Angled Tube Notching Jig | Fishmouth Guide 45°–85°

Angled fishmouth notch jig, 45° to 85°

Mark an angled fishmouth (saddle) notch so one tube sits tight against the side of another at anything from 45° to 85°, without a hole-saw notcher. Pick your tube size and joint angle, slip the sleeve on, scribe round its shaped end and cut to the line.

Angled notches are hard to get right by eye. The profile isn't symmetrical, and getting it slightly wrong leaves a gap on one side that you end up filling with rod. A sleeve made to the exact angle gives you a profile you can trust.

Which one do I need?

Joints between 45° and 85°: this product. The angle is the angle between the two tubes, so 85° is nearly square.
A straight 90° T-joint: use the 90° notch jig.
Tube sizes: both are for joining two tubes of the same diameter. Unequal sizes, such as 2" onto 3", can be made to order.

How it works

Draw a line along the tube to show which way the notch needs to face.
Slide the sleeve onto the tube end and hold it square, with the notch lined up on your mark. There's no stop or reference mark, so take a moment to get it square.
Scribe round the shaped end, take the sleeve off, then cut outside the line with a bandsaw or cut-off disc and dress back to it with a flap disc or half-round file.
Offer it up to the run tube and fine-tune until the gap is even all the way round. On thicker wall, file the inside edge of the points back slightly so the outside sits down.