Just a curious thought. Whenever I do glue ups of table tops or countertops, I just glue them and/or add biscuits or dominos. Never had any problem except with gluing up Ipe, which has its own issues as always.
So my question is whether if I were gluing up say some 5/4″ x 6″ pieces of wood edge to edge to make a table or countertop, what if I glued and clamped them, but also pocket screwed them together.
Think the screws would hold the joint closed as the wood expanded and contracted? or would the joint still try to open up since the screw doesn’t move while the wood does?
I suppose it’s worth an experiment anyway, but it just dawned on me that I’d never thought of using pocket screws for that purpose and thought maybe someone else has…
I could also go try this over at Knots, but I figured as soon as I mentioned the words “pocket hole” they would shut my computer down from their secret remote woodworking location.
Paul
Replies
The joint should be the strongest part of the filed if the wood is prepared correctly, and correct amount of glue is left in the joint.
A couple of big iffs.
The pocket hole screws would probably work to reinforce the joint, but depending on the wood, there might be a problem with them reflecting on the surface. I had biscuits do that once.
not sure what's to be gained from screws, seems it would only complicate things, glue up would only be good 1 side and exposed screws ..
I have yet to use my Kreg jig to make up a top but it seems like a natural.
When I got my jig I bought a couple of DVDs, showing different pocket screw applications. One of them is on building an oak coffe table using 1X4 for the top and other parts. Not my preference but a good example.
After selecting and numbering the pieces, the holes were drilled. Then the pieces were glued and screwed together on a smooth work table. Done. No clamping needed. Perfect alignment, ready to continue without waiting for the glue to dry.
If the holes underneath offend anyone's sensibilities, there are oak plugs available.
Hudson Valley,
That actually does seem like a bonus being able to line everything up and no clamping for the table top. I kind of enjoy the process when I have the time and am working in the home shop, but if I'm out on site somewhere and it's feasible, it seems like it could be a benefit.I'm with you on the holes underneath, plugs work. But I also don't look underneath tables too often. And other than the sink box sometimes, most underneath-countertops are pretty much hidden from view by the cabinets.Paul
http://www.pauljohnsoncarpentry.com
Dunno, about not clamping it, I've never had luck with pocket screws not shifting the pieces when screwed together. Especially when everything is lubed with glue. Maybe you mean clamped until it dries? I'd definitely clamp it during assembly...Z
I've had that happen alot with pocket screws where the faces end up not quite in the same plane.
I got one of those plate clamps from Kreg and it has minimized the problem. It's the 12" X 12" steel plate with a keyhole in the middle to which attatches a vice grip type device that puts some serious downward pressure on the pieces being screwed together. The other key is having both pieces absolutely the same thickness.
I've been pocket screwing Azek scraps together in order to make some victorian gingerbread brackets and I have been amazed at the slight variation in the thickness of what's supposed to be 5/4 stock.
Their clamps definitely make it much easier. Their right angle clamp is an absolute necessity IMO if building cabs or anything with corners. When I built my kitchen cabs, I ended up drilling a double pocket hole for every location using the B and C holes on my jig. Then I could use the clamp in one of the hole, while screwing the other, this got the clamping force as close to the screw location as possible and minimized the shifting. Even so, things will shift still, so I got good at accommodating it.Z
"they would shut my computer down from their secret remote woodworking location."
I got a chuckle out of that line.
'"they would shut my computer down from their secret remote woodworking location."I got a chuckle out of that line.'Glad you got a chuckle out of that...they scare the bejeezus out of me what with their secret half-blind dovetail handshakes and such.(interesting side note, the spell check doesn't highlight bejeezus. I guess it's a real word...even better, I just looked it up on an online dictionary and they include a definition for the phrase "beat the bejeezus out of someone", ....learn something new every day)Paul
http://www.pauljohnsoncarpentry.com
If you do use pocket screws you should use the shortest ones practical, so that the differential expansion effect is minimized.
Edited 9/23/2009 7:10 pm by DanH
Dan,That makes perfect sense. That's exactly the thing I was trying to think about, knowing that the screw could potentially be doing more harm than good in that situation depending on the wood species and shrinkage and such. Limiting the length seems to be the smart thing to do as much as is practicalPaul.
http://www.pauljohnsoncarpentry.com
I'm with Mack Z on that one - I've never had a pocket screwed piece not move "jes a smidge" when there's glue lubricating the join. For much of what's being done, a smidge doesn't much matter, but for a table top, I think it'd be a pain.
Mike
I'm in agreement with you.
I was talking about leaving the whole thing in clamps while the glue sets up (clamped width-wise). I still clamp things together when pocket screwed, it just potentially alleviates that extra 1/2-1 hour of having to have the piece clamped together and laying right in the middle of where I'm trying to get things done ;-)Paul
http://www.pauljohnsoncarpentry.com