How do I use a marking gauge?

A marking gauge answers a question that comes up constantly in joinery: put a line exactly this far from that edge, along the whole length, on several pieces, identically. It does it without any measurement after the first setting, which is why every piece marked from it matches every other piece.

What you'll need

• Marking gauge, cutting gauge or wheel gauge
• A workpiece with one straight, clean reference edge

Step by step

1. Choose the reference face and mark it.The fence runs on one face and one edge, and every line depends on them. Choose the flattest, straightest ones, mark them with a pencil face mark, and use the same ones for every gauge line on the piece. Switching reference faces halfway is the root of most gauge errors.
2. Set the gauge against the work, not against a rule.To mark a mortise the width of a chisel, set the gauge directly off the chisel. To mark a tenon shoulder, set it off the actual mortise. Setting from the thing it has to match removes a transfer step and the error that comes with it.
3. Lock it and check it has not moved.Tighten the thumbscrew and then re-check the setting. Many gauges creep slightly as the screw bites, and the check takes two seconds.
4. Hold the fence hard against the edge.Almost all the pressure goes sideways into the fence, not downwards into the marker. A gauge that lifts off the edge follows the grain instead, which is what produces a line that wanders.
5. Tilt the tool so the marker trails.Roll the gauge slightly forward so the pin or wheel drags rather than digs in, then push away from you along the edge. A vertical pin ploughs into the grain and dives off line.
6. Take two light passes.The first pass scores a shallow line the second can follow. One heavy pass tears the fibres and lets the marker be steered by the grain rather than by the fence.
7. Use a cutting or wheel gauge across the grain.A pin gauge tears badly across the grain because it is dragging a point through fibres it cannot sever. A knife-edged cutting gauge or a round cutter severs them cleanly, and is the better tool for dovetail baselines and shoulder lines.
8. Gauge from both faces where symmetry matters.For a mortise centred in a piece, gauge from one face and then from the other. If the two lines coincide, it is centred; if not, split the difference and reset. This is the same self-checking trick as centring with a combination square.

Tips

• A wheel gauge with a small circular cutter is the most forgiving type for a beginner — it cuts cleanly in any direction and it is very hard to make it dive.
• Keep the pin or cutter sharp. A blunt pin is what makes people press harder, and pressing harder is what makes the line wander.
• For a mortise gauge with two pins, set the pins first from the chisel, then set the fence from the workpiece. Doing it the other way round means resetting both.
• The gauge line is not just a mark: for a chisel it is a physical wall to register against, which is why joiners gauge rather than pencil.

Common mistakes

• Marking from whichever face is convenient — Timber is not perfectly parallel. Lines gauged from different faces will not line up on the far side, and a joint marked that way cannot close.
• Setting the gauge off a rule — It adds a reading error to a tool whose entire purpose is to avoid one. Set it off the mating part instead.
• Pushing hard on the first pass — A deep first cut lets the grain steer the marker. Light, repeated passes stay where the fence puts them.

Questions people ask