Holes and things

[Germs]

Need to make some tappings for various bits and pieces - 4mm, 6mm & 8mm - can anyone tell me what drill bit sizes I should use to make the holes for the tappings?

As always thanks for any help.

[AntonyJ]

Germs said:

Need to make some tappings for various bits and pieces - 4mm, 6mm & 8mm - can anyone tell me what drill bit sizes I should use to make the holes for the tappings?

As always thanks for any help.

Basically ,for standard metric tap sizes, take the pitch of the thread away from the tap size and this gives you
the drill size.

[Elwood]

Germs said:

Need to make some tappings for various bits and pieces - 4mm, 6mm & 8mm - can anyone tell me what drill bit sizes I should use to make the holes for the tappings?

As always thanks for any help.

4mm = 3.3mm
6mm = 5mm
8mm = 6.8mm

[Germs]

Probably there's a blindingly obvious answer to this but......how can you tell what the pitch size is - for example for an 8mm tap, the set I have has 2, one of 0.75mm and one of 1.00mm (with no guidance as to what this refers to) but to me this looks like a coarse or fine thread rather than the pitch size (rather like the "old" BSF/BSC).

Thanks for the previous help.

[AntonyJ]

Well a standard 8mm pin is 1.25 pitch.

Probably best to check the tap against the pin that you intend to use.

Where on the car are you looking to use the tap?
There is a mixture of imperial and metric on these cars.
Especially around the RV8 and the suspension(although there is not really anywhere that requires tapping on the suspension)

[Germs]

Antony, thanks for the response; the tappings are only for some brackets I'm making up to fit in the boot - I'm tired of things flying about (like the spare petrol can).