I'm doing a Half-pipe / skate ramp. I have to drill holes in a stainless tube but I wasn't able to with HSS Drill tips last night (I've followed youtube video tutorials). The stainless tube is this one.
Today I'm thinking about picking new drill tips, but not sure if this will work ?
Can someone experienced give me some advice? I'm using a driller and I also have a screw driver.
The steps: Lubricate, do it slowly, etc.
Best Answer
For drilling stainless steel (which is quite hard, thanks to the chromium), your best bet are cobalt-steel drill bits (here's an example). Cobalt steel drill bits are significantly harder than regular HSS drill bits and will cut the stainless steel much better, allowing easier drilling. They are characterized by a dark golden color (as opposed to lighter golden color of titanium-oxide coated bits, like the ones you've linked) and are more expensive than regular HSS bits.
Regarding technique, the trick for drilling hard metals is to drill with a slow speed and high pressure on the drill. The goal is to get the drill to "bite" the metal, cutting of shavings. A drill press will be very useful here (if you can get access to one). High speed drilling will often just overheat the drill bit and the metal, without actually doing anything. Cooling and lubricating are also important, but for 1.5mm wall thickness I think it's not that critical. Just make sure to cool the bit between holes.
In addition, the required hole size matters - for small holes (up to 3-4 mm) you'd need to be careful lest you break the drill bit (which is quite easy to do). For larger holes, it would be best to use progressively larger drill bits. Don't use drill bits that are too close in diameter, as this may cause them to screw into the metal instead of drilling it (for example, for an 8 mm hole, don't use 7mm and then 8mm. Use 5 and then 8, or 3, 6 and 8 or the like).
Use a center punch to get a starting point for the drill bit, to prevent wandering.
Finally, make sure you disable the percussion function of your drill when drilling. Percussion is used for masonry work, and will only damage the drill bit and work when drilling metal.