Diamond-point chisel to Digest.

Diamond-point chisel. (Mach.) Simi­lar to a cape chisel except that its point is shaped for the cutting of sharp-bottomed grooves.
Diamond~point tool. (Wood Patmkg.) A to.ol having two cutting edges inclined to each other and meeting at an acute angle. One face of the tool is flat, the other is beveled from the cutting edges.
Diamond wheel-dresser. (Shopwk.) A mounted industrial diamond used for tuning up a grinding wheel.
Diaper. (Art.) A form of surface deco­ration, either in squares or lo~nges. in which some design or ornament usually is repeated.
Diaphragm. (Elec.) A disk or sheet of metal or other substance flexible enough to permit vibration. (Photog.) A movable device which controls the amount of light enter­ing a camera lens.
Die. (Mech.) (I) An internal screw used for cutting an outside thread. (2) A formed piece used in stamp­ing out parts in quantity.
Die casting. (Mech.) A very smooth and accurate casting made by pour­ing molten metal or composition, under pressure, into a metal mold or die.

Diecasting metal. (Metal.) Light coloured alloys of aluminium, lead, zinc, or copper base of widely varying composition depending on the use to which they are to be put. For automobile hardware, an alloy of 90 per cent aluminium, 4 per cent copper, 4 per cent nickel, and 2 per cent silicon is much used.
Die chaser. (Mach.) A threaded sec­tion of a screw-cutting die.
Die clearance. Space allowed between punch and die to pro­vide for the thickness of metal being worked on.
Die forging. (Forg.) The making of forgings in dies, in quantity work, to secure a better product at re­duced cost.
Diehead. (Mach.) The device which carries the threading dies in a screw-cutting machine.
Dielectric. (Elec.) Any nonconduc­tor which intervenes between two conductors and permits electro­static attraction and repulsion to take place across it. A nonconduc­tor in general.
Dielectric constant. (Elec.) The ratio of the conductivity of a di­electric for electrostatic lines of force to that of air.
Dielectric strength. (Elec.) Voltage gradient at which a continuous

Diesel engine. An internal-combustion engine of high efficiency, in which a high temperature is obtained through compression; the oil is ignited by the heat thus developed.
Die sinker. One who makes, or cuts dies.
Die stamping. (Metalwk.) A piece, usually of sheet metal, cut out or formed by a die. (Print.) A process or printing raised letlers either with or without colour.
Die stock. (Mach.) A lever or wrench used in operating threading dies by hand.
Dietetics. The branch of hygiene which treats diet and dieting.
Differential. (Mech. Engill.) Relating to a construction in which a move­ment is obtained by a difference in two motions in the same direction, as in the rear axle of an automobile.
Differential block. A chain tackle which depends primarily on a pul­ley of two diameters fitled with lugs which fit the links of a chain; the larger diameter winds the chain in as the smaller diameter pays it out.
Differential calculus. (Math.) That part of calculus in which the func­tion is given and it is required to find its differential or derivative. This technique is applied to problems of time, rate, acceleration, maxima and minima, etc.
Differential gearing. (Auto. Mech.) That system of gearing which per­
. mits one rear wheel of an automo­bile to move independently of the other; thus avoiding excessive tire wear and strain on mechanical parts.
Differential heating. (Metal.) Heat­ing an article so that various parts reach different temperatures in order that different properties will be produced on cooling.
Differential indexing. (Mach.) In dif­ferential indexing on the milling machine the index plate is con­nected to the spindle on which the work is mounted, through change gears. Both plate and gears, there­fore, revolve to produce the proper indexing.
Differential motor. (Elec.) A motor with a compound-wound field, in which the series and shunt coils oppose each other.
Differentiate. To constitute a diffe­rence between; a mark distinguish­ing from.
Diffuse. To cause to spread, perme­ate, or circulate throughout.
Diffused. Applied to semi-conductor component in which the active junctions have been created by a process of diffusion of one substance into another.
Digest. (Plast.) To soften a substance by heat and moisture, sometimes under pressure. To remove certain substances from vegetable
products.
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