How strong is a pocket hole joint compared to a mortise
and tenon joint?
This is a question we get asked quite often. An independent lab completed
testing a few years back that showed that a pocket hole joint failed at 707
pounds when subjected to a shear load while a mortise and tenon joint failed
at 453 pounds (approximately 56% stronger). Pocket hole joints are tremen-
dously strong for a couple of reasons. 1) The use of a mechanical fastener
(screw) is significantly stronger than the material around it (wood), and 2) The
amount of direct clamping force placed on the joint by driving the screw
combined with today’s glue technology makes for a sensationally strong bond.
A second question we get asked from time to time is in what applications are
pocket hole joints appropriate. This is commonly asked when the project being
built is a swing set, deck, or bunk beds. Although pocket hole joints are
exceptionally strong, the rule of thumb is to
never use a pocket hole joint in
place of a structural bolt, hanger or fastening device.
The pocket hole plugs sit well over flush when placed in
the bottom of the pocket hole. Is this normal? What is
the best way to sand plugs flush?
Yes, this is normal. The depth that the plug seats into the bottom of the hole
depends on the depth of the hole that is drilled. We must make the plugs
with a certain tolerance of plug length to allow for varying hole depths. As a
general rule, the deeper you drill the hole, the less plug you will need to sand
off. There are a couple of different ways to trim plugs. If you will be trimming
very few plugs, a flush cut hand saw followed by a light sanding works very
well. If you will be trimming many plugs we recommend using a laminate
trimmer outfitted with a bull nose bit. Trim off the majority of the plug, and
then finish with a light sanding. See page 30 for more details.
The pocket hole plugs are too large for the hole, what can
I do to make them fit?
As odd as it may sound, a good way to shrink plugs is to place them in the
microwave for a few seconds. This normally removes enough moisture to
allow easy installation.
Should I use glue with pocket hole joinery?
Glue is not required for pocket hole joinery, but we normally recommend using
glue if you never foresee a need to take your project apart. With pocket hole
joinery, you only need a thin coat of glue to get an extremely strong bond
because of the immense amount of clamping pressure applied on the joint line
by the self-tapping screws. Glue squeeze-out as a result, should be minimized.
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