Author Topic: Rubbed glue joints vs. clamped joints  (Read 6141 times)

HSteier

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Rubbed glue joints vs. clamped joints
« on: November 29, 2008, 09:40:00 AM »
Rococojo commented in a prior thread that "a rubbed joint is all that is required with any glue". I do not believe that this is correct.
Do a simple experiment. Glue up two jointed boards with hide glue and clamp them. Then glue up two boards by rubbing them and don't use clamps. The next day, after the glue has dried, if you strain the joints, the rubbed joint will give at the glue line whereas the clamped joint will not (the wood will break first).
The same is true with yellow glue.

Howard Steier

Adam Cherubini

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Re: Rubbed glue joints vs. clamped joints
« Reply #1 on: November 29, 2008, 10:18:05 AM »
Depends on what's required, right?  Joe might be thing about a little glue block or a piece of a carving.  The facts are pretty clear.  To develop full bond strength PVA glues must be clamped and clamped tightly (150-250psi) to develop full properties.  It's likely most woodworkers aren't using enough clamps or cranking them hard enough to get the most out of titebond.  They also use it in spots where clamp pressure doesn't help (like dovetails and mortise and tenon joints).  In fact, for period woodworkers where these two joints dominate all others, titebond is disadvantageous.  Hot hide glue would be a better choice. It's dry condition is considerably stiffer than PVA and that stiffness results in higher bond strength in unclampable joints.  Liquid hide glue is considerably less stiff, so not as advantageous.

I think this is one of those things that reminds us to just do it like the old guys until we understand the science well enough to proove they were right.

Adam

rococojo

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Re: Rubbed glue joints vs. clamped joints
« Reply #2 on: November 30, 2008, 07:18:29 PM »
Hi Howard, in reply to your post,
 As Adam suggested I was indicating the little glue block or a piece of small carving, not a wardrobe side? This off course would include a joint to increase the gluing area
By possible 50% or more, sorry I didn’t make that clear, I thought we were talking about the small glue blocks,(cabriole leg) not larger joints.

        Joseph Hemingway (rococojo)
           40 years in business, 1968-2008


jdavis

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Re: Rubbed glue joints vs. clamped joints
« Reply #3 on: December 01, 2008, 11:13:44 PM »
Oh nooooo! When I read previously that "a rubbed joint is all that is required with any glue", I proceeded to glue up my 12 foot mahogany dining room table and proudly rubbed the joints so I could get it done on time. Just finished the whole thing over the Holiday. Does this mean the table could separate during Christmas dinner?

As the nearly 100 year old saying goes, "Say it aint' so, Joe!

Signed,
Panic Stricken

HSteier

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Re: Rubbed glue joints vs. clamped joints
« Reply #4 on: December 02, 2008, 05:25:24 PM »
Dear Panic Stricken

Not to worry. Place a pair of sawhorses under each board and enjoy Christmas dinner as usual. Just don't drink too much Christmas cheer and lean on the table.

Howard Steier

msiemsen

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Re: Rubbed glue joints vs. clamped joints
« Reply #5 on: December 02, 2008, 06:18:01 PM »
I usually rub my joints when I get up in the morning or when it is cold, knees mostly.
Mike
Mike Siemsen
Green Lake Clock Company
There are II kinds of people in the world. Those that can read roman numerals and those that can't

rococojo

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Re: Rubbed glue joints vs. clamped joints
« Reply #6 on: December 02, 2008, 07:06:32 PM »
ha,ha.
 Thank-you Panic Stricken/mike,you made me laugh,Ill live another day?possibly Now?thank's for  seeing the joke?
  http://www.furnituresociety.org/furn/index.php?dynamic=portfolio&id=4037

       this link as given a smile as well.(1,1/2 days)
           
                         Joseph Hemingway
                          40 years in buisiness, 1968-2008
« Last Edit: December 02, 2008, 07:09:53 PM by rococojo »

msiemsen

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Re: Rubbed glue joints vs. clamped joints
« Reply #7 on: December 15, 2008, 09:42:21 PM »
Nicholson talks about the process of rubbing glue joints on page 137 of The Mechanics Companion I will attach a copy which I hope you can see. As I read this he is talking about rubbed joints, without clamps, in long pieces. Maybe your table top is fine Mr. Davis and there is no need for panic, or sawhorses.
Mike
« Last Edit: December 15, 2008, 09:44:23 PM by msiemsen »
Mike Siemsen
Green Lake Clock Company
There are II kinds of people in the world. Those that can read roman numerals and those that can't

rococojo

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Re: Rubbed glue joints vs. clamped joints
« Reply #8 on: December 17, 2008, 06:27:11 AM »
Mike, I thank you sir,
 I was brought up by a long trading firm (1851-1992), there instruction,  take notice, we rub jointed on long pieces of timber all the time, never questioned the Master, just relied on his skill & knowledge, but today sapfm as shown me a great lesson, If one searches for written evidence? There could always be a mike to show the theory.
A great, interesting & enlightening post.

                                         Joseph Hemingway
« Last Edit: December 17, 2008, 12:00:15 PM by rococojo »