Hand Tools

Hand Tools and Devices

Ergonomically oriented hand tool design:

Maintain a straight wrist Maintain a straight wrist

Bent Nose Pliers. Such tools permit grasping, cutting, or turning objects while the wrist remains in a relatively straight position. Hammer With Deviated Handle. The slightly bent handle maintains a straight wrist during the final impact position.

Maintain a straight wrist Maintain a straight wrist

Soldering Iron. The perpendicular bend of the head permits application of heat to a distal object while avoiding deviation of the wrist. Saws, Power Wrench, Knife. A perpendicular handle (pistol grip) maintains a straight wrist during cutting, sawing, or rotary operations such as drilling or nut tightening.

Maintain a straight wrist Provide an optimal grip span

Cylindrical Handle. A tool for rotary action on a horizontal work piece maintain the wrist in a straight position. Excessive grip span does not allow optimal application of force and imposes undue stress upon the joints.

Avoid tissue compression Protect against heat, cold, vibration extremes

Excessively thin or short handles cause small surface areas which in turn cause excessive pressure on tissues, leading to loss of local circulation. Circulation is also affected by other factors such as vibration and temperature extremes from the tool of from the immediate environment. Gloves and insulating materials are used as protective devices.

Second handle Expanding spring

An additional handle for powered tools, located near the front end, helps support a heavy tool, resistance to excessive torque, and safe placement of the tool on to the work piece.

Expanding spring on handles opens handles without stressful operator effort.

Thumb stop Gloves

A thumb stop improves stability, increases thrust force, and avoids slippage. Gloves may be unavoidably used in inclement circumstances. Compensations must be made, when gloves are used, for a diminished grip force, diminished manual dexterity, and increased bulkiness which requires large handle dimensions.

General considerations Loss of grip

The functional assignment of the hands. Hands, when used with a tool, may be classified into the holding hand and the assisting hand. Dropped Tool. Power saw dropped on foot.

Loss of grip Loss of grip

Slipping Hazard. Hand slips on to unguarded surface. Curved Knife Guard.

Loss of grip Loss of grip

Knife. Ring guard. Enclosure for one finger. Knife. Handle guard. Enclosure for all fingers.

Balanced power tool Second handle

Handle located at center of gravity. A second handle near the front of a large tool allows added control. A second handle will also aid in resisting high torque forces.

Crushing in between Accidental activation

Handle Stops. Handle stops allowing at least 2.5 cm clearance prevent crushing fingers between handles. Trigger Guard. A trigger guard prevents accidental activation of a power tool.

Accidental activation Electric saws

Guarded Foot Switch. Metal enclosure prevents inadvertent activation of the pedal switch. Exposed areas of blade covered by guard. The guard should be interlocked into the power source to prevent unauthorized removal of the guard

Rounded edges Eye protection

The edges of square or rectangular profiled handles should have at least a 5mm radius to prevent excess pressure upon tissues. In chipping and striking operations, safety glasses should at least be used. In some cases, goggles or a face shield may be even more appropriate

Cutting Mushroomed chisel head

Sharp cutting tools should be moved away