A stair jig is a template used by carpenters to construct stair stringers. It consists of an ‘L’ or ‘V’ shape with one leg representing the lift and the other the rung. The jig ensures uniformity in tread depth and riser height, and can be made from wood, plastic, or metal. Most stairways have two stringers, one on each side, and there are two types: closed spar and cut stringer. The jig is used to draw guidelines for each riser and tread, ensuring uniformity. A closed transom can also be made using a stair jig.
A stair jig is a template-like device used by carpenters and carpenters to construct the stringers that support stairs. It looks like a large ‘L’ or ‘V’, with one leg representing the lift and the other leg the rung, with a bump extending forward from the rung representing the torus on most stair treads. The angle where the riser and tread meet is always a right angle, and when used correctly, the stair template creates a sharp angle that defines the angle at which the stairs or slope line rises. Many woodworkers make their own stair jigs, usually out of wood, but they are also commercially available, in wood, plastic, or metal.
The treads on most stairways are usually of the same depth unless a landing is involved, and the risers should be of uniform height, considerations addressed by the use of stair jigs. A simple stair consists of a series of treads supported by risers, usually running the width of the step. The risers are positioned at right angles to the tread surface and are generally set back approximately 1 inch (2.54 cm) from the front of the tread.
Most stairways have two stringers to support the treads and risers, one on each side. One type, called a closed spar, is a wide board into which horizontal and vertical grooves have been routed for tight fitting of treads and risers. A cut stringer is a long, wide board with a series of large cut notches, to which risers and treads are attached.
A carpenter, using a stair template, sets the tread depth and riser height once, on the template, then transfers those dimensions to a transom cut for any number of treads, so that each of the treads is absolutely identical to each of the others. After setting stops on each leg of the jig, the carpenter secures the jig to the crossbar and draws a line across the board using the jig as a guide. After cutting along the drawn lines, the carpenter uses the jig to draw guidelines for the next riser and tread. More experienced carpenters will lay out all the cuts first before making the first one. The stringer is a framework on which the treads and risers are fixed, and the treads and risers themselves must also be carefully cut to ensure uniformity.
A closed transom can also be made by using a stair jig, tracing the outline of the groove, and then using those lines to lock in the planks used to drive the router. Another approach is to create a router model out of plywood, by cutting out the outline of a stair jig. The template itself is securely attached to the crossbar and used as a router guide.
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