Re: Engine Rebuild Tips and Suggestions Needed!!!

Posted by Owen_Dyneto On 2015/4/23 11:21:29

What Wesley advises is certainly a preferred good practice and removing metal from existing fasteners (except when providing clearance for plating) is to be avoided, but Washburn's statement that using a tap or die "will be removing existing threads" is not necessarily true, it depends on the class of fit of the existing threads and the class of fit that the tap and/or die have been designed for. There are numeric specification for the various classes of fit but this chart from McGraw-Hill's Pocket Reference for Machinists and Metal Workers gives the various designations and some insight.

The class of fit should be considered when you purchase taps and dies. Personally, I don't have thread chasers and just use a well-worn 1A or 2A tap/die, saving the newer ones for actual thread cutting.

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