Sellers standardized screw threads by getting big buyers to demand them

By the 1860s, American machine shops each cut screw threads to their own house pattern — bolts, nuts and fittings made in one shop routinely would not fit hardware made in another, even for identical-looking parts. Britain had already solved this at home with Joseph Whitworth's 1841 thread standard, adopted because Whitworth was the country's dominant machine-tool maker and could set the pattern the rest of the trade fell in around; the United States had no equivalent dominant firm and no equivalent standard.

The available path was the one Whitworth had taken: publish a better thread design and let manufacturers adopt it voluntarily because it was technically superior.

Sellers had the Franklin Institute lobby big buyers like the Army and railroads to specify his thread, forcing suppliers to comply and standardize the market.

A few buyers controlled enough demand that suppliers had to comply or lose contracts.

Retooling for those buyers made it cheaper to use the same standard for all customers.

The standard radiated outward from mandatory buyers to the whole industry via cost incentives.

To force industry-wide adoption of a standard, win over the few dominant buyers who can require it in contracts, rather than persuading every supplier.

The Pennsylvania Railroad became the first major carrier to adopt the Sellers system for its rolling stock and infrastructure fasteners in 1869; government arsenals and the largest railroads followed within a few years. Because these buyers alone represented an enormous share of the national market for machined fasteners, any supplier who wanted their contracts had to retool to the Sellers thread — and having retooled, found it cheaper to use the same pattern for every other customer too rather than run two systems in parallel.