Metric and imperial leaves live on the same tool, and get mixed up
A thread gauge answers one question — what pitch is this? — by matching a stamped leaf against the thread until one seats without rocking. The specification is simply which pitches are covered and how clearly each leaf is marked; a worn stamp on a greasy leaf is the practical failure. Sets that carry metric and imperial leaves on the same pivot are convenient and are also where mistakes happen, since a 1.25 mm (0.05 in) leaf and a 20 TPI leaf sit side by side. We compare leaf counts and ranges, marking legibility, pivot strength, and whether the two systems are separated.
52 leaves · 24 metric 0.25–6.0 mm (0.01 to 0.24 in) · 28 imperial 4G–62G · stainless
A 52-leaf stainless set covering 24 metric pitches from 0.25 to 6.0 mm (0.01 to 0.24 in) at 60° and 28 imperial pitches from 4G to 62G at 55°, folding into a pocket-sized body.
Best for: A first thread gauge, where the job is identifying a bolt rather than certifying it.
52 leaves · metric 0.25–6.0 mm (0.01 to 0.24 in) 60° · imperial 4G–62G 55° · radius gauge included
A 52-leaf stainless set that also includes a radius gauge, and the only set in this hub sold across five European markets.
Best for: Anyone who wants the thread gauge available across Europe rather than on one market.
52 leaves · metric and imperial · 60° to international standards
A 52-leaf stainless set stating that its metric leaves follow the internationally recognized 60° angle, with clearly visible markings on each leaf.
Best for: The same job as every other 52-leaf set — pick on price and on which one is in stock.
52 leaves · every metric ISO pitch listed · trade catalog reference
The only set here that prints its contents: BGS lists every metric ISO pitch it carries, from 0.25 to 4.0 mm (0.01 to 0.16 in) and beyond, rather than quoting a range.
Best for: Anyone who wants to know a specific pitch is in the set before buying it.
The pitch with the gauge and the diameter with a caliper. The two together specify the thread; one alone is not enough.
The one that engages with no gap and no forcing, checked against the light. Two neighboring pitches are told apart by the light passing through.
Both coexist depending on origins and trades. A gauge covering one system alone leaves half the cases unanswered.
On a sound portion of the thread, yes. On a crushed area, the reading is wrong.
The diameter of a tapped hole is measured with a caliper at the root of the thread, which is approximate. A test screw is more reliable.
Fine pitches exist at the same diameters as standard pitches. A gauge that does not cover them leaves confusion possible.
Dry and lightly oiled, without forcing the leaves in their housing. A bent leaf no longer engages properly.
Look against the light: the right leaf lets no light through between its teeth and the thread. Two neighboring leaves often differ by a tenth, and the light settles it.
A thread is specified by its pitch and its diameter: the gauge alone is not enough. The right leaf engages with no gap and no forcing — check it against the light — and a fine pitch exists at the same diameters as a standard one, which makes confusion possible.
There is no table here, and the reason is in the listings. The figure published most often across these 4 products is leaves, given by 4 of them — short of the four in five a column needs to compare rather than to display gaps. Each product page says what its own maker published.
Specifications: manufacturer sheets for measuring instruments and the matching Amazon product pages. Prices and availability: Keepa.
Most recent revision in this category: August 31, 2026.
