Bench dogs: sizes, spacing and workholding layouts

A bench dog is a removable stop that locates work on a bench. One dog may register a board; another may oppose a vice dog so the board is trapped between them. Dogs can also define a repeatable position for planing, routing or assembly. They do not all clamp by themselves, and they are not the same thing as holdfasts: the useful action depends on the dog, vice, accessory and bench working together.

The holes are therefore part of a system. Their diameter, shape, spacing, distance from the front edge and relationship to the vice decide which workpieces can be held. Copying a grid before choosing that system can leave a neat pattern that misses the vice, conflicts with structure below the top or accepts neither the intended dogs nor the intended accessories.

§1 SystemsRound and square dogs solve the same problem differently

Traditional benches often use square dogs running in fitted mortises. The square section resists rotation and can present a flat face to the work, but the mortises are part of the bench construction rather than a quick drilling operation. Modern systems frequently use round holes because they are easier to produce with a drill, guide or router and can accept rotating dogs and other accessories.

Round systems are sold under several nominal sizes. You will encounter 19 mm, 20 mm and 3/4 in descriptions. The arithmetic conversion of 3/4 in is 19.05 mm, but that does not make every nominal 19 mm and 3/4 in component interchangeable. Actual hole diameter, dog diameter, manufacturing tolerance, surface finish and the fit expected by a particular product all matter. Choose a system, measure the hardware in hand and make a test hole in material that represents the finished top.

A dog that should slide and turn needs a different real fit from an insert intended to grip by friction. Seasonal movement and top wear can alter that fit again. The layout planner accepts the hole diameter you choose, but it deliberately does not recommend one or certify accessory compatibility.

§2 SpacingThere is no useful pitch without a workholding range

Dog-hole spacing is the centre-to-centre distance between available positions. A smaller pitch gives finer placement but creates more holes, more drilling and less uninterrupted top. A larger pitch keeps the top quieter but increases the distance a vice, clamp or adjustable stop must bridge. The right pitch follows from the work and hardware range, not from a universal number.

Start with the vice. Find the line of its moving dog or the accessories that will oppose it. Then look at the shortest and longest workpieces commonly held along that line. If an adjustable dog, spacer or vice travel can bridge the gap between grid positions, the pitch can be wider. If the system depends on near-exact registration, the pitch must support that relationship.

Keep the chosen pitch exact. If the available top length does not divide evenly, centre the run and put the leftover into the end margins. Stretching every interval by a little produces an attractive fill but destroys compatibility with a fixed drilling template and makes positions harder to transfer. The same rule applies across rows: use a known front-row offset, then repeat the pitch rather than measuring each row independently.

§3 RowsPut holes where work is held, not everywhere space exists

A front row can serve boards held against a face vice or planed along the front of the bench. A second row may support wider panels, assembly fixtures or hold-down accessories. More rows are useful only when there is a clear operation for them. Empty areas of the top remain valuable for layout, assembly and cleaning; they do not need holes simply because a grid could continue.

Before choosing row positions, map everything below the surface: vice screws and guide bars, front and rear aprons, cross rails, trestles, drawer units, fixing bolts and any planned power or extraction runs. Give that hardware a no-drill area with real clearance, including the hole radius. Looking only at the top face is how a geometrically correct coordinate lands in a piece of steel.

Top thickness also affects the system, but it cannot be chosen from a generic rule here. A hole must guide the selected dog as intended without conflicting with the bench structure. Some accessories depend on through access; others do not. Check the specific hardware and test the full depth in representative stock before drilling the bench.

§4 LayoutOne corner owns every coordinate

Pick a front-left datum corner and measure every hole centre from it. X coordinates run along the bench; Y coordinates run back from the front edge. Do not measure the second hole from the first, the third from the second and so on. Chained marking lets a small error accumulate. A coordinate ledger or drilling template keeps every position tied to the original datum.

Mark the grid lightly, then audit it before drilling. Confirm the first and last X margins, the front offset and rear clearance. Overlay vice and rail positions. Check that excluded holes were removed in every affected row. If using a physical drilling guide, confirm that its own pitch matches the coordinate plan rather than assuming two nominal dimensions agree.

Perpendicularity matters as well as the surface location. A dog leaning through the top does not present the same working face at every height. The method used to guide the drill or router must suit the tool, hole depth and top construction. This guide does not prescribe that operation; it separates the layout decision from the tooling decision so each can be checked honestly.

§5 SequenceA practical decision order

1. Choose the dog, vice or accessory system and measure the actual parts.
2. Make a representative test hole and confirm the intended slide, rotation or friction fit.
3. Map vice hardware, aprons, rails and fixings below the top.
4. Choose the front-row relationship to the vice and common work.
5. Choose a fixed pitch that the workholding range can bridge.
6. Fit that pitch inside honest end and rear margins; mark exclusions.
7. Generate or write a coordinate ledger from one datum corner.
8. Audit the first and last position in every row before selecting a drilling method.

The result is not automatically a “better” bench because it has more positions. A useful grid is one you can explain operation by operation: this row opposes the vice, these holes locate a panel stop, this clear area protects the vice screw. If a hole has no job and complicates the structure or surface, leaving it out is a valid layout decision.