What it is

The Zebra Spindle Index (ZSI) measures how much metal is being cut in the United States — not how shops feel about it. It is assembled every month from nine public federal series: industrial production for machine shops, weekly hours in machine shops, inflation-adjusted new orders for fabricated metals and metalworking machinery, kilograms of carbide inserts crossing the border, and U.S. exports of machine tools and inserts. Beside it we publish one signal nobody else has: the Zebra Coolant-System Activity Pulse, a delayed, aggregated reading of our own consumables and replacement-part activity. The Pulse is published alongside the index and is not an input to it.

100 means normal (the 2012–2024 norm). Every 10 points is one robust standard deviation. It is not a PMI: 110 is not "10% growth," it is one standard deviation above normal.

Why we built it

We sell coolant-management equipment. Our products only matter when spindles are turning, so we wanted a number that tracks spindles turning. The best-known metalworking indicator is a diffusion survey — the share of respondents saying "up" versus "down." That is useful, and it is faster than measurement. But it measures optimism. We wanted magnitude, and we wanted every number to trace to a .gov source anyone can check.

How to use it

• Read the level against 100. Above 100, activity is running ahead of its decade norm; below, behind it.
• Read the direction over three months, not one. Every input is a three-month average; single-month wiggles are noise by construction.
• Plan against the direction, not the level. Since 2005, when machine-shop output was growing, output over the next six months ran above the current quarter about four times in five; when it was contracting, below about three times in four. That is a historical regularity, not a forecast — and turning points are exactly where it fails.
• Read the components. The tiles on the index page show which domain moved — output, hours, orders, tooling consumption, foreign demand — and link to the source series.
• Read the Pulse beside it. When our own activity and the public index disagree for two months, one of them is about to be right; we say which in the monthly note.
• Don't forecast with it. It is a coincident index. We tested it — and backlog, capital-goods orders and expectation surveys — as leading indicators, and none earned the claim, so we do not make it.

How we built it

Each series is transformed to a growth rate or level change, standardized with a robust z-score frozen on 2012–2024, clipped at ±3, and combined with fixed published weights. Nothing is renormalized when data are late; we post a dated delay notice instead. Tooling imports are counted by weight so tariffs move the effective-duty-rate panel, not the activity number. Source revisions are disclosed — both the as-published and latest-revised histories are downloadable. Full methodology: spindleindex.zebraskimmers.com/methodology.

What it cannot do

It lags mood by about six weeks. It is coincident, not leading. Imports are a slice of tooling consumption. It measures the industry, not your shop. It will be revised. The Pulse is one company's activity, shown coarsely and with a delay.

Get the data

The public-data ZSI dataset (history, components, calibration, satellite panels) is free under CC BY 4.0 with a data key: get a free data key. The Zebra Pulse is proprietary and not included. Cite as "Zebra Skimmers, Zebra Spindle Index, [month] release."

Public beta. Published monthly around the 12th, two months in arrears, by Zebra Skimmers Corp., Solon, Ohio. Not investment or business advice.