A cut thread is gauged to the same ASME B1.1 class as a rolled one, so it assembles the same way. Because it is cut from full-size bar, the body stays at full diameter: ASTM F1554 sets the minimum body under a cut thread at the thread's minimum major diameter, against the minimum pitch diameter under a rolled one.
Cutting removes metal instead of moving it, so the grain of the bar is cut across at the flanks and the root is not cold-worked; under repeated loading a rolled thread lasts longer, and the order can call for one. Where a thread is too big or too coarse to form by moving metal, or the material too brittle to cold form, a die head carries on.
Read the full die-head thread cutting page →
model dataThe machine and die head are generic: a self-opening head with four radial chasers on a turning spindle, a carriage vise that holds the bar still, a trip inside the head that the bar end reaches, and a closing ring and lever, drawn without any maker's features. Chasers sliding radially in the head, the snap opening when the work reaches the trip, removal without reversing and reclosing for the next part: a published die-head patent. The throat spreading the cut over the first teeth: chaser makers' data. The full-size body under a cut thread: ASTM F1554 Table 4. Class 2A and the 8 UN series above 1 in.: ASTM A962. The bar is drawn as 2 in. with a 2-8 UN-2A thread (pitch 0.125 in.), each chaser's teeth set in step with the helix and the throat about two and a half teeth long; no speeds, feeds, tool angles or thread lengths are shown, and the cut is slowed down and partly time-lapsed.
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