Tap for M8 bolt

[Mike dubs]

Guys,
I trimmed a spare alloy axis mast down and need to tap the holes for the old M8 bolts.

There are different taps and it's confusing for the non mechanically minded, what tap do I need?

Cheers

Mike

[JonathanC]

It’s a standard M8 x 1.25 bolt. Just use a regular tapered tap. Most important thing of course is to get it all straight.
Good idea to use some sort of cutting fluid and wind in then back out then cut a bit more etc etc.

[Geoff C]

Here you go.
Bottoming chamfer is the best to use.

https://www.mcmaster.com/8305A59/

[Mike dubs]

Great thanks guys.

Mike

[PonoBill]

Actually, Geoff, since the mast holes go all the way through the mast there's no need for a bottoming tap. a regular tap will be easier to start and will dump chips better. Like Jonathon says, use cutting oil--the cutting oil for aluminum does the best job but who the hell has that (well, actually, me) but if you sneak into the kitchen and swipe a dab of your wife's coconut oil you be fine. Don't get bored with the process and just wind the tap in, your threads will be weak. The process is half a turn in, full turn out then run it in until it starts to cut and do another half turn, then full turn out. It's bitchy, but that breaks the chips off and releases them, giving you smooth, full-depth threads.

[Mike dubs]

Thanks guys  worked a treat, tapping was easy with your advice.
I now have a 75cm to go with my longer cedrus. Mike