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rrobson · 23rd April 2020, 16:41

Just as a side note, I wouldn't ever be worried about 1.6 microns on anything to do with cars

I think you meant 1.6 thousandths of an inch in which case grab your pair of feeler gauges and look at the thickness of the thinnest one. Isn't going to make a dot of difference in a hole of any size when running a tap down. You'll loose more than that drilling free hand.
Maybe you were thinking of m5 which has a 4.2mm tapping drill?

7/32 would be a bit big looking at the old Zeus book, just over 5.5mm. If you had to use an imperial drill you'll get away with a 13/64, which is about 5.15mm.
I have used 3/16 drills in the past, they are 4.75mm and it is very difficult to get an m6 tap started but will get you buy on soft materials.

23rd April 2020, 16:41	#5
rrobson I really should get out more....... 75 tourer cdti, MG ZS 180, nissan terrano & 1.8t rover 25 Join Date: Feb 2010 Location: Pontefract Posts: 2,647 Thanks: 17 Thanked 295 Times in 218 Posts	Just as a side note, I wouldn't ever be worried about 1.6 microns on anything to do with cars I think you meant 1.6 thousandths of an inch in which case grab your pair of feeler gauges and look at the thickness of the thinnest one. Isn't going to make a dot of difference in a hole of any size when running a tap down. You'll loose more than that drilling free hand. Maybe you were thinking of m5 which has a 4.2mm tapping drill? 7/32 would be a bit big looking at the old Zeus book, just over 5.5mm. If you had to use an imperial drill you'll get away with a 13/64, which is about 5.15mm. I have used 3/16 drills in the past, they are 4.75mm and it is very difficult to get an m6 tap started but will get you buy on soft materials. __________________ How to view a car - everything you need to help you inspect a used car VIS motor tester avalible to local members Injector removal tool and auto gearbox pressure tester now available