Star Nut Setter

The star-fangled nut is the small piece of metal that anchors a threadless headset's stem cap bolt. The bolt threads into the star nut; tightening the bolt pulls upward on the steerer through the star nut and preloads the headset bearings. If the star nut sits at the wrong depth, the bolt bottoms out before preload is reached. If the star nut sits cocked, the bolt loads it unevenly and the preload never feels right. The Star Nut Setter 1682/4 handles both the depth and the squareness in a single hammer-driven set.

What the tool does

Thread the star nut onto the setter's mandrel, drop the setter over the end of the steerer, and strike the setter's top face with a hammer. The 1682/4 is a one-piece setter: the star nut threads onto the replaceable M6x25 bolt at the working end, and a hammer strike on the knurled end drives the nut into the steerer. The optional 1682.1/4 guide (sold separately) registers on the steerer's outside diameter and keeps the setter centered so the nut cannot land cocked.

That is the entire operation. There is no field where this tool fails, provided the nut is sized to the steerer. The setter does the rest.

Compatibility

The 1682/4 installs the star-fangled nut on 1″ and 1 1/8″ threadless headset systems. One tool covers both sizes; there is no swappable collar.

For repeat-use shop benches we pair the 1682/4 with the matching Star Nut Setter Guide 1682.1/4. The guide registers off the steerer's outer surface and reinforces the square-driven set when you're running a batch of new-fork installs.

Specs

• Compatible steerer sizes: 1″ and 1 1/8″
• Dimensions: 124 mm long (L); diameters D1 29.5 mm, D2 15.2 mm, D3 24 mm; 557 g
• Material: premium plus carbon steel, blackened to DIN 50938; hammer-driven on the knurled end
• Made in Slovenia by Unior

Includes: the 1682/4 setter with its M6x25 drive bolt (article 1682.2, replaceable). Star nuts are not included; they ship with most threadless forks. The 1682.1/4 guide is sold separately.

Made in Slovenia, since 1919

Unior has been forging hand tools in Zreče since 1919, and sponsors professional road and mountain-bike race teams. The 1682/4 is a tool that does one operation and does it without ceremony; the one-piece body is premium plus carbon steel, blackened to DIN 50938, with a replaceable M6x25 drive bolt. There is nothing fancy about the tool, and that is the point: it is on the bench because every threadless fork install ends with this step.

Pro tip from our mechanics

A star nut driven crooked won't release evenly when the stem cap bolt is tightened. The rider will feel it as a stem that won't quite preload the headset correctly. They'll tighten the bolt to where the headset should be preloaded, and the headset will still rock under braking. If you find yourself chasing headset preload on a recent build and the cup pressing was clean and the race was set square, suspect the star nut.

The star-nut set is the last operation in the head-tube-up frame-prep chain: head-tube facing, crown-race pull and set, headset bearing press, then star nut. The full chain is documented in our walk-through: Frame prep: head tube, crown race, and star nut work →

FAQ

Which steerer sizes does the 1682/4 cover? Unior lists it for 1" and 1-1/8" threadless headset systems. The star-fangled nut lives in the top of the steerer, so a modern tapered fork with a 1-1/8" upper is in range; 1-1/4" and 1-1/2" steerers are not. Carbon steerers that take an expansion plug do not use a star nut, so they do not use this tool.

Do I need the 1682.1/4 Star Nut Setter Guide as well? The setter works on its own. Unior lists the 1682.1/4 as the matching accessory: a guide tube for 1" and 1-1/8" steerers that keeps the setter centered while you drive the nut. We sell it separately (SKU 619618).

What is the replaceable part on the 1682/4? The working end is a replaceable M6x25 bolt, Unior article 1682.2. The setter body itself is one piece. We do not stock 1682.2 as its own product; it is the official spare on the uniortools.com 1682/4 page.

What is the Star Nut Setter made of, and how big is it? Premium plus carbon steel, blackened to DIN 50938. The tool is 124 mm long and weighs 557 g; the official diameters are D1 29.5 mm, D2 15.2 mm, and D3 24 mm. Article 1682/4, SKU 616292, covered by Unior's lifetime warranty.