Collet and taper tools

Five calculators that run entirely in your browser — no sign-up, no data leaves the page. They exist because the questions behind them come up on every forum, every week.

Taper identifier

Every shop ends up with an unmarked arbor or a chuck shank of unknown parentage. The taper rate — how much the diameter changes per foot of length — is the fingerprint. Measure the large end, the small end and the distance between them with a caliper, and this tool compares your numbers against the published tables for Morse MT0–MT7, Jacobs JT0–JT33, the 7:24 family and R8.

Two cautions. First, caliper error of a few hundredths of a millimetre moves the result, so treat the answer as a shortlist rather than a verdict. Second, every 7:24 taper shares the same rate — BT30, CAT40 and SK50 differ only in their flange, drive slots and pull stud, so the gauge diameter is what identifies the size.

ER size finder

The ER system covers roughly 1 mm to 34 mm, but no single series covers it well: the wider the range a collet clamps, the less grip it transmits. Given your shank diameter, the finder lists every series that can hold it and highlights the smallest one — usually the right purchase, because a tighter-fitting collet grips better and runs truer.

If your shank is at the very bottom of a series' range, double-check the maker's own chart: lower bounds are the least consistent numbers in the whole ER system, and the ER size chart shows where the published values disagree.

Nut torque lookup

Under-tightened ER nuts let the collet spin and slip; over-tightened ones crack small-bore collets and distort the thread. The lookup returns the published value for the series and bore, adjusting for the small-diameter cases where makers specify less torque.

One honest warning: this is one of the messiest tables in the industry. Values for the same size differ between makers by up to 2.5×, and the number that counts is the one printed for your nut brand. See the full torque chart and its conflicts.

Overhang stiffness estimate

Deflection grows with the cube of overhang and falls with the fourth power of diameter — which is why 10 mm of extra stick-out hurts far more than 10% less feed does. Enter the stick-out and the holder diameter, and the estimate compares your setup against a comfortable 3×D reference.

It is a comparison tool, not a physics simulation: it ignores the spindle interface and the tool's own stiffness. Use it to decide between two setups — for the full reasoning, see extension rods and long-reach chucks.

Inch / mm converter

Tooling is sold across two measurement systems and catalogs mix them freely. This converter accepts fractions — 3/8, 1-1/2 — as well as decimals, and rounds millimetre values to the nearest fractional inch, which is what most imperial shank charts actually mean.

Where the data comes from

The same tables as the rest of this site: published standards (DIN 6499, ISO 296, DIN 2080 and friends) cross-checked against several makers' catalogs. Where the sources disagree, the pages say so and these tools lean on the better-corroborated value — and where a number is genuinely brand-specific, like nut torque, the tool tells you to trust your own maker's figure instead.