QUALITY FASTENERS MART
J C GUPTA & SONS
You can download the the suggested drill sizes for Tapping threads as under.
Tap Drill Sizes - METRIC
Tap Drill Sizes - UNIFIED
Stainless steel is a very important material for fasteners. It is becoming the prefered choice for a variety of reasons.
The most important grades are:
BIS : IS 1367 - [Part 14/Sec 1] deals with the mechanical properties of Bolts, Screws and Studs. The equivalent international standard is ISO 3506-1.
For most applications, the property class 70 is used with Austenitic grade stainless steel fasteners.
It is common belief that a simple test for stainless steel is to check with a magnet. If it attracts, the product is not stainless steel.
However, in the case of Stainless Steel Fasteners, this assumption is incorrect. All cold worked Stainless Steel Fasteners get magnetised. The extent of magnetism induced varies for different grades and is explained in ISO-3506-2.