Tapping is the process of creating internal thread features into a part.  Before deciding to tap stainless steel, it’s important to consider the
- thickness of the steel being used;
- 1.5 time the thread pitch is REQUIRED (e.g. M6x1.0 thread REQUIRES a minimum of 1.5mm), and
- 3 time the thread pitch (or thicker) is ideal.
- Angle of attack :
- Straight Center punched holes require 90 degrees, and
- Angled ‘platformed’ holes require machinist skills and tools (and if you don’t know what I’m talking about – the don’t attempt it)
Rivet nuts and nuts/washers can be used in straight holes for situations where your stainless steel is too thin to tap.
Unlike when you are drilling, it is best not to apply too much pressure when tapping stainless, as this can result in an uneven thread, or broken drill bits. Slowly guide your tap/bit through the predrilled hole, ensuring you hold your tool steady and straight. This process should be much easier than the initial drilling as less material is being removed.
Good Practice for conventional (straight fluted taps) tapping requires a proper sized hole in your stainless steel initially. Next insert the tip of the tap orthoganal to the material and ensure the fit is correct. Before beginning tapping, apply a liberal amount of tapping oil to the tap. The more evenly the oil is applied, the easier you will find this process.
Best Practice for tapping requires a center punched/drilled hole. Then put your spiral fluted Combination Drill Tap into your drill and ‘bang a hole’. A combination drill tap is self centering and cuts the material to the correct size BEFORE engaging its integrated tap feature and thus ensures the resulting threads are perfect. As always, any tapping, apply a liberal amount of tapping oil to the tap. The more evenly the oil is applied, the easier you will find this process.
And then there is: