MRO Today - Hand tool ergonomic basics

Hand tool ergonomic basics

Workers come in all sizes, and use hand tools in millions of different applications. Defining exactly which tool is ergonomically correct for any single person in any single application is difficult and best handled by trained professionals, called ergonomists.

What to look for . . .
Handle areas on ratchet wrenches, pliers and other hand tools should be at least 4 inches long. If gloves are to be worn while using the tool, add half an inch to handle length.

Avoid tools with finger grips molded into the handle. These “form-fitting” contours perfectly fit only one size of hand. Larger hands may overlap the ridges, causing pressure points and eventually calluses; smaller hands will have to spread their fingers to match the grooves, significantly reducing grip strength.

On power tools, strip triggers are better than one-finger triggers, especially if the trigger will be depressed for long periods, as when using grinders and buffers. Strip triggers allow the pressure of activation to be distributed over several fingers rather than limited to the index finger.

Hand and power tool handles should be 1.25 to 1.75 inches in diameter to give maximum grip strength for hammers, drills and other tools. Precision tools, like metal engravers and die grinders that will be held between thumb and index finger (like a pencil) are more comfortable and precise with handles in the quarter- to half-inch diameter range.

Non-slip handles require less grip strength and reduce muscle fatigue. Cushioning material can also reduce vibration transfer from power tools as well as insulate flesh from the chilling effect common in air-powered tools.

Handle span on plier-type tools, in the “open” position, should be from 2 to 2.75 inches. Wide spans decrease gripping strength; narrower spans force users to adapt a less powerful, more uncomfortable grip to control narrower handles.

Reduced weight is best. While lighter weight is generally desirable in tools, heavier weight can be helpful with grinders, buffers and other power tools that operate with a high speed, circular motion. The extra mass of the heavier tool resists the tendency to jump off the work surface, reducing the amount of energy the worker must expend to control the tool. If workers must lift such bulky tools on and off a work surface, consider using an overhead lift-assist to reduce the strain of lifting the tool.

This article appeared in the June/July 1998 issue of MRO Today magazine. Copyright, 1998.