Taps marked with drill size

[bob ward]

This set of 11/16" x 18 taps (old car tie rods) arrived today. Interestingly, as well as the usual tap info they also say on the tap what size to drill the hole, in this case its 16.1mm, I've never seen that on a tap before. I had to check that they were right of course, theoretically the size is 16.05 so 16.1 is close enough for me.

http://i237.photobucket.com/albums/ff28/sirrobertthegood/IMG_0052_zps171e583e.jpg (http://s237.photobucket.com/user/sirrobertthegood/media/IMG_0052_zps171e583e.jpg.html)

[nadroj]

I've only seen that on thread insert type taps.
I have a chart that gives alternative drill sizes, depending on the class of fit wanted.

Jordan

[C-47]

Bob,
I have a set of taps made by Vermont American and as sold by Sears some 30 years ago (when they made 1/2 decent stuff) and they also have a suggested drill size on the shank.

Sorry my picture taking quality is not in the same league as Anorak Bob's.

Alan

268812

[steran50]

HI:),
I have a Metric and Imperial Tap & Die set (separate sets - about 15 years old) in My Shed and both Sets have Drill sizes on them. I do have some newer Taps though and they don't have Drill sizes on them.
Drill sizes for Metric Taps are easy anyway ie 16mm x 1.5 use a 14.5mm drill and 8mm x 1.0 use a 7mm drill.