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MG TD TF 1500 - Drill bit for 1/4 26 BSF Tap.

I need to tap a 1/4 26 BSF thread. In looking online, it says us a 5.3mm drill bit. The conversion charts say that 5.3mm is between 13/64 and 7/32 drill bit.

13/64 is way too small. and I cant get the tap started in the 7/32 hole. Next size is 15/64 and that is too large.

I will see if I can find a 5.3mm drill bit at the store, but has anyone else done this and what did you use?
Bruce Cunha

A #5 is .205.
A #4 is .209
W A Chasser

To find the tapping drill size for any thread, obtain a nut of the thread size you want to cut. Select a drill that is a neat fit with in the the nut threads.

Saves looking for drill size tapping tables.

Graeme
G Evans

5.3mm is the correct size core hole.
https://www.gewinde-normen.de/en/whitworth-fine-thread.html
Benchmark this website-it is very useful.
Regards
Declan
Declan Burns

Bruce

Are you using a full set of taps? A good quality taper tap(First) will have no difficulty being started in a 13/64 diameter hole.

Graeme
G Evans

Bruce, a #4 drill is 0.209" in dia. which is 5.31 mm
As Bill pointed out use a #4 drill. It is highly unlikely you will find a metric drill that is 5.3 mm.
Hugh Pite
H.D. Pite

Thanks. I was able to find the correct drill online and thanks to Amazon, it will be here tomorrow.
Bruce Cunha

This thread was discussed on 17/11/2020

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