What a Hanger Bolt Is Called — US, UK, German, French and Other Markets
The part has one shape and a different name in every catalogue, and searching with the wrong one returns wooden dowels, roofing screws or stair kits. EKINSUN LTD is a custom parts manufacturer that makes hanger bolts to order, in the sizes on this page and in any length, thread or material outside them. The table gives the name buyers use in each market, the other names for the same part, and the look-alikes that are a different part.
| Market | Catalogue name | Also used for the same part | Not the same part |
|---|---|---|---|
| United States | hanger bolt | double-ended screw; hanger bolt with hex drive (the socket version); rail bolt — 5/16 × 3-1/2 in, sold as a stair kit with a nut and a wood plug | dowel screw: wood thread on both ends, joins wood to wood |
| United Kingdom, Ireland | hanger bolt | double-ended screw, wood-to-metal double-ended screw; handrail bolt (the kit with a nut) | dowel screw |
| Germany, Austria, Switzerland | Stockschraube | Stockschraube mit Innensechskant, mit Torx or mit Schlüsselfläche; Stockschraube mit Dichtung for roofs and solar mounting | Doppelgewindeschraube in timber building: a screw with two wood threads for on-rafter insulation |
| France, Belgium | vis double filetage | goujon double filetage bois-métal, goujon d'ancrage bois / métrique | goujon bois: a wooden dowel |
| Spain | espárrago rosca madera-métrica | tornillo doble rosca | — |
| Italy | vite doppio filetto | vite legno-metrica | — |
| Netherlands, Flanders | stokeind | stokschroef | — |
Need hanger bolts in a size, thread or material no catalogue lists? EKINSUN is a custom parts manufacturer: we make hanger bolts to your drawing, sketch or sample — steel, 304 or 316L stainless steel or brass — from 1 piece, quoted in 12 hours and shipped duties paid. Already a catalogue size? Ask us too — we may have it in stock, and larger quantities cost less per piece. All custom fasteners →
Three Forms — Plain, Centre Flats, Hex Socket
The wood end is the same on all three: a coarse, sharp thread on a thin core with a gimlet point, so it pulls itself into pre-drilled timber or a nylon plug. What changes is how torque gets into the bolt.
| Form | How it is driven | Usual material | Where it fits best |
|---|---|---|---|
| A — plain | two nuts locked against each other on the machine thread, or a hanger-bolt driver bit in a drill | zinc-plated steel, white or yellow passivated | general use; the lowest-cost form |
| B — centre wrench flats | open-end spanner on the flats between the two threads | zinc-plated steel | long bolts and hardwood, where two locked nuts slip |
| C — hex socket in the machine end | hex key or hex bit in the end of the machine thread | 304 stainless (1.4301, A2) | stairs, railings and outdoor work: nothing to lock, the visible thread stays clean |
Sizes and the Numbers That Go With Each
Size is written as the machine thread times the overall length: M8 × 80 is an M8 × 1.25 machine thread on a bolt 80 mm long from point to end. The lengths are the common ones; any length between or beyond them is made to order. The other columns are what you need on site to fit the bolt.
| Size | Machine thread | Common overall lengths L | Pilot hole in timber ≈ 0.7 × d | Wall plug Ø | Nut across flats | Inch look-alike (does not fit) |
|---|---|---|---|---|---|---|
| M4 | M4 × 0.7 | 35–50 | 2.8 (softwood: not required) | 6 | 7 | #8-32 UNC |
| M6 | M6 × 1.0 | 30, 40, 50, 60 | 4.2 (softwood: not required) | 8 | 10 | 1/4-20 UNC |
| M8 | M8 × 1.25 | 40, 45, 50, 55, 60, 70, 80, 90, 100 | 5.6 | 10 | 13 | 5/16-18 UNC |
| M10 | M10 × 1.5 | 60, 70, 80, 90, 100 | 7.0 | 12 | 16 (DIN 934: 17) | 3/8-16 UNC |
| M12 | M12 × 1.75 | 60, 80, 100 | 8.4 | 14 | 18 (DIN 934: 19) | 1/2-13 UNC |
Pilot hole: EN 1995-1-1 (Eurocode 5), 10.4.5 — screws up to 6 mm in softwood need no pre-drilling; all screws in hardwood, and screws over 6 mm in softwood, get a lead hole of about 70 % of the diameter over the threaded length. Above 500 kg/m³ (oak, beech) the standard says to find the hole by a test in an offcut. The column assumes the wood thread measures the same as the size; measure yours and take 70 % of the caliper reading. Wall plug: 2 mm over the size; fischer pairs M8 with a 10 mm and M10 with a 12 mm plug in its hanger-bolt sets. Nuts: across flats to ISO 4032, DIN 934 where it differs.
Fitting One — Timber, Masonry, and How to Drive It
In timber, drill the pilot hole as deep as the wood thread is long, drive the wood end in until the machine thread stands out by the length you need, and stop there: backing a hanger bolt out to adjust it loosens the thread in soft wood. In masonry, drill for the plug, set the plug flush and drive the wood thread into it. The plug carries the load, so the plug and the wall decide what the fixing holds, not the bolt.
To drive it, two nuts locked against each other on the machine thread give a spanner something to turn; release them by holding the lower nut and turning the upper one back. A hanger-bolt driver bit does the same in a drill. The flat form takes an open-end spanner. The hex-socket form takes a hex key in the end of the thread, which leaves the thread untouched — the reason stainless stair and railing bolts are made that way.
Measure First: Size and Pitch, Then Standard or Made
A hanger bolt goes into a nut or a tapped part that is already there, so the machine thread has to match it, not look like it. M8 and 5/16-18 differ by 0.06 mm on the outside diameter and a caliper alone will not separate them; ten threads will. Lay a rule along the thread and read the length of ten pitches:
| Metric thread | Outside Ø | Ten threads measure | Inch look-alike: outside Ø / ten threads |
|---|---|---|---|
| M4 × 0.7 | 4.00 | 7.0 | #8-32 UNC: 4.17 / 7.9 |
| M6 × 1.0 | 6.00 | 10.0 | 1/4-20 UNC: 6.35 / 12.7 |
| M8 × 1.25 | 8.00 | 12.5 | 5/16-18 UNC: 7.94 / 14.1 |
| M10 × 1.5 | 10.00 | 15.0 | 3/8-16 UNC: 9.53 / 15.9 |
| M12 × 1.75 | 12.00 | 17.5 | 1/2-13 UNC: 12.70 / 19.5 |
If diameter and pitch match a row of the size table, a standard bolt fits. If the reading falls between rows, if the thread is inch, or if the nut side has a fine pitch, that is the bolt we make: send the two numbers and the length. The full list of metric and inch threads that are mistaken for each other is on the metric vs imperial thread chart.
Hardware-Store Bolt or Made to Order
For a handful of standard bolts, a hardware store is the cheaper supplier, and we say so. Made to order, every size, thread and material is open, from 1 piece.
| What you need | In the catalogue? | What we make |
|---|---|---|
| A few zinc or A2 hanger bolts, M4 to M12, in a common length, for a shelf, a table leg or a handrail bracket | Yes — every hardware store | Buy it off the shelf; we also make it to order from 1 piece. Standard parts: ask us too — we may have them in stock. |
| The sizes on this page by the hundred or the thousand for a stair, railing or furniture run, in 304 with a hex socket or zinc-plated | Partly — small retail packs | Made to order in the quantity of the run; quote in 12 hours. |
| A length the lists skip, or a split between wood thread and machine thread that no list offers | No | Made to your lengths and split. |
| An inch machine thread — #8-32, #10-24, 1/4-20, 5/16-18, 3/8-16 — in a length or material the US lists do not carry | No | Made with the inch thread, in 304, 316L or brass. |
| A4 / 316L stainless for a pool, the coast or salted decking | Partly — short ranges | Made in 316L (1.4404), in the sizes on this page or your own. |
| M14, M16 or M20 for glulam, heavy beams or a machine base | Not in most lists | Made with the wood thread cut for the timber you name. |
| A collar, a sealing-washer seat for a roof, a left-hand machine thread or a different point | No | Made to the drawing or the old part. |
| A stair rail bolt kit to join two handrail sections | Yes — stair-part suppliers | Buy their set; we make the bolt when an old stair needs a length or thread the kits do not have. |
A stud with a machine thread on both ends is a double-end stud; a bar threaded end to end is a threaded rod. To extend a hanger bolt's machine thread, a coupling nut joins it to a rod; the spanner for each nut is on the wrench size chart.
Materials
| Material | Where it is used |
|---|---|
| 304 stainless (1.4301, A2) | stairs, railings, indoor and sheltered outdoor work; the usual material for the hex-socket form |
| Zinc-plated steel, white or yellow passivated | indoor furniture, pipe clamps, dry timber |
| 316L stainless (1.4404, A4) | pools, the coast, de-icing salt, and pressure-treated timber, whose copper-based preservatives attack zinc |
| Brass CW614N | decorative fittings, non-sparking use |
| Aluminium 6061 / 7075 | not used for hanger bolts: the wood thread strips in hardwood and aluminium galls in a steel nut; listed so the question is answered |
Where They Go
| Application | Usual size | What to watch |
|---|---|---|
| Stair handrail brackets on a wooden stair or a plugged wall | M8 | the hex-socket 304 form keeps the visible thread clean; pre-drill hardwood |
| Pipe clamps and hangers under joists or into a plugged wall | M8 or M10 connection thread | the clamp's boss decides the thread |
| Solar mounting on timber rafters | M10 or M12, 200 to 300 mm long | a sealing washer where the bolt passes the roof covering; bolts longer than 100 mm are made to order |
| Table and furniture legs (knock-down) | M8; 5/16-18 in US furniture | a threaded insert or T-nut in the leg takes the machine end |
What to Send
The machine thread (size and pitch, or the nut it must fit), the overall length, the wood-thread length if it matters, the form (plain, flats or hex socket), the material and the quantity. For a replacement, a photo of the old bolt beside a rule is enough. Quote in 12 hours.
Hanger Bolt FAQ
To give timber or a plugged wall a threaded stud with no head showing. The wood end is driven into the material, the machine end stays out and takes a nut, a bracket, a pipe clamp or a threaded insert. Typical jobs are stair handrail brackets, knock-down table legs, pipe clamps under joists and solar rails on timber rafters. Because the nut can come off the machine thread, the part it holds can be removed without disturbing the wood.
A hanger bolt has a wood thread on one end and a machine thread on the other, so it joins timber to metal or to a nut. A dowel screw has a wood thread on both ends and joins two pieces of timber. A stud with a machine thread on both ends is a double-end stud, which screws into a tapped hole rather than into wood.
About 5.6 mm, which is 70 % of 8 mm, drilled as deep as the wood thread is long; a 5.5 mm drill is the nearest size in most sets. That is the EN 1995-1-1 rule for screws over 6 mm in softwood and for all screws in hardwood. Up to M6 in softwood the standard asks for no pilot hole. In oak, beech and other timber above 500 kg/m³, drill a test hole in an offcut first.
A 10 mm nylon plug. The plug diameter is the bolt size plus 2 mm: M4 takes 6 mm, M6 8 mm, M8 10 mm, M10 12 mm and M12 14 mm, and fischer pairs M8 with its 10 mm and M10 with its 12 mm plug in its hanger-bolt sets. The plug and the wall decide the load, so for a handrail or anything that carries people, use the plug maker's figures for your wall.
Lock two nuts against each other on the machine thread and turn the upper one with a spanner; a hanger-bolt driver bit does the same in a drill. Bolts with centre flats take an open-end spanner on the flats. The 304 stainless bolts in the photo have a hex socket in the machine end and go in with a hex key, which leaves the thread untouched.
Yes; making them to order is what we do. The common sizes run from M4 × 35 to M12 × 100 in 304 stainless with a hex socket or in zinc-plated steel, and we make any other length, a chosen split between wood and machine thread, inch machine threads such as 1/4-20, 5/16-18 and 3/8-16, 316L (A4) and sizes from M14 up, all from 1 piece. Send the thread, overall length, material and quantity; quote in 12 hours.