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Pocket Hole Joinery Question

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Forum topic by PPD417 posted 03-17-2018 02:26 AM 461 views 0 times favorited 6 replies Add to Favorites Watch
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PPD417

3 posts in 71 days


03-17-2018 02:26 AM

Greetings….I’ve been perusing this site for a couple months and felt I probably should register and attempt to make a contribution.

But first, I have joinery a question that hopefully I can get some help with.
I’ve been working with wood for a number of years and I’ve done mortise and tenon, dovetail, dowel joinery and biscuits, but have never used pocket hole joinery. I have a project that I will be starting soon that pocket hole joinery would be the ideal fastening method, so I was looking at the Kreg K5.

My project is I will be removing my current MDF bench top and replacing it with a new, laminated maple top (2.25”) and raising it about 3.5” to accommodate a new bench vise. To do this I am planning to build a support structure under the new top with 2×4’s on edge, attaching the 2×4’s to the top with pocket hole screws. As you know, the actual dimensions of a 2×4 are really only 1.5×3.5. From what I’ve seen on You Tube, the pocket hole is drilled somewhat in the the top 2/3rds of the piece.

So, my question is since I’ll be drilling the pocket hole on the 3.5” side, how deep should I go and what length screws should I use? Also, I saw the Kreg HD for large material like 2×4’s. Should I use this instead of the K5?


6 replies so far

View bbasiaga's profile

bbasiaga

1233 posts in 1995 days


#1 posted 03-17-2018 02:56 AM

You can use the k5 just fine on 2×4s. I don’t have the chart handy, but you can probably find it online, that shows what length screw to use based on the thicknesses of the materials you are joining.

Another trick you .ca. do is set the jig as though your 2×4 were only . 75 thick, and put a set on each side. Not sure it’s recommended, but it has been done.

Brian

-- Part of engineering is to know when to put your calculator down and pick up your tools.

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PPD417

3 posts in 71 days


#2 posted 03-17-2018 05:20 AM

Brian….thanks for the info. I was hoping that all I needed was the K5.
Since I don’t have the K5 yet, what does setting the thickness to .75” do?

View Woodknack's profile

Woodknack

11631 posts in 2380 days


#3 posted 03-17-2018 05:22 AM

To be honest, when I used a Kreg I never worried much about it and just eyeballed where to set the jig for depth. Now I have a Porter Cable Quikjig and it does the figuring for me, all I have to do is turn a knob and it sets itself to the right depth. You didn’t mention it so I will, if crossgrain remember to wallow out the screw holes to allow for wood movement.

-- Rick M, http://thewoodknack.blogspot.com/

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bbasiaga

1233 posts in 1995 days


#4 posted 03-17-2018 01:49 PM



Brian….thanks for the info. I was hoping that all I needed was the K5.
Since I don t have the K5 yet, what does setting the thickness to .75” do?

- PPD417

When you get the jig, it will have instructions on how to set the stop collar on the drill bit, and the height of the drilling guide based on how thick the material is. Just pretend your 2×4 is a .75” thick when you do this. Test it out first. The same procedure is used to set it to 1.5” if you want to do it the normal way.

Brian

-- Part of engineering is to know when to put your calculator down and pick up your tools.

View KenKorch's profile

KenKorch

10 posts in 168 days


#5 posted 03-17-2018 02:30 PM

The height of the Kreg Jig (with the drill guides) – the distance from the Jig base – is what controls where the screw will penetrate the “gap” between the two pieces of material being fastened. You want that to be midway between the material edges. When setting that height using a Kreg Jig, use the actual width of the material which is being drilled into – the pocket hole material. My K4 Jig actually has lines on the bottom near the Jig’s fence that show the expected point of screw penetration (the bit shouldn’t actually penetrate the material). The lines are marked per the material’s thickness – and should match the Jig height setting value.

The position of the Kreg Drill Bit Stop Collar on the drill bit is set to place the tip close to the “gap” between the materials being joined without actually breaking through the pocket hole material. Many Kreg Jig users advise setting the Stop Collar by placing a U.S. nickel on the bottom of the base, sliding the Kreg Drill Bit into the Kreg Jig with the Stop Collar loose – inserting it until the bit tip gently touches the top of the nickel. Then tighten the Stop Collar to the Kreg Drill Bit. This nearly guarantees that you won’t accidentally drill through the Kreg Jig base.

I chuckled a bit when the Kreg Jig HD was released because its instructions specifically mention the use of a nickel’s thickness to place the drill bit collar. BTW, the reason you don’t want the drill bit to penetrate the pocket hole material is that material chips poking out from the hole could cause an actual gap between the materials being joined.

The length of the screw determines how deep the screw will penetrate into the material being fastened (fastened material) to the pocket hole material. Depending upon the thickness of the fastened material, if the screw is too long it could run all the way through the bottom of the fastened material or it could run out the side of the fastened material. The Kreg Jig tables give recommended screw lengths based upon the fastened material thickness, whether it is an edge joint (pocket material 90 degrees to the fastened material) or a face joint (pocket material edge meets the fastened material edge – this sounds like what you are doing), and the thickness of the fastened material.

The best way to be safe is to use scrap material to make a test pocket hole and actually fasten the scrap materials together to ensure it all works correctly – without over-penetration of the screw.

Using the standard Kreg Jig, doing an edge joint with 1-1/2 inch thick material, you would set the Jig height to 1-1/2 inches, set the Bit Collar using the Jig at 1-1/2 inch or using the nickel method, and use 2-1/2 inch screws. The height of the pocket hole material really doesn’t matter since the Kreg Jig references from the bottom of the material – touching the base of the Kreg Jig. Plywood cabinet panels can by more than 2 feet tall, but the pocket holes simply run along their edges.

The Kreg Jig HD uses thicker 14 gauge 2-1/2” screws that are epoxy coated, and thus drills a wider pocket hole. I would think that the standard Kreg Jig should be sufficient, and even better if you are adding glue to the joints.

To be safe, check to make sure that the drill won’t go through the Jig base, and test the setup on scrap material – including driving a screw – before making pocket holes on their project.

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PPD417

3 posts in 71 days


#6 posted 03-17-2018 09:00 PM

Brian, Ken…Thanks for all the detailed info, much appreciated. I now have a better feel for using pocket hole joints.

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