Strong and weak glue joints

MISSING IMAGE

Material Information

Title:
Strong and weak glue joints
Series Title:
Technical note ;
Physical Description:
4 p. : ill. ; 21 cm.
Language:
English
Creator:
Forest Products Laboratory (U.S.)
Publisher:
U.S. Dept. of Agriculture, Forest Service, Forest Products Laboratory
Place of Publication:
Madison, Wis
Publication Date:
Edition:
Rev. Dec. 1952.

Subjects

Subjects / Keywords:
Wood -- Bonding   ( lcsh )
Joinery   ( lcsh )
Genre:
federal government publication   ( marcgt )
non-fiction   ( marcgt )

Notes

Additional Physical Form:
Also available in electronic format.
Additional Physical Form:
Also available online.
General Note:
Caption title.

Record Information

Source Institution:
University of Florida
Rights Management:
All applicable rights reserved by the source institution and holding location.
Resource Identifier:
aleph - 029722426
oclc - 61286421
Classification:
lcc - TA419 .U45 no.211 rev.1952
System ID:
AA00026018:00001

Full Text
.f1 F


TECHNICAL NOTE NUMBER 211
UNITED STATES DEPARTMENT OF AGRICULTURE FOREST SERVICE
FOREST PRODUCTS LABORATORY
MADISON 5, WISCONSIN REVISED December 1952



STRONG AND WEAK GLUE JOINTS


The accompanying photographs of wood blocks glued with a good grade
of animal glue and then sheared apart in tests at the Forest Products
Laboratory show what may happen with the same glue rightly and wrongly
used. The blocks that sheared apart at the glue line indicate poor glu-
ing. Those in which failure occurred in the wood were good joints, as
strong as the wood itself.

The joints shown in the left-hand column were weak, since the failure
was all in the glue. In joint A the glue was allowed to get too cold before
pressure was applied. In joint B the glue was too thin and was squeezed
out of the joint. In joint C the glue had dried before pressure was ap-
plied. These three joints represent three of the most common errors
in gluing practice. They are known as the chilled joint, the starved
joint, and the dried joint.

The joints showninthe rows to the right of A, B, and C are strong joints,
each made by changing only one of the three conditions -- pressure,
assembly time, or temperature. These are the three most important
variables in the gluing operation when animal glue is used.

Thus a good joint can be made from chilled glue by increasing the pres-
sure, or the glue may be kept from getting chilled and a good joint ob-
tained if either the assembly time is decreased or the room temperature
increased. (See the top row of photographs, left to right. )

If the glue is thin, starved joints may be avoided if the consistency of
the thinglue is increased by increasing the assembly time, by decreas-
ing the room temperature, or by mjnin less water with the glue. De-
creasing the gluing pressure may al o impr, i u h such
practice is not always recommended. p4 tida4Trow of hoto-
graphs.)


SS. DEPOSIT






THREE COMMON TYPES OF WEAK ANIMAL GLUE JOINTS


POOR JOINTS
THREETYPES MADE UN-
DER THREE DIFFERENT
SETS OF CONDITIONS.


AND HOW THEY MAY BE AVOIDED

GOOD JOINTS
MADE UNDER SAME CONDITIONS AS POOR JOINTS TO LEFT EXCEPT
FOR A VARIATION IN EACH CASE OF ONE OF THE THREE FACTORS


ASSEMBLY TIME


TEMPERATURE

,I l


A-CHILLED JOINT
Medium glue spread.
Pressure of 150 pounds
per square inch applied
after 12 minutes closed
assembly. Room at 75 F,
Note areas of incomplete
contact.


- *' . :.
B-STARVED JOINT
Medium glue spread.
Pressure of 150 pounds per
square inch applied after
1 minute closed assembly.
Room at 90 F. No glue
remaining in joint.
No wood failure,


Pressure 400 pounds per
square inch. All other con.
ditione same as for A.


9r c"'nm h
Pressure 25 pounds per
square inch. Allothercon-
ditions same as for B.
Better joint than B, but
this pressure not recom-
mended.


I ,'1 I', '.ff
1 minute closed assem-
bly before application of
pressure. All other con-
ditions same as for A.


it-wir. M his"
12 minutes closed assem-
bly before application of
pressure. All other con-
ditions same as for B.


Room at 90 F, All other
conditions same as for A.


Room at 75F. All other
conditions same as for B.


C-DRIED JOINT
Medium glue spread.
Pressure of 150 pounds per
square inch applied after
25 minutes closedassembly
Wood heated 20 minutes at
120 F. Room at 80 F.
Note shlny areas of dried
glue.


No amount of pressure will
produce a good joint with
other conditions same as
for C.


ram mp _J
12 minutes closed assem-
bly. All other conditions
same as for C.


Wood heated 20 minutes at
90 F.All other conditions
same as for C.




UNIVERSITY OF FLORIDA


3 1262 09216 7427
No amount of pressure will produce a good jo30, irom arneo glue, Dut
by decreasing either the assembly time or the temperature to which the
wood is subjected, a good joint can be made before the glue has dried
out. (See the bottom row of photographs.)

Assembly time, room temperature, wood temperature, grade of glue,
and glue-water ratio are chief among the factors affecting the consist-
ency of an animal glue at the moment pressure is applied. Controlling
the temperaXture of the wood and the assembly time is often the most
practical method of insuring good glue joints.


Agr Icu Ilture-Mad ison


ZM318T73F