There may be several sizes you have to take into consideration when choosing a sprue cutter. These could include the total length or overall size, the jaw thickness, jaw width, and jaw length. All of these sizes could have a bearing on which sprue cutter is the best for your needs.
The total length of a sprue cutter is the length from the tip of the jaws to the base of the handle. This is the size of the sprue cutter that will be stated by a manufacturer.
Sprue cutters designed for cutting soft materials can range in total length from approximately 120mm (4¾”) to 155mm (6¼”), whereas cutters with a compound lever action have a total length ranging from approximately 200mm (8″) to 255mm (10″).
Sprue cutters with a shorter total length will be better suited to working on tightly packed sprues and with small, delicate parts. However, the shorter length means less leverage and so less cutting force is applied at the jaws of these sprue cutters, making them unsuitable for use with thicker or harder materials.
Small sprue cutters will often be designed to provide comfortable use with just the one hand.
Larger sprue cutters, often with a compound lever action, will be designed for use with two hands. Their greater length increases the leverage and therefore the cutting force they can apply. This makes them better suited to cutting thicker and harder materials. However, their greater size makes them unwieldy. This coupled with the two-handed operation makes them unsuitable for delicate work or removing parts from a tightly packed sprue.
Longer jaws have a greater reach for getting in and removing parts from a tightly packed sprue. However, the cutting ability of the jaws is vastly reduced further away from the jaws’ pivot point. So short jaws will have more strength and cutting ability at the tips of their jaws. Small sprue cutters have a jaw length that ranges from roughly 8mm (5/16″) to 16mm (5/8″). There is less variation in the jaw length of larger sprue cutters, with the jaws generally being around 20mm (3/4″) long.
The thickness of sprue cutter jaws varies depending on the thickness and type of material they are designed to cut. Unlike the total length and jaw length, the jaw thickness of a sprue cutter is rarely stated, which can make comparisons difficult, especially when comparing online.
Thicker jaws will be stronger and so able to cut through thicker sprues or ones made of harder materials. However, thicker jaws are less able to get into tight spaces so are not suited for removing small intricate parts from a sprue. Generally, thinner jaws are found on single-action sprue cutters designed for use with plastic model making, while thicker jaws are found on compound lever sprue cutters designed for use on metal by jewellers.
The jaw width of a sprue cutter is the measurement of the distance between the outsides of the two jaws. Sprue cutters with a greater jaw width will have stronger jaws that are better suited to cutting through thicker, harder material. However, sprue cutters with a greater jaw width will not be able to access and remove parts from a tightly packed sprue or small delicate parts.