stripped drain plug hole, drill bit size for tap

[98blaster+4]

so i went down to the hardware store and got a m14 x 1.25 pitch dainplug and a matching tap for 11 bucks. it says on the tap package to use a 1/2 inch drill bit. is the info accurate, i am tapping the trans plug hole and dont wanna drill the hole too big for the tap to work properly.
so my question is.....what size drill bit for a m14 x 1.25 tap??

 

[Awk08]

a standard size drill for a metric tap does not seem correct at all ????

i'm seeing 12.8mm drill on this chart (right side)...................

METRIC THREAD - Drill & Tap Chart (ISO) for Course Thread and Fine Thread Sizes | Kasthuri, India

or should i have posted "let me google that for you", hahahahaaaaa

 

[98blaster+4]

speaking of googling things.
thanks for the help awk, i also didnt understand why they say use a 1.2 drillbit for a metric tap.
here is a link to the first thing that came up from a google search for a 12.8 mm dill bit
Jobber Drill, Coolant Fed, 12.8mm, TiN - Coolant Fed Drill Bits - Machine Cutting Tools - Machining : Grainger Industrial Supply

 

[98blaster+4]

12.8mm.5039" M14x1.25 Fine
it seems like the 12.8 bit is only a touch smaller than 1/2 inch

 

[98blaster+4]

will i need to seperate the cases to drill and tap this out??? there doesnt appear to be any clearance inside the hole.(giggity)

 

[sicivicdude]

12.8mm is so close to 1/2" it's not even funny. The drill bit wobble will be more than the difference in those two sizes.

Go ahead and use the 1/2" bit to do the clearance hole. It will be fine.

You SHOULDN'T have to split the cases but there isn't a lot of room inside that hole (BWAHAHAH!). Per the PM, they make different taps for different applications and you MAY want to look into a bottom tap (X2 BWAHAHAHAH!) or perhaps a rubber or nylon drain plug gasket. That way you could cut the drain plug down shorter so less threads are required to seal the hole and the tap you have will cut enough for that plug to hold. With a soft gasket, about one and a half threads would be enough to hold the transmission fluid in.

 

[sicivicdude]

I have a rubber drain plug gasket on my drain plug right now. I hate the copper ones... they're more likely to strip things out and don't necessarily seal any better. Let one of the copper gaskets get a little nick in it, it'll seep oil forever! Nick the aluminum and a copper gasket may not seal it at all.... where the rubber or nylon gasket will "squish" into the nick sealing it...

 

[98blaster+4]

used a 1/2 inch drill bit from a bond auto parts chain, had a 135 degree angle on it . worked well.

 

[darealblaster]

When mine stripped, and it stripped really badly, i used a small chisel and rubber hammer, got it out after like 30 hits, but didnt have to drill anything

 

[98blaster+4]

i stripped the part that the plug threads in to, not the plug so i had to retap it to a bigger size.