Module or Metric Gears — French system of making gears with metric measurement. Pitch diameter in millimeters divided by the number of teeth in the gear.

Pin Gear - Gear with teeth formed by pins such as the old lantern pinion. Also formed by short projecting pins or knobs and only used now in some feeding devices.

Quill Gears

Gears or pinions cut on a quill or sleeve.

Skew Gears - See Helical.

Spiral Gears

Spur gears with spiral teeth

which run together at an angle and do the work of bevel gears.

Spur Gears - Wheels or cylinders whose

shafts are parallel, having teeth across face. Teeth can be straight, helical or skew or herring bone.

Staggered Tooth Gears

Made up of two or more straight tooth spur gears, teeth set so that teeth and spaces break joints instead of presenting a continuous pull.

Worm Gears Spur gears with teeth cut on angle to be driven by a

worm. Teeth are usually cut out with a hob to fit the worm.

A

B

Sprocket Gears-Toothed wheels for chain driving. A is the regular and B is a hook tooth for running one way only.

Gear Teeth - The projections which, meshing together, transmit a positive motion. The involute curve tooth is now almost universal. The older form has a 14 degree pressure angle but some are using a shorter tooth, known as a "stub" tooth, with 20 degrees pressure angle. An involute tooth rack has straight sides to the teeth.

Gears, Pitch of

Chordal, distance from center of one tooth to center of next in a direct line.

Circular, distance from center of one tooth to center of next along the pitch line.

Diametral, number of teeth per inch of diameter.

Geneva Motion A device which gives a

positive but intermittent motion to the driven wheel but prevents its moving in either direction without the driver. The driver may have one tooth as shown or a number if desired. Also made so as to prevent a complete revolution of the driven wheel.

German Silver An alloy of copper 60 parts, zinc 20 parts, nickel

Gib

20 parts.

Gland

- A piece located alongside a sliding member to take up wear.

A cylindrical piece enveloping a stem and used in a stuffingbox to make a tight joint.

Green Sand Molds Molds made of sand that is moistened for molding and not dried out or baked before pouring.

Grinder Wheel Dresser

Grinder, Disk

A grinding machine hav

ing steel disks which are covered with
emery cloth.
Some disks have spiral
grooves to give cushions under the
emery cloth.

A tool consisting of pointed or corrugated disks of hard metal which really break or pry off small particles of the grinding wheel when held against its rapidly revolving surface.

Grinding Machine

Common types of grinding wheels made of emery, corundum, carborundum and alundum, are the disk, ring, saucer, cup and cylinder. Disk and ring wheels are used on the periphery; saucer wheels on the thin edge; cup and cylinder wheels on the end. The latter are commonly used for surface grinding.

Gripe - Local name for machine clamp.

Ground joint A joint finished by grinding the two parts together with emery and oil or by other abrasives.

- A connection between the electric circuit and the earth. Local name for a trunnion or bearing which projects from a piece as a cannon.

Half Nut - A nut which is split lengthwise. Sometimes half is used and rides on screw, in others both halves clamp around screw as in the half nut of a lathe carriage.

Hammer, Bumping or Horning - For closing seams on large cans, buckets, etc.

Hammer, Drop Hammer head or "monkey" or "drop" is raised by hand or power and falls by gravity. Sometimes raised by a board attached to top of hammer head and running between pulleys. Others use a belt.