In structural steelwork, “near enough” isn’t good enough. When you’re suspended on a cherry picker trying to align a 2-tonne Universal Beam with a column, the difference between a quick fix and a nightmare often comes down to the shape of your drift pin.
While the barrel drift is common in fabrication shops, the carrot drift pins are the gold standard for site-based steel erectors and fixers.
The Geometry of Success: Carrot vs. Barrel
To the untrained eye, they are just pieces of tapered steel. To a pro, the taper is everything.
The Barrel Drift: Has a short taper at both ends and a long, straight “body.” It’s designed to be driven all the way through a hole.
The Carrot Drift: Has one continuous, long taper from a sharp point to its widest diameter.
Why the “Continuous Taper” Wins on Site
Superior Alignment Leverage
Because the carrot drift tapers gradually over 150mm–250mm, it acts as a massive mechanical wedge. If two holes are offset by 10mm, a barrel drift might not even “bite.” The sharp point of a carrot drift can enter the gap, and every strike of your podger hammer pulls the steel into alignment with increasing force.
No More Jammed Pins
A barrel drift has “shoulders.” If the steelwork moves slightly while the straight part of the barrel is in the hole, the pin becomes wedged. Because a carrot drift is always getting wider or narrower, it is much easier to “shock” loose or drive back out once the bolts are ready to be placed.
Applications: When to Reach for the Carrot
- Universal Beam (UB) Splices: When aligning heavy flange plates, the carrot drift provides the necessary “prying” action to line up multiple bolt holes simultaneously.
- RSA (Angle) Cleats: For smaller connections where space is tight, a 16mm carrot drift is often the only tool that can provide enough leverage to pull a stubborn cleat into place.
- Fixing Distorted Steel: On-site steel isn’t always perfectly straight. The carrot drift is the primary tool for forcing minor fabrication errors into compliance.
Safety and Material Quality: Don’t Buy “Soft” Drifts
A drift pin is a striking tool. If it is made from cheap, mild steel, two dangerous things happen:
- Mushrooming: The head splays out, creating sharp “meat hooks” that can cut your hands.
- Spalling: Small shards of steel can fly off at high speed when struck, acting like shrapnel.
Pro Tip: The “Two-Drift” Method
Never rely on just one pin. For large beams, use one carrot drift to get the initial alignment. Once the steel is held in place, use a second drift in an adjacent hole to “fine-tune” the rotation. This prevents the first pin from getting stuck under the full weight of the beam.
Carrot Drift FAQ
Q: What size drift pin do I need for an M20 bolt hole? A: For an M20 hole (which is usually 22mm), you should use a 25mm Carrot Drift. This ensures you can pull the hole completely “fair” before inserting the bolt.
Q: Can I use a drift as a centre punch? A: No. While they look similar, a drift is tempered for impact toughness, while a punch is tempered for extreme point-hardness. Using a drift as a punch will likely blunt the tip.
Q: Should I grease my drift pins? A: A light coating of oil helps prevent rust, but avoid heavy grease, as it makes the pin slippery and dangerous to handle at height.
