Blooming stainless, grumble moan complain

[Smiler]

Such a simple job, two brackets to connect an electric hoist to scaffold tubing up in the roof.

Pop a scaffold pipe sized hole through two pieces of box section, what could be easier. It's only 10 gauge

Couldn't find the ordinary box section, could only find stainless. Felt dread.

Lost a tooth or two on the bandsaw cutting it to length. £12.50 a blade.

Knew the mill wouldn't pierce it, decided to drill it 12mm first. Drill goes red hot and burns out.

What speed were you drilling? Rule for stainless is low speed high feed. Stainless when you buy it is soft but work hardens very quickly indeed. Once the drill starts to chatter or you see black swarf, you have lost. If drilling with a pistol drill, I find the best method is again, slowest speed, lots of pressure and pulse the drill, short 2 second pulses will get you through in no time and you will be surprised how many holes you can drill before the bit needs sharpening. Cutting fluid can also help but can also make the drill cut too deeply as you really do need to keep the pressure on to get through the "chewey" stainless.

Milling cutter doesn't want to open the slightly undersized hole out. It's bending the box section until it can stand no more then leaping back. Never seen that before. Turn off the CNC and drive it through by hand, cutter will never be the same after that.

CNC the hole bigger, table leaping all over the place. Ball screws displaced, backlash now 2mm, second part comes out undersize, table in need of repair.

Lock the slides and try to make it round with a boring head. The carbide tip soon shatters but there is one sharp edge remaining about 4mm back from the end and I get it done. This is becoming a war of attrition and I'm losing.

Now just 4 x 10mm bolt holes left to drill and I'm done. At that point I gave up for the night and came home.

Wonder how many drill bits I can nadger tomorrow.

I would have gone for a hole saw on slowest possible speed, a light touch pressure wise and good cutting/tapping fluid (not mystic). I know this is opposite to drilling but this is with the benefit of 30+ years of doing it day in day out.

Jeff.

[Robin Hewitt]

What speed were you drilling? Rule for stainless is low speed high feed.

I know what went wrong, I pushed too hard at break through and the metal extruded in to a collar on the inside of the tube. This collar instantly hardened undersize and started deforming to match the bit as it went round. Less than a second later the bit was red hot and deforming to match the collar

I got my 4 holes drilled this morning nil problemo. Should have binned the rest of the bar but didn't :D

[Smiler]

I know what went wrong, I pushed too hard at break through and the metal extruded in to a collar on the inside of the tube. This collar instantly hardened undersize and started deforming to match the bit as it went round. Less than a second later the bit was red hot and deforming to match the collar

I got my 4 holes drilled this morning nil problemo. Should have binned the rest of the bar but didn't :D

Stainless is an absolute pig! It's so temptimg sometimes when you are microns away from breaking through and the swarf turns dark to push just that bit harder.......next thing you know....home made step drill:D

Wasn't trying to teach you to suck eggs BTW.

Snowing buckets here at the 'mo :(

Take care all, Jeff.