15MM Tap......Drill Size

[Doozer]

Having a few basic engineering formulas in my head, like area, pressure, simple angle vectors,
has been key to my career and the reason I have gotten the job many times, over others.
It conveys your ability to think on your feet. I do not have to look to Google and a smart
phone for every little thing. If you don't think remembering a few key formulas and nowing
how to use them in your head is going to benefit you, then you will always be second place
to those who can. The only way ignorance can prosper, is if you were born into money.

--Doozer

[754]

I agree strongly with Danlb....
I have found though that some people dont even want to look stuff up, and just THINK they will figure it out.

[andywander]

What was your point? That it's an easy system, or that it isn't?

It seems really simple to me. If a guy can't divide 11 by 26 on a calculator and find the nearest matching drill bit size, he should probably avoid machining.

My point was that the original easy-to-do-in-your-head example given, which involved only 16ths of an inch, was not representative of most of the imperial threads that would be encountered, which are more difficult to figure out than the metric ones, because you need to convert TPI to pitch. A calculator would be handy, as you point out.

Or just use a chart......

[danlb]

Maybe machining is not for everybody.. You have to think a lot of the time, and do math often..
There are many other hobbies out there..

The telephone company (AT&T) was once known for extremely high work quality. One of the key components of that quality was that they did not want workers to rely on memory for anything complex or that workers did infrequently. Charts and checklists and procedures abounded. In the machining world we have the Machinerys Handbook for charts, formulas and procedures.

You don't need to do math quickly to be a hobby machinist. There's plenty of time to look up a formula, look at a chart or run some numbers through a calculator. There's nothing wrong with grabbing a cell phone to look up the right info for the job at hand.

[754]

Maybe machining is not for everybody.. You have to think a lot of the time, and do math often..
There are many other hobbies out there..

[Doozer]

Ignorant + Lazy = Stupid

Anyone want to check my math?

-Doozer

[Yondering]

Very happy-you proved my point perfectly.

What was your point? That it's an easy system, or that it isn't?

It seems really simple to me. If a guy can't divide 11 by 26 on a calculator and find the nearest matching drill bit size, he should probably avoid machining.

[Dave C]

Very happy-you proved my point perfectly.

Gimme the chart.

[andywander]

Sure.
1/2-13 becomes 1/2 - 1/13 which equals 13/26 - 2/26 which gives you 11/26.
1/4-28 becomes 1/4 - 1/28 which equals 7/28 - 1/28 which gives you 6/28 and reduces to 3/14.
Happy?

Very happy-you proved my point perfectly.

[RichR]

Great! Now do it for a 1/2-13 thread. or 1/4-28.....

Sure.
1/2-13 becomes 1/2 - 1/13 which equals 13/26 - 2/26 which gives you 11/26.
1/4-28 becomes 1/4 - 1/28 which equals 7/28 - 1/28 which gives you 6/28 and reduces to 3/14.
Happy?

[andywander]

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...

Great! Now do it for a 1/2-13 thread. or 1/4-28.....

[Highpower]

How do the heavy jets get serviced in Thailand?

I have no idea. I've only serviced jets in the US - and we used lbs. for fuel measurement. (USAF '75 - '80 / 43131)
The point of my link was to illustrate what can happen when you mix systems as Forrest was saying.

[Jaakko Fagerlund]

Maybe his Home Depot had only coarse thread available?

Only real bastard wildcat threads are on some milling machine or lathe collets, like 1,66666mm pitch.

Or threads used in some gun silencers. I remember one that was 8.4 mm OD and some really oddball fine thread with a no-standard crestform. Talk about vendor lockin...

[MattiJ]

Where did you get that only coarsest are standard?

Maybe his Home Depot had only coarse thread available?

Only real bastard wildcat threads are on some milling machine or lathe collets, like 1,66666mm pitch.

[Jaakko Fagerlund]

Metrification is not standardization. And I'm a bit put off that only the coarsest threads in metric are standard, while nearly ALL the metric threads seen on today's automobiles are FINE and so special. What sort of standard is that?

Where did you get that only coarsest are standard?