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glue-up vs. pocket screws

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Forum topic by harum posted 01-26-2014 06:02 PM 825 views 0 times favorited 13 replies Add to Favorites Watch
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harum

119 posts in 328 days


01-26-2014 06:02 PM

Topic tags/keywords: question joining pocket screws glue tabletops

Are there sources around (books, journal articles, etc.) comparing two methods of edge joinery of boards into tabletops: gluing and using pocket screws? And when one is preferred over the other? My understanding has been that gluing is used more but can only guess why. I think gluing is a better method when tabletop is assembled using narrow strips, say 4” wide and below, because, otherwise, pocket screws would take forever. For wider boards, 6” and above, with fewer edges to glue/screw the amount of work for two methods is already comparable.

What is common is that in both methods, spread glue or evenly spaced screws, connect the edges along the entire length of contact. Both methods require jointing for seamless joining.

Some say that pocket screws prevent tops from natural seasonal movement, but I can’t see why.
Any comment will be greatly appreciated. Thanks, h.

-- Having finished many DIY projects, I still don't know how things should be done, but I surely know how they should not be done.


13 replies so far

View GT350's profile

GT350

270 posts in 667 days


#1 posted 01-26-2014 06:20 PM

I can’t see how pocket screws would stop seasonal movement any more than gluing would. With either method the wood can expand across the width of the grain unless it is attached to something that doesn’t expand also. As for glue vs screws, I wood never use screws for edge joining a large panel, I prefer glue. Glue is less expensive, looks better and I never have to worry about hitting screw when cutting a piece down to size. I do use pocket screws other things though.
Mike

View CharlesA's profile

CharlesA

1647 posts in 483 days


#2 posted 01-26-2014 06:34 PM

I used pocket screws on my first glue up, none on a whole number after that. Given how strong a side edge glue joint is, I can’t see the purpose of going through the extra trouble to use pocket screws.

-- "Man is the only animal which devours his own, for I can apply no milder term to the general prey of the rich on the poor." ~Thomas Jefferson

View michelletwo's profile

michelletwo

2267 posts in 1701 days


#3 posted 01-26-2014 06:49 PM

gave up mechanical means to glue up large panels/table tops yrs ago. The new glues are stronger than wood IF done well.

-- We call the destruction of replaceable human made items vandalism, while the destruction of irreplaceable natural resources is called development.

View patcollins's profile

patcollins

1003 posts in 1550 days


#4 posted 01-26-2014 06:55 PM

I can see using pocket holes because you don’t have the clamps for a large glue up or simply because you have had trouble getting the glue up to not bow one way or another. I can also see using the pocket screws for the glueup then removing them after the glue dried.

View thesoninlaw's profile

thesoninlaw

96 posts in 470 days


#5 posted 01-26-2014 07:22 PM

I too can understand using screws for edge-joining wider panels, but would still glue them.

View bondogaposis's profile

bondogaposis

2590 posts in 1037 days


#6 posted 01-26-2014 07:27 PM

The only advantage that pocket screws would give over edge gluing is that you wouldn’t need to clamp w/ pocket screws. Personally I find clamping to be easier. The seasonal movement would be the same for either method. What is critical is how the top is attached to the the rest of the table.

-- Bondo Gaposis

View wseand's profile

wseand

2415 posts in 1727 days


#7 posted 01-26-2014 07:47 PM

IMO screws constrict the wood from moving, glue tends to move and contract with the wood better.
Gluing is a much stronger alternative to screws, no doubt about it in my mind.

Just like when you attach the top to the carcass you want to do it in a way that allows for movement.

I’ve made a lot of tables and done a lot of edge gluing, I would never consider using screws for any size of stock.
In fact it is easier to glue wider stock then thinner stock, IMO

If you are having trouble with alignment than I would suggest using domino or biscuit tenons.

-- Bill - "Freedom flies in your heart like an Eagle" Audie Murphy

View harum's profile

harum

119 posts in 328 days


#8 posted 01-26-2014 08:35 PM

Thanks for the responses! Pocket screws joinery also seems to be a method of choice when, for design purposes, gaps between edge-joined boards are allowed, like when joining rough boards with limited contact at the edges.

Unlike glue, pocket screws may prevent wood movement along the screw lengths, which is probably at least 1” on both sides of the joining line. Glues bind only two thin layers of wood right next to the edges; pocket screws bind by going through a few inches of wood. If using 2” screws on 6” boards, then about a third of a tabletop is restricted in cross-grain seasonal movements. Would this be enough to cause strain and warping? Don’t have any experience to answer this…

-- Having finished many DIY projects, I still don't know how things should be done, but I surely know how they should not be done.

View David Dean's profile

David Dean

526 posts in 1584 days


#9 posted 01-26-2014 08:58 PM

Im a big fan of Pocket screws joinery but I glue every thing I can most of my customer’s thats the frist thing they look for is glue and screw’s. Well think it is stronger but thats me.

View Jake's profile

Jake

324 posts in 316 days


#10 posted 01-26-2014 09:14 PM

Personally I use pocket holes with glue only because i don’t yet have enough clamps for some tops. I dislike the holes even if I can’t see them.

But i always use glue with any joint I make, screws or no screws the glues I use are tougher than any screws if done correctly.

-- Measure twice, cut once, cut again for good measure.

View CharlesA's profile

CharlesA

1647 posts in 483 days


#11 posted 01-26-2014 09:19 PM

Does anyone use domino tenons for alignment on glue ups? That seems odd to me. Despite their obvious similarities, I thought the Domino and the biscuit joiner are very different in application. Does a domino tenon swell? I know that some folks have had problems with biscuits swelling up too much in a table top glue up and causing swelling on the top. If Domino tenons swell, and the smallest size is almost half the thickness of a 3/4” table top, I would think it would have a greater possibility to cause swelling.

-- "Man is the only animal which devours his own, for I can apply no milder term to the general prey of the rich on the poor." ~Thomas Jefferson

View casual1carpenter's profile

casual1carpenter

353 posts in 1161 days


#12 posted 01-27-2014 12:44 AM

CharlesA, can’t really answer your question on the domino as it is out of my budget on a cost vs benefit level, but if I remember right, I believe biscuits are a dried and compacted animal specifically so they do swell and tighten in the joint. I would take a dowel or shop made loose tenon any day over the biscuit joiner.

View CharlesA's profile

CharlesA

1647 posts in 483 days


#13 posted 01-27-2014 12:52 AM

Turns out that folks do use a Domino for edge glue-ups and Domino tenons do not swell, see:

http://www.festoolusa.com/Web_files/Getting_the_most_from_the_Festool_Domino_Machine.pdf

-- "Man is the only animal which devours his own, for I can apply no milder term to the general prey of the rich on the poor." ~Thomas Jefferson

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