Joint clearance for gluing

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Forum topic by MrRon posted 11-24-2011 06:56 PM 2363 views 0 times favorited 18 replies Add to Favorites Watch
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5275 posts in 3483 days

11-24-2011 06:56 PM

How tight should a joint be at dry fit. My concern is if the fit is too tight, the joint will be starved of glue as the glue is forced out of the joint while assembling. If too loose, the joint will not be strong.

18 replies so far

View tenontim's profile


2131 posts in 3984 days

#1 posted 11-24-2011 08:25 PM

You shouldn’t have to hammer the joint together, but it should be snug enough that if you put the pieces together you should be able to hold it with the tenoned piece down, and it won’t fall apart. Be sure to brush glue on all of the surfaces of the mortise and the tenon, especially the end, and you shouldn’t have any problem with glue starvation.

View Sawkerf's profile


1730 posts in 3308 days

#2 posted 11-24-2011 08:39 PM

Like Tim says. If the joint falls apart, it’s too loose. If you have to beat it into submission, it’s too tight. A little gentle persuasion with a hand or hammer is ok.

Timely topic. SWMBO and #1 daughter are tearing the kitchen apart preparing Thanksgiving dinner. Recognizing my limitations in the kitchen, I just glued up a leg and apron assembly for a small table. M&T joints fit like a glove. – lol

-- Adversity doesn't build reveals it.

View a1Jim's profile


117417 posts in 3817 days

#3 posted 11-24-2011 08:48 PM

What Tim said is spot on. In a finewoodworking issue #192 the did a joint failure test and found no problems with starved glue joints even when just gluing one part of the Joint it did not fail . They tested for many aspects of gluing including types of wood ,types of joints and different kinds of glues. As I recall they found yellow glue was the strongest glue on wood and that half lap joinery was the strongest joints. Here’s a link showing how they tested the joints and glue but refer you to the article for the complete results.

The video

The article

-- wood crafting & woodworking classes

View MrRon's profile


5275 posts in 3483 days

#4 posted 11-24-2011 09:37 PM

Thank you all for your input.

View 8iowa's profile


1591 posts in 4001 days

#5 posted 11-25-2011 12:42 AM

Here’s something that will blow your minds!

At the past “Woodworking in America” conference, (9/30-10/2) Instructor Graham Blackburn introduced us to the “sliding butt joint”. He led off his discussion by stating “We’ve all heard that you can’t have enough clamps”. He then said that this statement is nonsence, promoted by those who make and sell clamps.

He told us that while teaching a class at the Marc Adams school, they all jointed their boards, applied glue to both edges, and then with a slight sliding motion he joined the two glued surfaces. He then remarked to the class that it was time to go to lunch. The outcry from the class was “Hey! what about the clamps?” Setting the boards carefully aside, Blackburn said “we don’t need clamps”.

Sure enough, when they returned from lunch the boards were perfectly glued together.

As Casey Stingel used to say….....amazin.

-- "Heaven is North of the Bridge"

View dusty2's profile


323 posts in 3669 days

#6 posted 11-25-2011 03:05 PM

I think I agree but I still feel compelled to apply those clamps.

Have you ever applied glue to the matting surfaces, put them together and then slide the pieces around a little “to spread the glue” and then tried to pull them apart?

-- Making Sawdust Safely

View 8iowa's profile


1591 posts in 4001 days

#7 posted 11-25-2011 04:22 PM

I did not mention one of Blackburn’s important points of his instruction:

He said that boards jointed on a power jointer actually have edges with many microscopic “scallops”, the result of the circular cutting motion. He then said that it would be a miracle if the “scallops” on two boards line up perfectly.

Blackburn takes a hand plane, set to take very thin shavings, and creates a perfectly flat surface on the mating edges.

-- "Heaven is North of the Bridge"

View MrRon's profile


5275 posts in 3483 days

#8 posted 11-25-2011 06:50 PM

I always slide the two surfaces together, but I still use clamps; never occurred to me, not to.

View a1Jim's profile


117417 posts in 3817 days

#9 posted 11-25-2011 07:14 PM

Using the slid together technique with clamps or no clamps butt joints are very weak joints because your gluing to end grain that should be reinforced with a biscuit ,screw,nail. spline or some other means to make it a strong enough joint to be viable for most projects, The other thing about using clamps is that you can hold your work in place to keep it square or where you want it to be held. The slid together technique may be ok for small pieces but I would avoid trying to use it for a project of any size.

-- wood crafting & woodworking classes

View Bernie's profile


422 posts in 3077 days

#10 posted 11-26-2011 06:12 AM

I have always used clamps but I don’t own an army of them. I have always used the slide method because I was told this eliminates any air pockets inside the joint.

-- Bernie: It never gets hot or cold in New Hampshire, just seasonal!

View Diamondsusie's profile


2 posts in 2497 days

#11 posted 03-28-2012 09:06 PM

I learn sooooooo much reading everyone’s posts!! This is such a great website!!

View stevenmadden's profile


174 posts in 3329 days

#12 posted 03-28-2012 09:39 PM

a1Jim: Thanks for all the information, good stuff. In your last post you mentioned a butt joint and end grain. By definition, is a butt joint end grain to long grain? I have been calling long grain to long grain edge joints, like gluing up a table top, butt joints. Is this incorrect? In the meantime, I guess I better look it up…


View Loren's profile


10477 posts in 3888 days

#13 posted 03-28-2012 11:32 PM

“Dry fitting can wreck the final fit.” Correct.

It depends on the glue.

It depends on the wood.

It depends on the finesse of the work.

Read James Krenov books. Well-fitted joints don’t require
much glue. Within a certain range glues can compensate
for not-so-well-cut joints.

View a1Jim's profile


117417 posts in 3817 days

#14 posted 03-28-2012 11:47 PM

I would call end grain to long grain a butt joint, long grain to long grain may technically be a butt joint but is not what I would normally call joining long grains together. End grain needs more than just glue to hold a joint together because of it’s porous nature . If you think of wood as a bunch of straws bundled together the long grain would be the the length of the straws that can easily be glued together but trying to glue the ends together is all but impossible because you keep filling the straws with glue and have very little on the ends.

-- wood crafting & woodworking classes

View waho6o9's profile


8539 posts in 2817 days

#15 posted 03-29-2012 12:50 AM

An old trick is to size (spelling?) the end grain. Put glue on the end grain, I apply glue to all the joints, wait a couple of hours or overnight, assemble the next day and it’s way strong.
I apply glue to all the joints after the project is sealed to avoid glue marks.

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