Looking for advice on how to tap some stainless.

[m_c]

As has been said, hole size is critical.
If you don't need maximum strength, then you can make the hole slightly over size, which will make tapping far easier.

Spiral point/flute are good options for speed, but another option is a set of serial taps, which come as a set of 3 taps and you run them through the hole in order. Arc Euro sell them.

If you've not got anything like Trefolex, I'd prefer to use some general purpose grease rather than oil.

[routercnc]

Does anyone know if thread milling would work in 303 ?

Does it need multiple passes therefore may work harden?

At least if the tap broke the work is recoverable

[magicniner]

303 taps nicely with Spiral Point and Spiral Flute taps of the right type and with the correct drill size, which will never be nominal OD less pitch BTW.
You will only get hardening if you fail to take a decent DOC, I've never had 303 harden on me.

[johngoodrich]

Does anyone know if thread milling would work in 303 ?

Does it need multiple passes therefore may work harden?

At least if the tap broke the work is recoverable

yes thread milling will work in 303. if I had to thread mill them with the small sizes of thread I would do them in one cut with a micro thread mill. personally though I would roll tap the threads as it will create no swarf to get stuck in the tap and 303 forms very well

[SequrCNC]

If your having problems with tapping like previous posts have mentioned a slightly oversized drill or threadmilling theres a supplier selling threadmills on a promo
www.smarttoolsuk.com starting at £32.50 had good feedback on them from the floor 2-3 passes i reckon on 303