# Excellent Tap Chart with Specials



## 90LX_Notch (Oct 11, 2011)

HMEM Members-

I found this excellent Tap chart while searching for the drill size for 1/4-40 NS.

http://www.bigblockdart.com/techpages/TapDrillChart.shtml

-Bob


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## Tin Falcon (Oct 12, 2011)

I use and like this one from LittleMachineShop.com 
http://littlemachineshop.com/Reference/tapdrill.php

more info and reference charts here:
http://littlemachineshop.com/Reference/reference.php
the above page is an excellent resource for the Mini mill and lathe owners or perspective owners. 
tin


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## kvom (Oct 12, 2011)

My drill index box lid lists tap and clearance drill sizes for most common imperial threads. The tap sizes are typically at the 75% fit size. I normally go one size up for steel to make tapping easier, and use the recommended sizes for aluminum and brass.


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## 90LX_Notch (Oct 12, 2011)

I guess I failed to articulate this well. This chart has the NS (National Special) threads and their required drill size. All of my other charts do not, including the Little Machine Shop one. Point being, it has all the threads in one nice chart. Easy enough to grab the info and print it for the shop wall.

I should not have used the word "excellent" to describe it. I should have titled the post "Tap Chart that includes National Special threads at 75%." :idea:


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## mklotz (Oct 12, 2011)

Nice chart but the entire chart can be replaced with a single equation that will also allow for *all* values of depth-of-thread.


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## Dan Rowe (Oct 12, 2011)

Marv,
The tap chart is quicker and does not require bateries.
Yes I have a spread sheet to work our special cases like NS.
It still takes longer than glancing at the LARGE print tap chart on the shop wall.
Dan


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## gbritnell (Oct 12, 2011)

Thanks Bob.
gbritnell


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## fltenwheeler (Oct 12, 2011)

Hi

Here is a chart that I came up with. Yes, all of the sizes are real. 

Tim 

View attachment thread.pdf


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## MachineTom (Oct 12, 2011)

I find that chart way too busy with the mix of metric and Imperial. A guy from another forum made an etched Al chart with the tap drills added as a % of thread depth, that is darn handy, the second is a website ( http://www.newmantools.com/tapdrill.htm#top) this is a calcilator, that I leave on the disktop. So last week a .900 X 24 thread was needed, whats the tap drill size, instant gradification, 7/8 x 36, 15/16 x 20, yeah, I have those taps.


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