Nut Types & When to Use Them
A nut is a nut… until the joint vibrates loose or you need it to stay put. Here’s what each style is built for.
Whatever the style, a nut has to match the bolt’s size and thread first — a fine nut won’t run onto a coarse bolt. Past that, the shape is about the job: hold under vibration, lock in a position, join two rods, or just hand-tighten. Every nut below is drawn from the side.
Everyday
Hex nut
The standard six-sided nut. The default for general bolting with a wrench or socket.
Flange nut
A hex nut with a built-in washer flange — spreads load and (when serrated) helps grip against loosening. Saves adding a separate washer.
Heavy hex nut
Thicker and wider than a standard hex nut, for structural and high-strength bolting (pairs with A325 / A490). More thread engagement, more load.
Jam nut
A thin hex nut. Run it against a second nut to lock the pair (“double-nutting”), or use where a standard nut is too tall to fit.
Locking
Nylon-insert lock (nylock)
A nylon collar grips the bolt threads to resist loosening. Great for vibration; reusable a few times. Heat-limited — not for high temperatures (the nylon gives up).
All-metal lock
A prevailing-torque nut (distorted thread or top) that locks without nylon — so it handles heat where a nylock can’t. For hot or demanding spots.
Castle (slotted) nut
Slots across the top take a cotter pin through a hole in the bolt — a positive mechanical lock that can’t back off. Axles, shafts, and safety-critical pivots.
K-lock / keps nut
A hex nut with a captive star washer built on — the washer can’t fall off and bites for light anti-loosening. Handy on assembly lines.
Special purpose
Coupling nut
A long nut that joins two threaded rods or extends a bolt — the workhorse for all-thread runs and turnbuckle-style assemblies.
Wing nut
Two wings for hand-tightening — no tool needed. For covers, guards, and anything you take on and off often.
Cap (acorn) nut
A domed nut that covers the bolt end — protects the threads and gives a clean, finished look. Railings, furniture, exposed bolts.
Tee & other inserts
Press- and drive-in nuts (tee nuts, rivet nuts) that add threads to wood, sheet, or tube where you can’t reach a normal nut. Ask us for the style that fits your material.
How three of them are used
Match the whole stack
Tell us the bolt and the job — vibration, heat, hand-tight, structural — and we’ll set you up with the right nut, plus the washer and grade to go with it.