Deliver dead-square mortises on the first try with SquareForm — a hollow-chisel and auger that bores square-walled holes in a single plunge, letting tenons drop in flush and joints lock without rocking.
The tool integrates a four-walled hollow chisel with an internal auger; the setup clears chips as you bore and the true-round shaft seats securely in the mortising machine’s bushing, preventing wobble and keeping corners true from start to finish.
Built for wood rather than metal, these bits are sized for pine, MDF, particleboard, linden, and most furniture-grade hardwoods. The cutting geometry targets wood fibers, and the edges arrive sharp out of the box—no honing required before the first hole.
Each size in the set combines a hollow chisel sleeve with an internal auger as a single unit. In a mortising machine, waste is cleared by the auger while the chisel faces square the walls, leaving a true mortise. The milled shaft is designed to fit standard benchtop mortising machines or drill presses with a mortising attachment, not handheld drills.
Options include a 4-piece kit (¼", 5/16", 3/8", ½") or a 6-piece kit that adds 9/16" and 5/8". Material is carbon steel with ground cutting edges and a milled true-round shaft. Each size includes a hollow chisel sleeve and an auger as a single assembly. Compatible with bench-top mortising machines and drill presses fitted with a mortising attachment; not suitable for handheld drills.
Your Questions, Honestly Answered
- Will these work in a regular handheld drill or bare drill press? No — they require a mortising machine or a drill press with a mortising attachment to keep the chisel sleeve square to the work.
- Are they sharp out of the box? Yes. The chisel walls and auger arrive ground and ready to cut.
- What woods can they handle? Pine, MDF, particleboard, linden, and most furniture-grade hardwoods like oak and maple. Do not use with metal, glass, plastic, or concrete.
- How do you prevent mid-cut binding? Leave a gap of 0.02–0.04 inches between the auger tip and the inside face of the chisel to give the chip a path to exit.
- Is it hard to achieve clean holes? With proper clamping, depth stop, and a single lever action, the hollow-chisel geometry does the squaring. After a few test holes, production mortises stay consistent.
Make tight mortises your default — set up the mortiser once and produce true mortise-and-tenon joints with repeatable, shop-tested results.
| SquareForm | Round Bit + Hand Chisel | Mallet & Bench Chisel |
|---|---|---|
| True-square walls in one plunge | ❌ | ❌ |
| Cuts 20+ mortises in an afternoon | ❌ | ❌ |
| Hardened edge holds through a full build | ❌ | ❌ |