Dado + kreg = why

[mike healey]

As a newbe to Kreg pocket hole technology I am to some degree puzzled as to why Gary Striegler in his trim carpentry instructional CD incorporates a dado in conjunction with pocket holes. I can see the potential for added strength and the opportunity to eliminate torsional movement. However, why do all the others not use a dado. 

Is it needed or not?   Same question on glue to Kreg,, if it is not needed why do they all use it... just built my first structure with neither glue nor dados, seems strong enough..  please put me out of my misery someone and explain what I'm missing...    cheers.. Mike..

[Hugh Clare]

Mike,

I don't know what the reasoning is for a pocket hole/dado combination. As for a pocket hole/glue combination, I use it. Gluing up a large panel like a table top can be awkward and cumbersome. The pocket holes eliminate the need for clamps. Once the glue is set, the screws are no longer needed and could be removed if one wanted to. Pocket holes have their place, but I don't think they're the answer for every joint.

[michael evans]

Mike sometimes i use dados just for positioning a mating piece too.Stops to much movement when adding pocket holes and glue does that make sense?

[KregRep]

Great question Mike. Dadoes are often used to help align pieces, as already said. part of that goes to tradition that sometimes is hard to break, even with the introduction of new technology like Kreg Joinery. 

Another time for a dado is if the piece will bear a lot of weight--such as for a shelf full of heavy books. You can accomplish the same thing, of course, by adding a cleat, but you may not want the cleat to be visible.

In general, you can often eliminate a dado by using Kreg Joinery and have no concerns about strength. When in doubt, add a few more screws.

If you're assembling a structure with lots of parts that have to go together exactly, dadoes can help simplify the process by "locking/indexing" the parts so they stay in place during assembly.

Remember that if you use dadoes you'll want to consider the length of screw and the stop collar setting. For instance, if you put a 1/4" deep dado into a 3/4" piece, you now have 1/2" of material left, so you'd use a screw and a stop collar setting that are appropriate for 1/2" stock.

As far as glue goes, the answer can also vary. Again, glue is a woodworking standby and many people still just use it automatically. And glue does add strength. I've assembled many door frames, cabinets, and more with Kreg Joints and no glue, though, and they hold up fine. 

To me, glue isn't necessarily about strength. I like to use glue to combat wood movement. Wood expands and contracts with seasonal humidity changes, and sometimes unglued joints can show gaps during dry times of year. Adding glue helps prevent this by bonding the two pieces together.

So, there's some of my advice. I know it doesn't give a concrete "use dadoes or glue in these exact circumstances" sort of answer. But I hope it gives a little insight that is helpful.

KregRep

[mike healey]

Thanks all for your advice and replies......   question answered.......   Regards, Mike 

[Jay Boutwell]

Excellent reply that describes all of the elements of why dadoes and screws and the use of glue.  I seldom use dadoes on any projects anymore and that is the beauty of the pocket screw.  Removes the need to dadoe which is time consuming and if any error is made at all you are hard pressed to correct it without cutting additional material.  I also use glue just to add that little bit of extra strength to the joint however there are times that I do not especially if it might need to be disassembled or modified in the future.

KregRep said:

Great question Mike. Dadoes are often used to help align pieces, as already said. part of that goes to tradition that sometimes is hard to break, even with the introduction of new technology like Kreg Joinery. 

Another time for a dado is if the piece will bear a lot of weight--such as for a shelf full of heavy books. You can accomplish the same thing, of course, by adding a cleat, but you may not want the cleat to be visible.

In general, you can often eliminate a dado by using Kreg Joinery and have no concerns about strength. When in doubt, add a few more screws.

If you're assembling a structure with lots of parts that have to go together exactly, dadoes can help simplify the process by "locking/indexing" the parts so they stay in place during assembly.

Remember that if you use dadoes you'll want to consider the length of screw and the stop collar setting. For instance, if you put a 1/4" deep dado into a 3/4" piece, you now have 1/2" of material left, so you'd use a screw and a stop collar setting that are appropriate for 1/2" stock.

As far as glue goes, the answer can also vary. Again, glue is a woodworking standby and many people still just use it automatically. And glue does add strength. I've assembled many door frames, cabinets, and more with Kreg Joints and no glue, though, and they hold up fine. 

To me, glue isn't necessarily about strength. I like to use glue to combat wood movement. Wood expands and contracts with seasonal humidity changes, and sometimes unglued joints can show gaps during dry times of year. Adding glue helps prevent this by bonding the two pieces together.

So, there's some of my advice. I know it doesn't give a concrete "use dadoes or glue in these exact circumstances" sort of answer. But I hope it gives a little insight that is helpful.

KregRep

[Jason Watkins]

Hey I know this is an old thread, but I just watched the trim carpentry episode where Gary builds the window seat and book cases.

It seems to me that the kreg screws are used to clamp the shelf into the dado in the side of the book case.

Since he glued the joint and the clamping pressure from the pocket screws was sufficient to close the joint while the glue dries, a frugal carpenter could then remove the screws from the dado joint, and everything would be fine. 

I may try this method in an upcoming build, to avoid fussing with my bessy clamps.

[Ken Darga]

Jason,

There are some applications, where using the Kreg pocket hole joinery is more suitable over using external clamps, while the adhesive is drying. 

Pocket-hole joinery is useful for this purpose, as well in ''pinning'' in light-duty use applications.

Some wood workers remove the pocket-hole screws, after the glue sets-up, and reuse the screws.

[Jay Boutwell]

A well placed screw with glue is usually better that a clamp and glue. In most instances it is much faster to apply that a clamp and then once the clamp is removed all that is holding it is the glue.
 
Ken Darga said:

Jason,

There are some applications, where using the Kreg pocket hole joinery is more suitable over using external clamps, while the adhesive is drying. 

Pocket-hole joinery is useful for this purpose, as well in ''pinning'' in light-duty use applications.

Some wood workers remove the pocket-hole screws, after the glue sets-up, and reuse the screws.

[Jason Watkins]

Oh yes, the screw will definitely be sufficient, and will add strength. It is just intriguing to me that the clamping force of the screw is enough to hold a joint together while the glue dries. A handy tip to remember for when you run out of clamps during a glue up. 

Of course this assumes that you have already drilled the pocket screws correctly to allow for the dado.