Replacement Chain Tool Pins

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 sponsors professional road and mountain-bike race 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 →

FAQ

Which Unior chain tools do the 1647.1/4A pins fit? The two workshop chain tools Unior lists for this spare: the Pro Chain Tool 1647/2ABI and the Master Chain Tool 1647/2BBI. Unior names both tools in the part's official title, and both tools' own spec sheets list 1647.1/4A as their replacement pin.

What are the dimensions of the replacement pins? Each pin is 24 mm long with a 3.4 mm working tip and a 4 mm stepped section that seats in the tool body. The set contains two pins and weighs 10 g. The dimension drawing on this page shows where each measurement sits on the pin.

How do I know when the pin in my chain tool needs replacing? Watch the tip. A worn driving pin mushrooms or takes a slight bend, and then it starts pushing chain pins through at an angle instead of on-axis — you'll see the chain's outer plate deform around the pin hole on a fresh break. Swap the pin at the first sign of tip deformation and the tool goes back to pushing straight.

Do the pins come singly or as a set, and what warranty applies? The 1647.1/4A is a set of two pins, so a workshop keeps one in the tool and one in the drawer. Like Unior's tools, the pins carry a lifetime warranty.