As I was working on my Hodgson Radial, I needed to accurately size the crank journals, but I didn’t want to risk tapering the ends as usually happens when polishing with sandpaper. So I made myself a set of external hones (photo of my set on the left), based on a set that I remembered seeing on Ron’s Model Engineering and Model IC Engines website interestingly named the Nikapena Hone.
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Machining Blanks for Hones
Since most of the work on these hones will be in the fixturing and setup, it makes sense to machine more than one hone while you are at it. Each of these three 7075-T6 aluminum blocks will make both halves of one frame for a total of three hones.
Cut Out Hones and Machine
Sawing the Shapes
To make the sawing operation a little easier, I printed out copies of my stock plan and glued them to the stock.
The blocks are then split at the bandsaw. Don’t remove any of the waste at this point. We’ll use the orthogonal surfaces for location in future operations.
Finish External Hone Project
Dry fit all the pieces and make sure each of the hone bodies opens and closes smoothly with no drag or catching. Any sloppiness in the hinge will affect the hone’s ability to hold close tolerances.