Dogbone Generator — Free CNC Fillet SVG & DXF Tool

CNC Dogbone Generator

No code, no CAM to learn, no plugin to install. Paste your shape, set the bit, download SVG or DXF in real millimetres.

Tap a corner dot to turn that relief off.

Units

Width (in)Height (in)

Bit diameter (in)

Relief style

Minimal dogbone (default)Full cornerT-bone

Paste SVG

Output size: 4.01 × 2.042 in (outer extent, reliefs included). Check this against your design before cutting.

This file is the finished pocket contour, not a cutter-center toolpath. Import it and generate a normal inside/pocket path with the same bit. Do not offset the geometry by the cutter radius again. Always verify bit diameter and dry-run before cutting.

Add a reference layer to the SVGDraws the original outline and a bit-sized circle at each relief, on a separate guides layer. For checking in a drawing app — delete it before generating toolpaths or your CAM will cut it. Not included in the DXF.

How to use

Pick millimetres or inches — the tool stores millimetres internally and only the labels change. Enter pocket width and height, or paste a closed SVG path. Choose a bit. The default style is a minimal dogbone: the smallest overcut that still lets a square tenon seat. Download SVG or DXF, then run a normal inside/pocket toolpath in your CAM with that same bit. Do not offset the exported contour by the cutter radius again.

What is a CNC dogbone fillet?

A round cutter cannot mill a sharp internal corner. The leftover radius interferes with a square tenon, drawer box, or shelf dado. A dogbone (and its cousins, the full corner and the T-bone) nibble extra material at the corner so the mating part fits. This generator does that in the browser. It does not emit G-code and it does not build a whole box — it rewrites the corner of a single closed outline.

Full vs Minimal vs T-Bone

Let R be the bit radius. On a 90° pocket corner the three styles share one radius and differ only in where the arc sits:

Full corner — centre on the vertex. Overcut depth is R. Each adjacent edge is consumed by R.
Minimal dogbone (default) — centre sits on the angle bisector at distance R. The bulge past the original corner is R(1 − 1/√2) ≈ 0.293R. Each edge is consumed by √2·R.
T-bone — centre sits on one wall. Overcut depth is R on that wall only. The facing edge is consumed by 2R; the other edge is consumed by 0.

T-bone only clears interference on one side of the corner. Pick the wall that still has leftover length after the other corner’s relief is accounted for — not “whichever wall looks longer”. If neither wall can take 2R plus the opposite corner, the tool refuses to export.

Bit diameter and corner clearance

A 1/8″ bit is 3.175 mm diameter, so R = 1.5875 mm. Minimal bulge is about 0.466 mm; each end of an edge needs √2·R ≈ 2.25 mm. A 1/4″ bit is 6.35 mm, R = 3.175 mm, bulge ≈ 0.930 mm, and each minimal dogbone eats about 4.49 mm of wall. Two of them plus 0.05 mm of tolerance need just over 9 mm of edge — a 16 × 50 mm slot still passes. An 8 mm wall with both ends on does not. Turn one corner off, or drop to a smaller bit.

Export SVG or DXF for LightBurn and Carbide Create

SVG user units are not millimetres. LightBurn, Inkscape and older Carbide builds will treat a unit as 1/96 inch unless the file also carries a physical size. This exporter writes both width/height in millimetres and a matching viewBox, and it keeps corners as SVG A arcs — not Bézier approximations, which CAM tools tessellate badly. DXF R12 is unitless; the coordinates are millimetres. Choose millimetres on import. The two files share one normalisation, so a vertex that is (12.400, 3.175) in the SVG is the same pair in the DXF (after undoing SVG’s Y-down flip).

This file contains the finished pocket/part contour, not the cutter-center toolpath. Import it into your CAM software and generate a normal inside/pocket toolpath using the same bit diameter. Do not manually offset the exported geometry by the cutter radius again.

Guides

Dogbone vs T-Bone: Which Corner Relief Should You Use?
Compare full-corner, minimal dogbone, and T-bone fillets: overcut depth, edge consumption, and when each style actually seats a square tenon.
Dogbone Size for a 1/8" CNC Bit
Exact millimetre numbers for a 3.175 mm bit: relief radius, minimal bulge, full-corner overcut, and the shortest wall that still fits two dogbones.
Dogbone Size for a 1/4" CNC Bit
Exact millimetre numbers for a 6.35 mm bit: relief radius, 0.293R bulge, edge consumption, and why a 16 mm wall still clears two minimal dogbones.
How to Add Dogbones in LightBurn
Export a millimetre SVG from this generator and import it into LightBurn without the 96 dpi scale trap. Then cut a normal inside/pocket toolpath.
How to Add Dogbones in Carbide Create
Import a DXF in millimetres into Carbide Create, confirm the pocket contour is not a toolpath, and generate an inside cut with the same bit diameter.
How to Add Dogbones in Inkscape
Paste or import a millimetre SVG, keep circular arcs as arcs, and avoid the 96 dpi document-unit trap before sending the file to a CAM tool.
How to Add Dogbones in Inventables Easel
Bring a millimetre SVG into Easel as the finished pocket contour, set the same bit diameter, and let Easel offset the toolpath — do not offset again by hand.
SVG vs DXF for CNC: Which File Should You Download?
SVG needs width/height in millimetres plus a matching viewBox. DXF R12 is unitless — pick millimetres on import. Same geometry either way.

FAQ

Is this a toolpath?

No. It is the finished pocket outline. Your CAM still offsets by the bit radius, and that offset is correct — just do not apply your own on top of it.

Why millimetres in a DXF?

DXF R12 has no unit field worth trusting. The coordinates are millimetres, so pick millimetres in the importer dialog.

Why did download disable itself?

Either an edge is too short for the reliefs at both of its ends, or a pasted path still needs an actual width in millimetres before it has a physical scale.

Can I do outside cuts or outline mode?

Not in this version. Pocket, slot and opening cover the usual box-joint cases, and mixing modes is how people mill the wrong side of a line.

How much bigger does a minimal dogbone make my pocket?

It bulges past each relieved corner by R(1 − 1/√2), about 0.293 of the bit radius. That is roughly 0.47 mm for a 1/8 inch bit and 0.93 mm for a 1/4 inch bit.

Which corners get a relief?

Convex vertices between 85° and 95°, measured after any pasted transform is baked in. Reflex corners are left alone because the bit already reaches them, and you can switch any corner off by tapping its dot in the preview.