WHAT YOU SHOULD KNOW ABOUT WEIGHT SELECTION PINS
Virtually all selectorized weight machines,
whether they are universal gyms or single station strength
units, have weight selector pins that get inserted into the
weight stack and pass through the selector rod to choose the
number of weight plates to be lifted.
There are several different styles of weight pins, often called weight selector keys, that are specific to particular brands and models of strength equipment. They are not necessarily interchangeable. The manufacturers choose the style that will work safely with their gym equipment.
Some of the older weight keys were "L" shaped
and had a hump in the middle of the long section or a short
bar welded on top of the long section that was designed to
lock into a port the bottom of the cast iron weight plates
that were used on the gym. A Universal Centurion gym used that
type of weight selection key. Once locked in place, it couldn't
fall out of the weight stack because it had to be turned ninety
degrees to be extracted.
Most home gyms and commercial
strength units made today have steel weight plates that have
a straight hole through the center of each weight plate to
receive the weight selector pin. These take weight pins that
are straight round shafts about four to five inches long with
a knob or t-handle on one end. At first glance, they may not
appear to have significant differences, but the shafts come
in different lengths, different diameters, some have detent
balls and some have a magnetic knob that holds them firmly
in place against the selected weight plate.
Those locking selector pins
that have detent balls near the end come in two varieties.
One design allows the detent balls ( small spring load BB's
that lock the shaft into with weight plate ) to be depressed
just by the force needed to insert the pin into the weight
stack. The other design has a push button on the handle that
must be depressed in order to allow the detent balls to release.
Others weight pins are just
plain shafts with a knob on one end. This style offers the
poorest grip on the selector rod.
Always use the correct weight
selector pin for a particular piece of equipment. Using the
wrong weight key could cause the pin to back out during use,
allowing the weight plates to fall off the selector rod, resulting
in injury to the user. For the same reason, never use bent
or damaged pins, substitutes, like bolts or pins whose detent
balls are missing or inoperative.
When trying to find a replacement weight selection pin, you will need to know the brand and model of the gym equipment and if that is not sufficient, or if the manufacturer is no longer in business, you will need to know the diameter of the shaft, the length of the shaft, excluding the knob, the "locking space",
the distance from the knob to the detent balls, if so equipped,
and whether or not the knob is magnetic. Weight selector keys
that have magnetic knobs do not have detent pins and vice versa.
Additionally, some weight
selector pins come with a tether to keep them from getting
misplaced or used on the wrong equipment. The tethers are usually
a coil of plastic wire that look like a phone cord or a length
of steel cable. In either case, one end of the tether gets
permanently attached to the knob and the other end gets attached
to the top of the respective weight stack or one of the weight
Replacing defective weight
selector pins is cheap insurance against injury. It is a good
practice for health clubs or other commercial fitness center,
like high school weight rooms, to keep spare selector pins
on hand. A missing selector pin can keep a piece of single
station strength equipment, such as a leg curl machine or a
leg extension machine from being used and may tempt someone
into use something inappropriate in place of the proper weight