Machining Ponderosa Pine and Douglas-Fir

VOL. X. N O. 1 • FOREST PRODUCTS JOUR NAL JANUARY, 1960

1 • • • EFFECT OF GROWTH RATE AND DENSITY

Fig. 2.-Turning samples of panderoso pine graded I , 2, and 3 Fig. 3.-Boring and mortisi ng samples af ponderaso pine, showing for smoothness of cut. quality of grades 1 to 4. Note the relationship between number of growth rings and smoothness of cut.

E. M. DAVIS Technologist, Forest Products Labora tory', Forest Service, U. S. Department of Agriculture

LEAR WOOD O F ANY SPECIES may For the more exacting uses, Since the two sets of material are prac C vary widely in its properties, de tica lly the same in specific gravity but pending upon such things as density, growth rate and specific vary widely in number of rings per rate of g rowth, and grain peculiarities. gravity have a significant inch, the d ifference· in results can be To a large degree, the intended use attributed almost wholly to the ring determines the essential properties that effect on the machining factor. are required. Most fabricated products, such as fixtures, flooring, furniture, properties of ponderosa pine In the case of planing, the d irection and millwork requi re lumber with and Douglas-fir, with of cut was parallel to the grain; in good machining properties. Altogether, order to show any significant differ these p roducts consume yearly over 5 the number of rings per inch ence in the results obtained, it was billion board feet of lumber, which is being especially important. finall}' necessary to do part of the plan evenly divided between hardwoods and ing with sharp knives and part with softwoods. dull knives. The remaining operations This paper deals with the relation cut across the grain rather than parallel T!te Aul/tor: " Jeff" Davis holds a BS from Iowa State ships between the machining proper to it, and are therefore more severe College and an MF from the ties of ponderosa pine and Douglas tests than planing. In all four instances University of \Xlisconsin. He served with the Edison Labo fir and their density and g rowth rate. the slow-grown material machined bet r>tories, Long-Bell lumber ter than the fast-grown material. Co. • and the \Xlar Production Test Results Board before joining the U. S. Forest Products Labo- T able 1 summarizes the results of 1 A contributed paper received March 1 9~9 . ratory. 'l Maintained at M~dison, \'\/is. in cooperation machining tests on ponderosa pine. with the University of Wl isconsin. FOREST PRODUCTS JO U RNAL Table 1.-- Percent. or detect.- free nn;>les in ma.chining tests ot ____, ) .--Specific gravity and growth rate or r..at.arhl f or machining tests eondorosa pine

Machining operation : fa.st-grown! vood : Slov-gro~ vood Species Source !';;.eci fie crarl t; Rings per inch ------: ------: ------or : ------: ------Percent r-.at.erial ~ ------: ------: ------: ------: ------: ------: ------: ------Planing, shsry lmi ves . ... : 01 9L : : : : : t onderosa yine: Challenge , CallC.: O. Jl : 0.55 : c . 1.2 : 20 8 l'laning, dull knives ..... : 65 85 : Do . ~ S tock~ . J6 . ~L . LL : 10 LO 2S Shaping, end grain ...... : 15 89 .. Do . :Medford, Urec . .L6 .ss . Lo : 6 20 l S !urning•.•• •. . .••...•..•• : c J6 .. : B<>ring ••.•..• . •••••. . • • .. : JB Douglas- fir ~ Oa\crid Ge, Oree . . JS .63 .so : Lo 16 : : : 1 Mortioi ng •..•...••.•....• : 0 11 Do . : ...... do ...... : .LS : 9 : : Uo . ~ ...... do ...... li : .S2 : 21 l ,her96e syecific gravity 0 . ~ 2; average ntmher of rins:s per inch 6 . : : Do. ~ •.•.• ,oo ....•.•2 : . ~s : 12 ZAverage s;"'d n c ,!ravt ty O . ll ~ i average mi=.ber or rings per inch 2fl . : : : Do . : •••••• do ...... ~ : .ss : 19

1 Table 2. - - fercentai;i! of grades 1 and 2 sanples in IQOlchining tests !!ased on veight when oven dry and volume when green. of Dou s-fir 2 '""'5tock lun.ber f'rori un'

f'laning, sharp kni~s .... : LS 7S 2rieavier group . Shaping, end grain ...... : SS 100 rurnlng ...... : 22 33 ing operation. The direction of cut in Boring ...... : 20 8S planing is parallel to the grain, which Mortising •.•.. •. . •• . •.... : 30 50 makes it a less severe test than opera tions that cut across the g rain. ~ea.n Number or rings per inch 9; r:ea..'l spe cific gravi ty 0 . 48 . 2 rl:ean nW'lber of rings ,..er inch 21; 111ean sveci!ic gravity 0 .$2 . P onderosa Pine: T able 4 compares the results when planing fast·grown and slow-grown ponderosa p ine of about equal density, first with sharp The results of machining tests on the v1cm1ty of Oakridge, Oreg. The knives and then with dull ones. With Douglas-fi r are summarized in T able samples were selected to represent the sharp knives, the difference in results 2. D ouglas-fir does not machine as well ranges in density and in number of was too small to be significant; dull as ponderosa pine, and relatively few growth rings per inch of the test mate knives, however, made the test more defect-free samples were obtained. rial. The mean specific gravity of all severe. The slow·grown pine made a Comparisons were therefore based on samples was 0.50, as compared with mud1 better showing, producing 86 percentages of grade 1 (defect-free) the 0.48 value for this species. percent of defect-free samples as com samples and grade 2 samples (those T o determine the effect of growth pared to 65 percent for the fast-grown only slight ly defective) in order to rate upon machining properties, the material. show relationships more plainly. In samples were divided into fast-grown Douglas-fir, the two lots are somewhat and slow-grown groups and tested D ouglas-Fir: In D ouglas-fir, the further apart in mean specific gravity separately. The effect of specific grav effect of growth rate upon planing was than in ponderosa pine. Although ity upon machining properties was also guite evident even with sharp knives. Tables 1 and 2 are not directly com tested with light and heavy samples of The s l ow ~r-grown wood, witn a mean parable, the trends are parallel; that is, Douglas-fir. Results of tests are given of 21 rings per inch, produced SO per in all the operations the slow-grown in Table 3. cent more good samples than the faster material machined better than fast grown portion that had a mean of 9 grown material of approximately the Test Procedure rings per inch. Densities of both same specific g ravity. The tests included planing, shaping, groups were relatively close together turning, boring, and mortising. The with 0.48 for the fast·grown portion Test Material procedures followed, which have been and 0.52 for th e slow-grown g roup. in use at the Forest Products Labora Among the group separated on the Pon derosa Pine: T hree different tory for some time, are described in basis of specific gravity, the heavier sources of ponderosa p ine were repre detail in Laboratory Report No. 2108, samples (mean specific gravity of sented. As shown in T able 3, they dif " Development of Methods for Evalu. 0. SS) gave 16 percent more good fered sig nificantly in specific gravity ating the Machining Properties of samples than the I ighter ones (mean and more especia lly in rate of growth. \'{food and Wood-Base Materials." specific gravity of 0.45). It is gues T wo earlier Forest Products Labora Samples of both ponderosa pine and tionable how much of this difference is tory investigations gave mean specific D ouglas-fir were graded after each ma due to variation in density alone, be gravities of 0.41 and 0.42 for a large chining operation on a 5-gracle sca le cause the heavy specimens averaged 19 number of samples. On this basis, the based on smoothness of cut. G rade 1 rings per inch, as compared with 12 fast-grown material from Challenge, represented perfect, or practically per rings for the lighter lot. Calif., was about average specific grav fect, mach ine work, and grade S rep ity; the stock material was slig htly resented a reject quality. These grades Shaping above average; and the samples from are ill ustrated in Figures 1, 2, and 3. Medford, Oreg., we re substantially Ponderosa Pine: Side-grain cuts failed to reveal significant differences above average. Planing in ponderosa p ine. With end-grain Doug las Fir: All Douglas-fir test Next to sawing, planing is the com cuts, which are a more severe test, the material came from 28 trees grown in monest and most important workwork- yield of high-grade samples increased

2 JANUARY, 1960 - rapidly as the number of rings per inch and sharp edges that might not count increased, as shown in Table 5. Specific in many sorts of turnings. gravity alone appeared to have a minor infl uence on results. The grades re Boring and Mortising ferred to in Table 5 are illustrated in Ponderosa Pine: Flat-grained sam Figure 1. ples were used in tests of the boring Douglas-Fir: Although the aver and mortising p roperties of ponderosa age quality of machined surfaces was pine; therefore the direction of cut was poorer in Douglas-fir than in ponder perpendicular to the rings. In both of osa pine, the trends were similar. these operations, the lot that was Again the influence of density appears slightly heavier but slower grown gave to be small and effect of growth rate to much better results than the lighter, be important. The slow-grown samples faster grown material. These two lots yielded twice as many good surfaces of test material were of so nearly the as those from fast-grown wood. same density that the d ifference in re sults can be attributed almost enti rely Turning to differences in rate of growth. T able 7 ~om pa res the results of tests Pooderosa Pine: T urning typ ically on the boring and mortising properties involves cuts at various angles to the of the two lots of samples. Figure 3 grain rather than parallel to it. In illustrates the quality of the different turning, as in shaping, the slow-grown grades as well as the consistent rela pine gave much better results than the tionship that was found between rate fast-grown material, as shown in Table of g rowth and smoothness of cut. 6. Figure 2 illustrates the pattern used and the turning grades referred to in D ouglas-Fir: T he s l ow-grown Table 6. The turnings in ead1 of these Doug las-fir with a mean of 21 rings three grades were weighed collectively, per inch and a specific gravity of 0.52 and they showed a defin ite trend gave four times as many grade 1 and 2 Hilll 111111111 l111111111111111 ll toward better work at the higher spe holes in boring as d id the fast-grown • ll~ '21 cific gravities. T aking the average Doug las-fi r with 9 rings per inch and weight of turnings of the poorest a mean specific gravity of 0.48. In grade (No. 3) as a base of 100, the mortising, the diffe rence in favor of Fig. 1.-End-grain cuts in ponderosa pine, No. 2 turnings averaged 111, and the the slow-grown materia l, though Jess showi ng samples grade d 1 to 4 on the bosis No. 1 turnings averaged 125. pronounced, was still substantial. of machinability. Doug las-Fir: A lthough the slow grown wood turned noticeably better Conclusium pie of ponderosa pine or Douglas-fir than the fast-grown, rate of growth Although the amount of test mate affect its machining properties to a de did not affect results nearly as much rial was not large enough to exclude gree that is highly significant, at least in Douglas- fir as in ponderosa pine. all effects of interrelationships, the fol for the more exacting uses. Within the range covered by these lowing conclusions are believed to be In ponderosa pine and Douglas-fir, samples at least, density had little ef justified: the number of rings per inch has more fect on the results. The weakness of Both the number of rings per ind1 effect on the machi ning properties than Douglas-fi r in this test was in detail and the specific gravity of a given sam- does specific gravity.

T•ble L.--?19llln,,, proyert.ies o!' ponderosa pine scu:plP.s from di.CCerent sources Table 6 . --rurninu properties o f oonrtero!I R~ froa diCfer'!nt sources

: Yean : KeM : Grade ot turnings Source :Condi.tion: ¥..ean : ¥.ean :Defect-:Chlpped: Fuz.zy : Raised Source of : of :.specl.Cic: nu.-.ber : f ree : grain : grain : grain or : speci fie: nu&ber : ------~terial : gra7ity,of rincs: 'lo. l : llo. 2 : 'lo. ) : No . L ..aterial : 'mlves :gravity :of rings: :per inch: : : ------: ------:------: ------·:------: ------: : : - : :Percent.:~:Fercent : fercent. ------: ------: ------: Pucent : ~ : ~ : Percent. : : : : : : : Challenae, Calif.: Sharp o. L2 8 91 9 0 0 Challenge , 1;a1 1 r , : 0. 1.2 0 18 82 0

Stoc~l : 3harp . LL 28 9L 6 0 : 0 Medford, Oree: . .LS JS )0 10 0 0

3toc~ . L ~ 28 J6 0 Challen,:e, Cali r. : Dull .L2 8 65 22 l) 0

Stockl : Dull .LL 28 86 6 0 : 8 !stock lw:.ber rron unknown .. curce .

Table 7 . .. .. Corln1: and mortising properties of ponderosa plne f1"ott1 tock lumber f ro• unknown source. ls d1 fferent sources

--:our co : ~ean Mean : Grade of holes and nortisea of :s,ecific n~~r : ------Table 5 . -Shapin~ prorert.ies of ponderosa pine tro::a dlrrerent sources naterial :grnity of rincs: No . l : llo. 2 No . J No . L

Source : Mean : Mean Grades in end-grain shaping or : apeciCic: nu.r:iber : ------EOHI OO material : gr avity: of r ings: No . l : No . 2 ' No . ) : No . L : per inch: ------: ------: ------:------: ------:------:------Challengf', ~oal 1 r.: (\ . !.:~ 6) ) 1 :Percent :f crcent :Percent. ;~ Stock! .l l 20 ) ~ Ll 21 () Challenge, Calif. 0. 42 8 19 6L 9 t .Otu'! ~l' ir. Mtdford, Oreg. . ~8 15 so LO 10 0 i..nallenc:e , ..: .. ur.: .U2 8 0 l ) 39 f, 8

Stoc~ .w. 28 89 11 0 0 ;;) toct:l . bb 2~ 11 b7 b2 0

1st.ock lu-e.ber rrom unknown source. 1st-o~"' l w..b~ r frOA unknolo1l SOlU' C'e .

fORES T PR ODUCTS J OU R NAL 3