Screw size for DIFFERENT sized lumber

[Steve Gronsky]

I seem to recall from a previous post somewhere that when choosing your screw size you should select the screw for the "receiving" piece of lumber rather than for the drilled piece.

e.g.  when joining a 2x4 to a 3/4 thick piece you should use the 1 1/4 inch screw.

as opposed to joining 2 2x4 to each other - you would use a 2 1/2 inch screw.

Have I got this correct? 

[Alien]

i was just about to ask the very same question. i'd like to hear the the answer to this question myself.

[Henry Parslow]

when joining a 2x4 to 3/4 stock you would have to use the 3/4 settings and 1-1/4 screws this will not be as strong . Put as many pockets in your 2x4 as you can within reason. A possible other way would be to use the 1-1/2 setting and a 2" not a 2-1/2 screw .

[Jenny]

If I am joining a 2x4 and a 1x3 (3/4 stock), does it make a difference if I am starting the screw in the 2x4 as opposed to the 1x3?

I use the jig and drill bit settings for the piece where I am starting the screw.
But for the screw length, do I select that according to the receiving piece thickness?

[Dan F.]

When you are working with two different thicknesses you will want to set everything up and use the screw length for the thinner thickness of the two. For example if you are drilling your holes in a 2X4 and attaching it to a 3/4" piece you will want to set the jig and the depth collar for the 3/4" setting and use a 1 1/4" screws. If you are going the opposite way and drilling your holes into the 3/4" piece and joining it to the 2X4 you would set everything up the same, but you can use a little bit longer screw to give you some more strength.

Now when you are choosing which thread you will need to use, it will be determined by the piece you are joining to. For example: if you drilled your holes into a piece of plywood but you are attaching an oak piece you will want to use a fine threaded screw since the majority of the threads will be in the oak piece.

Hopefully this made some sort of sense lol.

[KregRep]

Dan F. said:

When you are working with two different thicknesses you will want to set everything up and use the screw length for the thinner thickness of the two. For example if you are drilling your holes in a 2X4 and attaching it to a 3/4" piece you will want to set the jig and the depth collar for the 3/4" setting and use a 1 1/4" screws. If you are going the opposite way and drilling your holes into the 3/4" piece and joining it to the 2X4 you would set everything up the same, but you can use a little bit longer screw to give you some more strength.

Now when you are choosing which thread you will need to use, it will be determined by the piece you are joining to. For example: if you drilled your holes into a piece of plywood but you are attaching an oak piece you will want to use a fine threaded screw since the majority of the threads will be in the oak piece.

Hopefully this made some sort of sense lol.

+1 - Dan is correct. About the only thing I would add is that it's impossible to have an 'official' setting for each unique circumstance... so it's always best to test it a couple of times first on some sample stock. Practice makes perfect!

[Steve Gronsky]

Thanks everyone. This answers the question. And thanks too for the "fine" vs. "coarse" comment. That makes perfect sense.

As our KregRep said ...... try a couple PRACTICE joints.

[DAVID CZUPRYN]

Not sure if this will help you.If the 1x3 is a table apron,the 2x4 the leg I would drill into the 1x3[with the gain]using the 3/4 setting and the 1&1/4 screw.Point being drill hole with grain,screw into cross grain. Dave

Jenny said:

If I am joining a 2x4 and a 1x3 (3/4 stock), does it make a difference if I am starting the screw in the 2x4 as opposed to the 1x3?

I use the jig and drill bit settings for the piece where I am starting the screw.
But for the screw length, do I select that according to the receiving piece thickness?

[Dan]

I don't quite remember who originally postedd this, but it may help when deciding which screw size to use. I believe the sizes outside the grid are the "whole" pieces and the sizes inside the grid are the "screw into" pieces.

[Kim C]

This is a wonderful chart! And one I will certainly hang in the workshop. I want to make clear... which is the receiving lumber? The horizontal numbers? The vertical numbers have the pocket holes?

Dan said:

I don't quite remember who originally postedd this, but it may help when deciding which screw size to use. I believe the sizes outside the grid are the "whole" pieces and the sizes inside the grid are the "screw into" pieces.

[Dan]

The vertical numbers on the left side of the chart represent the lumber that will have the pocket whole, the hortizontal numbers along the top of the chart represent the recieving lumber.

I'm glad that someone posted this because I was always confused on what length screws to use when the lumber dimensions weren't the same. All the other Kregg charts talk about using the same dimensions - joining a 1 x 2 to a 1 x 2. I printed this chart out and have it with my Kreg Jig for quick reference.


Kim C said:

This is a wonderful chart! And one I will certainly hang in the workshop. I want to make clear... which is the receiving lumber? The horizontal numbers? The vertical numbers have the pocket holes?

Dan said:

I don't quite remember who originally postedd this, but it may help when deciding which screw size to use. I believe the sizes outside the grid are the "whole" pieces and the sizes inside the grid are the "screw into" pieces.

[Don Grubish]

A simple way I remember this is: "lowest common denominator." I guess my math teachers had more of an impact on me than I thought. Whatever the thinner wood size is, set your Kreg Jig for that. The DVD doesn't really touch on this, and that screwed me up in the beginning. I had to learn that on my own. I think that's why I have drilled right through the base of my jig a couple of times. Live and learn...

[Ron davey]

I was just about to ask all the same questions as posted here. Thanks to all for the heads up when joing two different thicknesses of lumber. Is there a definate formula for figuring it out? If I understand this correctly, the jig should always be set-up to the piece that the pockets are being made, and the only other consideration is the length of screw to be used, depending on the thickness of the receiving piece?