What's inside
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What each gauge marks
A mortise gauge has two marking pins: one is usually fixed, and the other moves to set the width between them. That makes it useful for marking the two sides of a mortise and, when the spacing matches, the two cheeks of a tenon. A wheel marking gauge has a fence and a small circular cutter. It makes one line at a time, so you reset it for the second cheek.
For repeated tenons, the practical difference is not simply speed. A mortise gauge holds a pair of lines at a fixed distance apart; a wheel gauge makes a clean, single line and is quick to reset from a reference face. Your stock, layout method, and need to match a mortise determine which matters more.
Mortise gauge vs wheel gauge
| Factor | Mortise gauge | Wheel gauge |
|---|---|---|
| Lines per setup | Two, spaced to the mortise or tenon thickness | One; reset for the second line |
| Best use | Repeated paired lines, especially tenons that match a mortising chisel | Single shoulder, cheek, or reference line; general-purpose marking |
| Setup | Set pin spacing and fence offset; both pins must cut reliably | Set one offset; straightforward to check against a rule or test piece |
| Typical weakness | One pin can drift, snag, or cut poorly if its adjustment is loose | More resetting for paired lines; cutter can follow grain or crush fragile edges |
| Value | Worthwhile when paired lines are frequent and repeatability saves time | Often the better first gauge if you need one tool for varied layout |
Choosing for repeated tenons
Choose a mortise gauge when you cut many tenons to a consistent thickness and want both cheeks marked in one pass. Set its pins to the mortise width, then use the same face side and face edge as references on every workpiece. This is particularly convenient when the tenons are sized to a particular mortising chisel: the paired marks give you a direct visual target while sawing or paring.
But a mortise gauge does not guarantee a correctly centered tenon. If the stock thickness varies, keeping both pins in contact with the face edge still produces a fixed thickness, not necessarily equal shoulders. For centered tenons, measure or mark from both faces, or establish the shoulder layout separately. Confirm the pins are actually set to the intended width; a small adjustment error repeated across a batch becomes a batch-wide mismatch.
A wheel gauge is a good choice if tenons are occasional, vary in thickness, or need to be laid out from a particular face. Mark one cheek, reset from the same reference face for the other, and check the result on a sample. It takes an extra setting, but avoids paying for a paired-pin arrangement you may rarely use. A well-made wheel marking gauge can also handle shoulder lines, board edges, and other single-line tasks around the shop.
Set up once, then verify
Start with straight, square stock and identify a consistent reference face and edge. Use a rule or caliper to set the gauge; do not rely on counting turns or guessing by eye. On a mortise gauge, measure the distance between the two cutters, not between the points of the pins where they enter the wood. Make a test mark on scrap from the same stock, then measure the marked width and compare it with the mortise.
For a batch, mark one tenon completely before marking the rest. Check that the gauge fence stays flat against the edge and that both cutters leave continuous lines. A loose fence, a pin that shifts under pressure, or changing reference faces can create tenons that differ even though the gauge setting has not changed. Recheck after a knock or adjustment, and keep the tool’s lock screw snug rather than forcing it.
With a wheel gauge, set the offset and test it on scrap. A wheel can skate across end grain or be pulled off course by strong grain. Use light pressure for the first pass, then deepen the line with a second pass if needed. Heavy pressure is more likely to crush soft wood or make the cutter wander than to improve accuracy.
Marking is only part of the fit
Gauge lines are guides, not a substitute for checking the joint. After sawing, test a tenon in its mortise. It should enter with controlled hand pressure rather than hammering, and its cheeks should not rock from side to side. A tenon that is too thick can split a narrow mortise cheek; one that is too thin leaves a loose joint that glue cannot reliably correct.
Keep the gauge cutter sharp and clean. A dull cutter tears fibers and makes a fuzzy line that is hard to follow accurately. On pale or open-grained timber, a deep cut may be useful for guiding a chisel, but a heavy mark can also leave damage outside the finished joint. On brittle or figured wood, make a light pass and inspect before committing to a deeper one.
For an adjustable paired-pin tool, look for pins that lock securely and a fence that slides without wobble. A two-pin mortise gauge is a sensible purchase if you often make matching mortise-and-tenon joints. If you mainly mark one line at a time, spend less on a single-pin gauge instead; a single-pin marking gauge is enough for many shop tasks.
Which one to buy
Buy a mortise gauge for repeated, paired tenon marks and frequent work to a consistent mortise width. Buy a wheel gauge if you want a versatile single-line tool, make tenons only now and then, or prefer to set each cheek from a chosen reference face. The cheaper single-line option is entirely adequate for occasional joinery, provided you take time to reset and verify it.
Whichever style you choose, prioritize a firm fence, a cutter or pins that hold their setting, and easy-to-read adjustment. Before starting a batch, make one test tenon and fit it to the mortise. That check catches a wrong setting before it is repeated across every piece.