Veneer cutting and drying properties

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Title:
Veneer cutting and drying properties
Physical Description:
Mixed Material
Creator:
Forest Products Laboratory (U.S.)
Publisher:
U.S. Dept. of Agriculture, Forest Service, Forest Products Laboratory ( Madison, Wis )
Publication Date:

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Rights Management:
All applicable rights reserved by the source institution and holding location.
Resource Identifier:
aleph - 29294953
oclc - 226351563
System ID:
AA00020540:00001

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FORESI l'RODLU(IS LABORAI01R t f!)RI.. I b %.\l I.
7U. S. DEPARTMENT I1 A(R.I L' I.A RK.

VENEER CUTTING AND DRYING PROPERTIES
1


TUPELO ..


There are three commercially important taptlo specit r' Water tipe+-4
(Nyssa aquatica, black tupelo (N, sylvatica). and swamp tupelo (N,
sylvatica var. biflora). Water tupelo and swamp tupelo, as the names
indicate, are water-loving trees and grow principally in the fresh-water
swamps and along the edges of streams and ponds in southeastern United
States. Black tupelo, which has a much larger range, grows throughout
most of the eastern half of the United States

The wood of the various tupelos is similar, and no attempt to separate the
species is made by commercial lumber inspectors The heartwood is light
brownish grey, and the sapwood is nearly white Black tupelo and swamp
tupelo sometimes have darker colored heartwood than water tupelo The
wood is diffuse porous and has a close, uniform texture It has very inter-
locked grain, which prevents it from splintering under heavy wear and makes
it difficult to split. 1- The interlocked grain tends to cause warp during the
seasoning of the lumber. The wood is rated as moderately heavy and
moderately strong and hard.

Tupelo lumber is used principally for shipping containers, flooring, and
furniture. Rotary-cut tupelo veneer is used mainly for the interior plies
of stock panels and for wirebound boxes Because of its light color, moderate
strength, and resistance to splitting tupelo is a preferred box wood Some
tupelo is used for pulpwood, railway ties, and cooperage


Selection, Handling, and Preparation of Logs for Cutting


One 16-foot and four 8-foot logs of water tupelo and a similar sample of swamp
tupelo were used in Laboratory tests of the rotary veneer cutting and drying
properties of these species. This material was part of a shipment sent to the
Laboratory through the cooperation of the Southern Forest Experiment Station

-Betts, H.S. Tupelo. Amer. Woods Ser Forest Serv U S, Dept of Agr
1945.

McMillen, J. M Kiln Drying Water and Swamp Tupelo Proc Forest Prod
Res. Soc. 1953.


Report No. 1766-9 September 1953
t Maintained at Madison 5, Wisconsin in cooperation with the University of Wisconsin
Agriculture Madison







and the Mississippi Products Company. The logs came from Livingston
County, La in the Bayou Barbary Swamp Z5 miles southwest of Hammond,
La. They were reported to be of veneer or good saw-log quality.

The test logs were from 15 to 31 inches in diameter at the small end. The
specific gravity of the test material varied from 0. 31 to 0. 51; the lower
value represented the sapwood from a swelled butt log.

Judging from defects observed in the 10 test logs, fire scars, ring shake,
and swelled butt logs should be avoided when selecting tupelo for veneer
cutting.

Tupelo veneer of moderate quality can be cut from bolts at room tempera-
ture. Bolts heated in water at 160 F. yielded smooth, tight rotary veneer
1/16 and 1/8 inch thick.

A temperature of 140 F. at a core diameter of 8 inches can be attained in
8-foot bolts of different diameters by heating them in water at 160 F.
according to the following schedules:

Average log diameter Heating time
Inches Hours

12 7
24 42
36 94


Veneer Cutting


Burls were common in 8 of the 10 test logs. They did not seriously inter-
fere with cutting, but sometimes rough veneer was cut in the short grain
areas around them. Interlocked grain also resulted in occasional patches of
rough cutting.

Fire scars or shake occurred in two-thirds of the logs cut. They caused
breakage at the lathe and a corresponding reduction in veneer recovery.

Knots were not a big problem in the test logs. About one-half of the test
bolts were cut almost to the core diameter before knots were encountered.
When knots were encountered, they did not seriously interfere with cutting,
nor did they degrade a large percentage of the veneer.


Report No 1766-9


-2-







In general, good-quality veneer was cut from the tupelo test bolts that
had been heated at 160' F. by using the lathe settings-' given in table 1.
Veneer cut from bolts heated at 200 F. was fuzzy and subject to "shell ii,,"
or separation of the springwood from the summerwood.


Veneer Drying


The heartwood of the swamp tupelo had an average moisture content of about
115 percent, and the remainder of the test material had an average moisture
content of about 145 percent.

Temperatures of 250 and 320 F. were satisfactory for drying tupelo veneer
in a small roller-conveyor dryer. Table 2 lists the drying schedules used.

For practical purposes, 1/16-inch veneer, both heartwood and sapwood, of
water tupelo and swamp tupelo can be dried on the same schedule. Similarly
1/8-inch sapwood veneer of both species can be dried on the same schedule.
To obtain the most favorable drying schedules, however, 1/8-inch heartwood
and 1/8-inch sapwood, and possibly 1/8-inch heartwood of the two species,
should be separated and dried on different schedules

During drying the sapwood veneer of both tupelo species sometimes developed
a dark-brown surface discoloration. This stain was shallow and could be
sanded off

The heartwood veneer, but not the sapwood veneer, sometimes buckled
slightly during drying.

Tangential shrinkage during drying to a moisture content of 2 to 4 percent
averaged 5 to 7 percent of the green width.


Veneer Yields


The total yield of dry veneer from the 10 test logs was 2 percent greater than
the log scale (International Log Rule). Approximately one-half of the veneer
was of grade 1 or face veneer when graded according to Commercial Standard
CS 35-49 for hardwood plywood. The yield from the swamp tupelo was better
in quantity and quality than that from the water tupelo.
3
-Fleischer, H. 0. Experiments in Rotary Veneer Cutting. Proc. Forest
Prod Res. Soc. 1949


Report No 1766-9


-3-






The favorable veneer recovery indicates that some tupelo veneer could
be used for such products as interior wall panels and furniture.


Other Factors


Tests on tupelo blocks indicate that good glue joints can be made with this
wood. 4

Interlocked irregular grain, common in tupelo veneer, may cause tupelo
plywood to warp more than plywood made from straight-grained species.


4


-Truax, T. R
1929.


Report No. 1766-9


I-


The Gluing of Wood. U S. Dept. of Agr. Bull. No. 1500


-4-







Table 1 --Lathe s ttting-s used to Lilt tlupcli, t cr-ri 'r


Verneer : Knife angle : Horizontal : Vertical r1ose-
thickness : nosebar opeiiiring bar opening

Inch :Degrees Minutes : Inch Inch


90 30

89 45


0 050

110


0 016

028


Table 2 --Drying schedules for tupelo veneer


Veneer :
thickness :

Inch


Heartwood or
sapwood


Temperature
in dryer


F

Water tupelo


Time in
dryer


Minutes :


SFinal mois-
:ture content


Percent


Heartwood
Sapwood
Heartwood
Sapwood

Heartwood
Sapwood
Heartwood
Sapwood


Heartwood
Sapwood
Heartwood
Sapwood

Heartwood
Sapwood
Heartwood
Sapwood


Swamp tupelo

: 320
: 320
: 250
: 250


320
320
250
250


Report No. 1766-9


1/16


1/8


1/8





1/16


: 30
: 18
: 60
: 40


320
320
250
250

320
320
250
250


: 2
S 2
S 2
S 2

: 2
: 2
: 2
S 2


-4
-4
-4
-4

-4
-4
-4
-4


1/8


1/16


S24
: 20
: 50
S 40


: 2
S 2
2
: 2


-4
-4
-4
-4


: 2-
2 -
S 2 -
2 -








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