Kreg Pocket Screw Joints - To Glue or Not to Glue?

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Mike Camp

New User
Mike
I'm going to embark shortly on building some kitchen cabinets and I was wondering what most of you all do when it comes to Kreg pocket screw joints. Do you follow the "Kreg way" and not use glue at all or do you use glue?
 

FredP

Fred
Corporate Member
95% of my kreg screw use is end grain so glue doesn't really add much to the joint. also glue will make the parts slip and slide adding to the adventure.....:gar-Bi so no.
 

ehpoole

Administrator
Ethan
I'm going to differ a little with FredP, I'm not opposed to gluing the joints (even if endgrain) when using pocket screws. But keep in mind that I frequently clamp my pieces together before driving the pocket screws home. I also pre-screw the pocket screws so that the very tip of the screw is just proud before assembly as well -- so slippage is greatly reduced even without clamps. Nor am I opposed to the use of biscuits or a few strategically placed 21/23ga pins to hold everything in place, if necessary. Despite conventional wisdom, even endgrain-to long-grain glue joints can provide a good deal of strength for a number of years (especially if seasonal humidity swings are mild). There is one exception though, I would avoid glue where the grain of the two pieces comes together perpendicular to one another (horizontal grain in one piece, vertical in the other) -- especially with wide joints (narrow joints can be Ok though) -- because the two pieces will tend to fight one another at the joint due to differing expansion and contraction rates.

This said, if it is an item that will never be subjected to any stress then I would not bother. Nor would I use glue if I felt there was some reason I might ever wish to disassemble the item.

I should provide the following caveat: I use pocket screw joints primarily for quick-and-dirty construction and jigs (a good bit of my shop is built with pocket screws). For more permanent items where I value strength and longevity I tend to be more predisposed to glue combined with biscuits, brads/finishing nails, or mortise and tenon (incl. floating tenon/dowel) construction. I'm not knocking pocket holes one bit (I even own a K3 Master Kit, micro jig, and a thousand or so of nearly every size and type of Kreg screw). I love them for some jobs and tend to avoid them for others simply because such fits my tastes.
 

Bob Carreiro

New User
Bob
I use glue on most pocket screw apps, including end grained joints (usually just one of the peices). I do agree with FredP however, that glue doesn't take well to end grain, but I believe the screw counters the weaknesses of the glue and vice-versa. Here's why:

Since the glue doesn't "sink in" to end grain and bite into the pores to "get a grip" so-to-speak, it tends to stay on the surface (of the end-grain peice, anyway). With that said, what makes a joint fail is a combination of either, or both perpendicular and lateral forces working against the glued surface, or "plain" created by the stresses we subject the item to during use. The screw works to counter the "pulling apart force" perpendicular to the glued surface, but does less to counter the side-to-side lateral forces. This is where the glue adds strength to the joint - it works to prevent, or hinder lateral forces, i.e., rubbing the two pieces together like you would your hands when washing them - not the pulling of them apart. Working together, screws AND glue form greater stability for the two peices than either one can provide alone. It's kinda like the two bishops in the board game of chess; both have a greater combined value than the some of each individually. IMO.

happy WWing,
Bob
 

Joe Scharle

New User
Joe
I don't glue either, especially on face frames. Like Fred said, slippery jointing surfaces are a real aggravation when trying to pull a 10ft FF together. Here's a pic of a shop cabinet on wheels. There's no glue anywhere in this box; drawers included. I think this is 4-5 years old now and still tight.

Rolling_Shop_Box.JPG

View image in gallery
 

Glennbear

Moderator
Glenn
I use glue on most pocket screw apps, including end grained joints (usually just one of the peices). I do agree with FredP however, that glue doesn't take well to end grain, but I believe the screw counters the weaknesses of the glue and vice-versa. Here's why:

Since the glue doesn't "sink in" to end grain and bite into the pores to "get a grip" so-to-speak, it tends to stay on the surface (of the end-grain peice, anyway). With that said, what makes a joint fail is a combination of either, or both perpendicular and lateral forces working against the glued surface, or "plain" created by the stresses we subject the item to during use. The screw works to counter the "pulling apart force" perpendicular to the glued surface, but does less to counter the side-to-side lateral forces. This is where the glue adds strength to the joint - it works to prevent, or hinder lateral forces, i.e., rubbing the two pieces together like you would your hands when washing them - not the pulling of them apart. Working together, screws AND glue form greater stability for the two peices than either one can provide alone. It's kinda like the two bishops in the board game of chess; both have a greater combined value than the some of each individually. IMO.

happy WWing,
Bob

My methodology/rationale most closely resembles yours. As Fred said slippage is an issue but I always clamped the heck out of everything on assembly anyway. When I built my largest face frame to date (6 feet + for a shop project) I found that just screws alone allowed too much wiggle between components. :wsmile:
 

Steve_Honeycutt

Chat Administartor
Steve
Corporate Member
Mike,

I built an 8' wide, 8' tall, 24" deep entertainment center. I used almost 300 pocket screws and the only glue that I used was on some of the dowels to hide the pocket holes. This unit was built in two pieces and I figure it weights close to 300 lbs unloaded. I have had no issues. The only caution would be to avoid over-tightening the screws.

Steve
 

Mike Camp

New User
Mike
Thanks for your input guys! The advice of NCWWers has been invaluable as always. I think I am going to put down the glue bottle on this project, and see how it goes.
 

Jeff

New User
Jeff
Thanks for your input guys! The advice of NCWWers has been invaluable as always. I think I am going to put down the glue bottle on this project, and see how it goes.

+1 to no glue if the consecutive screws are properly spaced at about 6-9" apart. If your cabinets are plywood then expansion/contraction movement issues are essentially nil. Same with the solid wood face frames because of the much narrower width of the components IMHO.

"Sizing" of end grain glue joints is supposed to be a useful technique when needed.

http://www.finewoodworking.com/item/25142/make-it-stick-a-guide-to-glue-ups/page/all
 

bluedawg76

New User
Sam
for cabinet shelves, are biscuits and pocket screws sufficient for the weight?
i would've thought a dado would be needed in which case either dado and glue or dado and pocket screw. Obviously with the dado you're no longer gluing just the end grain of the shelf but have some long grain as well. However, pocket screws are a heck of lot faster and don't tend to slide once they're seated like a wet glue joint. that said, i don't build cabinets routinely, so i defer to those who know what they're talking about. I would think face frames are a very different scenario wrt gluing and screwing due to the width of the pieces.

Sam
 
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