Buy Die Nuts Online in Australia
Die nuts are hexagonal thread-chasing dies, driven by a standard spanner or adjustable wrench, used to clean up and restore damaged external threads on bolts, studs and pipe ends. They're a maintenance tool first and foremost — where a round split die in a die stock is built to cut a brand-new thread from plain bar, a die nut is built to follow an existing thread and knock the burrs, corrosion and cross-threading back into line. AIMS Industrial stocks die nuts from Sutton Tools, Bordo and Goliath across metric, UNC/UNF, BSW/BSF and BSP/BSPT/NPT pipe thread forms, in HSS, chrome alloy and carbon steel, as singles, left-hand, oversize and boxed sets. We've put together a Thread Restoration Tools Guide: Die Nuts, Chasers, Files & Restorer Kits — When to Use Each if you'd like more detail before you buy.
Die Nut Quick Reference
| Thread Form | Governing Standard | Common Sizes Stocked | Typical Application |
|---|---|---|---|
| Metric Coarse (MC) | ISO 261 (AS 1721 in Australia) | M3–M30 | General Australian/European fastener repair |
| Metric Fine (MF) | ISO 261 (AS 1721 in Australia) | M3–M24 fine pitch | Automotive, hydraulic fittings, thin-walled sections |
| UNC (Unified Coarse) | ASME B1.1 | No.10 – 1½" | US-origin machinery and fasteners |
| UNF (Unified Fine) | ASME B1.1 | No.10 – 1½" | Aerospace, precision automotive, fine-pitch repair |
| BSW (Whitworth) | BS 84 | 3/16" – 1½" | Older Australian/UK machinery, vintage equipment |
| BSF (British Standard Fine) | BS 84 | 1/4" – 3/4" | Heritage British machinery, cylinder heads, restoration |
| BSPF / G (parallel pipe) | BS 21 / ISO 228-1 | 1/8" – 1½" | Hydraulic ports and fittings sealing on a washer or face |
| BSPT (taper pipe) | BS 21 / ISO 7-1 | 1/8" – 1½" | Pipe and fitting joints sealing on the thread itself |
| NPT (American taper pipe) | ASME B1.20.1 | 1/8" – 1½" | US-origin hydraulic and pneumatic fittings |
For cutting a brand-new external thread on plain bar stock, a round split die in a threading die stock is the correct tool, not a die nut. For damaged internal threads, use a tap instead.
Die Nuts vs Round Split Dies vs Button Dies
All three cut or restore the same external thread forms, but they're built for different jobs. A die nut is a solid hexagonal block, driven directly by a spanner, with no diameter adjustment — its job is to run down an existing thread and clean it up. A round split die (see our threading dies range) sits in a die stock and can be closed down for a roughing pass then opened slightly for a finishing pass, which is what makes it the right choice for cutting a genuinely new thread from bar. A button die (see our button dies range) is a small, thin round die, also fitted to a die holder rather than driven by spanner, generally used for lighter thread-chasing work in tighter spaces.
In practice: reach for a die nut when you're restoring a burred, corroded or cross-threaded bolt, stud or pipe end in the field. Reach for a round split die when you're producing a new thread on a blank. Both belong in a well-equipped maintenance kit — many of our tap & die sets pair taps with round dies, while our die nut sets here are the hex-driven, spanner-friendly companion for site and workshop repair work.
Metric and Unified (fastener) thread die nuts
Sutton Tools and Goliath both supply metric coarse and metric fine die nuts to ISO 261, adopted in Australia as AS 1721, spanning M3 through M30 depending on set. Goliath also lists metric coarse/fine combination sets (e.g. M6–M24) that cover both pitch series from a single set, useful where you're not sure in advance which pitch you'll meet on site. UNC and UNF die nuts to ASME B1.1 cover imperial fasteners on US-origin plant, vehicles and imported equipment — Goliath's combination UNC/UNF sets (e.g. 1/4"–1" covering both) and Sutton's individual UNC and UNF die nuts and 10-piece sets are stocked for this. Always confirm both nominal diameter and pitch (TPI) before ordering: M10 x 1.5 and M10 x 1.25, or a UNC and UNF thread of the same diameter, look identical to the eye but won't chase each other's threads.
BSW, BSF and pipe thread (BSP/BSPT/NPT) die nuts
BSW (Whitworth) and BSF (British Standard Fine) die nuts to BS 84 cover older Australian and British machinery, vintage vehicles and agricultural equipment still running Whitworth-form fasteners — Sutton, Bordo and Goliath all stock these individually and in sets. For pipe and fitting threads, the range covers three distinct standards that are easy to mix up: BSPF (also called G, parallel) to ISO 228-1, which seals on a bonded washer or face rather than the thread; BSPT, a taper thread to ISO 7-1 that seals on the thread itself; and NPT, the American taper pipe thread to ASME B1.20.1, which looks similar to BSPT but has a different thread angle and is not interchangeable with it. Goliath supplies dedicated BSPF, BSPT and NPT die nuts and sets, including combination BSPF/BSPT/NPT sets for workshops servicing mixed-origin hydraulic and pneumatic equipment. If you're restoring a damaged fitting from a hydraulic or pneumatic system, confirm which of the three pipe thread standards you're dealing with before ordering — see our hydraulic fittings and pipe fittings ranges for the fittings themselves.
Material and construction: HSS, chrome alloy and carbon steel
Goliath's die nuts are predominantly HSS (high-speed steel), giving good edge retention across mixed rethreading work on steel and stainless fasteners. Bordo's range is described as chrome alloy construction across its metric, UNC, UNF, BSW and BSP die nuts. Sutton's range spans carbon steel (e.g. the M448 BSF die nut) through to standard HSS grades depending on the specific thread form and set. As a rule of thumb: HSS suits harder materials, stainless fasteners and higher-volume maintenance work where tool life matters; carbon steel is a perfectly serviceable, lower-cost option for occasional rethreading on mild steel fasteners. None of these are precision, close-tolerance thread-cutting tools — they cut to standard commercial tolerance, which is what you want when restoring a fastener that was itself made to standard tolerance in the first place.
Left-hand and oversize die nuts
Most fasteners use a right-hand thread, but left-hand threaded components do turn up — certain gas cylinder fittings, some rotating machinery designed to resist loosening, and older bicycle pedals among them. Goliath stocks left-hand die nuts in both metric coarse (MC) and UNF forms for exactly this situation; using a standard right-hand die nut on a left-hand thread will not chase it and can damage both the die and the fastener. Goliath's oversize hexagonal die nut is built for threads that have been slightly damaged or built up with corrosion, cutting fractionally larger to true the thread back up rather than simply following whatever distortion is already there.
Single die nuts vs boxed sets
If you only ever meet one or two thread sizes in your work, a single die nut is the economical choice. Where a workshop or service vehicle needs to be ready for whatever turns up, Goliath's EDN-series sets group a run of sizes in one thread standard — from compact sets (e.g. 1/8"–1", M6–M12) through to Goliath's "Ultimate" die nut set, which spans multiple standards in one case. Sutton also offers 10 and 16-piece boxed sets in UNC, UNF, BSW and metric coarse. A set is generally better value per die than buying singles once you need more than three or four sizes, and keeps everything organised in one case on the van or bench.
People Also Ask — Die Nuts
What is a die nut used for?
A die nut is used to clean up, or "chase", a damaged external thread on a bolt, stud or pipe end — removing burrs, light corrosion or the effects of cross-threading so the fastener runs freely again. It's driven by a spanner or adjustable wrench directly onto the hex body, no die stock required, which makes it a quick tool for in-situ maintenance work rather than production thread cutting.
What is the difference between a die nut and a round split die?
A round split die sits in a die stock and can be adjusted — closed down for a roughing cut, then opened slightly for a cleaner finishing cut — which is what makes it suited to cutting a brand-new thread on plain bar. A die nut has no adjustment: it cuts (or rather, follows) a fixed thread form, and is built to run down an existing thread rather than start one from scratch. Use a round split die from our threading dies range for new work; use a die nut for repair.
What is the difference between BSPF, BSPT and NPT?
All three are pipe thread standards but they aren't interchangeable. BSPF (also called G) is a parallel thread to ISO 228-1 that seals via a bonded washer or flat face, not the thread itself. BSPT is a taper thread to ISO 7-1 that seals on the thread. NPT is the American taper pipe thread to ASME B1.20.1 — similar in concept to BSPT but cut to a different thread angle, so an NPT die nut will not properly chase a BSPT thread even though they look alike. Check which standard your fitting uses before ordering.
Can a die nut cut a new thread on plain bar stock?
It can, in soft material, but it isn't the right tool for the job. With no diameter adjustment, a die nut is hard to start square on a blank and tends to cut an oversize or "drunken" thread. For new external threads, use a round split die in a die stock, taking a roughing cut followed by a finishing cut. Keep die nuts for rethreading and cleaning up existing threads.
How do I use a die nut to repair a damaged thread?
Clean the thread and apply cutting oil (or leave dry on aluminium and brass), then start the die nut by hand at the good end of the thread and work it along with a spanner, backing off a half-turn every so often to clear swarf. Let the die nut follow the existing thread rather than forcing a new path, and keep it square to the bolt or pipe. The aim is to restore the original thread profile, not deepen or widen it.
How do I identify the thread before ordering a die nut?
Measure the outside diameter with calipers, then check the pitch with a thread pitch gauge, or count the number of threads over 25mm for an imperial estimate. Together these tell you the nominal size and whether you're dealing with metric coarse, metric fine, UNC, UNF, BSW, BSF, or one of the pipe thread standards. Getting both diameter and pitch right matters — threads of the same diameter but different pitch will not chase each other.
Should I choose an HSS or carbon steel die nut?
HSS (high-speed steel) die nuts hold an edge longer and cope better with stainless and harder alloy fasteners, making them the better choice for regular maintenance work or higher-volume use. Carbon steel die nuts are a lower-cost option that's perfectly adequate for occasional rethreading on mild steel fasteners in general workshop use.
When would I need a left-hand or oversize die nut?
A left-hand die nut is needed when the fastener itself has a left-hand thread — some gas fittings, certain rotating machinery and a handful of legacy components use this to resist loosening in service; a standard right-hand die nut will not chase it. An oversize die nut is intended for threads that have swelled slightly from corrosion or minor damage, cutting a touch larger to true the thread rather than simply following the existing distortion.
Are die nuts and tap-and-die sets the same thing?
Not quite. A tap-and-die set typically pairs taps (for internal threads) with round split dies (for cutting new external threads) in one case — see our tap & die sets range. Die nuts are a separate, hex-driven tool aimed specifically at rethreading damaged external threads rather than cutting new ones, and are sold here as dedicated singles and sets by thread standard.
Order Die Nuts from AIMS Industrial
AIMS Industrial stocks die nuts from Sutton Tools, Bordo and Goliath across metric, UNC/UNF, BSW/BSF and BSP/BSPT/NPT thread forms, in singles, sets, left-hand and oversize options. If you're not sure which thread standard you're chasing, send us the diameter and pitch (or a photo of the damaged fastener) and our team will confirm the right die nut for the job. Call us on (02) 9773 0122, get in touch via our contact us page, or submit a request a quote for trade and bulk pricing.