15MM Tap......Drill Size

[tlfamm]

Dan,

Some of us are comfortable with math, some aren't.
...
.

Marv, I immediately thought of Margittai Neumann Janos, a mathematician who was renown for tilting his head back, entering "compute mode", and solving complex mathematical problems with no other apparatus than his own brain. Outside of his native Hungary, he was known as John Von Neumann.

[j.bain87]

Keep it Simple, eh.

How much simpler could it be for METRIC ?

Much simpler than that archaic "MONGREL" you dumb yanks want to hang on too.

K.I.S.S. ----------- Keep It Simple STUPID.

[danlb]

Dan,

Some of us are comfortable with math, some aren't. If you like your shop papered with cheat sheets, go for it.

Math's not a problem (much). The problem is faithfully remembering the hundreds and hundreds of formulas that one has to use from time to time. Cooking, welding, gardening, painting, machining, electronics, graphics... they all have formulas. And they often have derivative formulas too.

In this day and age, if you have to double check the formula, then you might as well look up the answer too.

"Siri what is the drill bit for 75% engagement of a 15mm thread?"

Dan

[spinningwheels]

About all that you need to know
http://mdmetric.com/tech/M-thead%20600.htm

[Lew Hartswick]

How much simpler could it be for METRIC ?

Much simpler than that archaic "MONGREL" you dumb yanks want to hang on too.

K.I.S.S. ----------- Keep It Simple STUPID.

What is the tap drill for a 3/8 - 16 thread? Well a 16 tpi is 1/16 of an inch pitch and 3/8" - 1/16" is 5/16 Well how about that . If you can't do that you probably shouldn't be trusted with any power tools.
...lew...

[RichR]

Much simpler than that archaic "MONGREL" you dumb yanks want to hang on too.

I'm not familiar with that acronym. What does it stand for?

[Randy]

Here's an online calculator that I like:

http://theoreticalmachinist.com/TapDrillSizeCalculators

Good for forming taps, too. BTW it appears, from looking at a few examples, that D - .5 X pitch works for form taps at 75%. Has anyone found that to be a generally applicable rule?

Interesting that the calculator defaults to 77%. I've never seen that before.

[dave_r]

Math's not a problem (much). The problem is faithfully remembering the hundreds and hundreds of formulas that one has to use from time to time. Cooking, welding, gardening, painting, machining, electronics, graphics... they all have formulas. And they often have derivative formulas too.

In this day and age, if you have to double check the formula, then you might as well look up the answer too.

"Siri what is the drill bit for 75% engagement of a 15mm thread?"

Dan

That's what tattoo's are for.

[tom_d]

Keep it Simple, eh.

How much simpler could it be for METRIC ?

Much simpler than that archaic "MONGREL" you dumb yanks want to hang on too.

K.I.S.S. ----------- Keep It Simple STUPID.

Has anyone other than the "dumb yanks" walked on the moon using a better system?

[754]

If you cant access tap charts online, or beg steal or borrow old ones, you may not want to play with macbine tools.. The info cor 95 percent of taps is very accessible.
Besides tap size formula is a 1.5 out of ten ...simple stuff compared to say gear cutting or hobbing.

[Doozer]

What is the tap drill for a 3/8 - 16 thread? Well a 16 tpi is 1/16 of an inch pitch and 3/8" - 1/16" is 5/16 Well how about that . If you can't do that you probably shouldn't be trusted with any power tools.
...lew...

Lew,
Stated perfectly.
Why do all you nutpicks insist on complicating things??
All math is easy. I just needs to be explained the right way.
That is the huge problem with our schools.
Subjects are taught with an agenda of some sort,
and learning is not considered.
---Doozer

[Paul Alciatore]

Marv,

I know you are well versed in math and did not mean to imply that you do not know how to use a four banger.

I wasn't trying to make your formula more accurate, I was trying to make it easier to remember when you are out in the shop and have grease and chips on your hands and under the nails. For myself, I do find the whole number 75 easier to remember than the decimal number 0.013. Memorization was never my strong suit.

When I started the post, I was going to say that the 75 factor in the denominator was more accurate than the 0.013 in the numerator, but I did a quick, back of the envelope (literally) calculation and it seemed to indicate that the 0.013 factor was actually a tiny bit more accurate. But given the facts that you can almost never get an actual drill that is the calculated size and the other known fact that drills will make holes that are somewhat larger than the drill size (but there is no accurate way to know how much larger), the small amount of difference between them does not amount to a tinker's damn. I did not bother to confirm that quick calculation because either one is definitely close enough. 1/75 = 0.0133333... so the difference is really small. I believe I erased all reference to the 75 factor being more accurate from my post.

Dan,

Some of us are comfortable with math, some aren't. If you like your shop papered with cheat sheets, go for it.

A chart will never be complete or, alternatively, if it is it will be too big and unwieldy. An equation covers all cases including "tap drill" sizes for which there are no taps. See if your chart will tell you the size hole to bore for a 2.5 - 8 thread with 85% DOT.

Paul,

I know how to do the calculation on a 4 banger, thanks very much. I use an RPN which makes it much simpler yet.

The difference between 1/75 and 0.013 isn't going to be enough to matter. Drills don't come in sizes that closely spaced and, besides, they don't drill on size, not to mention that the percentage engagement is going to be a guess at best.

[mklotz]

Has anyone other than the "dumb yanks" walked on the moon using a better system?

Having worked on the LEM AGS system for a number of years, I can safely say that we got to the moon in spite of our inferial measurement system, not because of it.

[Mcgyver]

I like a chart because I haven't yet seen a formula the tells me the right letter number or fraction drill bit to reach for. Anybody can do the math for a 5/16 24 and get that the TD should be .271......then what? Faster imo to look at chart for and then reach for an "I" drill....keep the formula for custom sizes

[Highpower]

Pick a system of calculation and stick with it. Mix them up and you'll either confuse yourself or screw up the job.

Really? How bad could it be?

https://www.wired.com/2010/11/1110ma...server-report/