Driving pins wear long before the tool body does, and a mushroomed or slightly bent tip starts pushing chain pins through at an angle the outer plate pays for. The set drops two factory-spec pins into a Pro 1647/2ABI or Master 1647/2BBI: 3.4 mm with a 4 mm stepped section, 24 mm long, lifetime warranty.
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Forged in Zreče, Slovenia since 1919. Official technical partner of multiple World Tour and downhill teams.
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The pin is the part of a chain tool that wears. The body lasts, the spindle threads hold up, the handle keeps its grip; the driving pin takes the load of every chain break and eventually mushrooms at the tip or develops a slight bend. When it does, the pin starts to push off-center, the chain plate deforms, and the chain tool stops being precision equipment.
The Replacement Chain Tool Pins 1647.1/4A are the fix. Two pins per set, sized and finished to factory spec, and you swap them in instead of replacing the whole tool. Lifetime warranty backs the parts.
Compatibility
The 1647.1/4A pins fit two tools in the catalog:
- Pro Chain Tool 1647/2ABI; the workshop screw-type, primary use case for daily chain-break benches.
- Master Chain Tool 1647/2BBI; the modular-insert workshop tool, where the pin sees the most varied work across chain standards.
Buy a set ahead when you start to see the pin tip taking visible deformation under a 10× loupe, or after you've broken a few hundred chains on a busy bench. The replacement is something a shop plans for, not a panic part.
When to swap the pin
A pin that's still doing its job pushes a chain pin out on-axis through the entire stroke. A worn pin starts to wander: the chain pin enters the outer plate at a slight angle, the plate distorts at the rim of the hole, and the reinstalled link won't pivot cleanly. If you start to see the outer plate showing a faint elongation at the pin hole on a freshly-broken chain, the chain tool's pin is the cause, not the chain. Swap the pin, the problem goes away.
Specs
- Set of 2 pins
- Pin diameter: 3.4 mm (with secondary 4 mm stepped section) × 24 mm length
- 10 g per set
- Compatible with Unior 1647/2ABI (Pro Chain Tool) and 1647/2BBI (Master Chain Tool)
- Lifetime warranty
- Article number: 1647.1/4A
Built in Zreče, Slovenia
Unior has been forging hand tools in Zreče since 1919, and is the official technical partner of multiple World Tour and downhill teams. Selling replacement parts for a tool that's been in production for years is the half of the catalog people don't see: it's how a workshop tool stays a workshop tool. Buy the chain tool once, replace the pin when it wears, keep using the same body for the next decade.
Pro tip from our mechanics
If you're not sure whether the chain plate damage is from the chain or from the chain tool, break one outer plate at a fresh location and inspect: clean push means the chain tool is fine, off-center push means the pin needs replacing. Our chain-replacement guide walks through diagnosing the difference between chain-side and tool-side break problems, plus the routing details that prevent the wrong-plate-deformation issue from happening in the first place: When and how to replace your chain →
Tech Tips
When and how to replace your chain
