All the websites I find tell me to use a m6 bit, but I don't have one of those readily available. I used a customary size bit the other day to tap a m7 but I can't remember which one it was. Anyone know?

 

It depends on what you're trying to do. If you're trying to clean the threads on a M7 threaded hole, use a M7 tap and make sure you use the right thread pitch. Depending on the material and how damaged it is, you can restore the threads to a degree.

 

"Cutting oil" helps. If you are trying to restore aluminum threads, they're awful...
Ace Hardware or NAPA usually carry nice inserts for blown threads.

You just have to know your bolt size, SAE/metric,threads per inch or pitch.
Good Luck!

Also, the torque wrench helps you get a feel.

 

15/64th is pretty close to exactly 6mm

 

7 mm = 0.275591 millimeter to inch conversion

.2656 = 17/64 ( just under 27 )

or

.2812 = 9/32 ( a bit over )

 

I think this is like an impromptu reading comprehension test. My version is that the OP is drilling and tapping a new hole. The ‘tap drill size’ guide directs him to drill a 6mm pilot hole and use the 7mm tap to cut the threads out to a perfect 7mm threaded bolt hole. He just needs the equivalent size of a 6mm bit in a fractional size bit. He doesn’t need to repair or ‘clean up existing threads nor does he need the size equivalent of 7mm (he has that tap and bolt size already)

 

All you ever need to know OP

http://lmgtfy.com/?q=metric+drill+tap+chart
























https://littlemachineshop.com/Refere...DrillSizes.pdf

 

More like an impromptu guessing contest, as the OP didn't provide enough real information on what he was trying to do in the first place. Not that he's alone, as more than half the posts asking for advice on this board are so poorly worded (or omit critical information) it's a wonder they get any educated responses at all.

 

It's in the title - What Size Drill Bit to Tap M7 Hole?

Thank you

This is exactly what I am trying to do. I stripped the threads to a hole that was orignally a metric 6, so I am expanding the hole and making new threads.

I don't understand your chart. What does "L" mean for closest American drill?

simmer down

 

L is a 0.2900 inch drill bit which is just a hair larger than 9/32 (0.2813").

 

Huh, I've never seen it like that. Thank you

 

A 9/32 drill bit converts to 7.145mm and the chart for M7 calls for 7.40mm so I'd say it will probably work.

What material are you tapping the hole in?

 

Its an sr20det upper oil pan so aluminum

 

Yeah a 9/32 would more than likely work then if you don't have an L sized drill bit.

Just take it easy and use lube.

 

The thing also to know is what s the Thread , Course or Fine , which are either : M7 x 1 = Course Thread , drill bit 6 mm needed or Fine Thread M7 x .75 with needs drill bit 6.25 mm .

As stated above , use tapping or cutting lube .

 

ok I will be using m7x1.00 so it will be coarse

 

Dkmura is right about you not giving enough info about what you are doing. Since this is a 6mm bolt hole that has damaged threads it is already the correct size to accept your 7mm tap. Luckily for you both the 6 and 7mm bolts will be 1 thread per mm pitch, so if you carefully start the tap in the existing thread remnants it will make a clean job of cutting the thread out to 7mm. If there is a lot of torn up debris in the existing stripped hole you can lightly run the 15/64th drill bit (6mm equivalent) in and out once to clean it. If you have a hand chuck do it by hand, if using a electric drill keep it straight and don’t wobble it around needlessly enlarging the hole. If this is a blind hole, start with a tapered 7mm tap and finish with a 7mm straight-sided bottoming tap. For aluminum my dad always used a bit of kerosene, WD40 or super light oil as a cutting lube.

I don’t know why people are telling you about the equivalent fractional sizes for a 7mm drill bit. You must not use any of them, as they will make the hole too big to accept any 7mm thread at all.

My dad who was a machinist had every tap, die, reamer and drill bit known to man, but it seemed like he would send me out almost daily to pick up more of them. Ask me any question about drilling, tapping or thread pitch.

 

To tap a 7mm hole you need a 6mm drill. The nearest to a 6mm drill is 15/64th, this is.002" smaller. A 15/64th drill is 0.234". A 6mm drill = 0.236". Simples. This information comes from The Society of Engineers Standard drill, tap and die imperial and metric conversion handbook. I spent many years as a fitter building steam turbines and totally agree with Jennifer about using cutting lube. When cutting or recutting a thread turn the tap half a turn and then back half a turn just to clear the swarf and continue like that until you have finished cutting the thread.
You can't expect to cut a 7mm thread by drilling a 7mm hole, there is no logic to that.

 

Guys. I know how to tap a hole. I have a tap and die set as well as cutting oil. The 15/64th part answered my question

 

I appreciate the help from everybody