Learn How to Bore and Key a Coupling Hub

While Lovejoy generally ships coupling hubs to customers with finished bores and keyways (with a tremendous amount of finished inventory as well as a Quick Ship program to quickly supply unique requirements), many coupling customers or distributors like to have rough stock (small bore) hubs on their shelves so that they too can quickly size a coupling hub in an emergency. Another reason why someone may want to re-bore and/or re-key a coupling hub is if they have old or obsolete inventory and they would like to re-used their existing inventory by increasing the bore and keyway to something that they need or will use.

Under either scenario, the re-bore and re-key will almost certainly be performed at a local machine shop. To best help Lovejoy customers and end users who do not have access to precision high volume CNC equipment at Lovejoy's Downers Grove, Illinois & South Haven, Michigan facilities... we turned to Keith Fenner, a well-known and well-respected master skilled machinist who enjoys sharing his knowledge through his free YouTube tutorials (which have over a mind boggling 13 million views).

When we approached Keith about producing a video on his channel showing how a coupling hub could be bored and keyed using the equipment in his machine shop, he was immediately receptive as he already had a long history and thought very positively about the Lovejoy brand. We sent Keith a few L line jaw coupling hubs, a few shirts (as you will see in the video), our catalog, and a company history book... and left the rest up to him.

A few months later, he sent Lovejoy an email notifying us that he had shot and released a comprehensive 79 minute video, that not only covers the technical fundamentals of coupling bore & keyway cutting, but also dives quite deep into Lovejoy's rich history (which was something we didn't expect or ask for... but certainly didn't mind him sharing). 

The views and perspectives shared in this video are Keith's own (Lovejoy did not provide a script and/or even have access to the video prior to Keith releasing it publicly). If you are a machinist and enjoyed watching the video (shown below), we certainly encourage you to subscribe to Keith's YouTube channel and get to know him just a bit better. 

Enjoy the show!

Shaft Keyway Damage

During inspection of a shaft prior to installing a replacement coupling, a technician found the shaft keyway had some damage. I was asked if this damage would have any impact on the coupling. (The image above shows the shaft keyway in question).

First, I commended the technician for inspecting the equipment and asking about its condition. Second, we dove into what the impact the damaged shaft keyway could have on the system once a new coupling was installed.

For this application (the coupling hubs having interference fit bores), torque is transmitted between the shaft and coupling hub through two methods: (1) the friction caused by the shaft interference fit and (2) via the surface of the key.  When the surface of the keyway is damaged, the key no longer has proper contact and the shaft & hub connection/joint may not be able to fully transmit to the torque level as designed.

For this application, as the new coupling might not be able to transmit a full torque capacity as rated, a recommendation was made that the shaft should be reworked/replaced to ensure a proper keyway fit.