Upset Bolt
- Machine bolt with an upset (enlarged forged) head for higher bearing
- Upset head spreads load on wood without a separate washer
- ANSI C135.1, hot-dip galvanized to ASTM A-153
- Thread 5/8 / 3/4 in; square nut supplied
- Resists head pull-through on timber structures
- For crossarm and pole fastening in softwood
Technical Specifications
| Catalog | Thread | Length (in) | Head | Nut | Surface |
|---|---|---|---|---|---|
| RAX-UB-58 | 5/8 in | 4–16 | Upset | Square | HDG |
| RAX-UB-34 | 3/4 in | 6–24 | Upset | Square | HDG |
| Custom | Other sizes / configurations — send your conductor & structure spec | ||||
Application & Installation
Where it is used
The upset bolt is a machine bolt whose head is upset (forged larger) to give a wider bearing area. The enlarged head spreads the clamping load on soft timber, resisting the head pulling through the wood under tension — useful on crossarm and pole connections in softwood poles.
Installation sequence
- Select the thread and length for the timber members.
- Bore the pole / arm for the shank.
- Drive the bolt so the upset head beds into the timber.
- Fit the square washer and nut on the far side.
- Tighten so the members draw tight without crushing.
Buyer’s Guide: Upset Bolt
1. What an Upset Bolt Is
An upset bolt is a machine bolt with a forged, enlarged head. The “upset” forging widens the head so it bears over more timber, spreading the clamping load and resisting the head pulling into or through soft wood under load.
2. Why the Upset Head
On softwood poles a standard square head can crush into the timber or pull through under sustained tension. The wider upset head spreads that bearing, holding the joint tight without a separate large washer.
3. Where It Is Used
On timber crossarm and pole connections, especially softwood, where bearing area matters. On steel or where a washer is used anyway, a standard machine bolt is sufficient.
4. Thread & Length to ANSI C135.1
ANSI C135.1 in 5/8 in and 3/4 in threads, lengths to suit the timber stack. Otherwise it installs exactly like a machine bolt.
5. Galvanizing
Hot-dip galvanized to ASTM A-153, square nut tapped to run over the zinc, for long outdoor timber-structure service.
6. Pairing
Square washer and nut supplied; pairs with the same hardware as a machine bolt where a washer is still wanted on the nut side.
