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Securing workbench shelf/top with pocket holes

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Forum topic by JoeWhite posted 04-11-2013 08:48 PM 3704 views 1 time favorited 10 replies Add to Favorites Watch
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JoeWhite

24 posts in 1401 days


04-11-2013 08:48 PM

I’m working on a rolling workbench for my shop. I’d like to attach a lower shelf to the 2X4 rails using pocket holes, but I’m having trouble figuring out what to set my jig up for. The 2X4’s are vertical, and they will be holding 1/2” MDF for the shelf. I tried setting the jig for the 2X4 settings, but then the 2 1/4” screws are too long, and the others are not long enough. Should I be setting the jig up for 1/2” and then using the 1” screws? Also, am I supposed to use fine, or coarse screws for MDF? I will also be using MDF as the workbench top, built up to 2 1/4” thick, so length of screw won’t be as big of an issue as screw type.


10 replies so far

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Brandon

4151 posts in 2419 days


#1 posted 04-11-2013 08:52 PM

There’s two different settings that you use when doing the pocket hole set up. One, the collar on the actual drill bit is set for how deep you want it to go, so I’d set that for 3/4 since that’s the presumed width of the mdf. The other is the depth for the thickness of the material that the pocket hole is going into, that’s on the jig itself. Set that for 1 1/2” because of the width of the 2×4. At least that’s how it works on my set up. I hope that made sense.

-- "hold fast to that which is good"

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Brandon

4151 posts in 2419 days


#2 posted 04-11-2013 08:53 PM

Also, use coarse thread for MDF. Here’s a nice chart from Kreg: http://www.kregtool.com/prodimages/ScrewChart.pdf

-- "hold fast to that which is good"

View bbasiaga's profile

bbasiaga

759 posts in 1463 days


#3 posted 04-11-2013 09:07 PM

I’m not sure if this is the correct procedure or not, but I have always used my Kreg jig by setting the jig and the drill stop to the depth of the board I’m drilling in to (typically the thinner board). And if I am then screwing to a thicker board I can go up one length of screw (at least) and generally be safe.

-Brian

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

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JoeWhite

24 posts in 1401 days


#4 posted 04-11-2013 09:20 PM

Most of the stuff I’ve seen so far pertains to joining wood perpendicularly, as if making a frame, or joining legs to a rail or something. In this instance, I’m trying to join a very thin shelf top (1/2” MDF) to a very wide rail (2X4). In this instance I have to drill in to the thicker stock, the 2X4 to secure the thinner 1/2” MDF shelf. If I set the drill bit and jig to the 1/2” settings, then the screw will not come through the 2X4 centered. It actually comes through very close to the edge of the 2X4. If I then set the drill bit, and jig to the 1 1/2” setting for the 2X4, the screw comes out centered, but the screws tend to be too long or too short. I guess I’ll just have to mix and match settings to see what will actually work. I was hoping someone had a quick solution.

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hotbyte

844 posts in 2443 days


#5 posted 04-11-2013 09:22 PM

I found this info from ‘Dan’ on the Kreg site forum a while back.

“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.”

Jig Setting and Screw Guide

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Brandon

4151 posts in 2419 days


#6 posted 04-11-2013 09:23 PM

Joe, That’s what I was saying. You have to set the jig and the bit separately. I said 3/4” but meant 1/2”.

-- "hold fast to that which is good"

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JoeWhite

24 posts in 1401 days


#7 posted 04-11-2013 09:49 PM

Well that chart is very handy. Why doesn’t that come with the darn jig. Good info. I’m printing a copy for my jig storage box. Thanks.

View BentheViking's profile

BentheViking

1763 posts in 2032 days


#8 posted 04-12-2013 02:35 AM

Make sure to put some supports under the middle of the shelf so that it doesn’t sag from the weight of heavy tools and wood

-- It's made of wood. Real sturdy.--Chubbs Peterson

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Picklehead

1019 posts in 1397 days


#9 posted 04-12-2013 12:47 PM

I admit that I’m not sure the following piece of info applies in this case, since I can’t quite picture the orientation of the pieces to be joined, however:

Sending a screw into the edge of a piece of MDF without predrilling (if the MDF were the “receiving” piece, not the “pocket hole” piece) will result in a big delaminated mess. Screwing into the face of MDF without predrilling is also a waste of time, for different reasons. MDF is great stuff, I love it, I hate it.

-- You've got to be smarter than the tree.

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JoeWhite

24 posts in 1401 days


#10 posted 04-12-2013 02:44 PM

I’ve got supports under the shelf. Thanks.

Picklehead, I will not be screwing in to the edge of the MDF. I will be screwing in to the bottom face of the MDF to secure the shelf down to the support rails. I’m going to give it a shot later today and I’ll let you know how that chart worked out.

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