A thumb rule to select a drill bit for a specific internal thread size?
wat is common rule to select a drill bit size to drill a hole for a specific internal thread size…………. for example i want to make M12 internal threads in a stainless steel rod which drill bit should i use to drill the hole and why to use it……….
As previous answerer says, best to use tables – e.g this one:
http://www.efunda.com/designstandards/screws/screwm_coarse.cfm
e.g. for M12, the tap drill size (i.e. hole needed for internal thread tapping) is 10.2mm.
This assumes you’re using standard coarse metric taps (you probably are). An alternative set of threads – the metric fine series – also exists. There are, of course, all sorts of old imperial standards as well!
Gold Plating Stainless Steel.