Hands come in different sizes and shapes. When choosing a tool for the job picking a tool that fits your hand makes the work more efficient. A handle too large or too small will cause early fatigue because of over or under gripping. How do you decide what is the right size tool for you?
The first step is to determine the size of your hand. According to: Champney 1979: Muller Borer1981: NASA 1978; The 50th percentile hand length for male is 7.5”, female 7.2”. Grip diameter 1.9” male, 1.7” female
Take 20% of your hand size to determine your grip diameter. For example if your hand size is 7.5” multiply it by .20 for your grip size. (7.5”X.20=1.5”) so your grip diameter is 1.5”.
Once you know your grip diameter you can calculate your grip size. Simply multiply your grip diameter by 3.14 (aka Pi) for your grip size. In the example above grip diameter 1.5”X3.14=4.7”grip size
Once you know your grip diameter and grip size you can select tools that fit your hand and will be more efficient to use. For a power grip like hammering NIOSH recommends tool handle diameters between 1.25” – 2”. Use your grip diameter and find the tool handle closest to your size. Handles can be built up with tape or foam padding to increase their diameter.
See NIOSH’s link below for a booklet on how to select non-powered hand tools.