Tap And Drill Wall Chart

MSC Direct has a couple different wall charts available. One is by SPI:
http://www.mscdirect.com/product/details/78010360

and another is by Accupro:
http://www.mscdirect.com/product/details/69811578

I have a couple older ones in the shop by Kennedy. The charts are approximately 22" wide by 32" high. they have all drill types (fractional, metric, numbers and letters) defined in decimal equivalents up to 1". They also have SAE and Metric tap and drill sizes up to 2" and 14MM respectively.
 
:+1: on signing up for the free stuff from Starrett. I got mine.
 
With TPI threads for the middle tolerance subtract the lead from the major diameter for a tap drill size.
Examples
1/4-20 (1/20) = .05 lead, .25 -.05 = .200. tap drill chart will list a #7 drill which is .201
3/8-16 (1/16) = .062 lead, .375 - .062 = .312 tap drill chart will list a 5/16 drill
and so on.

M profile threads are denoted by major diameter and lead instead of major diameter and threads per inch , this makes it much simpler.

An M5-1 thread would use a 4 MM hole, an M10-1.5 would use an 8.5 MM hole. An M20-2 would require an 18 MM hole and so on.

This being said, in difficult materials it is best to consult the actual min/max dimensions as defined by the ANSI.

Example
ANSI 3/8-16 internal thread
2B fit, minimum minor diameter .307, maximum minor diameter .321.
This means that it would be within standards to tap a 3/8-16 2B thread into a .320 hole rather then the smaller .312 hole that one will find on a free tap drill chart. You probably have no idea how much less force it takes to tap a tough material with that extra .008 in diameter.

I suspect that the reason this is data is not on common free charts is that it is To Much Information and they are in the business of selling drill bits.
They do not stock .320" drills.
 
Thanks all. I signed up with Starrett and ordered their wall chart--FREE!
 
Wreck™Wreck said:
With TPI threads for the middle tolerance subtract the lead from the major diameter for a tap drill size.
Examples
1/4-20 (1/20) = .05 lead, .25 -.05 = .200. tap drill chart will list a #7 drill which is .201
3/8-16 (1/16) = .062 lead, .375 - .062 = .312 tap drill chart will list a 5/16 drill
and so on.

M profile threads are denoted by major diameter and lead instead of major diameter and threads per inch , this makes it much simpler.

An M5-1 thread would use a 4 MM hole, an M10-1.5 would use an 8.5 MM hole. An M20-2 would require an 18 MM hole and so on.

This being said, in difficult materials it is best to consult the actual min/max dimensions as defined by the ANSI.

Example
ANSI 3/8-16 internal thread
2B fit, minimum minor diameter .307, maximum minor diameter .321.
This means that it would be within standards to tap a 3/8-16 2B thread into a .320 hole rather then the smaller .312 hole that one will find on a free tap drill chart. You probably have no idea how much less force it takes to tap a tough material with that extra .008 in diameter.

I suspect that the reason this is data is not on common free charts is that it is To Much Information and they are in the business of selling drill bits.
They do not stock .320" drills.
Click to expand...



Thanks, That's some good info.
 
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WreckWreck said:
With TPI threads for the middle tolerance subtract the lead from the major diameter for a tap drill size.
Examples
1/4-20 (1/20) = .05 lead, .25 -.05 = .200. tap drill chart will list a #7 drill which is .201
3/8-16 (1/16) = .062 lead, .375 - .062 = .312 tap drill chart will list a 5/16 drill
and so on.

M profile threads are denoted by major diameter and lead instead of major diameter and threads per inch , this makes it much simpler.

An M5-1 thread would use a 4 MM hole, an M10-1.5 would use an 8.5 MM hole. An M20-2 would require an 18 MM hole and so on.

This being said, in difficult materials it is best to consult the actual min/max dimensions as defined by the ANSI.

Example
ANSI 3/8-16 internal thread
2B fit, minimum minor diameter .307, maximum minor diameter .321.
This means that it would be within standards to tap a 3/8-16 2B thread into a .320 hole rather then the smaller .312 hole that one will find on a free tap drill chart. You probably have no idea how much less force it takes to tap a tough material with that extra .008 in diameter.

I suspect that the reason this is data is not on common free charts is that it is To Much Information and they are in the business of selling drill bits.
They do not stock .320" drills.
Click to expand...

Wow- thanks Wreck Wreck- great to have this method at hand- in my mind.
 
Attached is a pdf file of Starrett's chart.
 

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