Correct drill size for Athaya 8mm Brevet crown for 6538 case

[denimhead]

Hi Guys

I'm attempting to fit one of Athaya's Brevet 8mm crowns to a 6538 case this weekend, I have the correct tap which is 4mm with a 0.5 pitch. But how big a hole would i need to drill to get things moving? 3.5 or 4mm

Any advise greatly appreciated!

Cheers DH 

[FxrAndy]

It Should be about a 3.5 but

If it is a thin Case you may not have enough case to drill and cut a thread with out deforming the back or cutting into the o ring seat in the back of the case

When I have fitted these in the past I have has to remove the threads on the tube drill the case and make a fit that way

To be water resistant I make th fit so tight that I have to warm the case and freeze the tube to get them together

[civic4982]

Just curious as I've never done this myself before but what kind of drill and stand do you use to drill these cases?

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[stevedrk]

I have a post somewhere that lists the bits and equipment I used to drill and tap. I'm too lazy to find it right now, though.

Sent from my LG-P999 using Tapatalk 2

[denimhead]

Thanks guys,

Andy its one of the Tiger cases which looks very close to the silix thin case, so yep it might be a tricky one.I think the 3.5mm drill bit looks the closest to the shank measurement of the tap exclusing the threads. I also have a 4mm so I'll work my way up if need be. Wish me luck!

Cheers DH

[FxrAndy]

Just curious as I've never done this myself before but what kind of drill and stand do you use to drill these cases?

Sent from my iPad using Tapatalk HD

I have a proxon mini drill stand with an x y mill table fitted

[automatico]

Drill bit size to tap chart:

http://brassmein.com/tech/taps.htm

[denimhead]

Drill bit size to tap chart:

http://brassmein.com/tech/taps.htm

Thanks A, its done. I'll post a picture Thursday