Re: Key crankpin size


Thanks for the input John,

On Jun 14, 2018, at 7:53 PM, John Stutz <john.c.stutz@...> wrote:


If recent, they are probably metric, so try some of the standard metric sizes. Preferably in brass, and tried very gently.  Better yet: try matching diameter and pitch against any remaining crank pin screws.

I believe many of the older Japanese built engines used 1/16" Whitworth, which per the table on Wikipedia's British Standard Whitworth(BSW) page is 60 tpi or 1.588mm diameter x 0.432mm pitch.  Unfortunately there is nothing in the US Unified Thread Standard that matches: it is a shade larger than a #0 with a coarser thread than the UNC #1-64 or UNF #2-64.  The ISO metric standard is similar, with a 1.6mm diameter standard thread, but at much finer pitch of .35mm.

However NWSL has (had?) 1/16 BSW taps and dies, now quite expensive, and reported to be easily broken.  If you want to make your own crank pin, I would consider brass or NS for ease of cutting.  If you require steel, get the free machining Ledloy leaded steel alloy.  On second thought: best bet might be to use a stainless steel sleeve cut from hypodermic tubing for the crank pin's bearing surface, with a plain brass screw through the tube.  But this will require very thin wall tubing.

John Stutz

On 06/14/2018 05:15 PM, jczul36 via Groups.Io wrote:
Group, I was wondering if anybody knows what size the crank pin screws are on the C class engines Key did.

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