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Workshop know-how · Pipe layout

How to miter pipe: corners and kinks without a step

In a miter joint two pipes are cut at the same slant and butted together. The cut angle is always half the change of direction: for a 90° corner each pipe is cut at 45°, for a 30° kink at 15°. Both cut faces are then ellipses of the same size and cover each other.

Dipl.-Ing. (FH) Thorsten W. Recklebe · Updated

Why half the angle

Two pipes that meet at a corner must show the same cross-section at the joint – otherwise one of them stands proud. That is only the case when the joint bisects the angle between the pipes exactly. Cutting one pipe at 30° and the other at 60° also adds up to 90°, but the two ellipses have different lengths.

Change of direction Cut angle per pipe Length difference at 42.4 mm (1.669 in) OD
30° 15° 11.4 mm (0.447 in)
45° 22.5° 17.6 mm (0.691 in)
60° 30° 24.5 mm (0.964 in)
90° 45° 42.4 mm (1.669 in)

The length difference is the amount by which the outside of the corner is longer than the inside: diameter × tan(cut angle).

Mitered 42.4 mm pipe: corner with a 90° change of direction, joint at 45°, below it the unrolled cut line with a depth of 42.4 mm
Top: the corner seen from the side. Bottom: the unrolled cut line for a pipe of 42.4 mm (1.669 in) diameter.

The template

A saw with an angle stop needs no template. It helps where sawing is not possible: on installed pipe, on large diameters or when cutting with an angle grinder. The unrolled cut line is a simple sine wave over the circumference:

h(θ) = r · tan(cut angle) · (1 + cos θ)

The same template fits both pipes; for the second one it is applied turned by 180°.

Getting the corner right

  1. Scribe a line along both pipes that will later be on top.
  2. Always measure the length on the same side – usually the outside of the corner.
  3. Align the template to the scribed line, mark and cut.
  4. Grind the cut faces flat and tack the pipes in a square or a fixture.
  5. Check the angle before welding out: the weld pulls the corner closed as it cools.

Handrails: the kink between stair and landing

Where a handrail changes from the pitch of the stair to horizontal, the change of direction equals the pitch of the stair. At 34° pitch each pipe is cut at 17°. If the stair also turns in plan, the result is a compound angle – then a bend or two separate kinks are the better choice.

Distortion and weld

Thin-walled pipe distorts easily at a miter. Tack at four points crosswise and weld in short sections on opposite sides. On stainless handrails the weld is then ground flush and re-finished in the grain of the pipe, so the corner looks like one piece.

The pipe miter template delivers the 1:1 pattern for any angle. If a pipe meets the side of another pipe, it is not a miter but a saddle cut; wide bends are built as a segmented bend.

Questions

Short answers

Why is there often a step at a mitered corner?

Because the two cuts are not in the same plane. If one pipe is clamped slightly rotated for the second cut, the ellipses no longer match. A line scribed along both pipes prevents this.

When is a bend better than a miter?

On handrails, where the hand slides along, a bend is more comfortable and has no weld. In pipework a sharp miter slows the flow; large angles are built from several segments instead.