The Feed of Circular Saws may be either (1) by hand, upon a table, and generally along a guide; (2) by smooth gripping-rolls, as in the resaw; (3) by rough rolls, which hold the board down to a table while they dig into the wood and force it along; (4) by a spur-wheel, which grips it; or (5) by a carriage. The carriage (I) may have wheels which run upon a smooth track; (2) may run on stationary wheels below it; (3) may be drawn by a rope or a chain; (4) may be propelled by a pinion gearing into a rack upon the carriage; or (5) may be attached to the cross-head of a long-stroke steam-engine, which gives direct feed. Or, if the timber is long, it may be fed along rollers upon a frame; this, however, serves only for stock having practically but one plane side. The material may be fed upon a table supplied with rollers, or may be guided and fed between hori zontal rollers for ripping, or by vertical rollers for splitting and for resaw ing boards. Pressure-rolls for feeding in logs should have a powerful spring, but so flexible that the rolls may yield to a log which is thickest at the tail. Where there is a roll-feed for resawing-machines the two sets of rolls should be self-centring, so as to give equal pressure from both sides, and, no matter what its thickness, to present to the saw the centre of the strip or board. Self-feeding saw-tables should have, in line with the saw, the spur-wheel which draws the lumber, so that the mark of the wheel will be effaced, and the wheel should be slightly "cut around," so that the piece to be ripped will be pressed to the gauge.
The Carriage (i) may be on rollers or wheels, guided by a track, or (2) may have on it rails guided by rollers on the floor. The log or other wood may either rest upon or be held out bodily from its side. The carriages of long mills are best made in sections of. from 15 to 16 feet in length, con nected by rods and dowels. Having the ways on the carriage and the rolls on the floor prevents the raising of the carriage by bark or sticks and makes it run lighter and easier. It is also less difficult to keep rolls in line and on a level than on a track; they do not obstruct when the mill is being swept or when it is crossed with barrows, etc. ; they last longer, because each revolves only as the carriage passes over it, instead of continually, as when on a carriage; they are more readily replaced and are more econom ical, because those opposite the saw-frame, which are most used, can be moved to the ends. One peculiar form of a power-fed edging-machine (pl. i 1, fig 7) has a carriage attached to a rope-feed run by friction-gearing and with rollers which run upon ways on the bed.
It is well to have the gig-feed driven from the saw-arbor, so that what ever affects the speed of the saw will in the same proportion vary that of the carriage. The objections to racks and pinions for feed are the annoy ance and delay caused by breaks. To make them extra wide and heavy adds too much to the weight of the carriage. Chain-feeds neither slip nor "run bad," as belts often do, and this is in most cases an advantage.
While in some instances belt-slip relieves the machinery and prevents breakage, it is usually better to have " give " iu the frietion-feed of drive and chain than in the belt. Feed-works should have from three to five different rates of speed, according to the timber, and should run ordinarily from ;; an inch to 3 inches per revolution if there are five changes. It is well to have an extra set of cone-pulleys, to give different rates if desired. For feeding saw-tables a paper friction-feed allows the carriage to be moved fast or slow, and to be stopped and started at any point of travel. Such paper gear should be protected from snow, dirt, and moisture. There should be no friction device which is likely to start the carriage while the lugs are being put upon it.
Shot sun rapid cutting in soft woods there is employed in the Western portion of the United Sta-tes the " shot-gun " feed, which might be called a direct-acting steam-feed. The device for moving the carriage is a telescopic piston and cylinder of such length as to give a throw longer than the longest log to be sawed. The carriage-head is fas tened to the piston-rod, and Stearn is admitted to the front or to the back of the piston by a three-way cock controlled by the sawyer. The cylinders are from IS to So feet in length, and from 7 to to inches in diameter. To advance the carriage and to make the cut the sawyer admits live steam behind the piston, and to return it the valve is so shifted that live steam enters in front of the piston and the back cylinder-end exhausts. The rates of feed and return are almost incredible.
The Accessories of the Carriase are the head-blocks and uprights with their dogs, the feed-works, the gig-back, the set-works, and the log-turner.
Fences and accurate ripping there are needed guides, which must be parallel with the blade. There are also used cut-off guides for insuring that a certain quantity is cut off at one end of every piece; also mitre-gauges, to make all the angles of the mitres the same.
Set-works, or devices for advancing the log by the amount of the thick ness of the board before each cut, are composed (r) of the head-blocks with their side-supports or uprights (fii. ut,fig. 6), to hold the log firmly; (2) of the set-beam or slide, which carries the blocks and advances them all alike if so required; (3) of the setting-mechanism, by which the log and its supports are moved; (4) of the drawback, which brings the set-beam and the slides back after each cut; and (5) of the indicator or scale, which shows at a glance the distance between the saw and the uprights. There are generally three slides, to prevent the log from springing. Set-works usually consist of a shaft turning in bearings and having pinions engaged in racks fastened to the head-block side. Suitably-rigged gearing enables the blocks to be moved toward the saw any desired fraction of all inch. In improved mills the operator, by pressing his foot upon a pedal while gigging back, can raise or set back the uprights any desired amount, the actual work being done by friction devices.