edited November 17
From 1930 through 1950, Yale's OC-5 was the main competitor to S&G's 6730. The OC-5 uses a flipper fence rather than a drop lever, and the last turn is left to stop (rather than right to stop like the 6730). The OC-5 is a tricky lock to drill. The sweet spot for a no-transfer scope hole is the size of a pea. But we can hit it! The DP below provides a starting point for our discussion. As the thread develops, I will post additional photos showing the basic technique in more detail, and will also post an alternative DP that is pretty cool, because it eliminates angle drilling and removes all risk of damaging the roller gear. Let's get started!

In the olden days, back when safecrackers traveled by horseback amidst the dinosaurs, we angle drilled the OC-5 through the dial ring at 86, at a compound angle down and in.  This caused a little puckering and sweating of virtual bullets to get the angles just right.  This was improved upon by an LA burglary detective named Ed Barr who suggested we dispense with the compound angle difficulty and just use ONE angle.  This is accomplished by drilling through the dial ring at 83, over at a slight angle to the right, with NO up or down angle.  Shown below, this method quickly became a favorite of safecrackers across the country and is the gold standard today.  


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    Here is an alternative to the angle-drilling method.  I really like this method, especially if I am working on a safe whose thickness I am unsure of. (The amount of angle depends entirely on the thickness of door, so when we aren't sure of thickness we cannot be sure of angle.)  

    Our target is the lower mounting screw.  The Drill Point (DP) is: 1 7/8" L, 13/16" D.  Below I show this method being used on both the OC-5 and its close cousin.  It has the advantage of allowing us to drill STRAIGHT IN, which greatly minimizes the chance of an airhole or of causing damage to the lock. Try it the next time you have an OC-5 to drill.  I think you'll like it!

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