Counterweight plate is a flat weight usually made of cast iron, which can be used in combination with barbells or dumbbells to produce barbells with ideal total weight for physical exercise.
There are two general categories: "standard" plates, with a core hole of approximately 1 inch (25 mm), and "Olympic" plates for mounting on the 2 inch (50 mm) sleeve of the Olympic barbell. Although there are standard barbells and Olympic dumbbells, the standard board is usually paired with adjustable dumbbells and Olympic boards with full-size barbells.
The counterweight plate can have a portable hole (called a "grip plate"), or it can be a solid disc (especially for racing). Noncompetitive plates usually have variable diameter and width, for example, on the adjustable dumbbells shown on the right, heavier plates are usually larger in diameter, thickness, or both. Counterweights are usually round, although there are 12 sides and other polygon forms. [5] Most plates are coated with enamel or hammer to prevent corrosion. The more expensive varieties can be chrome, rubber or plastic.
The weight range of the plate is very wide. Standard (1-inch center hole) plates usually have a face value of 2.5, 5, 10, and 25 pounds, while rare are 1.25, 7.5, 12.5, 50, and 100 pound plates. [8] The common kilogram dishes are 1.25, 2.5, 5, 10, 15 and 20 kg, while the rare ones are 0.5, 7.5 and 25 kg.
The average Olympic (2-inch center hole) plate has a face value of 2.5, 5, 10, 25, 35, and 45 pounds, while the rare 1.25 and 100 pound discs. Kilogram plates are 1.25, 2.5, 5, 10, 15, 20, and 25 kg in size, while 0.25, 0.5, and 50 kg discs are less common.
Bumper plates are usually 10, 15, 25, 35, 45, and 55 pounds, or 5, 10, 15, 20, and 25 pounds in kilograms.
A small number of companies sell "fractional" weight plates weighing no more than 1 pound (0.5 kg). These make great "micro load" can bring very small power increment to senior strength students. Another option for microloads is to use a set of washers with one or two inch center holes.
The nominal weight of a low-cost plate may vary widely. The difference of 2% or 3% is not uncommon, and some manufacturers' plates often show 10% or more above or below (a 45 pound plate may weigh as little as 40 pounds, or as much as 50 pounds). Tom lincir, founder of ivanko barbell, encountered a 45 pound plate weighing 38 or 59 pounds.
Plates can be weighed and marked with true weight on the device (using paint pens or other permanent markers).
Calibration plates are available from high-end manufacturers; many advertised that the accuracy of these plates was within 10 grams (0.02 pounds) of the marked weight, a tolerance set by the International Weightlifting Federation for plates used in competitions.
Standard (1-inch hole) "vinyl" boards are often sold in pairs with dumbbells or barbells as a low-cost option for recreational strength training. These plates are made of cement or sand coated with PVC sheath. The cement will decompose over time and leak out of the hole in the sheath, and the density of the weight is less than that of iron, so there is less coordination on the given reinforcement.
