I I 
 
 •Us riation and al I 
 
 FOREST PRODUCTS LABORATORY I FCREST SI 
 U. S. DEPARTMENT OF AGRICULTURE 
 
 SMALL SAWMILL IMPROVEMENT 
 
 PRACTICAL POINTERS TO FIELD AGENCIES 
 
 FRQl. VARIATICi: 177 QA7I777; FRECISI 377 
 
 
 sustained "by small mills results IV :• #&!L"y3RY 
 
 A major lot 
 cut lumber. Tiie produi 
 
 stiffor sales resistance than that from the more accurately cutting b- 
 mills. A more obscure loss is the excessive manufacturing waste that 
 results from inaccurate cutting. 
 
 Studies* by the Forest Products Laboratory indicate that 
 portable-mill operator, in sawing for thj^ckness, cuts only about 20 percent 
 of the boards within 1/32 inch of the thickness he sets for. The r . .■ ining 
 80 percent may van- in thickness from as much as 8/32 inch on the \ - ide 
 to as much as 3/32 inch on the thick side. (Jig. lj upper pile.) Conse- 
 quently the operator must set to cut most boards too thick so that th . 
 will not be too many that arc excessively thin. Each 1/32 inch thus added 
 to avoid thin boards, reduces the possible cut exactly as if the sac 
 were increased 1/32 inch. This waste can be minimized oy keeping the 
 Lpment in good condition. 
 
 main causes for inac : lumber are: (1) Faulty 
 
 condition of the saw, such as uneven filing of saw teeth, excessive or unev 
 
 ■ , dull teeth on one side, unequal tension; (2) worn bearings in mandril, 
 carriage wheels, and particularly in the set-works; (3) poor installation of 
 carriage and saw, chips between log and headblock or on track; (4) careless 
 setting, inadequate manipulation of dog:'., miscalculation Ltin, in T 
 last board cut from each log being either undersized or oversized; (3) 
 frozen timber, unusual stresses in wood. These will not be el; rated upon 
 now. 
 
 By adjusting the saw, carriage, and track for the most accur 
 work possible, sales advantage due to more -ir--n- t ]•- - ■ rii 1 slobtained. 
 To get the second advantage, an increased y 
 thinner. Note that two steps are os: L: 
 - icy and (2) setting for thinner lumberi 
 not be increased because the effect of truinJ 
 closer to the intended 1/32-inch group and 
 extremely thick and thin boards. . 1, 
 
 accuracy shows in middle pile. If 28/32 inc 1 i taken PlA~ida\ 
 dry thickness th ill produce the softwood \t p-.fi -^ . - ■ U » ; »)> V- 9* 3,'°',^ ^} - 
 can be moved either by 1/32-inch intervals, i I '_ i' i ■ """ 1/lb 
 inc l, placing a 1/lb-inch leaf in the back stop so that the entire cut 
 is j/y<l inch thinner. Lower ile. Tlie consequent i:v in yield 
 4-1/2 percent.) 
 
 
 t Maintained at Madison. Wisconsin in cooperation with the University of Wisconsin. 
 
 See outline in Small Sawmill Improvement Working Plan, March 1930, for explanation of indexin 
 
 g system proposed 
 

The ideal sotting does not attempt to qualify 
 rather to set for thinner boards until a point is r 
 from increasing yield balanced by the loss from . 
 
 reached when a 1-1/2 p i • it increas* in rejects results : : 
 setting 1/32 inch thinner, hence continue to set thinner by 1/32-inch 
 intervals until the number of thin rejects increases by than 1-1/2 
 percent over the previous setting* The ideal adjustment is 1/32 inch 
 thicker '.. is settin. . 
 
 Thin rejects for each sotting can be determined by measuring to 
 the nearest 1/32 inch at the thinnest place, exclusive of th 1 r dnal foot, 
 mndred fr sawed, nominally 4/4-inch boards. 7 r of boards 
 .- than the thickness required to meet standar . :ifications plus an 
 allowance for shrinkage in drying is the total percent of thin rejects. 
 Consequently when the rejects fro:;, setting 1/32 inch thinner increase two 
 or more boards pur hundred set for th ct thicker 1/32 inch. 
 
 SOFTWOODS 
 
 An allowance of 1/32 inch: must be made for shrin] a of inch 
 softwood lumber from a green to the equivalent of a thoroughly air-dry 
 condition. Moreover, most softwood grading rules ad .1' percent 23/32- 
 inch rough dry lumber; hence, the 23/32-inch green lumber group is the 
 thinnest to qualify. A mill cutting lumbei as in the upper pile in Figure 
 1 should therefore sot 1/32 inch thinner, since the 1-1/2 percent increased 
 yield is but partly offset by the 1 percent increase in rejects. For a mill 
 grouping its cut as in the lower pile in Figure 1, a 1/32 inch thinner set, 
 although gaining the 1-1/2 percent increased yield, results in an increase 
 of 3 percent in rejects. 
 
 HARDWOODS 
 
 The set-up for hardwood differs in that 2/32 inch must be 
 allowed for shrinkage (3/32 for beech and hickory) and I . Li i r ile base 
 
 is 32/32 inch for rough dry lumber so that j^/'j>P. inch i. ; thinnest green 
 board to qualify. A mill grouping its out as in the pile i: .re 1 
 
 for hardwoods should set four places thicker, so that th< ; rcent shown 
 in the 30/32-inch group would be in the 34/32-inch group. 
 
 Contributed yj C. J. Telf< 
 Small Mill Specialist, 
 Forest Products Laboratory, 
 October k, 1 
 
 R899-2 
 
> 
 
/ M 
 
 Before o.dj 
 
 accurc 1 tting 
 
 -■ 
 
 30 JT 
 
 ! 
 
 ■ t to 
 optirau-a thick 
 
 Tlii ' . (Thirty-seconds of an inc 
 
 1. — I: 
 
 l"ui a cut at 
 
 
.■Stiff