These dividers were designed with a few key objectives in mind. First, they needed to have the ability to be quickly adjusted. Many dividers are fitted with thumb screws used to open and close the arms. This method is fine for some tasks, but falls short when rapid adjustments are needed, such as when using with the sector where adjustments are frequent and over a large range. These are fitted with a friction hinge allowing the legs to be rapidly set anywhere along its range of movement. A thin Teflon washer between the arms provides a smooth, consistent motion throughout the range of movement.
The friction of the hinge is also adjustable. In use, they should be easy to set, but hold position without unintentional movement. This is accomplished by means of a screw and whats known as a wavy washer at the pivot point. All that is needed to adjust the tension is a straight tipped screwdriver.
The dividers are machined from a pre-hardened alloy known as 4140PH. This steel has a hardness of 28-32 Rc, making the tips less prone to distortion in use, and yet soft enough to be easily dressed if needed.
These dividers are available in two sizes. The smaller size is 5" from the pivot point to the tips, and 5 3/8" long overall. They will comfortably open to a working distance of 6 inches. The larger size is 7½" from the pivot point to the tips, and 7 7/8" long overall, and will work at distances in excess of 9".
The tips come sharp and ready to use out of the box. Red Rose Reproductions recommend slightly blunting the points with a fine stone when using them with the sector. Otherwise, the points can be too grabby when locating in the drilled holes in the sector arms.
The dividers are made in the USA. They come packed in a sturdy cardboard box with a fitted insert to keep them out of harm's way. A users guide is included.
A compass attachment is available here