clamps that are as wide as you need or you don't have enough of them,

you put your boards together like this you drill your pocket holes coming across like that

and you can make this as wide as you want as long as your edges are square

and you have enough glue in it, those pocket screws will actually act as clamps while the

glue dries. Once the glue dries the screws really don't do very much but it helps you in that

clamping phase to get everything nice and flat. Before I had the clamps and the setup that I do

today I made a dresser with a tabletop that was about 24 inches wide this was made up of

four inch wide boards that I pocket screwed along the bottom to make my entire tabletop.

I've had this dresser for nine years and I haven't had any problem with that separating.

Now we're going to talk about when not to use pocket screws. As you probably know when you

drill a pocket hole it makes an oval shaped hole in your board. This is typically something that

you don't want to see on a piece of furniture. You have two options you either put in a wood plug,

cut it flush, and then sand it, or you can just design your piece of furniture so that the pocket

holes are on the back side and you don't ever see it. If you have something that's going to be seen

on both sides it's probably not a good application for a pocket screw. There are also a lot of times

when you want to do traditional joinery when pocket holes are totally out of the question.

I made a big farm table that was all traditional mortise and tenon joinery with no fasteners.

There's a time and a place for every kind of joint and you get to choose when you use pocket screws

and when you don't. Another place that you should definitely not use pocket screws is attaching a

skirt to a table top. So we're going to say here that this is my table top and this is my skirt I

would not want to use pocket holes here because this table top is going to expand to the right

and to the left. I don't want the board to split or warp as it expands and contracts over time.

There are a lot of options in terms of fasteners or blocks that you can use to attach your

tabletop on while still allowing for expansion and contraction. Just do a google search on tabletop

fasteners: there's figure eight fasteners, there's z brackets, or there's just the sliding block in

a mortise and tenon that you can make yourself. So whatever you do don't attach the table top to

your piece of furniture using pocket hole screws! You can also control the wood expansion if you

only want it to expand in one direction for example, I just built a cabinet with a secret

compartment inside but the top has a two inch thick slab of black walnut that I did not want to

expand into the wall. I wanted it to only expand out towards the front of the cabinet. So what I

did was I put screws directly into the bottom of that along the back edge. That locks that

position in place and I can put three screws in a row because I'm going with the grain. But then

on the front edge out here that had the live edge I wanted to be able to move and expand that way,

so the front connections were two brackets that I had that had slots in them. That is a great

way to account for wood expansion too. Another time you would not want to

use pocket hole screws is if you're attaching something into a wide board

If I was going to attach something horizontally into this, I would definitely not use pocket hole

screws because again it does not account for that expansion contraction across the width of

the board. Let's say this was the side of a shelf and I wanted to have my shelf in here like this.

If I attach this with pocket hole screws over time that expansion and contraction is going

to cause it to break or fail in some way, but another option would be for me to cut a dado

or even a stopped dado across the length of my board and put my shelf inside. That that way as

it expands and contracts I'm not concerned about the shelf buckling or tearing through something.

These two boards are about four and a half inches wide. If I was to put these together using pocket

screws, I would be concerned because this is almost six inches and over six inches I have

about a sixteenth inch of movement on it so this would not be a good place to use pocket screws

however if the boards were not quite that wide you wouldn't run into that problem. These two boards

are about an inch and a half wide. I could put these together do two pocket holes on the back

and not be concerned at all about wood expansion and contraction because it's so minimal. Using

pocket hole joinery in your furniture designs and your builds can be very efficient. It's fast,

it's a good strong joint, and it'll last. I have not seen one of these joints come apart if it was

done properly. My favorite pocket hole jig is the Kreg jig. it's a very common one out there;

you can find them at big box stores, you can find them at woodworking stores,

or you can find them online. I would recommend using pocket hole screws that are specifically

designed for pocket holes because they have three major features on them that make them ideal for

doing pocket holes. The first thing they have is a washer head which is basically a large flat head

that can go down and hit the bottom of your pocket hole where you've drilled and hold there.

If you have a countersunk head it'll keep going in and it can start splitting your wood.

Another thing that's crucial on this is the shaft at the top part does not have threads on it. If

you have threads the entire length of this screw it makes it so that as you put two boards together

you can actually get a gap between them and the screw will not pull it together. With this design

even if you get a gap or if it separates as you're putting the screw in once it hits that bottom it

will pull the other piece in and you'll get a nice tight joint. The third thing is this little

cut at the tip this makes it so that as you're putting the screw in it grabs the wood better

and it doesn't split quite as easily. Now you know when to use

pocket screws and when not to. Let me know in the comments if you agree with

this video or if you disagree or maybe I missed something or if you have a good application of

pocket screws that i haven't explained in this. Don't forget to subscribe if you like this;

I have a lot of other videos with projects, explanations, shop tours, and everything.

This is one of my passions. I love woodworking and I love

making videos about it. Now go build something and we'll see you next time!