These are hardened tool steel hingepins, precision ground, sold in your choice of diameter. Shaft diameter tolerance is a very consistent and precise +0.0003". They've been hardened with a molten salt bath heat treatment. They have a minimum Rockwell hardness of C60.  How hard is that?  This is the same stuff used for drill bits and machinist cutting bits.  Out of the box, the finish is amazing smooth.  If desired, you can polish them very quickly to a mirror shine since they are so close to begin with.

Why use these hardened steel hinge pins?

Less slop and choice of diameter
For 30+ years, the hingepins diameter standard has been based on .078" piano wire. Which means that manufacturers will drill their upper arms to .079".  So using a .078" diameter hingepin can create some slop in your front suspension. Some hingepins, like the IRS Hingepin kit we sell, can be as small as .076" diameter. It's great to have .078" and .079" diameters in your tool box to use as needed.  If you'd like to request other diameters, let us know.

Harder, smoother, consistent
As soon as you hold these in your hand, you'll know. The hardness of the surface makes for a great finish. Great foundation for polishing to a mirror shine.  The surface hardness will then keep that finish for a long time. Almost zero fluctuation in diameter, as these have been precision ground to within .0003" tolerance.

Perfectly flat head
Some hingepin heads are slightly rounded which can cause bind as they dig into the upper arm hole. The underside of these hingepin's head is perfectly square so there is no binding.

NOTE: The length of these are 2.5" so they need to be cut down with a Dremel and cutoff wheel (or similar).  While you are at it, you can cut some of the top off to save weight (like in our pictures).

Sold in pairs.