Talk:Drill and tap size chart

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[edit] UNF vs UNC

On the Drill and tap size chart, the chart shows a 10-24 tap uses a #25 drill. I am using a 10-23NF tap and both the tap and drill indes and a drill and tap set I bought from Home Depot made by Irvin use a #21 dirll. Is the difference because of the threading???

Robert Heard <email removed>

Yes. See here --Coolhandscot 07:36, 19 August 2006 (UTC)

If I am correct in assuming the tabulated "Theoretical percentage of thread" figures are based upon the 60 degree included thread angle used for US and Metric threads it should be remembered that legacy standard threads e.g. Whitworth, British Association etc. will be significantly different from those tabulated figures. 7severn7 (talk) 18:44, 19 November 2007 (UTC)