Stainless steel is one of those materials that gives you a nod of respect when you get it right — and a swift kick when you don’t. It’s strong, corrosion-resistant, and downright beautiful when finished properly. But if you’ve ever tried drilling into it, tapping a thread, or tightening a bolt a touch too far, you’ll know stainless doesn’t suffer fools lightly.

Here at Bolt-In Co Sunshine Coast, we’ve spent decades helping both pros and DIYers work smarter (not harder) with stainless. Whether you're fitting marine-grade fasteners to a boat in Mooloolaba or bolting together a custom ute tray in your garage, knowing how to properly drill, tap, and torque into stainless steel can save you time, gear, and a fair bit of cursing.

So let’s dig in — no nonsense, just practical tips for getting the job done right.

Drilling Stainless Steel: Patience Beats Power

There’s something about stainless that makes people think they need to go in hard and fast. Wrong. That’s how you cook your drill bits and glaze the surface so badly that nothing cuts after that.

Key Tips:

• Use the right drill bits – High-speed steel (HSS) is your bare minimum. Cobalt drill bits (like M35 or M42 grade) are better. Keep your bits sharp — stainless will blunt them quicker than mild steel ever could.
• Slow and steady wins the hole – Drill speed is critical. For stainless steel, slower RPMs with steady pressure work best. If your bit is screaming, you’re going too fast.
• Lube it up – Use a proper cutting fluid. WD-40 in a pinch, but something like CT-90 or Trefolex will reduce heat and make your bits last longer.
• Start small, finish clean – If you’re drilling larger holes, start with a pilot bit (say 3mm), then step up in stages to your final diameter. Jumping from 3mm to 12mm in one go is how holes go sideways and bits snap.

Pro tip: Clamp everything securely. Stainless has a nasty habit of grabbing the drill bit when it’s almost through, spinning the workpiece — or your wrist — if you’re not careful.

Tapping Threads Into Stainless: Cut, Don’t Force

Threading into stainless is doable, but it’s not like tapping into pine or even aluminium. You’ve got to respect the material — otherwise, it’ll chew up your tap and leave you with a half-threaded hole and a fresh reason to go to the pub early.

Essential Tips:

• Use a quality tap – Cheap taps are a waste of time. Go with high-speed steel or better. Spiral point taps are great for through-holes; spiral flute taps are better for blind holes.
• Proper tapping fluid – Use tapping compound or paste, not general-purpose lubricants. Stainless is sticky — you need something that helps chip evacuation and reduces galling.
• Back it out – Every full turn forward, give it half a turn back to break the chips. If you feel it bind up — stop. Back it out, clear the chips, and go again.
• Don’t overdo it – If your project needs a tapped hole and you’re planning to insert a stainless steel bolt into stainless steel threads, beware of galling. That’s when the threads seize together and you’re left with a fused lump of metal and shame. Consider using an anti-seize compound or using dissimilar metals (e.g., stainless bolt into a mild steel or brass insert).

3. Torque Matters: Don’t Let Stainless Turn Against You

So you’ve drilled the hole, tapped the thread, and you’re ready to bolt everything together. Job done, right? Not quite. Stainless steel has a few last tricks up its sleeve — and one of them is galling under torque.

What You Need to Know:

• Thread galling – This is where stainless fasteners — especially SS316 bolts and nuts — seize while being tightened. It’s caused by heat and friction during assembly. You’ll feel it: one second the nut’s turning fine, the next second it’s locked solid. And it’s not coming off without a grinder.
  
• Use anti-seize – Always apply an anti-seize lubricant on threads when assembling stainless into stainless. It helps reduce friction and prevents galling, especially in high-load or high-speed applications like automotive fasteners or marine gear.
• Don’t overtighten – Unlike high-tensile bolts (like Grade 12.9 fasteners) that are built to handle serious torque, stainless is more prone to stretching under load. Use a torque wrench and stick to spec — especially when dealing with stainless steel balustrades, where overtightening can crack fittings or damage the wire.
• Choose the right finish – Polished or passivated stainless fasteners tend to resist galling better than rough-finish or untreated ones. Another reason to buy quality — which, let’s be honest, is why we’re still in business after 50+ years.

Conclusion: Stainless Isn’t Difficult — It Just Doesn’t Tolerate Rushing

Fastening into stainless steel isn’t impossible — it just requires a bit of respect. Drill too fast, tap too dry, or torque too tight, and it’ll let you know you’ve stuffed up. But if you follow the basics — quality bits, plenty of lube, measured force — you’ll get clean holes, crisp threads, and a finish that lasts.

At Bolt-In Co Sunshine Coast, we stock only high-quality stainless steel fasteners because we know that using cheap gear isn’t saving anyone anything. We carry SS316 marine-grade fasteners, high tensile bolts, concrete fixings, automotive fasteners, and all the nuts, bolts, and balustrade fittings you could dream of. We’re based in Maroochydore but ship fasteners Australia-wide, so whether you’re in Yandina or Yarra Glen, we’ve got you sorted.

Got a job involving stainless and not sure what gear you need? Drop into the shop, give us a call, or send an email with too many photos. We’ve drilled, tapped, and torqued more stainless than we care to admit — and we’re happy to help you avoid the rookie mistakes.

And remember: when it comes to stainless, don’t rush it. It’ll outlast your house if you treat it right.