Knife Switches

 

 

What is a Knife Switch used for?

 

A knife switch is a form of switch- all or nothing- On and off, and for this reason it is often used as a master switch or main-disconnect. the single pole single throw has one switch blade, not the cutlery variety, which vaguely resembles a knife, hence the name, when the handle is down and touching the contacts the switch is closed and the power is on. Lifting the handle disconnects the circuit. They are used for instructional purposes in shop and science classes. A Double Pole, Double Throw knife switch- or circuit breaker, is in everyday use and has defied obsolescence since the days of Edison. The DPDT is used on master switches and controls two circuits, usually with a center off position. They were used as aerial switches- to select transmit or receive in early shortwave and ham sets. they are very much around and have been nicknamed (Mousetraps) from their shape and outline. very much in use and I have a l907 electrical handbook that illustrates them some have shunts or condensers across the base ( wood or plastic, usually) of the switch. this has various uses but keeps the currents at a safe value in radio use. Knife switches are becoming more rare, finding use largely in science experiments where the position of the switch may be plainly seen in demonstration. The knife switch is extremely simple in construction and use.

Abbreviations:

S = Single 

D = Double

P = Pole

T = Throw

i.e: SPDT would be Single Pole, Double Throw 

Here a knife switch is being used to turn 

the motor on the paddle boat on/off. 

Knife Switch, SPST

Product Code: SPST

Knife switch, single pole single throw, with screw type binding posts. and 2 screw holes for mounting on a board. Good for experiments and science projects.

High quality, deluxe version. Screw type binding posts may be both black or one black, one red.

Weight = 25g

Measurements:

Base Alone: Length = 74mm  Width = 35mm  Height = 10mm

Length with Pole = 98mm   Height with Pole = 33mm

Knife Switch, SPDT

Product Code: SPDT

Knife switch, single pole double throw, with screw type binding posts. and 2 screw holes for mounting on a board.

Good for experiments and science projects. High quality, Deluxe version.

Weight = 41.5g

Measurements:

Base Alone:  Length = 74mm  Width = 35mm  Height = 10mm

Length with Pole = 105mm   Height with Pole = 29mm

Knife Switch, DPST

Product Code: DPST

This Knife Switch is double pole, single throw with screw type binding posts. 3 screw holes for mounting on a board. Good for experiments and science projects. High quality, Deluxe version.

Weight = 46g 

Measurements: 

Base Alone:  Length = 74mm  Width = 50mm   Height= 10mm

Length with Pole = 100mm   Height with Pole = 29mm

Knife Switch, DPDT

Product Code: DPDT

This Knife Switch is double pole, double throw with screw type binding posts. 3 screw holes for mounting on a board. Good for experiments and science projects. High quality, Deluxe version.

Weight = 73g

Measurements:

Base Alone:  Length = 74mm  Width = 52mm  Height = 10mm

Length with Pole = 106mm  Height with Pole 29mm

Simple Switch (Knife Switch)

Product Code: KSWITCH

This small size simple switch is used by students to make electrical circuits. This quality knife switch is perfect for science projects and electronic experimentation. With its pre-drilled holes, it can easily be mounted on any wooden surface or project board. Because of the open structure of the switch, you can visually determine if the circuit is closed or open.

Weight = 9.3g

Measurements: 

Base Alone:  Length = 36mm  Width = 24mm  Height = 7mm

Length with Pole = 50mm   Height with Pole = 23mm