What the jig has to do
Joining wood with dowels means drilling holes in two parts that line up exactly, then gluing round pins into both. Any error shows: a hole off-centre in the thickness leaves the faces out of flush, a hole drilled at an angle pulls the joint askew, and holes spaced differently in the two parts will not go together at all. A dowel jig fixes all three. It clamps to the part with a reference against the face or edge, holds a bushing — a guide tube for the bit — over the hole position, and keeps the bit square to the surface while it drills.
Whether dowels suit a joint is a design question covered in choosing a wood joint; Leigh, for example, suggests doweling where the strength of a mortise and tenon is not needed. No source reviewed tests dowels against other joints, so none is ranked here.
Kinds of dowel jig
| Type | How it places the hole | Example | Suits |
|---|---|---|---|
| Multi-bushing jig with registration marks | Bushings of several sizes screw into holes that centre on set stock thicknesses; V pointers align the jig with a pencil line | General Tools 841: edge, corner and surface doweling | Several dowel sizes and joint layouts with one jig |
| Single-size jig | One bushing fixed for one stock thickness; a hairline cursor aligns it with a pencil line | POWERTEC 71496, 71497 and 71498, one per stock thickness | Repeated work in the stock sizes the jigs are made for |
Each maker's own description of its jigs. Other designs exist, including self-centring clamping jigs, and each has its own instructions. Not a ranking.
'Dowel joiner' is also used for powered doweling machines; this guide covers the jigs that guide an ordinary drill. Slots for biscuits are explained in the biscuit joiner guide.
Bushing, dowel and stock
| Jig | Dowel and bit | Stock it centres on |
|---|---|---|
| 71496 | 1/4 in | 1/2 in |
| 71497 | 3/8 in | 3/4 in |
| 71498 | 1/2 in | 1 in |
POWERTEC's pairing for its own three jigs, each sold with its matching bit and stop collar. Other jigs pair sizes differently; General Tools' example uses 5/16 in dowels in 3/4 in boards. Not a rule for dowel size.
The bushing, the bit and the dowel are one size. Use the bit made for the jig's bushing — POWERTEC supplies each jig with its own, and General has the bushing chosen to fit the dowel size, with a 5/16 in bit for 5/16 in dowels in its example. Bit types for wood are compared in the drill bit guide.
Setting the depth
Depth comes from the dowel's length, split between the two parts, plus whatever the jig and bushing add above the work. A stop collar on the bit sets it. General Tools works this out for its 841 with 1-1/2 in dowels: its jig and bushing together add 1 in, so the collar sits at the hole depth plus 1 in.
| Joint | Hole depth | Collar, from the bit's end |
|---|---|---|
| Edge to edge, each board | 3/4 in | Slightly more than 1-3/4 in |
| Corner, edge piece | 1 in | 2 in |
| Corner, surface piece | 1/2 in | 1-1/2 in |
General Tools' figures for its 841 jig and 1-1/2 in dowels; the extra on the edge holes allows room for glue. A jig with a different bushing length has a different collar setting. Not a universal chart.
Tips from the makers
- Mark both parts together. Lay the parts out as they will be assembled and draw location lines across both — General marks the inside face of a corner joint, POWERTEC squares its line across.
- One reference face. Keep the same face against the jig's reference on every part, so any small offset is the same in both and the faces still come out flush.
- Clamp and keep it straight. POWERTEC clamps the jig to the work and asks for the drill to be kept as straight as possible; check its hairline is square to the body if marks stop lining up.
- Dry-fit first. General assembles the joint dry before gluing, then glues the pins or the holes and wipes away the squeeze-out; see wood glue and clamps.
Safety— Clamp the work, not your hand
Clamp both the jig and the work before drilling, so the bit cannot spin the part, and handle drill bits by the shank. Drill handling is covered in the drill guide and woodworking safety rules.
The other joinery jigs — pocket hole, dovetail, box joint and tenon — are mapped in the pocket hole guide.
Before drilling dowel holes
- Dowel size chosen to suit the jig's bushings and the stock
- Bit matched to the bushing; stop collar set from the jig's own figure
- Location lines drawn across both parts together
- Same reference face against the jig on every part
- Jig and work clamped; drill kept square
- Joint dry-fitted before glue
Sources
Bushings, collar settings, dowel and stock sizes are each maker's for its own jig — General Tools' for its 841, POWERTEC's for its 71397 kit — and are not a universal chart. No dowel size, depth or spacing is given as a rule, and no strength ranking of dowels against other joints is made, because no source reviewed tests one.
- 1.
E•Z Pro Dowel Jig (No. 841) instructions. General Tools & Instruments (hosted copy).
Used for: The E-Z Pro jig's edge, right-angle (corner) and surface doweling; an example with 5/16 in dowels and bit in nominal 3/4 in boards; the bushing screwed into the hole that centres on the stock's thickness, and the jig's 2 in registration line set in the matching V pointer; holes 3/4 in deep in each board for 1-1/2 in dowels in an edge joint, 1 in in the edge piece and 1/2 in in the surface piece in a corner joint; the collar set at the hole depth plus 1 in for the jig and bushing — slightly more than 1-3/4 in for edge holes, 2 in and 1-1/2 in for the corner; location lines drawn across both parts on the inside face; a dry assembly before glue on the pins or in the holes, and squeeze-out wiped away.
- 2.
Complete Doweling Jig Kit (71397) instructions. POWERTEC (retailer-hosted copy).
Used for: Three single-size jigs, each designed for one stock thickness: 1/4 in for 1/2 in stock (71496), 3/8 in for 3/4 in stock (71497), 1/2 in for 1 in stock (71498), each with its bit, stop collar and wrench; the jig flat on the work with its hairline centred on a squared pencil line, then clamped; hole depth set from the dowel's length; the drill kept as straight as possible; the hairline re-squared to the body if marks do not align.
- 3.
FMT Pro Frame Mortise & Tenon Jig User Guide. Leigh Tools (a Lee Valley Tools company).
Used for: Leigh's note that doweling may suit where the strength of a mortise and tenon is not required.
About this guide
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