Description
The Bolt That Ties Two Crossarms Together on One Connection
Many pole structures don’t carry a single crossarm; they carry two, mounted back-to-back on either side of the pole for the strength a heavier line or a corner demands. That double-arm construction needs a fastener that can pass through both arms and the pole between them, securing the whole sandwich as a single connection.
That fastener is the double-arming bolt: a long machine bolt threaded at both ends, run through the two crossarms (and the pole), with a nut and washer drawn up at each end. One bolt, one clean connection, both arms held instead of two separate bolts and the alignment problems that come with them.
It’s the defining fastener for double-arm and braced-pole construction. This page covers what it does, how it differs from a standard machine bolt, and how to size it.
(This page describes the long, threaded-both-ends double arming bolt)
Why Buyers Choose DAPENG Double Arming Bolts
- Threaded both ends, made to span two arms: The bolt takes a nut and washer at each end, securing both crossarms in one connection the length and thread made for the double-arm sandwich, not improvised from a single-arm bolt.
- Hot-dip galvanized, threads that turn on site: Galvanized to ISO 1461 / ASTM A153 class coatings, with both threaded ends cleared and nuts run before packing because a long bolt with a bound thread at one end is a bolt a crew fights at height.
- The utility sizes: Commonly M16 (5/8″) and M20 (3/4″) in the long lengths double-arm construction needs, sized to your arm-and-pole thickness.
- Supplied complete both ends: Kitted with two nuts and washers per bolt (one each end), plus eye nuts where an end must present an eye, so the connection assembles complete. Double-arm bolts are the fastener crews most often find short a nut we count them in pairs.
- Volume for the build: Cartons counted and marked by size, batched to your programmer.
Use-Case Deep Dive
What is a double arming bolt used for?
Through-bolting two members on one bolt. The classic case is double-arm (or double dead-end) construction two crossarms mounted on opposite sides of the pole, common at line angles, dead-ends, and heavier-loaded structures where a single arm isn’t enough. The double arming bolt passes through both arms and the pole, with a nut and square washer at each end drawing the assembly tight. It’s also used to through-bolt a crossarm and a back brace, or any two-member connection needing a single long through-bolt. Where only one arm is bolted, the standard square head machine bolt is the right tool; the double arming bolt earns its place the moment two members share the bolt.
How do I size a double arming bolt?
The length is the critical dimension, and it’s different from a single machine bolt: it must span both crossarms plus the pole (or the two members) plus a nut projection at each end. Add the arm thicknesses, the pole diameter (or member stack), and the two thread projections your standard wants too short and one nut won’t land with full thread; too long and the excess fouls. The diameter (M16/M20) follows the connection’s load. Send the arm dimensions and pole diameter (or the members being joined) and we return the bolt length that spans them correctly, with the nuts and washers for both ends.
Double arming bolt or machine bolt which do I need?
By how many members the bolt secures:
- Square head machine bolt a single crossarm or member, one nut. The default single-connection bolt.
- Double arming bolt (this page) two crossarms, or an arm and a brace, on one long bolt threaded both ends, a nut each end.
If the structure is double-arm (two crossarms), or an arm plus a brace shares the bolt, it’s the double arming bolt; a single arm takes the machine bolt. Tell us the construction and we confirm we make both, so the answer is about the joint.
Specifications and What They Mean for You
| Specification | What we supply | What it means for the buyer |
|---|---|---|
| Form | Long bolt, threaded both ends | Secures two members on one connection |
| Sizes | M16 / M20 in long lengths | Spans two arms plus the pole |
| Length | To your arm + pole + projections | Both nuts land with full thread |
| Material & coating | HDG to ISO 1461 / ASTM A153 class | Outdoor pole-line corrosion life |
| Threads | Both ends cleared, nuts run before packing | Threads on site at both ends |
| Pairing | Two nuts + washers per bolt, kitted | The double-arm connection assembles complete |
Straight Answers to Common Buyer Concerns
“Can’t we just use two machine bolts instead of one double arming bolt?” For a true double-arm construction, the single long bolt is the correct method: it aligns both arms on one axis, draws them tight together against the pole, and makes one inspectable connection instead of two that can load unevenly. Two separate bolts don’t tie the arms to each other the same way. Where the design calls for a double arming bolt, that’s the fastener that makes the construction behave as intended and it’s one bolt to install, not two.
“We keep coming up short on nuts for these can you fix that?” Yes, and it’s a common complaint precisely because a double arming bolt needs two nuts and washers, one per end, and single-count ordering leaves crews short. We count and kit them in pairs two nuts and two washers per bolt so the connection arrives complete and nobody’s improvising a nut at height.
“Can you match a utility standard or a legacy arming bolt?” Send the standard reference, the arm-and-pole dimensions, or a sample. Manufacturing double arming bolts to a utility’s specification (diameter, length, thread, grade, marking) is routine export work, with confirmation before production. A double-arm structure built to a standard deserves the bolt that standard specifies.
Complete the Assembly
- Square head machine bolts the single-arm through-bolt
- Square washers, hex nuts, eye nuts the nuts and washers for both ends
- Upset bolts, U bolts, thimble eye bolts, forged eye bolts the wider bolt range
- Steel cross arms, D brackets the crossarms these bolts join
- Pole line hardware and all overhead line fittings
Get a Construction-Matched Quote Within 24 Hours
Send your double-arm construction detail the two crossarms’ thickness, the pole diameter (or the members being joined), and your diameter and grade requirements or the standard you build to. Our team returns double arming bolts sized to span your construction, in the coating your project needs, kitted with two nuts and washers per bolt, typically within one working day.
After You Order
Length and size confirmation before production, material certificates with shipment, both thread ends run and cleared, cartons marked by size and kitted with paired nuts and washers, and an engineering contact who answers quickly because double-arm structures carry the heavier loads, and a supply question on the bolt that ties them shouldn’t hold up the build.
