Acme Nut & Lead Screw Guide
Acme nuts and Acme-threaded rod are built to move loads, not just clamp them. The trapezoidal Acme thread transmits motion efficiently and carries heavy axial force, which is why it runs clamps, presses, vises, jacks, valves, and machine lead screws. This guide covers how the thread differs from standard fasteners, the nut types, and choosing bronze vs steel for a lead screw.
How the Acme Thread Works
A standard UN thread has a 60-degree V form optimized for clamping. An Acme thread has a 29-degree trapezoidal form with a flat crest and root, optimized to transmit motion and carry load along the screw axis with less friction and more wear surface. Acme nuts and rod are a matched system — they are not interchangeable with standard nuts and bolts.
Finished vs Heavy Acme Hex Nuts
- Finished Acme hex nut: standard hex dimensions for the diameter; the general choice for most Acme assemblies.
- Heavy Acme hex nut: larger across the flats and taller, with more thread engagement for higher load and longer wear life.
- Bronze Acme nut: the traditional lead-screw nut — bronze running against a steel Acme screw gives low friction and excellent wear resistance. Available to order.
Bronze vs Steel for a Lead Screw
For a hand-wheel or motion lead screw that cycles often, a bronze nut on a steel screw is the classic pairing: the dissimilar metals resist galling, the bronze wears in preference to the harder screw (so you replace the cheaper nut, not the screw), and friction stays low. Steel nuts are fine for intermittent or static Acme uses (jacks, clamps, adjusters) where wear cycling is light. Tell us the duty and we'll recommend the material.
Sizing & Pairing
Match the nut diameter and pitch to your Acme rod exactly (for example 1-5 Acme, 3/4-6 Acme). We stock finished and heavy Acme hex nuts from 3/8 inch through 2 inch in standard pitches and the matching Acme threaded rod, so you can order a complete motion assembly. Left-hand and centralizing-class Acme are available to order.
Frequently Asked Questions
What is an Acme nut used for?
An Acme nut mates with Acme-threaded rod or a lead screw to transmit motion and carry heavy axial loads — in clamps, presses, vises, jacks, valves, machine slides, and hand-wheel screws — rather than for general clamping like a standard nut.
What is the difference between Acme and standard threads?
Standard UN threads use a 60-degree V form for clamping. Acme threads use a 29-degree trapezoidal form optimized to move loads along the screw axis. They are not interchangeable; Acme nuts only fit Acme rod.
Should a lead-screw nut be bronze or steel?
For frequently-cycled lead screws, bronze on a steel screw is the standard — low friction, good wear resistance, and the nut wears in preference to the screw. Steel nuts suit intermittent or static Acme applications.
Do you carry Acme rod to match the nuts?
Yes. We stock Acme threaded rod alongside finished and heavy Acme hex nuts, so you can order matched rod-and-nut motion assemblies from one source.
Acme Nuts & Rod, Matched
Finished and heavy Acme hex nuts, steel or bronze to order, plus matching Acme rod.