Chapter H: H Hz

H

H

Symbol for the element hydrogen.

hacking knife

A knife for cutting heavy sheet metal. The cutting blade has a wide back which can be struck with a hammer.

hacksaw blade

A very hard, narrow saw blade made of hardened and tempered carbon tool steel, high speed steel, or high speed tungsten or molybdenum alloy steel. The length of the blade is determined by the distance between the holes that are used to mount the blade in the hand frame or power saw. Blades having teeth of various sizes are used, depending on the kind of metal being cut. The number of teeth per inch, called the pitch, normally range from 14 to 32 for a hand hack saw frame, and the teeth have a standard set. The set comes from making the blade with the alternate teeth bent slightly outward. Fourteen pitch blades are normally used for mild material and large sections and 32 pitch blades are used for fine stock, tool steel, brass and copper tubing, thin sheet metal, etc. Eighteen pitch blades are commonly used on all kinds of metal. Coarse, ten-pitch blades can only be used in a power saw. Blades are generally mounted in the frame with the teeth pointed forward (away from the handle), so as to cut on the forward stroke only. The blade is held in square-sectioned blade holders and is pulled taut in the frame so that the blade is under sufficient tension to keep it...