Veneer cutting and drying properties

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Material Information

Title:
Veneer cutting and drying properties redwood
Series Title:
Report ;
Portion of title:
Redwood
Physical Description:
5, 3 p. : ; 27 cm.
Language:
English
Creator:
Forest Products Laboratory (U.S.)
Publisher:
USDA, Forest Service, Forest Products Laboratory
Place of Publication:
Madison, Wis
Publication Date:

Subjects

Subjects / Keywords:
Veneers and veneering   ( lcsh )
Lumber -- Drying   ( lcsh )
Genre:
federal government publication   ( marcgt )
non-fiction   ( marcgt )

Notes

General Note:
Caption title.
General Note:
"June 1959."

Record Information

Source Institution:
University of Florida
Rights Management:
All applicable rights reserved by the source institution and holding location.
Resource Identifier:
aleph - 029294933
oclc - 226379287
System ID:
AA00020539:00001

Full Text
I ', l II [ '( 1 `1 1 N' W I I? N I 'l ,Y t F IR 1rI -. VVICE
U. .-. II iPAR I M l '. I I W l 14 i'1 1 I w .

VENEER CUTTING ANI' DRYING IOI'L/Kl'll'J-
.. -


Redwood (Sequoia se:nCirv Lrons) ts n htru'; :.oftw'c! treoa. rcoud in n7rt-,-
western Calli i'or i.:; :..2,,, : fonl.i-'.',_.'-.',ni "- i.

The wood is moderately ll'.ht in 'o,.J:t; the rjlrin.yood of thr, annual ri.nr.'s
is considerably less denso than the LLnncrwood. Most rcdwoori iz strriht
grained and shrinks and cwolls comp.rDtiv.'oly little. The r,'dlch-bro'.n
heartwood is pleasing in appearance and hns l:i19, decay reistar.Cu, Tr.he
narrow band of sapwood is almlost vhite.

Redwood lumber is used in houses and industrial structures for such items
as siding and finish. The decay resis.tance of the heart-woorl rakec it
valuable for use in tanks, silos, coffins, onld woorl-stave 7ipc._ In recent
years, a small amLount of redwood has been mrde into plywood. Information
given in this report is based on tests made at the Forest -roJucts Labora-
tory and on observations in commercial plants.


Selection, landing, and Preparution of Test LogCs

Eotary veneer cutting and dry-ing tests were made on four los, 3 feet long.
As shown in table 1, they grew at various heights in the tree. Each lo,.
was cut into -two bolts about 4 feet long.

Sliced veneer cutting and drying tests were made on one log 21 feet lenr.
Two bolts about 8 feet long were cut from this log. One bolt wes cut into
flitches for quarter slicing and the other into flitches for flat slicing.

All of the logs were old-growth redwood that had been selected and sent
to the Laboratory through the cooperation of the Southwestern Forest and
Range Experiment Station and the Simpson Timber Company. A description of
the test logs is given in table 1.

Some characteristics and defects to be avoided when selecting redwood for
veneer logs are large end checks, Imots, flutes, flared butts, eccentric
pith, compression wopd 2 and exceptionally high moisture content (often
found in butt logs)._,2 Large checks can sometimes be eliminated when
sawing flitches.
i Originally issued May 1953.
2Botts, H. S. Redwood. American Uoods Series, Forest Service, U. S. Dept.
of Agr. Tech. Bull. 1o. 305. July 1952.
Compression Wood: Importance and Detection in Aircraft Veneer and Plywood.
Forest Products Laboratory Report No. 1586. Sept. 1943.
S-Paul, Benson H. Some Comparative Characteristics of Second-Growth and Old-
Growth Redwood, Forest Products Research Society Proceedings, Vol. 5, 19531.
Luxford, R. F., and Markwardt, L. J. The Strength and Related Properties of
Redwood. U. S. Dept. of Agr6 Tech. Bull. lJo. 305, July 192.
Report No. 1766-8 i.eviscd June 1:5,
t Maintained at Madison 5, Wisconsin in cooperation with the University of Wisconsin





Tight veneer was not produced from bolts or flitches cut at room temperature.

Moderately tight veneer was cut f-om r. dw.ood bolts ierited in hot water at
160 and lC00 F. until the tcmoperature throughout tlhe bolt had come to Lwithin
100 F. of the heating temperature. Boltr conditioned at 180 F. sometimes
developed excessive end checking. ETnd checking was not pronounced at 160 F.
Because of the large diameters of most redwood logs, and the danger of end
checking it appears advisable to hcat bolts in water at 160 F. only until
the temperature at the final cutting diameter comes to about 120 F.

Steam is preferred to water in some commercial operations because some red-
wood bolts are comparatively light in weight and difficult to submerge in
water. Heating schedules that may be used for redwood veneer bolts 8 feet
long are given in table 2.

Hard knots may not be sufficiently softened by the suggested heating schedule
to be cut without damage to the lathe knife. It may be practical to drill
or chop out knots or cut knotty portions into core veneer with a blunt lathe
knife.

The flitches were heated in hot water at 180 F. without damage. The hard
knots in the flitches were softened enough to cut easily. A temperature of
180 F. seems to be suitable for conditioning redwood flitches. Heating
schelules that may be used for redwood flitches 8 feet long are given in
table 5.


Veneer Cutting


Rotary Cutting

The lathe settings6 given in table 4 were found suitable in most cases for
producing well-cut redwood veneer from heartwood of normal moisture content
No settings were found that would permit consistent cutting of satisfactory
veneer from sapwood and "wet" heartwood. The principal difficulty was
"shelling." This is a separation of the sprinbgwood from the sunmerwood.
It is generally associated with excessive nosebar pressure on softwood species
in which there is a sharp contrast in density between the springwood and
the summerwood. When the nosebar was retracted enough to eliminate shelling,
the veneer was loose and rougi.

Commercial experience has shown that redwood veneer cut from bolts at room
temperature has deep lathe checks and is very brittle, a condition that causes
much breakage as the veneer comes from the lathe and in subsequent handling.
Veneer with less pronounced lathe checks can be cut from heated bolts. Red-
wrood veneer is brittle, however, even when cut from heated bolts.
-Fleischer, H. 0. Experiments in Rotary Veneer Cutting. Forest Products
Research Society Proceedings, vol. 5, 1949.


Report No. 1766-8


-2-






Tiie c"uoothu s,,t rO' -cm, )ro
by the orh ntel^t-,, of t.h ror.
the l,,int of contact buV,+n t e b.
ciL: *'l o I, "' '
%t tC tI
rli,t .tt thic point 'oii.....'" iw h.1 +'
coiuntoc11ekie hf :tc!o iI
*' .:i r.. -. rn< : ," "' + tl : +:h +-o l. > t
r'Ir :li. a; u e rc;ailt, "' ,.',n '. !,r
veneer a r' o r Ivol tioi :'"


*v<;l:^;*. r p o r H to '(".t'.ijr ';kc',*
t i.1 r<.'<\, i, ti 'U : ;',i ''*;, in ,y7:m .i~ M'lin t~o
ta. ; !'*; .. .. I ] + ;..*: ", +1 |;t to tji^ + ^t
"" I; !''' '>'" ; 3 i; ." t4 i1 ]] 0 --; ,*;*.;.n '.;'
i 'i

Lc "+ 1,." ]Lt t /u~t. .L ,
A : a
11!?'} D L:rolh YILt W 5}L~Jt{}I


Slicin_


The slicer L...,: -, ; -; in thi i ;
sett nj. ,-'r' suit',).' for :' ,:., tion ...
rekdwoo.i in a var -'. of thicLiesc r.


-tests -re ,-ven in table e ''.e
*,' veneer 7 .v J1rter-slic'.
I,/,) to 7/li '.c .


All of the f]I.t-:.llcei, ],. -inci veneer :.', .'- ,,; the flat-Ilice.i l) -
inch v(er.ecr 'i-. ;:.:oth enou h for u e as faces. 7 ..-' i lit-.-i.:,-'X v . that
was 1/ -inch l hi:': or :.r-,.],r w.. r .. '

The vrioorhn'ie:: of the slice., r,,i' .oc'. v<,. ,- :.. :' .L"'>.,-: r -. .
to the -I :.--! ,.t '.-.iLh ',C mife cuts z... w :-.,,". :.joth v..-.'. ..rr
usua-ll :"ro I'.ed .'K.cn ',- ..... ,I ';,' '.. t, the :,' face of the '.;'em a
line r-.aallel to ".....,:j"-I r:-" at the ,:.,. of ,:,l ..t with the .v .e w
less thLm '-'C0. Half of each sheet of :* _'::, flat-slic',A veneer as usaly
rough, because t":e r;-s L.a'l a favorable or',it.ttlo'o for orti" ar-t the cut.
In contrast, the quarter-sllced flitches were sawn so tibt all of the -:.'-cr
was cut wit'i a favorable orientation of the rr0s.

Shelling occ .:.rre, in some of the 1/10-inch ani thicker flat-eli::" veneer,
but did not occur in the lu-ter--lce' v-n':.

Most of the redwood veneer sliced thicker than 1/10 inch had dc. :U'Le chec:-.


Yen.-r -


The moisture content of the test lors variei fr'omra 7-' to "5 :r.-'':: ino the
hesart.,ool an~ from 135 to 240 percentt in the- ..-o. 'tr st' ':- -
dicate that the moisture content of red;;ooI: eart.ecod from butt 0lo,-; ,-.rj
averages about 15?', percent mand that it increases a-,rcciabl. from: t r pi-!'
outward. A.t 60 to 5K feet above the around, td., moi-t-'re content it- ut
one-half as :_-reat as at the butt r-_r is more imiform t-_-roi_'. -""out "-s
section. LL-aited co.-erc-.ia exCerience has ins iat-:. th:-t butt r z .o::-:. s-
are not desirable rpeelers because of cutting; ar 1ryi-n; proble-mz. ..i- is
true even thourj-, butt logs are frequently clear of knots. For t.e rf :-
the second lo.: in the tree often is the -reforren-d v-n-.er 1-". 7''ts at ..2.
Laboratory show that redwood with a hi.jh moisture content can be mae ir.-.
veneer of good '-.,alit, by quarter sliclr-.


Report No. 1766-3






The voneor was dried in a mechanical roller-conveyor veneer dryer in
accordance with the schedules given in table 6. Wet heartw'ood, which is
readily identifiable in the green veneer, may be dried according to the
schedule used for sapwood.

In the rotary-cut veneer a few sheets containing wet streaks developed a
slight buckle at the streak during drying. Much of the shelling that was
prominent on the green veneer was no longer visible after the veneer was
dried.

The sliced veneer dried flat and without any visible drying defects. Prong
samples cut from the 7/16-inch-thick veneer showed minor casehardening.

The veneer was dried to 2 to 15 percent moisture content. The range of
moisture content was usually smaller in thin veneer than in veneer 1/4l-inch
thick or thicker. Shrinkage of the veneer dried to 2 to 4 percent was low,
the tangential shrinkage averaging about 5 percent of the green width and
the radial shrinkage about 4 percent.


Veneer Yields


The actual yield of dry rotary-cut veneer from test bolts 1 through 4 showed
an overrun of 3 percent when compared with the International Log Rule. With-
out patching, 31 percent of this yield was of A and B grades.! With a patch
limit of five patches to a 4- by 4-foot sheet, 32 percent of the yield was
of A grade and 20 percent of B grade.

Most degrade of the rotary-cut veneer was caused by knots, roughness, and
shelling.

The log from which the flitches were sawed was of good quality. A high pro-
portion of face-grade veneer was cut from flitches that were quarter sliced.

There was a good yield of clear veneer from the flitches that were flat sliced.
The roughness of the flat-sliced veneer 1/4-inch thick and thicker would
limit its use.

Most of the degrade in the sliced veneer was caused by knots, rouhnmessand
decay.

Black Stain

Wet redwood veneer develops a black stain when it remains in prolonged contact
with iron or steel. When pronounced, this stain may be so deep that it will

7The veneer vas graded by Commercial Standards CS 122-56 for lIestern Soft-
wood Plywood.


Report No. 1766-8


-4-







not :,ii. out of the 1ir. v, r.- LI .t tin V iI I. can readily b1
r(. i,.)vr'd rrcro~i the ,,r, ;,',, ,. '. . r, I'.. It w ith t h t o(u1jic n+cit : 1 )-
ccMi'u'n is the :..:,ua, as that unod for the rumiuvul or :L',,,. rft+in in 6 ._.





!.cdvLood is one :,' the easier : .." : to l, .- ;'-c'. ';e of the sunc. I. ili'.
of the 0wood to -1u2 .1 .'L,-2 I rU carc should be taken when us.."u an all.alne
glue.-= Comvncrcial j'iro',li-tion (o' r ,*],,,d pl,":.'od in recent yersf hnas how-
ever, been limit-,,' alost ,jt*tlrtAy to the use of resin iuos.





Redwood veneer hl.vinr a highi moi7tuxre content is re;,ortt .I to be easily over-
compressed in a hot press. Core urmntly., dry veneer should be used when hot
pressing redwood plywood. A pre;o ur,- o0" 125 pcounr.; per "PuFre inch is I -
quate for gluing redwood plywood.





Limited commercial e)-rorience has indicated that, because of the of't char-
acter of the fiber, redwood is somewhat difficult to sand and that the ia-er
is inclined to fill up. The sanded panels are also subject to abrasion, so
that care must be taken in handling the finished plywood.


Exterior x2posur e


For exterior service plywood faced with quarter-sliced redwood veneer li:o
edge-grained redwood lumberz-= is rated high in resistance to checking eand
in paint integrity.

On the other hand, laboratory tests and limited commercial experience ir. li-
cate that painted redwood plywood faced with rotary-cut veneer (flat o-i:,)
and exposed to the weather is subject to face checking and c )o1in:. cti-
of house paint fail prematurely over the broad suimerwood bends.

2Downs, L. E. Bleaching Wood. Forest Products Laboratory 7erort :,o. 17C'.
July 1950.
2Truax, T. R. The Gluing of Wood. U. S. Dept. of Agr. Bull. ".o. 15CO. JLune
192 9.
L20ccurrence and Removal of Glue Stains. F.P.L. Tech. Note :o. 146. 1-.
l-ood Properties and Paint Durability. U. 3. Dcrit. of A.:'Tic. "'-i;-c. PR1. ..
629, July 1947.


Report No. 1766-8


1.-


-5-






T"'b].e l 1.---lT d4 oo J l o.1:, u;';,.: for venrlclr *,u' Ltiri I ,nL rj-,'ir. f (-r-. ,rjimcnts


Log :Approx-: Avoeragnc : Avcrie :Length:Iuriber of: Tuot.-il :Average:Average
Jo.: inmate :diameter:difference: of : rings : nxTunl.er : width : eccen-
:height :(inside : between : log :per inch :of rings,: of :tricity
above :bark at: mxiwn" :-- :--------. :midlongth :sowood of
Sthe : small :and mini- : :Max.:Min.: pith
tu. r): end) mum log :
dirmeters:

Feet : Inches : Inches : -eot : :Inches :Inches

1 : 16 :47-1/2: 3 :8-1/2: 53 : 5 : 560 : 2 : 1

2 : 70 : 45 : 2 :8-1/2 : 45 : 11: 531 2 :1-1/2

5 : 14 : 39 : 6 :8-1/2 : 66: 9: 612 : 2 :1-1/2

4 70 : 41 : 4 :9 :69 : 10: 488 2 : 3

209 :.......: 48 : 8 :21 :76 11: 805 1-1/2 : 1



Table 2.--Approximate heating schedules for attaining a temperature of
1200 F.1J at midlength, and at a diameter of 24 inches, in
redwood bolts 8 feet long

Average : Heating medium and : Required
log diameter : temperature : heating time

Feet : : Hours

5 : Steam at 2120 F. 11
4 : Steam at 212 F. : 59
5 : Steam at 212 F. : 76

5 : W'ater at 160 F. 25
4 : Water at 160 F. 76
5 : ter at 160 F. 150
1
-This temperature is not sufficient to soften knots in the inner portion of
the log for cutting with a freshly ground knife. This heating will, how-
ever, aid in cutting a good-quality face veneer from the outer defect-
free portions of the log.


Report No. 1766-8







Triblo 5.--,An roxii:intr, li t0 in- :" oii ,- ", ir tA' i i, I '.:'... '. '
li iC0 .'. In tll,- , lili r I* ,-'', ,.- 1*-:l t..L,, ,.,.t i,,r _


Avermio end : HeatUIn ,LL. _.uirod
dimcnc Ion :and ,;:;iieraturo heatli:,; time
of flitcli

Inches : :s-. s


Stuamn
Steam
Steam
Steam

Water
Water
'.-;ater
Water


2120
212
212
212

180
180
180
180


Table 4.--Lathe settings used to cut redwood veneer


Veneer : Knife :Knife: Nosebar settings : Nosebar
thickness : angle :bevel: ----------------------- : bevel
:Vertical : Horizontal
------------ ---------------:---------. -. .......-- .. ........-_-:
Inch :Degrees-Minutes: e_.: Inch : Inch Degrees

1/8 89-50 : 22 : 0.028 : 0.115 15
(0.125) :
5/16 89-50 : 22 : .032 : .175 15
(0.188)


Report No. 1766-8






Table 5.--Slicer settings used to cut redwood veneer
: : :__-C
Veneer : Knife', :Knife: FoscObnr settings : Nosebar 5_
thickness : angle :bevel: -----------------------: bevel __
:Vertical : Horizontal :--
------------ -------- -------- -- --------------- W-o
Inch :Degrees --Minutes: eg.: Inch Inch Degrees -

1/4_o 90-20 21 0.030 0.023 2
(. 025)-
B
i/40 : 90-20 : 21 : 0.050 ." 0.025 12 UI "
(0.025) : -
1/10 90-20 : 21 : .050 : .095 12
(0.100) :
1/4 90-20 21 : .050 : .240 12
(0.250) : :
7/16 90-20 : 21 : .050 : .427 12
(0.458) : :



Table 6.--Schedules used for drying redwood veneer



Veneer : Type of : Dryer : Time : Final
thickness : wood! : temperature : in moisture content
dryer
---------------------- ------S------- -----------------------
Inch : F. : Minutes Percent

1/40 : Heartwood : 250 2 : 4-8
Sapwood : 250 : 4-1/2 : 9-11

1/10 : Heartwood : 500 : 8 : 4-10
Sapwood 300 : 17 2-6

1/8 : Heartwood : 520 : 10 : 2-4
Sapwood. : 520 25 : 2-4

5/16 : Heartwood : 520 20 2-4
Sapwood 520 40 2-4

1/4 : Heartwood : 520 25 : 8-15
Sapwood : 520 50 4-12

7/16 : Heartwood : 520 58 : 6-11
Sapwrood 320 : 148 : 5-7

l"Wet" heartwood (containing 150 percent or more of moisture) dries at
approximately the same rate as sanwood.


Report To. 1766-8