Inch Wood-to-Machine Hanger Bolts
No. 6-32 – ½-13 · ⅝ – 14″The standard hanger bolt, in the industry's fixed lengths and thread splits, in zinc plated steel or stainless.
SS 304 Solar & Wood Hanger Bolts: Manufacturer & Supplier
A hanger bolt has no head: one end carries a coarse wood thread with a gimlet point, and the other a machine thread. The wood end goes into timber, and the machine end takes a nut. A fixture can then be fitted, tightened and removed again and again without wearing out the wood.
Exotic Alloy manufactures hanger bolts in Mumbai, India, rolling both threads on one blank so they are concentric. We make inch wood-to-machine hanger bolts in the industry-standard lengths and thread splits, metric M6 to M12 hanger bolts, and long M10 / M12 stainless solar hanger bolts with EPDM seals and flange nuts. We supply furniture, building-services and solar mounting companies in India, and export to the Netherlands, Europe and the Americas.
Custom Lengths
The standard inch lengths ship from stock in zinc plated steel and stainless. Solar hanger bolts are made to your rail system's length and thread split, with or without driving features, seals and nuts.
No. 6-32 – ½-13
M6 – M12
Wood + machine thread
Solar sets with EPDM
Steel, SS 304, A4
Hanger bolt at a glance
- Form
- Headless; wood thread one end, machine thread the other
- Threads
- UNC or metric machine thread; coarse wood thread with gimlet point
- Sizes
- No. 6-32 to ½-13 inch; M6 to M12 metric
- Material
- AISI 1008 / 1010 steel; stainless 303, 304 (A2), 316 (A4)
- Driven by
- Two locked nuts, a hanger bolt driver, or a built-in drive
- Related
- Lag bolts, threaded rods, nuts
Hanger Bolt Specification
The range we manufacture and supply.
BasisIndustry-standard inch dimensions (thread split by length); metric and solar hanger bolts to drawing; ISO 3506-1 stainless classes; ASME B1.1 UNC / ISO metric machine threads
Size rangeNo. 6-32, 8-32, 10-24, ¼-20, ⅕-18, ⅜-16, ½-13 from ⅝″ to 14″; M6 to M12 metric; solar M10 × 180 to M12 × 300 mm and longer to order
ThreadsMachine end UNC 2A or metric 6g; wood end coarse wood thread with gimlet point; both rolled
DrivePlain (driven with locked nuts or a driver); hex socket in the machine end or hex collar on solar bolts to order
PropertiesSteel No. 10 to ⅜″: core hardness B80–B100, 74 ksi minimum tensile on the machine-thread end; stainless to ISO 3506 class or bar condition
MaterialsAISI 1008 / 1010 steel; stainless 303, 304 (A2), 316 (A4); other alloys to order
FinishZinc plated clear or yellow; plain; passivated stainless
Solar setsHanger bolt with EPDM sealing washer and DIN 6923 serrated flange nuts; adapter plates to order
ToleranceLength ±1/16″ up to 6″, ±1/8″ over 6″; metric to drawing
PackingBoxes of 50 or 100, bulk cartons, or retail packs; solar sets bagged with nuts and seals
Types of Hanger Bolts We Manufacture
Solar Hanger Bolts
M10 / M12 · 180 – 300 mm · A2 stainlessLong hanger bolts for PV rails on corrugated metal and fibre cement roofs, with an EPDM seal, flange nuts and a drive feature.
Metric Hanger Bolts
M6 – M12 · to drawingMetric machine thread with wood thread, for European furniture fittings, ceiling suspensions and fixtures.
Stainless Hanger Bolts
303 · 304 (A2) · 316 (A4)For outdoor timber, decks, boats, food plants and treated wood, where zinc plating would rust.
Hanger bolt, lag screw or dowel screw?
| Feature | Hanger bolt | Lag screw | Dowel screw |
|---|---|---|---|
| Head | None | Hex head | None |
| Threads | Wood + machine | Wood only | Wood on both ends |
| Holds the part with | A nut on the machine thread | The head | Joins two wood parts end to end |
| Removable part | Yes, nut off, part off; bolt stays | Only by backing the screw out | No |
| Typical use | Table legs, fixtures, solar rails | Ledgers, heavy timber | Furniture joints |
Hanger Bolt Dimensions & Thread Lengths
There is no ASME or ISO standard for hanger bolts. The inch lengths and thread splits below are the ones the US industry stocks; solar hanger bolts follow each mounting system.
| Thread | Length C in | Machine thread A in | Wood (lag) thread B in | Plain centre D in |
|---|---|---|---|---|
| 6-32 | ⅝″ | ¼″ | ⅜″ | – |
| 6-32 | ¾″ | ⅜″ | ⅜″ | – |
| 6-32 | ⅞″ | ¼″ | ⅝″ | – |
| 6-32 | 1″ | ⅜″ | ⅝″ | – |
| 8-32 | ⅝″ | ¼″ | ⅜″ | – |
| 8-32 | ¾″ | ⅜″ | ⅜″ | – |
| 8-32 | ⅞″ | ¼″ | ⅝″ | – |
| 8-32 | 1″ | ⅜″ | ⅝″ | – |
| 8-32 | 1¼″ | ⅝″ | ⅝″ | – |
| 8-32 | 1½″ | ⅝″ | ⅞″ | – |
| 8-32 | 1¾″ | ¾″ | 1″ | – |
| 8-32 | 2″ | 1″ | 1″ | – |
| 10-24 | 1″ | ⅜″ | ⅝″ | – |
| 10-24 | 1¼″ | ⅝″ | ⅝″ | – |
| 10-24 | 1½″ | ⅝″ | ⅞″ | – |
| 10-24 | 1¾″ | ¾″ | 1″ | – |
| 10-24 | 2″ | 1″ | 1″ | – |
| 10-24 | 2½″ | 1″ | 1½″ | – |
| 10-24 | 3″ | 1½″ | 1½″ | – |
| 10-24 | 3½″ | 1½″ | 2″ | – |
| 1/4-20 | 1″ | ⅜″ | ⅝″ | – |
| 1/4-20 | 1¼″ | ⅝″ | ⅝″ | – |
| 1/4-20 | 1½″ | ⅝″ | ⅞″ | – |
| 1/4-20 | 1¾″ | ¾″ | 1″ | – |
| 1/4-20 | 2″ | 1″ | 1″ | – |
| 1/4-20 | 2¼″ | 1″ | 1¼″ | – |
| 1/4-20 | 2½″ | 1″ | 1½″ | – |
| 1/4-20 | 2¾″ | 1¼″ | 1½″ | – |
| 1/4-20 | 3″ | 1½″ | 1½″ | – |
| 1/4-20 | 3½″ | 1½″ | 2″ | – |
| 1/4-20 | 4″ | 2″ | 2″ | – |
| 1/4-20 | 4½″ | 1⅛″ | 3″ | ⅜″ |
| 1/4-20 | 5″ | 1⅜″ | 3″ | ⅝″ |
| 1/4-20 | 6″ | 1½″ | 3″ | 1½″ |
| 5/16-18 | 1½″ | ⅝″ | ⅞″ | – |
| 5/16-18 | 1¾″ | ¾″ | 1″ | – |
| 5/16-18 | 2″ | 1″ | 1″ | – |
| 5/16-18 | 2¼″ | 1″ | 1¼″ | – |
| 5/16-18 | 2½″ | 1″ | 1½″ | – |
| 5/16-18 | 2¾″ | 1¼″ | 1½″ | – |
| 5/16-18 | 3″ | 1½″ | 1½″ | – |
| 5/16-18 | 3½″ | 1½″ | 2″ | – |
| 5/16-18 | 3¾″ | 1¾″ | 2″ | – |
| 5/16-18 | 4″ | 2″ | 2″ | – |
| 5/16-18 | 4½″ | 1⅛″ | 3″ | ⅜″ |
| 5/16-18 | 5″ | 1⅜″ | 3″ | ⅝″ |
| 5/16-18 | 5½″ | 1½″ | 3″ | 1″ |
| 5/16-18 | 6″ | 1½″ | 3″ | 1½″ |
| 3/8-16 | 1½″ | ½″ | 1″ | – |
| 3/8-16 | 2″ | 1″ | 1″ | – |
| 3/8-16 | 2½″ | 1″ | 1½″ | – |
| 3/8-16 | 3″ | 1½″ | 1½″ | – |
| 3/8-16 | 3½″ | 1½″ | 2″ | – |
| 3/8-16 | 4″ | 2″ | 2″ | – |
| 3/8-16 | 4½″ | 1⅛″ | 3″ | ⅜″ |
| 3/8-16 | 5″ | 1⅜″ | 3″ | ⅝″ |
| 3/8-16 | 5½″ | 1½″ | 3″ | 1″ |
| 3/8-16 | 6″ | 1¼″ | 3″ | 1¾″ |
| 3/8-16 | 8″ | 2½″ | 3″ | 2½″ |
| 3/8-16 | 10″ | 2½″ | 3″ | 4½″ |
| 3/8-16 | 12″ | 2½″ | 3″ | 6½″ |
| 3/8-16 | 14″ | 2½″ | 3″ | 8½″ |
| 1/2-13 | 3″ | 1″ | 2″ | – |
| 1/2-13 | 3½″ | 1½″ | 2″ | – |
| 1/2-13 | 4″ | 2″ | 2″ | – |
| 1/2-13 | 5″ | 2″ | 3″ | – |
| 1/2-13 | 6″ | 2½″ | 3″ | ½″ |
| 1/2-13 | 8″ | 2½″ | 3″ | 2½″ |
| 1/2-13 | 10″ | 2½″ | 3″ | 4½″ |
| 1/2-13 | 12″ | 2½″ | 3″ | 6½″ |
Industry-standard lengths and thread splits as published by US hanger bolt suppliers. In every row, A + B + D = C, which we checked. Length tolerance: ±1/16″ up to 6″, ±1/8″ over 6″.
| Size | Pilot hole, hardwood in | Pilot hole, softwood in | Standard lengths in, from the table |
|---|---|---|---|
| 1/4-20 | 3/16″ | 5/32″ | 1″ to 6″ |
| 5/16-18 | ¼″ | 7/32″ | 1½″ to 6″ |
| 3/8-16 | 5/16″ | 9/32″ | 1½″ to 14″ |
Supplier guidance for typical woods; there is no standard. Try it in an offcut of the same timber first.
| Maker (example) | Size | Metric thread mm | Wood thread mm | Stainless class | Drive |
|---|---|---|---|---|---|
| Eurotec | M10 × 180 | 85 | 80 | A2-70 | SW 7 |
| Eurotec | M10 × 200 | 85 | 80 | A2-70 | SW 7 |
| Eurotec | M10 × 250 | 90 | 80 | A2-70 | SW 7 |
| Eurotec | M12 × 300 | 150 | 100 | A2-70 | SW 9 |
| K2 Systems | M10 × 250 | 85 | 67 | A2-40 | hex socket 7 |
Published sizes from two European solar mounting makers, shown as examples of the common lengths and thread splits. The K2 bolt carries German general approval Z-14.4-602. We make solar hanger bolts to your system's drawing.
Hanger Bolt Length Finder
Tell us how much machine thread must stick out (fixture plus washer plus nut) and how deep the wood thread should go, and we pick the shortest standard length.
Your joint
Picks the shortest standard length whose machine thread A and wood thread B both cover your figures. Machine thread needed = fixture thickness + washer + nut + two threads’ clearance.
Suggested hanger bolt
5/16‑18 × 2‑1/2″
shortest standard length
Machine thread A:1 in
Wood thread B:1.5 in
Plain centre D:–
Pilot hole (hard / soft wood):1/4 / 7/32 in
Installing Hanger Bolts
1
Mark & drill
Drill a pilot hole square to the face, as deep as the wood thread.
2
Lock two nuts
Run two nuts onto the machine thread and tighten them against each other, or fit a hanger bolt driver.
3
Drive in
Turn the upper nut or the driver until the wood thread is fully buried and the bolt is square.
4
Release
Back the nuts apart and remove them; the machine thread is undamaged.
5
Fit the part
Fit the fixture, washer and nut, and tighten without spinning the bolt in the wood.
Do
- Use the larger pilot hole in hardwood
- Drive into side grain where possible
- Use stainless in outdoor, wet or treated timber
- On roofs, seal at the crest of the corrugation, not in the valley
Don't
- Grip the machine thread with pliers or a pipe wrench
- Drive without a pilot hole in dense hardwood
- Over-tighten the nut so the wood thread strips
- Hang loads in end grain without a design check
Hanger Bolt Grades & Finishes
| Material | Properties | Use |
|---|---|---|
| Steel, AISI 1008 / 1010 | No. 10 to ⅜″: core hardness B80–B100; 74 ksi min tensile on the machine-thread end | Indoor furniture, fixtures, building services |
| Stainless 303 / 304 | Per bar condition; A2 classes on request | Outdoor timber, decks, food plants |
| A2-70 stainless (ISO 3506-1) | 700 MPa min tensile, 450 MPa min yield | Solar hanger bolts |
| A4 stainless (316) | A4-70 on request | Coastal roofs, boats, treated timber |
| Finish | Specification | Notes |
|---|---|---|
| Zinc plated, clear | ASTM F1941 | Standard indoor finish |
| Zinc plated, yellow | ASTM F1941 | Better salt-spray life than clear |
| Plain | Oiled | For painting or dry interiors |
| Passivated stainless | ASTM A967 / A380 | 303, 304, A2 and A4 hanger bolts |
Hanger Bolt Materials
Every grade links to its datasheet on this site.
How Our Hanger Bolts Are Made
1
Cut blanks
Wire straightened and cut to length, with the wood-thread end pointed.
2
Roll the wood thread
The coarse wood thread and gimlet point are rolled on one end.
3
Roll the machine thread
The UNC or metric thread is rolled on the other end, concentric with the wood thread.
4
Drive feature
Hex socket or collar formed on solar bolts, when specified.
5
Finish & kit
Zinc plated or passivated, then packed with nuts and seals if required.
Where Our Hanger Bolts Are Used
Furniture
Table and bed legs, removable frames and knock-down fittings.
Solar roofs
PV rails on corrugated metal and fibre cement roofs over timber rafters.
Building services
Hangers for pipes, conduits and light fixtures under timber joists.
Shopfitting & signs
Removable displays, signs and panels on timber framing.
Boats & outdoor
Stainless hanger bolts in decks, docks and boat fittings.
Instruments & crafts
Small 6-32 and 8-32 hanger bolts in wooden cabinets and craft work.
Hanger Bolt Inspection & Certification
| Check | Method | Applied to |
|---|---|---|
| Length & thread split | Against C, A, B and D | Every lot |
| Machine thread | Ring gauges | Every lot |
| Wood thread & point | Visual and profile check; drive test in timber | Every lot |
| Straightness / runout | V-block | Long and solar bolts |
| Hardness | Rockwell B | Steel lots |
| Material | Mill certificate; PMI on stainless | Every heat |
Every shipment includes
- Mill certificate with heat number
- Dimensional report
- Coating or passivation record
On request
- EN 10204 3.1 certificate
- ISO 3506 class test report for solar bolts
- Pull-out test in your timber
Hanger Bolt Questions, Answered
A hanger bolt is a headless bolt with a coarse wood thread and gimlet point on one end and a machine thread on the other. The wood end is turned into a pilot hole in timber, leaving the machine thread sticking out so that a part can be fixed with a washer and nut and removed again without damaging the wood. They are used for furniture legs, ceiling hangers, fixtures and solar roof mounts.
Drill a pilot hole for the wood thread, then drive the bolt by its machine thread. Either lock two nuts against each other on the machine thread and turn the upper one with a spanner, or use a hanger bolt driver in a drill. Stop when the wood thread is fully in the wood, then remove the nuts. Do not grip the machine thread with pliers, which damages it.
Supplier guidance is about 3/16 inch in hardwood and 5/32 inch in softwood for 1/4-20 hanger bolts, 1/4 and 7/32 inch for 5/16-18, and 5/16 and 9/32 inch for 3/8-16. Denser wood needs the larger hole. Test in a scrap of the same wood, because a hole that is too small can split the timber or twist the bolt off.
By machine thread size and overall length, since there is no head. A 5/16-18 x 3 inch hanger bolt has 1-1/2 inch of 5/16-18 machine thread and 1-1/2 inch of wood thread. On longer bolts the wood thread stops at 3 inch and the machine thread at about 2-1/2 inch, with a plain centre section between. Length tolerance is plus or minus 1/16 inch up to 6 inch.
A solar hanger bolt is a long M10 or M12 stainless steel hanger bolt that fixes PV mounting rails through a corrugated sheet or fibre cement roof into the rafter below. It comes with an EPDM sealing washer and flange nuts: one seals the roof sheet and two clamp an adapter plate for the rail. Typical sizes are M10 x 180 to 250 mm and M12 x 300 mm, in A2 stainless. For structural use, choose products with an approval such as German general approval Z-14.4-602.
A lag screw has a hex head and one wood thread, so it clamps a part directly to timber. A hanger bolt has no head and a machine thread on the outer end, so the part is held with a nut and can be removed and refitted. A dowel screw has a wood thread on both ends and joins two pieces of wood end to end.
Standard steel hanger bolts are made from AISI 1008 or 1010 steel. For No. 10 to 3/8 inch sizes, the core hardness is Rockwell B80 to B100 and the machine-thread end has a minimum tensile strength of 74,000 psi. Stainless hanger bolts are made in 303 or 304, and solar hanger bolts in A2 stainless to ISO 3506 classes such as A2-70.
It depends mainly on the wood and how much wood thread is engaged, not on the steel. Hanger bolts are not tabulated in the US timber design code (NDS) the way lag screws are, so for structural or overhead loads use a product with published, approved values or have an engineer test or design the connection. Never hang loads from hanger bolts in end grain without such a check.