.4S211 
 
 FOREST PRODUCTS LABORATORY t FOREST SERVICE 
 U. S. DEPARTMENT OF AGRICULTURE 
 
 SMALL SAWMILL IMPROVEMENT 
 
 PRACTICAL POINTERS TO FIELD AGENCIES 
 
 SAW LEAD 
 
 A considerable number of small mlll^— sajrvers do hot 
 maintain the correct lead in the saw. T4ii^^y ;: ~b'e' due-, to in- 
 accurate adjusting for lead, skewing of thehulhr-by the belt 
 pull levered through the mandrel, creep of sills from rain or 
 frost, etc. The result is a saw which dodges in the cut, heats, 
 and performs very much like one in need of hammering. 
 
 Lead is put in a circular saw to counteract the tendency 
 of the saw to cut out of the log in slabbing and to give clear- 
 ance of the back of the saw on the gig back. Normally 1/8 
 inch in 20 feet is used, or a saw 4 feet in diameter has the 
 front edge 1/40 inch closer to the track than the back edge. 
 If this saw is run in a perfectly vertical position, the back 
 edge will clip on the board side approximately l/32 inch until 
 the spreader is engaged. Additional lead increases the depth 
 of this clipping. When the front edge is l/lO inch closer to 
 the log than the back edge, the board side contacts the saw 
 about half way back and forces the blade against the log face 
 at the extreme back of the saw, thus effecting a clamp which 
 usually heats the rim and the midportion of the saw, 
 spreader is engaged the pressure may be reli< 
 itial 4 feet of feed under this clamping a^iqn- 
 enough to cause the saw to dodge even when\s£wVn 
 in cants. Apparently as the log passes th: 
 reaching the spreader, the side thrust at 
 is accompanied by a tendency of the saw to 
 volves out of the log, hence the cutting ed^ 
 slightly out of the log. As the spreader isl 
 thrust is eliminated and the cutting edge ca^fo^^- bj[£ 
 is liable to dodge from a true cut if hsating-4*««*^5ccurred. 
 
 Of the several methods used to measure lead, the follow- 
 ing is recommended for simplicity and accuracy: Stretch a 
 string or fine wire over the track to extend about 6 feet each 
 side of the mandrel, being careful that it is exactly in line 
 with the part of the guide rail that controls carriage align- 
 ment -- the top of the V in this type or the inside edge where 
 flat-topped rails are used. Remove the saw, and clamp the end 
 of an edging 5-1/2 feet in length between the collars. Use a 
 short piece of the edging on the opposite side of the mandrel 
 so that the collars have contact at opposite sides of the 
 
 Mimeo. No. R899-20 
 
 tMaintained at Madison, Wisconsin in cooperation with the University of Wisconsin 
 
 *See outline in Small Sawmill Improvement Working Plan, March 1930, for explanation of indexing system proposed 
 
3 1262 08926 9764 
 
 mandrel. Turn the stick down until the free end is suspended 
 opposite the track by turning the mandrel pulley; do not try 
 to turn by pulling the stick. Measure the distance from the 
 stick to the string, marking the point on the stick from which 
 the measurement is taken. Turn the stick over, by turning the 
 pulley, until the undamped end is again opposite the rail, 
 and measure from the marked point to the string. The distance 
 at the deck end should be l/l6 inch less than at the opposite 
 position. Adjust to the required position by slewing the 
 mandrel, in mills provided with adjusting screws, or by slew- 
 ing the husk when such mechanism is lacking. In slewing the 
 mandrel before adjusting the box nearest the saw, relieve the 
 other boxes so as not to strain the mandrel. 
 
 The use of lag screws to anchor the husk to the mudsills is not 
 recommended. Bolts from the tie plates or husk should extend 
 through the mudsills and heavy washers should be used at each 
 end of the bolt. A plate or block on the top of each mudsill 
 fixed between the track and husk adds rigidity. 
 
 Contributed by 
 C. J. Telford, 
 Small-Mill Specialist 
 April 1944. 
 
 Mimeo. No. R899-20 
 
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