Spring for Nipple Insertion Tool

The springs that keep the Nipple Insertion Tool 1751/2T's grip mechanism working fail eventually. Workshop tools used through hundreds of build sessions accumulate metal fatigue, and the spring is the wear part. These replacement springs come as a pack of five; enough to keep the insertion tool functional through the rest of its working life.

The 1751.1/7T springs are dimensioned specifically for the 1751/2T insertion tool's grip mechanism. A spring from a different tool won't engage the geometry correctly, and the grip will either be too weak (the nipple drops) or too strong (the tool won't release the nipple after the spoke is threaded in).

Replacement is straightforward: pop the old spring out of the tool body, push the new one in, test the grip on a sample nipple. The tool returns to working order with a few minutes of bench work, no service appointment needed.

Compatibility

• Tool: Nipple Insertion Tool 1751/2T.
• Pack: 5 springs per unit.

Specs

• Spring: dimensioned for the 1751/2T grip mechanism.
• Quantity: 5 per pack.

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 springs for the 1751/2T is the kind of accessory decision that reflects how Unior tools are designed: as service-able workshop equipment, not as disposable consumer goods. A spring is a wear part; the rest of the 1751/2T outlasts many of those springs. Letting the customer keep the tool in service indefinitely (rather than replacing the whole insertion tool) is the workshop-friendly choice.

Pro tip from our mechanics

When the 1751/2T starts feeling like it's dropping nipples more often, replace the spring before the next build session. The spring degrades gradually; the symptom isn't “it broke,” it's “I'm noticing the nipple slips more than it used to.” Five springs is enough to last most workshops several years of regular use; we keep ours in the same drawer as the insertion tool itself, so the replacement is a two-minute job when the need arises. The full wheel-building workflow is in How to true a bike wheel →

FAQ

Which tool does the 1751.1/7T spring fit? It is the official spare for the 1751/2T nipple insertion tool. Unior's 1751/2T page states "the spring is interchangeable, item 1751.1/7T" and links this 5-piece set in its spare-parts list. It is not a part for the 1751/2 slotted driver or the 1751/2Q square driver; those are one-piece drivers.

How many springs are in the pack? Five. Unior's official name for article 1751.1/7T is "Spring for nipple installation tool, 5 pcs set", code 623300. The tool takes one spring at a time; the rest are spares for the drawer.

How do I know the spring needs replacing? The grip fades gradually. When the 1751/2T starts dropping nipples more often than it used to, the spring is worn. Pop the old spring out of the tool body, push the new one in, and test the grip on a sample nipple before the next build.

What does the spring do in the insertion tool? The 1751/2T's firm spring grips a spoke nipple so you can feed it through a double-wall rim's outer hole and screw it onto the spoke without losing it between the rim walls. It releases once the spoke threads in. The spring does the holding, which is why it is the tool's wear part.