The Importance of the Press Fit

When making field connections on your chain, it is extremely important to NOT grind your pins. Not only will this void your warranty, it will cause you many headaches in the coming months. When discussing chain, the old saying “Your chain is only as strong as your weakest link” has never been so true. Grinding a pin creates a weak link.

 As machining and hole punching processes get more precise, we can use these processes to our advantage and add more value into the chain for our customers. Our current processes allow us to reproduce a consistent and repeatable interference fit between the pins and the sidebar holes. With this repeatability, we solely rely on our press fit to keep the pins stationary in the sidebar. When you grind the pins or ream out the sidebar holes you are compromising the press fit that we have worked hard to achieve. This will transfer the load bearing surface from the designed area, the pin outside diameter and the barrel/bushing inside diameter, to the unwanted area, the pin outside diameter and the thickness of the outside sidebars.  

If the press fit is compromised, then based upon the friction of the components, the pin will want to stay with the inner portion of the chain, the bushing/barrel, when the chain articulates around the sprocket. This will transfer the wear to the outside diameter of the pin and the two thicknesses of the sidebar. Ultimately, reducing the pin bearing area which drastically increases the rate at which this link will elongate. 

The press fit also allows us to eliminate the shaped holes in the sidebars. Sharp corners in the holes create high stress concentration points in the sidebar. The high stress concentration points can lead to fatigue fractures and chain failure over a period of time.

Key takeaways:

1. The press fit between the sidebar and the pin is the main method we use to keep our components from spinning in their respective sidebar holes. This will keep the general chain wear on the surfaces designed to take the wear.
2. The press fit also adds compressive stresses around the sidebar holes, which improve the fatigue fracture resistance of the sidebar material around these holes.
3. By having a good press fit the shaped/flatted pins and sidebar holes are not needed to help keep the pins rotating with respect to the sidebars they are pressed into.