FREE Delivery
Australian Owned
Spend DISCOUNTS
All Categories
Socket Allen Screws
Compare your fastener to our visual size guide to confirm M-size, pitch and length.
Match your Allen / hex key AF (across-flats) to the screw size it fits. Our reference chart covers every metric and imperial size we stock.
Socket Allen Screws for Precision Engineering and Machinery
Socket screws cover a huge range of engineering, manufacturing, electronics and construction applications — from tiny M2 grub screws holding a set collar on a shaft to large cap head bolts clamping structural components in heavy machinery. They share an internal hex (Allen key) or Torx drive in the head, driven with a hex key or socket bit, plus a fully-threaded uniform-diameter shank that threads into a pre-tapped hole or a nut — they don't cut their own thread the way self-tapping or chipboard screws do.
Check our reviews from DIYers, tradespeople, builders, manufacturers, government, councils, engineers across Australia.
We've been supplying these online from Brisbane for over 15 years. With 25,000 stock lines and over 200 million pieces in stock, we carry one of the most comprehensive ranges of socket screws available in Australia — from common metric sizes to specialist imperial, British Association (BA) and nylon grades. Save more as you buy more — we offer up to 13 price breaks plus 3 spend-tier discounts.
Socket screws are fully threaded with uniform threads — the same diameter throughout the entire length. This distinguishes them from self-tapping or chipboard screws which have tapered threads.
MATERIALS AND COATINGS
Zinc Plated — Bright silver finish, internal use only. The most economical option for dry, protected environments. Widely used in electronics, machinery and general assembly.
Black (Plain Finish) — Unfinished bare steel with no protective coating. 'Black' is an old industry term for plain finish. Will rust over time without additional protection. Used where the fastener will be concealed, painted over, or where appearance is secondary.
A2-70 G304 Stainless Steel — The most popular stainless grade. Marked A2, A2-70, 304 or G304 — all the same specification. Excellent corrosion resistance across most Australian environments. G304 is largely non-magnetic — A small degree of magnetism from work-hardening during manufacture is normal.
A4-70 G316 Marine Grade Stainless — The highest corrosion resistance available. For marine, coastal, chemical and food industry environments. G316 is largely non-magnetic — Same note on work-hardening magnetism applies.
UNDERSTANDING THREAD PITCH
Thread pitch (metric) is the distance between the peaks of two adjacent threads, expressed in millimetres. A thread pitch of 1.50mm means adjacent threads are 1.50mm apart. All our metric socket screws use standard metric coarse pitch unless otherwise specified.
Imperial sizes are measured in TPI (threads per inch). To identify the TPI of an unknown screw, measure 1" (25.4mm) along the threads with a ruler and count how many thread peaks fall within that span — that number is the TPI. On smaller screws the threads can be hard to count by eye — use a pen or thin drill bit to step from one thread to the next as you count, and a torch (or your phone light) for better visibility.
HOW FASTENER LENGTH IS MEASURED
For socket screws, length is measured from under the head to the tip — because the head sits above the surface, only the shank and thread are embedded. The exception is countersunk head screws, where the head sits flush — in that case length is measured from the top of the head to the tip.
A NOTE ON GALLING
Galling can occur when a nut is tightened onto a bolt under excessive pressure — common with stainless fasteners but can affect any material. To reduce the risk: tighten slowly, use a lubricant or anti-seize compound, avoid using damaged or contaminated threads, and never spin a nut on with power tools without first running it on by hand.
OUR RANGE
Cap Head Socket Screws — The workhorse of precision engineering. High clamping force, hex socket drive, compact cylindrical head.
Countersunk Head Socket Screws — Flush-fitting with internal hex drive. Clean finish for panels, brackets and any application where a protruding head is not acceptable.
Button Head Socket Screws — Wide, low dome head with hex socket. Greater bearing surface than cap head for thin materials.
Button Flange Head Socket Screws — Button head with integrated flange washer for extra load distribution.
Low Head Socket Cap Screws — Reduced height cap head for space-restricted applications.
Socket Set Screws (Grub Screws) — Headless. Used to lock components onto shafts and in collars, pulleys and hubs.
Shoulder Socket Screws — Precision ground smooth shoulder for use as pivot pins, axles and bearing surfaces.
Need help choosing the right grade or size? Our Technical PDF's Library has specification guides and technical charts. Prices include GST and free standard delivery anywhere in Australia.
FREQUENTLY ASKED QUESTIONS
Can stainless fasteners be used with aluminium?
Yes — and for most applications, no special precautions are needed. The combination is widely used in industries where strength and corrosion resistance matter (marine, automotive, structural aluminium). For applications with sustained moisture or salt exposure, a few simple steps (barrier washer, sealant, matched-anodising) prevent any long-term galvanic corrosion concerns. Full guidance: Can stainless fasteners be used with aluminium?
What's the difference between a cap head, button head, and countersunk socket screw?
A cap head (socket head cap screw) has a compact cylindrical head — the workhorse of precision engineering, used wherever high clamping force is needed. A button head has a wide low dome — softer profile and larger bearing area. A countersunk head sits flush with the surface when driven into a matching countersunk hole — used where the screw must not protrude. All three are driven by an internal hex (allen key).
What allen key size do I need for an M-something socket screw?
Standard hex key sizes for metric socket head cap screws: M3 = 2.5mm, M4 = 3mm, M5 = 4mm, M6 = 5mm, M8 = 6mm, M10 = 8mm, M12 = 10mm, M16 = 14mm. Button head and low-head variants are usually one size smaller. Always check the spec sheet for the exact product — particularly for shoulder screws and imperial sizes.
What does Class 12.9 mean and when should I use it?
Class 12.9 is the highest standard high-tensile metric grade — ultimate tensile strength 1200 MPa, yield 1080 MPa. Around 50% stronger than Class 8.8. Used in high-load mechanical engineering: machinery, automotive, mining equipment, any joint needing maximum clamp force in a compact bolt. Trade-off: more brittle than 8.8, so less tolerant of impact loading.
Can I use socket allen screws in stainless steel?
Yes — A2-70 G304 stainless for general external use and A4-70 G316 marine grade for coastal or chemical environments. Class 12.9 equivalent in stainless is available via A4-80 G316 high tensile. One caution: stainless against stainless is prone to galling (cold welding) under tightening — use anti-seize compound and tighten slowly to mitigate.
What's a grub screw and how does it lock things in place?
A grub screw is a fully-threaded headless set screw — driven entirely below the surface of the threaded hole. The exposed end has a point (cup, cone, flat or dog) that bites into the shaft or component you're locking. Used to fix pulleys, gears, collars and similar onto shafts. Cup point is the most common — it digs in slightly and resists rotation reliably.
Why does my stainless socket screw seize when I tighten it?
That's galling — cold welding between stainless threads under high contact pressure. The thread surfaces effectively fuse together. To prevent it: tighten slowly (don't power-drive), apply a thread lubricant or anti-seize compound, avoid running the screw on and off with power tools, and never spin a stainless nut onto a stainless bolt at high speed.
Are Class 12.9 socket cap screws stronger than Class 8.8 hex bolts?
Yes — substantially. Class 12.9 has ultimate tensile strength of 1,200 MPa and yield of 1,080 MPa, compared to Class 8.8 at 800 / 640 MPa. That's roughly 50% more strength for the same diameter. Most stocked socket cap screws are 12.9 plain black; the matching head shape also concentrates clamp load efficiently. Use them where you need maximum clamp in a compact form.
Why is my Allen key cam-ing out (slipping) when I tighten the screw?
Usually one of three reasons: (1) the wrong key size — imperial keys cam out on metric sockets and vice versa, even when they feel close; (2) a worn or rounded Allen key — replace the key, the socket isn't repairable; (3) the screw was already tight and you're now trying to overtorque it. Use a quality ball-end or T-handle key for hard-to-reach work.
Can I use socket cap screws underwater or in marine environments?
Yes, but in A4-70 G316 marine-grade stainless only — never plain black 12.9. The standard plain black high-tensile finish has no corrosion protection and will rust within days in salt spray. A4-70 G316 is alloyed with molybdenum for chloride resistance and is the only material we'd recommend within 300m of the coast or in submerged applications.
What's a shoulder bolt and when do I need one?
A shoulder bolt (also called a stripper bolt or socket shoulder screw) has a precision-ground unthreaded shoulder between the head and a smaller threaded shank. The shoulder acts as a bearing surface for rotating parts, sliding mechanisms, jigs and dies. Use one when you need a screw that doubles as a pivot, locator, stop or bushing carrier.
How do I stop my stainless socket screws from galling (seizing)?
Stainless-on-stainless is prone to galling because the soft passive layer welds under friction. Fix: apply an anti-seize compound (copper-based or nickel-based) to the threads before assembly, slow your tightening speed, never use an impact driver on stainless, and make sure the threads are clean. Galled threads are unrecoverable — you'll cut the screw out.
WHY AUSTRALIA TRUSTS BOLT & NUT
With 15+ years selling fasteners online from Brisbane, we hold over 25,000 stock lines and 200 million pieces — 98.75% of online orders placed before 1pm leave same day. Save more as you buy more — we offer up to 13 price breaks plus 3 spend-tier discounts. Read our customer reviews or get in touch if you need help picking the right socket screw.
-
Button Flange Head Socket -
Button Head Socket -
Countersunk Head Socket -
Low Head Socket Cap -
Shoulder Socket -
Socket Head Cap -
Socket Set (Grub)
-
Free shipping
In stock
-
Free shipping
In stock
-
Free shipping
In stock
-
Free shipping
In stock
-
Free shipping
In stock
-
Free shipping
In stock
-
Free shipping
In stock
-
Free shipping
In stock
-
Free shipping
In stock
-
Free shipping
In stock
-
Free shipping
In stock
-
Free shipping
In stock
-
Free shipping
In stock
-
Free shipping
In stock
-
Free shipping
In stock
-
Free shipping
In stock
-
Free shipping
In stock
-
Free shipping
In stock
-
Free shipping
In stock
-
Free shipping
In stock
-
Free shipping
In stock
-
Free shipping
In stock
-
Free shipping
In stock
-
Free shipping
In stock
-
Free shipping
In stock
-
Free shipping
In stock
-
Free shipping
In stock
-
Free shipping
In stock
-
Free shipping
In stock
-
Free shipping
In stock
-
Free shipping
In stock
-
Free shipping
In stock
-
Free shipping
In stock
-
Free shipping
In stock
-
Free shipping
In stock
-
Free shipping
In stock
-
Free shipping
In stock
-
Free shipping
In stock
-
Free shipping
In stock
-
Free shipping
In stock
Find the right socket Allen screws for your project at Bolt & Nut Australia. We stock a huge range online — cap head, button head, countersunk, grub set screws and shoulder bolts. Available in high-tensile black Class 12.9, stainless A2-70 G304 and A4-70 G316 marine. Order online for same-day Brisbane dispatch and free delivery Australia-wide.
