Webster engine cam method

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Well-Known Member
May 29, 2012
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Perhaps someone else will find this method useful :

I'm working on what may well turn out to be the longest time for a Webster engine build - I started years ago, but had to shelve the project for a number of reason. However, the project is back off the shelf, and I recently found myself looking to make the exhaust cam. I looked at the methods used by some others for making cams, but I ultimately decided to go with a kind of "manual CNC" (MNC?). The method is pretty simple - turn a blank at 5° increments and mill to a previously calculated depth of cut at each interval. This requires 68 cuts, but since 52 of them are identical, it goes pretty fast - less than 45 minutes to complete in my case.

The picture and PDF show the cut table I used to make the cam. I used a home made electronic indexer to make this, but a manual indexer or rotary table should work as well. The dimensions in the cut table were taken from a 3D CAD model; in the drawing the sides of the cam look straight, but there is actually a very gentle curve.

Download a pdf version here :


The method results in a faceted profile, but the facets (while visible under magnification) are imperceptible to the touch. The photo below shows the cam after case hardening.


Note that my cam design is a bit different than the design in the plans, as I made it to insert into a home made gear:


Milling the gear in the indexer - only partially done at this point :

Thank you for posting this great information. I know that this is an old thread, but I just found it. I'm building my first IC engine (Webster) and I reached the point when I have to make a cam. So I followed your posting and made one. It was a best way to make a cam on mini-mill. I tried a different way to fold a blank (horizontal) but there was too much chatter and tons of needle like chips. This approach is just right for a small mill. I also followed your thread on building a Webster on your website along with a few selected other builds that were well documented.

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