Re: 9N main bearing studs

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Posted by TheOldHokie on September 30, 2020 at 08:32:39 [URL] [DELETE] :

In Reply to: Re: 9N main bearing studs posted by JimN on September 30, 2020 at 07:18:49:

With all due respect to your machinist torqued main caps are not going to shift during a line hone. Simple table clamps with no registration mechanism whatsoever reliably hold heavy machining forces far far greater than that.

So what exactly were factory tolerances? I have looked at a number of original Ford prints and there is zero chance the factory held cumulative stud hole spacing tolerances to anything close to .002. It simply wasn't practical given the production volumes and machine tools being used. For precision close fits the old prints typically specify a tolerance of .003 on EACH hole. That translates to a potential cumulative tolerance of .006. The line boring and honing operation with the caps bolted into those holes effectivel elininates that error.

If your concern is registration during reassembly after honing consider knurling the shoulders on the studs. You can easily close up the bolt hole clearances and essentially make them a "snap" registration fit in the same fashion the snap fit on modern blocks with distorted/loose cap registration recesses are restored by peening with a chisel.

Personally I'd be more concerned by the integrity of the old studs that have been stretched and distorted by 70 years of beating, heat cycling, and metal fatigue.



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