. Appleton's dictionary of machines, mechanics, engine-work, and engineering. in oil.—This process is slow, laborious, and costly ; it isalso disadvantageous, because the saws become warped, and require to be hammered up straight againby hand. The present improvement consists in tempering and straightening the saws at one operation. Thisis done by heating the saws to the proper degree, and then pressing them, with a sudden and powerful»troke, between the two surfaces of cold iron. Drop presses are employed for the purpose. The en-graving shows a pair of presses conjoined, one for long the othe
. Appleton's dictionary of machines, mechanics, engine-work, and engineering. in oil.—This process is slow, laborious, and costly ; it isalso disadvantageous, because the saws become warped, and require to be hammered up straight againby hand. The present improvement consists in tempering and straightening the saws at one operation. Thisis done by heating the saws to the proper degree, and then pressing them, with a sudden and powerful»troke, between the two surfaces of cold iron. Drop presses are employed for the purpose. The en-graving shows a pair of presses conjoined, one for long the other for circular saws. After being heatedthe saws are supported in mid air, on buttons attached to the framing at the base of the machine. Theheavy drop-weights A A, are now liberated by pulling the cords B B, and the weights fall upon their SAWS, TEMPERING AND STRAIGHTENING. 585 respective saws, drive them down, and press them upon the solid iron hase C, with tremendous forceThe sudden Mow hardens the metal by rendering it more dense, and also straightens the saw. SCALE, a line drawn upon wood, ivory, etc., and divided into parts, the lengths of which may botaken off by the compasses and transferred to paper. SCREW. Screws are of two kinds, external or male, and internal or female. The first kind consistsof a cylinder, on the surface of which is a projecting fillet, or thread, passing spirally round so as to makeequal angles with lines parallel to the axis of the cylinder. The second kind of screw consists of :i cylin-drical perforation through a solid block, bearing a spiral groove, corresponding to the male thread to?which it is adapted. The screw is usually regarded as a continuous circular wedge. The pitch of the screw is the dis-tance betwoon two contiguous centres of the same thread, and the screw will bo coarse orjine accordingto the pitch. The screw will be a right-hand or a left-hand screw, according as the wedge is woundupon tho cylinder, to tho right hand or
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Keywords: ., bookcentury1800, booksubjectmechanicalengineering, bookyear1861
