A bench dog and a holdfast do different jobs. A dog stands in a hole in the top and gives the work a fixed point to push against, usually with a second dog in a vise squeezing the work towards it. A holdfast pins the work down from above, wedged in a hole through the top. How the whole bench holds work — vises, dogs, holdfasts and planing stops together — is explained in the workbench guide; this page goes into the dogs and holdfasts themselves.
Bench dogs
Round dogs sit in drilled holes. Veritas's brass dogs fit a 3/4 in hole: 4-3/8 in long for a bench of standard thickness, with shorter 2-3/8 in Bench Pups for tops up to 2 in thick or where the apron is shallow. A side spring holds each at whatever height it is set, and the face that meets the work is cross-hatched and angled in by 2°. Veritas notes the holes can be drilled vertically in the top or horizontally.
Square dogs sit in square or rectangular holes, which stop them turning. Lie-Nielsen's bench has rectangular dog holes 1.150 × 0.950 in, and Benchcrafted makes the dog holes for its tail vise as angled dadoes with a step rather than drilled holes. Dogs for one of these benches are made for its holes.
20 mm dogs belong to a different system: multifunction tables with a grid of 20 mm holes, like Festool's MFT/3, which says only that its top has a uniform hole pattern for clamping. These are the dogs track saw users mean. Bessey's BH-MFT dogs, for example, are made for 20 mm holes in a plate at least 19 mm thick, have 20 mm bolts and knurled nuts, and double as stops. A 20 mm dog is not a 3/4 in dog: 20 mm is about 0.79 in, so the two are not interchangeable.
Holdfasts
A holdfast is a rod bent over at the top into an arm. Set it in a hole with the arm resting on the work and strike the top of the arm, and it pins the work; strike the side of the post, and it lets go — Gramercy's instruction for its own holdfasts. The blow flexes the arm and tips the post in its hole so that it binds against the hole's wall near the top on one side and near the bottom on the other, and the arm's spring keeps the pressure on. That is why holdfast makers care about the fit, the surface of the shaft and the thickness of the top: the hold comes from friction in the hole.
Two makers show how far apart holdfasts can be. Gramercy's are cold-formed steel for a 3/4 in hole in a top at least 1-3/4 in thick, reach 6-1/2 in, and clamp up to 7-1/4 in in a 2 in top; Gramercy suggests rubbing the stems round, not up and down, with 150 or 220 grit, and says they work better in pairs. Crucible's are ductile iron with a 1 in untapered, rough shaft 17 in long, for a 1 in hole reamed to fit each holdfast; Lost Art Press says they work in benches from 2 to 8 in thick, reach 6-5/8 in and hold work up to 8 in off the top, and warns never to oil them or let oil into the holes. Each is made for its own hole: neither maker's holdfast is sold for the other's.
| Item | Hole | Top | Stated details | Maker |
|---|---|---|---|---|
| Round dog | 3/4 in | Standard thickness; Pups for tops up to 2 in | 4-3/8 in long (Pups 2-3/8 in); side spring; face angled 2° | Veritas |
| Square dog | 1.150 × 0.950 in, rectangular | 4 in maple | Dogs and holes made for that bench | Lie-Nielsen |
| Tail-vise dog | Angled dado with a step | 4 in | Made as dadoes, not drilled | Benchcrafted |
| 20 mm dog | 20 mm | Plate at least 19 mm | 20 mm bolt and knurled nut; doubles as a stop | Bessey (BH-MFT) |
| Holdfast | 3/4 in | At least 1-3/4 in | Reach 6-1/2 in; up to 7-1/4 in in a 2 in top | Gramercy |
| Holdfast | 1 in, reamed to fit | 2 to 8 in | Shaft 1 in × 17 in; beak 6-5/8 in; up to 8 in off the top | Crucible |
Each row is one maker's figures for its own product. No maker here publishes a holding force. Buy dogs and holdfasts to suit the holes you have, or drill the holes for the system you choose.
Placing the holes
- Spacing. There is no standard spacing. Dogs that work with a tail vise need to be closer together than the vise opens, so that a board of any length can be caught between a dog in the top and the vise's dog; the spacing follows from your vise and the work you hold.
- Holdfast holes. Put them where you need to pin work: in the area you saw and chop on, near the front edge, and — as the workbench guide notes — in a front leg to hold work against the bench's face.
- Top thickness. The top decides what fits. Gramercy's holdfasts want 1-3/4 in or more, Crucible's 2 to 8 in, and Veritas sells shorter Pups for tops up to 2 in. Check the top, including any apron, before buying.
- Drilling. Bore square to the top with the bit the system calls for, after a test hole in scrap with that bit and the dog or holdfast itself; Crucible's holes are bored at 1 in and then reamed to fit. Bits are covered in the drill bit guide.
- Wood movement. In a solid top the row of dog holes usually runs along the length, which is along the grain, and the Wood Handbook gives lengthwise shrinkage as only 0.1% to 0.2% from green to ovendry. Across the width, shrinkage is many times larger, so the distance between rows of holes changes more with the seasons. The wood movement calculator estimates it.
Using them
Common ways to hold work
Between dogs
Set a dog in the top and the vise's dog, lay the board between them, and close the vise until the board is held. Keep both dogs below the face you are planing.
Against one dog
For light planing across or along a board, a single dog — or a planing stop — gives it something to push against, without a vise.
Under a holdfast
For sawing, chopping or routing a part on the top, set a holdfast over it, protecting the surface with a scrap pad if needed, and strike the top of the arm; strike the side of the post to release it.
On the bench's face
With a hole in a front leg, a holdfast holds a board against the front of the bench for working its edge.
Dogs and holdfasts are not the same as tracks and clamps. A track-and-clamp system uses a profile in a slot, and its parts fit only that profile; see T-track. Clamp types and how they apply pressure are in the clamps guide. How vises close on dogs, and why a jaw racks, is in the vise guide, and a vise you can carry to the work is compared in how to choose a portable bench vise.
Safety— Keep the tools clear
A dog standing higher than the work is in the path of a plane's iron or a saw: set dogs below the surface you are working. Strike a holdfast with a mallet on its arm and post, not near your other hand, and check the work is held before you cut. See woodworking safety equipment and woodworking safety rules.
Before buying dogs or holdfasts
- The hole size the dog or holdfast is made for matches the bench's holes
- The top is within the maker's stated thickness for it
- Dogs are short enough for the top and apron
- Dog spacing is closer than the vise opens
- Holdfast holes are where you saw, chop and hold work on the bench's face
- The holes are bored square, tested in scrap first
Sources
Every size, thickness and reach is the maker's own for its own product, and the systems are not interchangeable; nothing here is a standard. No maker cited publishes a holding force for a dog or holdfast, and none is given. The Bessey figures are from a distributor's listing because the maker's page did not show them. Nothing was tested for this guide.
- 1.
Holdfasts. Gramercy Tools (Tools for Working Wood).
Used for: Made for a 3/4 in hole in a top 1-3/4 in thick or more; 6-1/2 in reach; up to 7-1/4 in of clamping in a 2 in top; cold-formed steel whose bends give it spring; set by striking the top of the arm and released by striking the side of the stem; better used in pairs; the stems rubbed round with 150 or 220 grit abrasive.
- 2.
Crucible Iron Holdfast. Lost Art Press (Crucible Tool).
Used for: Ductile iron, for a 1 in hole reamed to fit the individual holdfast; working in benches 2 to 8 in thick; a 1 in untapered, rough shaft 17 in long; a beak extending 6-5/8 in from the shaft; holding work up to 8 in off the top; never oiled, nor oil let into the holes.
- 3.
Veritas Round Bench Dogs. Veritas Tools Inc..
Used for: Brass round dogs for a 3/4 in hole, drilled vertically or horizontally; 4-3/8 in long for standard benches, with 2-3/8 in Bench Pups for tops up to 2 in thick or a shallow apron; a side spring holding the dog at any height; a cross-hatched face angled inward 2°.
- 4.
BH-MFT bench dog set (BESSEY). Hoffmann Group (distributor listing).
Used for: Bench dogs for multifunction tables with 20 mm holes and a plate at least 19 mm thick, such as the Festool MFT and Sortimo WorkMo; 20 mm bolts with knurled nuts; usable as a stop for workpieces.
- 5.
MFT/3 Multifunction Table. Festool.
Used for: A 45 × 30 in (1157 × 773 mm) table with a uniform hole pattern for clamping and a 35 in (900 mm) working height.
- 6.
7' Standard Workbench. Lie-Nielsen Toolworks.
Used for: A 4 in solid maple top with rectangular dog holes 1.150 × 0.950 in, 3/4 in holdfast holes and a tail vise.
- 7.
Split Top Roubo Bench. Benchcrafted.
Used for: A 4 in thick top with 1 in holes placed for Crucible holdfasts, a leg vise and a tail vise.
- 8.
FAQ. Benchcrafted.
Used for: Dog holes for the tail vise made as angled dadoes with a step rather than drilled holes.
- 9.
Chapter 4: Moisture Relations and Physical Properties of Wood. USDA Forest Service, Forest Products Laboratory — Wood Handbook, FPL-GTR-282, 2021.
Used for: Longitudinal shrinkage of 0.1% to 0.2% from green to ovendry for most species; shrinkage across the grain many times larger, tangential about twice radial.
About this guide
Written by BenchRoot Editorial. How BenchRoot sources, checks and corrects its pages is set out in the Editorial Policy. If something here is wrong or unclear, the contact page explains how to tell us.