When the Thread Doesn't Exist in the Catalogue
Some threads simply aren't stocked anywhere. Left-hand threads for machine spindles and bicycle pedals. Fine-pitch metric threads in diameters the catalogue skips. British Whitworth and BSF on vintage motorcycles and industrial equipment made before metric standardisation. BA threads on scientific instruments. Custom power-transmission threads — ACME, square, trapezoidal — on lead screws and jacks.
These threads can only be produced by cutting them on a lathe to the measured or specified pitch. EKINSUN does exactly that — from a sample, a drawing, or a verbal specification of diameter and pitch.
Thread Types We Machine
Left-Hand (LH)
Counter-clockwise tightening — spindles, pedals, turnbuckles, specific wheel studs and wherever forward rotation would loosen a standard thread
BSW / Whitworth
55° flank angle, rounded crest and root. Standard on British machinery and vehicles pre-1970. We cut any BSW diameter and pitch combination
BSF
British Standard Fine — same 55° form as BSW, finer pitch. Common on British motorcycles, car engines and precision instruments
BA (British Association)
Small-diameter instrument thread — 0BA to 10BA — used on vintage electronics, cameras and scientific instruments
Metric Fine / Odd Pitch
Metric threads in fine pitches not listed in DIN catalogues, or intermediate pitches between standard series — cut to the exact measured pitch
ACME / Square / Trapezoidal
Power-transmission threads for lead screws, jacks and clamps — machined to standard or custom specification
Don't know the thread spec? Send the bolt and we gauge it. We identify metric, UN, BSW, BSF, BA and non-standard pitches. See also how to reverse-engineer an unknown thread and replacement bolts from a sample for the full from-sample process.
Frequently Asked Questions
A left-hand thread tightens counter-clockwise. Many are marked L, LH or with a groove on the head. Common applications: bicycle pedals (left-side pedal), some lathe and machine spindles, turnbuckles, and specific automotive wheel studs. Send the bolt and we confirm the hand before machining.
Yes. We gauge the pitch directly from the sample using thread gauges and optical measurement. Custom, intermediate and genuinely non-standard pitches are turned on the lathe to the measured value — we do not need it to be a listed standard.
Yes. BSW and BSF use a 55° flank angle — unlike the 60° of metric and UN threads — and specific pitches per diameter. We cut these forms correctly to the BSW or BSF standard for the diameter you need. Common on vintage British vehicles, motorcycles and industrial machinery.
Send the bolt. We measure the major diameter, pitch and flank angle, identify the thread family, and report back. If it is a known standard we name it. If it is genuinely non-standard, we give you the exact pitch and reproduce it.
Yes. Power-transmission thread forms for lead screws, jacks, vices and clamping devices — machined to standard or custom specification from a drawing or from a sample of the mating nut.
From a single bolt upwards. Legacy thread bolts for vintage machinery and vehicle restoration are often needed in quantities of 1–20. There is no tooling cost on lathe-cut threads so small quantities are fully viable.
Get Non-Standard Thread Bolts Quoted
Sample or spec — both accepted. Engineers reply in 24h.