Let's explore the manufacturing process to better understand how a curling stone is manufactured, and which parts of the manufacturing process can cause weight variations.
Here, we will briefly explore how curling stones are manufactured. First, slabs of granite are pulled off from fractures in the rock. These slabs are massive, and then cut into more manageable pieces. From here, curling stone 'templates' are drawn onto the rock. Next, cylindrical 'stones' are cut from the rock for further processing. Note that each cylinder will become a curling stone.
Next, these 'stones' are refined into their final shape. This is one of the areas where curling stones can begin to develop a weight variation. Machines with strong abrasives shape one-half of the curling stone, and then stones are flipped over so the other half can be shaped. This machine only shapes the stone, and does not take the weight of the stone into consideration. Note that this process is the main contributor as to why curling stones have different weights.
After shaping, a hole is cut through the middle of the stone so that the handle may be attached to it. The handle is not attached just yet.
Then, glass beads are shot at the stone to better distribute the impact forces of the stone when it collides with other stones on the ice. Here, very small amounts of material are removed from the stone, but how much material varies. Thus, we have reached the other step that contributes to the reason why curling stones can vary in weight.
Lastly, the handle is attached to the curling stone via a thin bolt that runs the length of the channel previously cut in the stone. The handle is made of plastic, and does not add much weight to the stone. Your curling stone is now produced and ready to be used at a local curling club!
Here, we will briefly learn about the steps that transform a massive chunk of granite into many curling stones. The first step is to pry large chunks of granite off of the rock surface. The chunks must be pried rather than blast-mined because that would fracture the rock. Next, the chunks are cut into smaller pieces, and curling stone 'templates' are traced across the granite. Machines then bore into the granite and cut out curling stone 'cylinders'. Each 'cylinder' now gets cut and smoothed into its traditional curling stone appearance, and a hole is drilled through the middle of the stone. The main part of the curling stone is now produced.
Next, the top and bottom of the curling stone will pass over some sandpaper. This helps the stone maintain traction on the ice. The stone then goes into a chamber to get pitted with glass beads. This is done so that the impact of curling stones hitting each other is better distributed along the surface of the rock. Lastly, a handle is attached (possibly with an engravement), and a curling stone is produced. Keep in mind that this is a very basic summary of how curling stones are produced.