On 21/09/2013 19:51, Andy Burns wrote:
At some point in the next week or two, I'll want to drill and tap a
dozen holes into stainless steel tube, this is 2mm wall thickness, 42mm
diameter handrail, I'll have a 100-200mm offcut to practice on.

Now, we didn't do metalworking at school, so I'm lacking in the basics,
but a bit of searching seems to suggest ...

For M5 bolts, use a 4.2mm drill, assuming it's 0.8mm course pitch (need
to check) hopefully an 18V cordless drill/driver isn't going to struggle?

Drill slowly to avoid work-hardening

Lubricate (use WD40 at a push)

As I'm tapping through, rather than into, the steel use a spiral point,
rather than spiral flute, tap.

What flavour of HSS (cobalt, vanadium, extra vanadium, nitride/oxide
coating etc) does the tap need to be to cope with 304 stainless?

I see 1/4" hex shank taps are available, e.g.
http://uk.rs-online.com/web/p/threading-taps/6699384

Will these work OK in the drill/driver? Or should I hand tap?

Given I'm unlikely to ever want/need a full tap/die set, can you buy
screwdriver or T-handle style single taps?

Any other tips appreciated.


To drill stainless steel, use a slow speed drill, and don't put too much
pressure on the drill. Also, I strongly recommend you use proper metal
cutting fluid or paste.

You said you were going to tap the drilled holes, so make sure you use
the correct sized drill bit for the tap size.You can do a search for that.
Well I've done it for you:
http://www.engineershandbook.com/Tab...ictapdrill.htm

I have only had about 30 odd years experience in the engineering trade,
so I know nothing, lol.

Good luck