The mortise gauge is a special type of marking gauge and it is used to mark wood so that a mortise can be cut into it. The diagram to the right represents a typical mortise and tenon joint. The mortise is marked out using the mortise gauge although it must be set to the correct size of mortise chisel very carefully. A mortise chisel is then used to remove the waste wood.
The mortise gauge is normally made from a hardwood such as rose wood with brass being used for the parts that slide along the stem.

QUESTION: Draw the diagram of a mortise gauge (shown above) and label all the parts. Explain how the distance between the fixed spur and adjustable spur is adjusted.

MARKING WITH THE MORTISE GAUGE

1. The distance between the fixed spur and the adjustable spur is set so that it matches the width of the mortise chisel. This done by turning the brass thumb screw. The width of the mortise chisel should match the width of the mortise to be cut in the wood.

2. A try square and a marking knife are used mark the lines at the top and bottom of the mortise.

3. The stock of the mortise gauge is pressed against the side of the wood. It is then pushed along the wood until the mortise is marked out correctly.

QUESTIONS: Using notes and diagrams describe how a mortise gauge is used to mark out a mortise and tenon joint.

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