How it works

Three tools, one handle, and the numbers that actually fit it.

  • 1

    Stitch math

    Pricking iron spacing in mm or SPI, a hole layout that lands a hole on every corner, how to walk a multi-prong iron, and saddle-stitch thread length.

  • 2

    Whip taper

    Strand drops for leather lace or paracord: where to drop each pair, lace width along the thong, a taper chart, and how much to cut.

  • 3

    Knot grid

    Turk's head and Gaucho knots by leads and bights, with the length that fills the mandrel, coverage, strand angle and cord to cut.

Covers Turk's head Gaucho Herringbone Saddle stitch Whip taper Leather wrap Paracord
In the app

What it looks like in use.

Tying with both hands fullOne pass at a time in large type with big over/under tokens. Tap anywhere, or press a Bluetooth page-turner. It reads each step aloud, keeps the screen on, and remembers where you stopped.
Tying with both hands full
Printed to work straight fromA rectangle piece prints whole, tiled across sheets when it is bigger than one, and custom segments print as strips that join end to end — both at full size, to tape on and prick straight through. A knot grid prints one circumference wide, to wrap round the mandrel.
Printed to work straight from
Where every pair dropsA taper chart for the whole thong, with lace width or cord coverage as it narrows, and the cut list underneath.
Where every pair drops
A hole on every cornerThe layout solves the spacing so corners land on holes, for a rectangle or for custom segments that join end to end.
A hole on every corner
Detail

The parts that took the longest.

  • Ruler arithmeticFractions to the nearest 1/16, or 1/32 under half an inch, so 550 paracord reads as 5/32 in. Fields take decimals or fractions and show the ruler reading of what was typed.
  • Answer firstEach tool leads with its answer on a stitched tag; the inputs follow, and the reasoning folds away under “How this is worked out”.
  • Honest defaultsUntil a tool's numbers are changed, its answers say plainly that they come from example numbers.
  • One layer to the nextA finished whip layer becomes the core of the next one in a single tap, and the handle diameter carries into the knot tool.
  • Free, with ProThe app is free to download. Pro is a one-time US $6.99 purchase and unlocks hands-free tying, printing at true size, and sharing without the “Made with Mandrel Bench” line — with the first three print jobs and the first three knots free, so the tools can be tried on a real piece first.
  • Somewhere to startForty worked examples load real numbers into a tool — a knife handle, a walking stick, a bracelet mandrel — and one tap puts your own back. Five over-under codings are built in: a plain Turk’s head, a Gaucho over two under two, and three herringbone codings, one of them with locked edges.
Fitting a knot to a given handle.
Fitting a knot to a given handle.
A spiral strap wound round a grip.
Sleeves, tapers and spiral grips, with the strap to cut.
Forty worked examples to start from.
Forty worked examples, each loading real numbers you can put back.

Where it stands. 1.0.9 is built, signed and in closed testing on Google Play as com.jdcapone.mandrelworkshop, ahead of a public release. It was called Mandrel Workshop until October 2026, when it took the Bench name its sibling apps use; the Play id keeps the original spelling, as Play ids are permanent. Privacy policy.