Low-Tensile / Cyclone
Double-Ended Screws (Hanger Bolts), BSW & Wood Thread
Double-ended screws (hanger bolts) with a wood thread one end and a BSW machine thread the other, for bolting legs and brackets to timber.
About the Double-Ended Screws (Hanger Bolts), BSW & Wood Thread
Double-ended screws, also called hanger bolts, have a wood thread on one end and a machine thread on the other, for fixing legs to tables and benches, brackets to timber, and anything you want to bolt to timber and take off again. Hobson files them under lag screws, but they are not the hex head coach screws most people mean by that name (those are on our coach screws page). They are zinc plated mild steel with a 1/4, 5/16 or 1/2 inch BSW thread, 1-3/4 to 6 inches long, in packs of 100. Choose the size and length above; the guide below covers thread lengths, pilot holes and fitting.
Also called hanger bolts, dowel screws or BSW double-ended screws.
Features
- Zinc plated mild steel
- BSW machine thread one end, wood thread the other
- Imperial sizes 1/4", 5/16" and 1/2"
Applications
- Fixing legs to tables, benches and furniture
- Bolting brackets and fittings to timber
- Removable fixings into timber
What these double-ended screws are
A double-ended screw (also called a hanger bolt or dowel screw) has no head: one end has a BSW (British Standard Whitworth) machine thread, the other a wood thread that ends in a point. Screw the wood end into timber and the machine end is left standing proud, ready for a nut, a bracket, a leg or any fitting with a BSW tapped hole. Hobson lists them, under lag screws, with its low-tensile hardware in zinc plated mild steel.
They are not hex head coach screws. If you want a heavy screw with a hex head to fix timber or a bracket, see our coach screws page. Hobson publishes no grade, load or strength data for these double-ended screws.
Sizes and thread lengths
Every double-ended screw we carry, smallest first. Select a row to open that size in the selector.
Size is diameter x overall length in inches, as Hobson lists it; mm is by arithmetic (1 inch = 25.4mm). Machine thread is BSW with threads per inch (TPI). Machine thread length (M) and wood thread length (W) in mm from Hobson's listing; on the longer sizes they add up to less than the overall length. All zinc plated mild steel. Pack is the minimum order quantity. Tap a number to show it in the selector above.
| Size | Length (mm) | Machine thread | Machine thread length M (mm) | Wood thread length W (mm) | Pack |
|---|---|---|---|---|---|
| 1/4" x 2" | 50.8 | 1/4" BSW, 20 TPI | 19 | 32 | 100 |
| 1/4" x 3" | 76.2 | 1/4" BSW, 20 TPI | 32 | 32 | 100 |
| 5/16" x 1-3/4" | 44.5 | 5/16" BSW, 18 TPI | 16 | 29 | 100 |
| 5/16" x 2" | 50.8 | 5/16" BSW, 18 TPI | 22 | 29 | 100 |
| 5/16" x 3-1/2" | 88.9 | 5/16" BSW, 18 TPI | 32 | 38 | 100 |
| 1/2" x 6" | 152.4 | 1/2" BSW, 12 TPI | 32 | 110 | 100 |
Pilot holes
Hobson publishes no pilot hole sizes for these double-ended screws, so we do not give one. Ask us if you need help choosing.
How to fit a double-ended screw
- Drill a pilot hole (ask us for the size). Drilling it at least as deep as the wood thread is long is common practice, not a Hobson instruction.
- Run two BSW nuts onto the machine thread and lock them against each other. This is common practice for driving a headless screw, not a Hobson instruction.
- Turn the top nut with a spanner or socket to drive the wood thread into the timber until it is fully in.
- Undo the two nuts, fit your bracket, leg or fitting over the machine thread, and fasten it with a BSW nut. Zinc plated BSW hex nuts in 1/4, 5/16 and 1/2 inch are on our hex nut page.
Zinc plated: indoors and dry only
This range is zinc plated (RoHS compliant): about 5 microns, rated low corrosion resistance and recommended for indoor and non-corrosive environments in Hobson's finish comparison. Hobson's corrosion guide only accepts zinc plating for enclosed fixings in the very low and low zones; anything exposed to the weather, such as decks, pergolas, fences and outdoor furniture, calls for stainless steel or hot dip galvanising, which these do not come in.
Because Hobson publishes no load rating for these double-ended screws, do not use them for structural, load-bearing or safety fixings (decks, pergolas, balustrades, anything overhead) unless an engineer or designer has specified them; use a product with published ratings instead.
Imperial BSW fixings in Adelaide
Allmat supplies imperial double-ended screws, BSW nuts, washers and coach screws, with the timber, to carpenters, joiners and builders across Adelaide and South Australia. Add them to a quote with the rest of your list and we will price the lot.
BSW double-ended screws for your timber fittings
Imperial double-ended screws, BSW nuts, washers and coach screws are available to order from Allmat for carpenters, joiners, cabinet makers, builders and trade across Adelaide and South Australia. Order through Allmat, we pick and pack it, then click and collect from the Allmat yard or have it delivered to site.
Goes with
Questions
What is a screw with a machine thread on one end and a wood thread on the other?
A double-ended screw: a BSW machine thread at one end and a wood thread at the other. The wood end screws into timber and the machine end takes a nut or a tapped fitting. Ours are zinc plated mild steel in 1/4, 5/16 and 1/2 inch.
Is a BSW double-ended screw the same as a coach screw?
No. Many people use lag screw and coach screw for the same hex head screw, and our coach screws page covers those, with Hobson's pilot hole sizes. The double-ended screws on this page are different: they have no head, a BSW machine thread at one end and a wood thread at the other.
Is a hanger bolt the same as a double-ended screw?
Yes. Hanger bolt, double-ended screw and dowel screw all describe a headless screw with a machine thread at one end and a wood thread at the other, like these BSW ones. Solar hanger bolts, which mount solar rails through a roof, are a different kit on our solar hanger bolt page.
What thread are these double-ended screws?
BSW (British Standard Whitworth): 1/4 inch at 20 threads per inch, 5/16 inch at 18 and 1/2 inch at 12, from Hobson's listing.
What size pilot hole for a BSW double-ended screw?
Hobson publishes no pilot hole sizes for these double-ended screws. For hex head coach screws, see our coach screws page. Ask us if you need help choosing.
How do I screw in a double-ended screw with no head?
The common practice is to lock two BSW nuts together on the machine thread and turn the top nut with a spanner or socket. Once the wood thread is fully in, undo the nuts and fit your bracket or fitting.
Can I use these double-ended screws outdoors?
No. They are zinc plated, which Hobson recommends for indoor and non-corrosive environments. Exposed fixings call for stainless steel or hot dip galvanised.
Where can I buy BSW double-ended screws in Adelaide?
Order through Allmat. Order ahead by phone on 1300 03 03 63 or send your list for a quote, then click and collect from 25 Kapara Road, Gillman, or have them delivered to site.
Double-Ended Screws (Hanger Bolts), BSW & Wood Thread: sizes and finishes we supply
6 lines by type and finish. Pick one above for its product code and pack sizes.
| Type | Finish | Sizes | Lengths | Lines |
|---|---|---|---|---|
| Double-ended | Zinc Plated | 1/4, 5/16, 1/2 | 1-3/4, 2, 3, 3-1/2, 6 inch | 6 |
Data sheets and documents
The documents for the product you choose are listed with the selector above. Here is every Double-Ended Screws (Hanger Bolts), BSW & Wood Thread document from Hobson Engineering.
All Double-Ended Screws (Hanger Bolts), BSW & Wood Thread documents (2)
Data sheets and technical data (1)
Guides and articles (1)
Need them in bulk?
Add the sizes you need to your quote, or send us your list and we’ll price the lot and supply it with the rest of your order.
Browse all bolts