What is a 5/8 inch NS HSG tap & drill size

[kedarg6500]

1. what is meant by NS HSG tap
2. what drill size is required for 5/8 inch 18.25 NS HSG tap
3. what is meant by 18.25? is it TPI
4. where i can search this information on internet about taps terminology

kedar

 

[Stijloor]

A Quick Bump!

Can someone help?

Thank you very much!

 

[smkeilman]

The 5/8"-18.25 is the basic Major Diameter and pitch in TPI. NS is the thread form, American National, Special thread. HS is the tap material, High Speed Steel. This can also be noted as HSS. G means the tap was ground.

Most tap drill sizes are at approximately 75% of full thread. The drill sizes for 100%, 75%, and 50% are as follows:

100% - 0.5657"
75% - 0.5805"
50% - 0.5953"

There is less than 0.001" difference in drill size between this thread and the more standard 5/8"-18 UNF thread. The chart on my wall for this thread shows a drill size of
37/64", or 0.578125"

 

[Dean Frederickson]

1. what is meant by NS HSG tap
2. what drill size is required for 5/8 inch 18.25 NS HSG tap
3. what is meant by 18.25? is it TPI
4. where i can search this information on internet about taps terminology

kedar

1. Not sure about the NS but the HSG is High Speed Ground.
2. The drill size for 5/8-18 is .5781.
3. It is Threads Per Inch
4. Google " Drill Tap Terminology"