This is a headtube facer & reamer tool. The reaming portion of the tool is made by Park and has a diameter of 43.95mm. The facing tool is also from Park and has a diameter of 57mm. Bill Davidson combined the two into a single tool for the lathe chuck. This was the last step necessary before the frameshop starts building my next bike project. It’s a titanium bike with S&S couplings and a couple features that have never been used on a Davidson before. This tool is for one of them, an internal headset. With headset cups and bearings nestled within the headtube, the ID of the headtube balloons out from 34.0mm to 44.0mm with an OD of 50mm. The new tool is machine the headtube post-welding to fit the Chris King “InSet” (internal cup) headset.