ASME B18.31.3 specifies the dimensions and tolerances for inch left-hand fully threaded rod. The full dimensional table is reproduced below, followed by the DIN, ISO and ASME parts that match or supersede it.
- Standard
- ASME B18.31.3
- Product
- Inch Left-Hand Fully Threaded Rod
- Governing standards
- ASME B18.31.3 and ASME B1.1 LH
Equivalence between national standards is dimensional, not always metallurgical. Check the property class separately when substituting.
The table below lists the dimensions catalogued for inch left-hand fully threaded rod under ASME B18.31.3. The scope of ASME B18.31.3 itself is not summarised here — where a figure matters, confirm it against the published document.
ASME B18.31.3 — Scope
The table below lists the dimensions catalogued for inch left-hand fully threaded rod under ASME B18.31.3. The scope of ASME B18.31.3 itself is not summarised here — where a figure matters, confirm it against the published document.
Tolerance & Product Grades
Product grade is a concept from dimensional fastener standards and does not apply to ASME B18.31.3. Tolerances for this part are the limits shown against each dimension in the table.
Dimensions Specified by ASME B18.31.3
| Nominal size | Thread hand | Thread class | Standard lengths (in/ft) | Material options | Reference standard |
|---|
| 6-32 | left-hand | 2A | 12 / 24 in and 3 ft | zinc-plated steel / 18-8 stainless / 316 stainless | ASME B18.31.3 and ASME B1.1 LH |
| 8-32 | left-hand | 2A | 12 / 24 in and 3 ft | zinc-plated steel / 18-8 stainless / 316 stainless | ASME B18.31.3 and ASME B1.1 LH |
| 10-24 | left-hand | 2A | 12 / 24 in and 3 ft | zinc-plated steel / 18-8 stainless / 316 stainless | ASME B18.31.3 and ASME B1.1 LH |
| 1/4-20 | left-hand | 2A | 12 / 24 in and 3 ft | zinc-plated steel / 18-8 stainless / 316 stainless | ASME B18.31.3 and ASME B1.1 LH |
| 3/8-16 | left-hand | 2A | 12 / 24 in and 3 ft | zinc-plated steel / 18-8 stainless / 316 stainless | ASME B18.31.3 and ASME B1.1 LH |
| 1/2-13 | left-hand | 2A | 12 / 24 in and 3 ft | zinc-plated steel / 18-8 stainless / 316 stainless | ASME B18.31.3 and ASME B1.1 LH |
Companion Standards
A complete specification for inch left-hand fully threaded rod normally cites several documents: one for the geometry, one for the material or mechanical properties, and one for the finish. ASME B18.31.3 is one of them, not all of them.
When to Specify ASME B18.31.3
ASME B18.31.3 is the inch-based reference; for metric programs choose the ISO equivalent instead.
Custom manufacturing · Made to drawing
Need a bolt to this standard in a non-standard size?
Parts built to ASME B18 31 3 are already in the catalog, so a special is usually a variation on existing tooling rather than a new design — which is what keeps the cost down. Made by cold heading or hot forging.
Minimum order from 2,000 pieces; samples within 7 days of drawing approval.
Custom bolt manufacturingSend a drawing
Applications & Industries
Where Inch Left-Hand Fully Threaded Rod are used, and what decides the specification in each case. Stocked from 6-32 to 1/2-13 (screw size).
Industries that specify Inch Left-Hand Fully Threaded Rod
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Opposed adjusters
Left-hand and right-hand rod pairs used to change length without disconnecting the joint.
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Rotating equipment
Threaded adjustments arranged to resist self-loosening in service.
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Machine fixtures
Inch adjustment rods where the thread hand is part of the mechanism.
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Repair and fabrication
Replacement rod matched to existing left-hand nuts and couplers.
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Pressure equipment & flanges
Studs and nuts on flanged joints, where both ends are tightened and the assembly is inspected.
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Plant & machine installation
Anchoring and levelling machines onto bases and frames.
Typical applications
- providing a left-hand threaded member for an opposed adjuster
- matching the rod to a left-hand nut rather than a standard right-hand nut
- holding a threaded adjustment against rotation in a paired mechanism
- specifying inch thread class, hand, length and material together
- clamping a joint from both ends where a headed bolt will not fit
- suspending services from a soffit on threaded rod
Service conditions to specify against
- Marine and coastal
- Available in A4 (316) stainless for chloride exposure — coastal structures, pool halls, water treatment and deck hardware, where A2 will eventually pit.
- High load
- Supplied in ISO 898-1 property classes, so the joint can be designed to a stated proof load and tightened to a calculated torque rather than by feel.
Where to use something else
- Do not pair a left-hand rod with an ordinary right-hand nut; the threads will not engage correctly.
- Not for a joint that must be tightened from one side only — there is no head to hold.
Full application guide: where Inch Left-Hand Fully Threaded Rod are used, how to specify them, and the cases they are wrong for
