Pocketholes and tables - Woodworking Talk - Woodworkers Forum
 
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post #1 of 9 Old 01-22-2016, 10:29 PM Thread Starter
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Pocketholes and tables

This guy did a test on these screws. his test showed that they failed at 115lbs 110lbs and 140lbs. I averaged these results and came up with 121.6666. Theres no way one can put this much force on a dining table leg joint or coffee table joint.

Heres the link
https://www.woodgears.ca/joint_strength/index.html

all of my dining tables use 2.5 to 3.25 inch square posts so what I do is if u use a 1x5 for an apron I use the 2.5 inch screws instead of the short screws. I haven't had any issues with my tables and no one ive sold a table to has come back and said they have had a bad experience. I just wanted to see what everyone else thought about this.
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post #2 of 9 Old 01-22-2016, 10:30 PM Thread Starter
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Also in those joints with the 1x5 I use as many screws as I can.
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post #3 of 9 Old 01-22-2016, 10:55 PM
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I built a desk for my nephew to use at college. Three years and counting. It is still in one piece...and he is a big guy. The aprons are joined to the legs with pocket screws.

I have asked more than once if he has had any problems, and he says no. :-)
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post #4 of 9 Old 01-22-2016, 11:20 PM
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MidGa, Don't believe everything posted on web. The link you gave he used the wrong screws to start with.....You dont use a drywall for structual strength... He used a wood screw meant for other connection...If you noticed he had screw head pull through failures before adding washers. So I also wonder about his pocket hole being bored correctly.

Pocket screws are designed for pocket holes. the threads are self cutting and the heads are designed for the pull through prevention. Also a scew running into end grain is the last resort you want....IT WILL pull out sometime with enough pressure the soonest/least pressure...end grain just WON'T hold screws well due to parallel grain with threads.

I prefer Kreg screws myself. and they also have a HD 2 1/2" that works great with 2x materials....you pay for what you get!!!!

Just saying the info you went by is ALL AROUND WRONG to begin with.

Have a Blessed and Prosperous day in Jesus's Awesome Love, Tim
........www.TSMFarms.com.......... John 3:16-21 ..........
Reveling God's awesome beauty while creating one of-a-kind flitches and heirlooms.
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post #5 of 9 Old 01-22-2016, 11:43 PM Thread Starter
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I watched the guys videos and wondered. thinking about it now I agree with you Tim. I guess I'm just second guessing myself.
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post #6 of 9 Old 01-22-2016, 11:43 PM
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While the Kreg screws are an accepted method of manufacturing cabinet faceframes it's my opinion that furniture deserves a better class of craftsmanship. With cabinets they are attached to a wall to where they are not constantly pushed and pulled in different directions. This is a lot to ask of screws. With a wood joint glued together the parts are bonded together at the cellular level. This would provide a more durable joint.
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post #7 of 9 Old 01-23-2016, 04:45 AM
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Just because something can be done doesnt necessarily mean it should. Sure, the pocket-hole screw may come in at 100 pounds in a strength test, which seems like a lit in the test, but that test does nothing to show factors other than a constant load, like impact resistance or longevity.

Ive got nothing against pocket screws, but personally i wouldnt trust them for something like attaching legs to an apron. Screws loosen over time, and if the screws are the only thing holding the legs of a dining table on, well, eventually that leg will loosen. Thats also to say nothing about something whacking against the table, like a dog or a small child. I could very easily see something bumping the leg near the bottom causing the threads of the screw to pull out. Plus, like steve i think furniture deserves a slightly higher level of craftsmanship. A dowel joint doesnt take a lot more time than a pocket hole would, and is a lot stronger of a connection.

Plus, dowels are cheaper than screws, assuming you have wood on hand

I need cheaper hobby
etsy.com/shop/projectepicfail
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post #8 of 9 Old 01-23-2016, 11:12 AM
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I agree with Steve and Epic it's not the higher level of craftsmanship that a fine piece of furniture deserves .
Yes I have used them in certian situations BUT try not be a habit with my furniture due I'm more purist craftsman.
IF you choose to use them I don't condemn your choice, I ONLY recommend you to learn the proper process, screws and limitations. Building of furniture has been using screws and pocket screws in the fast production world for ages and is getting more used. We can't get away from using none in all situations....tops have to float and a screw is needed for a cleat if used or slide bored so wood can move under screwhead.

Don't get hung up over the many opinions....please keep enjoying building furniture....that's always improving over the last piece we built. Build quality, learn techniques correctly, gather all info you can then sift through the trash and keep the good info that line-up together.

You've got several learning posts going on at this time....take them one step at a time...crossroads and growing businesses seem to go hand in hand....it can be overwhelming.

Again, ENJOY your building!!!

Have a Blessed and Prosperous day in Jesus's Awesome Love, Tim
........www.TSMFarms.com.......... John 3:16-21 ..........
Reveling God's awesome beauty while creating one of-a-kind flitches and heirlooms.
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post #9 of 9 Old 01-23-2016, 12:34 PM
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I won't argue whether or not the pocket screws are right for this application, but I'd contend that one could easily exceed that force.

Because the leg is a lever and the joint is a fulcrum, you need to consider overall rotational force or torque. Since Length x Force = Torque, if the legs are, say, 2 feet long, and a 150lbs person leans into the table with 1/2 their weight, it's actually 75lbs x 2ft = 150 ft-lbs of torque.

Again, not arguing that you shouldn't use pocket screws (I know I've beat the crap out of some pocket screw joints), but if you're going to use woodgears math, you gotta consider the whole picture.
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