Joining 2x4 to 3/4" Plywood

[Talley Sue Hohlfeld]

I want to attach 2x4s to the underside of a piece of plywood to make a platform with legs.

I figured I'd drill pocket holes in the 2x4s.

What jig setting should I use, and what length of screw?

I know a 2-1/2" screw is used for joining 2x4s, but my "target" wood is only 3/4" thick. 

And, would it be sensible to put one screw in from one side of the 2x4, and the other from the other side, so they make an X? I don't need to worry about how it looks.

[Don Foley]

I would use the drill setting and screw length for the 3/4" plywood.  As for drilling the 2 by 4's from both sides, I did that when I made a frame for my router table.  The legs are 4 by 4's and the stretchers 2 by 4's.  I also used pocket screws to attach the Rockler router table top to the completed frame, using the settings and screws for 3/4" wood. 

Hope this helps, Don

[Talley Sue Hohlfeld]

Thanks, Don--that is useful.

And if I want to test my legs out on a scrap of plywood, I can do that, can't I? And just back the screws out, then reattach them to the real platform? 

Did you have any trouble w/ the tip of the screw breaking through? I've had that happen to me with the 3/4" settings every now and then. 

Don Foley said:

I would use the drill setting and screw length for the 3/4" plywood.  As for drilling the 2 by 4's from both sides, I did that when I made a frame for my router table.  The legs are 4 by 4's and the stretchers 2 by 4's.  I also used pocket screws to attach the Rockler router table top to the completed frame, using the settings and screws for 3/4" wood. 

Hope this helps, Don

[KregRep]

Hi Talley,

When joining a 2x4 to 3/4"-thick material, you will need to use the 1/2" marking as your Kreg Jig Setting and 1-1/4" pocket-hole screws. I have attached a Kreg Screw/Jig Setting Chart for your reference in the future.

Your screw tip may be breaking through the surface of your material if you are not using the correct screw length and/or Kreg Jig setting, so be sure those are correct before trying again. It could also be due to your drill setting. We recommend starting lighter; somewhere around 4-6. Our friend Chris at Chief's Shop recommends starting somewhere in the middle. For softwoods, go a bit lower, and for hardwoods, a bit higher. He offers more tips on drill/driver settings here: http://www.youtube.com/watch?v=Oj-zXtt6ZJU.

If you decide to test out your table legs on a piece of scrap plywood, be sure to back your screws out slowly and carefully to avoid damage to the table legs and/or stripping out your screws.

Best of luck!
KregRep

[Talley Sue Hohlfeld]

Thanks! I may have that chart, down in the basement w/ the jig itself, but thanks for the link; I'll print it out. Someone else had suggested I drill the hole using the setting for 1-1/2" stock on the jig--but I'll trust you 

I thought there was some trick to setting the jig to avoid the breakthrough. My drill doesn't have a setting, actually; it's variable speed, so it's all in the trigger. I don't usually pull that hard, but that might be part of it. I thought it was much more the angle than anything else. 

KregRep said:

Hi Talley,

When working with 3/4"-thick material, you will need to use 1-1/4" pocket-hole screws. For your Kreg Jig setting, use the 3/4" marking. I have attached a Kreg Screw/Jig Setting Chart for your reference in the future.

Your screw tip may be breaking through the surface of your material if you are not using the correct screw length and/or Kreg Jig setting, so be sure those are correct before trying again. It could also be due to your drill setting. We recommend starting lighter; somewhere around 4-6. Our friend Chris at Chief's Shop recommends starting somewhere in the middle. For softwoods, go a bit lower, and for hardwoods, a bit higher. He offers more tips on drill/driver settings here: http://www.youtube.com/watch?v=Oj-zXtt6ZJU.

If you decide to test out your table legs on a piece of scrap plywood, be sure to back your screws out slowly and carefully to avoid damage to the table legs and/or stripping out your screws.

Best of luck!
KregRep

[KregRep]

My mistake, Talley. I misread your question. You should always set your jig's setting based on the thickness of material you are drilling into. So, in this case, you would set your jig for 1-1/2" stock. You choose screw length based on the thickness of the material you will be driving the screw into, which is 3/4" in this case. So use 1-1/4" screws for best results.

You also need to make sure that your depth collar is properly adjusted, to ensure proper pocket-hole depth. Place your bit inside the depth setting gauge on your Kreg Jig, with the step of the bit at the 1-1/2" marking. Slide the depth collar towards the jig base and lock it in place with the Allen wrench.

If you have any further questions, feel free to contact our Customer Experience Team directly. You may reach them by phone at 800-447-8638. They will be more than happy to assist you.

[Don Foley]

Talley,

I did not have problems with screws protruding through the top on my router table build. 

I am currently building a coffee table with a 3/4 oak plywood top edged with 3/4" by 1-1/4"oak.  While practicing on some scrap pieces, using pocket holes to attach the edging, the screw heads created bumps in the plywood. (In this case I was drilling into the plywood, with the screw going into the oak hardwood.) By time I sanded the plywood smooth I had sanded through the thin oak veneer and into the MDF core layer below.  Consequently I used the biscuit joiner to attach the edging. 

During my practice session I also used pocket screws to attach 3/4 oak into the plywood through the bottom, simulating using pocket screws to attach the table top to the stretchers on the frame.  (In this case I was drilling into the hardwood with the screw going into the plywood) The tips of the screws did not break through the plywood.  

Hey Kreg Rep, since I'm worried about breaking through the plywood, could I use the 3/4" setting but instead of a 1-1/4" screw use a 1" screw?  Would the 1" screw penetrate enough to provide any holding power?  My other option is to use Rockler table top fasteners.

Don

Talley Sue Hohlfeld said:

Thanks, Don--that is useful.

And if I want to test my legs out on a scrap of plywood, I can do that, can't I? And just back the screws out, then reattach them to the real platform? 

Did you have any trouble w/ the tip of the screw breaking through? I've had that happen to me with the 3/4" settings every now and then. 

Don Foley said:

I would use the drill setting and screw length for the 3/4" plywood.  As for drilling the 2 by 4's from both sides, I did that when I made a frame for my router table.  The legs are 4 by 4's and the stretchers 2 by 4's.  I also used pocket screws to attach the Rockler router table top to the completed frame, using the settings and screws for 3/4" wood. 

Hope this helps, Don

[KregRep]

Don,

Rather than going out and buying 1" screws (unless you already have some), first try adjusting the stop collar on your drill bit so that the bit doesn't drill as deep. This would mean backing it off to somewhere between the 1/2" setting and 3/4" setting. Once you've done that, try a test joint in some scrap stock.

Also make sure that you aren't driving your screws too hard, which could cause them to compress the wood in the pocketed piece and "pull" further into the mating piece. If your drill has a clutch, set it at about 1/4 to 1/3 of its maximum setting for driving screws.

If both of these methods fail, then yes, a shorter screw could theoretically work. With the 1" screw, you should still get sufficient holding power.

Don Foley said:

Talley,

I did not have problems with screws protruding through the top on my router table build. 

I am currently building a coffee table with a 3/4 oak plywood top edged with 3/4" by 1-1/4"oak.  While practicing on some scrap pieces, using pocket holes to attach the edging, the screw heads created bumps in the plywood. (In this case I was drilling into the plywood, with the screw going into the oak hardwood.) By time I sanded the plywood smooth I had sanded through the thin oak veneer and into the MDF core layer below.  Consequently I used the biscuit joiner to attach the edging. 

During my practice session I also used pocket screws to attach 3/4 oak into the plywood through the bottom, simulating using pocket screws to attach the table top to the stretchers on the frame.  (In this case I was drilling into the hardwood with the screw going into the plywood) The tips of the screws did not break through the plywood.  

Hey Kreg Rep, since I'm worried about breaking through the plywood, could I use the 3/4" setting but instead of a 1-1/4" screw use a 1" screw?  Would the 1" screw penetrate enough to provide any holding power?  My other option is to use Rockler table top fasteners.

Don

Talley Sue Hohlfeld said:

Thanks, Don--that is useful.

And if I want to test my legs out on a scrap of plywood, I can do that, can't I? And just back the screws out, then reattach them to the real platform? 

Did you have any trouble w/ the tip of the screw breaking through? I've had that happen to me with the 3/4" settings every now and then. 

Don Foley said:

I would use the drill setting and screw length for the 3/4" plywood.  As for drilling the 2 by 4's from both sides, I did that when I made a frame for my router table.  The legs are 4 by 4's and the stretchers 2 by 4's.  I also used pocket screws to attach the Rockler router table top to the completed frame, using the settings and screws for 3/4" wood. 

Hope this helps, Don

[Don Foley]

Thanks Kreg Rep.  I never thought about adjusting the stop collar back.  I already have 1" screws and the alternative table top fasteners.  Since the 1" screw should provide adequate holding power I think I'll use it.  The pieces are also getting glued so the screw isn't providing all the holding power.

[Talley Sue Hohlfeld]

I've left my stop collar in the factory position, thinking it would be finely calibrated for the default 3/4". But I may ease it back a little. That had occurred to me, but I was worried I wouldn't be able to get it in the right place again (sort of like when you mess with the bobbin tension on a sewing machine--you may find it hard to get it to the right setting). But then, if it's so tricky, why would you guys even make it adjustable, right?

Thanks!

KregRep said:

My mistake, Talley. I misread your question. You should always set your jig's setting based on the thickness of material you are drilling into. So, in this case, you would set your jig for 1-1/2" stock. You choose screw length based on the thickness of the material you will be driving the screw into, which is 3/4" in this case. So use 1-1/4" screws for best results.

You also need to make sure that your depth collar is properly adjusted, to ensure proper pocket-hole depth. Place your bit inside the depth setting gauge on your Kreg Jig, with the step of the bit at the 1-1/2" marking. Slide the depth collar towards the jig base and lock it in place with the Allen wrench.

If you have any further questions, feel free to contact our Customer Experience Team directly. You may reach them by phone at 800-447-8638. They will be more than happy to assist you.

[Ralph Hulslander]

KregRep said:

So, in this case, you would set your jig for 1-1/2" stock. You choose screw length based on the thickness of the material you will be driving the screw into, which is 3/4" in this case. So use 1-1/4" screws for best results.

If you have any further questions, feel free to contact our Customer Experience Team directly. You may reach them by phone at 800-447-8638800-447-8638. They will be more than happy to assist you.

So how did you come up with 1-1/4" for 3/4" material?

[Talley Sue Hohlfeld]

Ralph Hulslander said:

KregRep said:

So, in this case, you would set your jig for 1-1/2" stock. You choose screw length based on the thickness of the material you will be driving the screw into, which is 3/4" in this case. So use 1-1/4" screws for best results.

If you have any further questions, feel free to contact our Customer Experience Team directly. You may reach them by phone at 800-447-8638800-447-8638. They will be more than happy to assist you.

So how did you come up with 1-1/4" for 3/4" material?

The screw's actual length isn't the same as the material's actual thickness. You need a screw long enough for some of it to stay inside the pocket hole itself, and then only enough sticks out to go into the 3/4" plywood. 

So to drive a screw into 3/4" thick plywood, you need 1/2" of screw to be in the wood, and 3/4" of screw to be inside the leg, encased inside the pocket hole itself. 

(that said--every time I've used 1-1/4" screws w/ 3/4" plywood, it breaks out the other side. I've started using someone else's settings, because Kreg's default setting don't work.)