I have a habit of ruining drill bits while trying to drill mild steel. I've used HSS (which I now know is too soft) and cobalt bits. do I need to go to titanium bits to avoid ruining my life? I find even cobalt bits don't last very long before they become useless. Is there a special technique for drilling steel?
In breif. Yes. Little bits at a time and a cutting spray helps.
What about stepped drill bits?
Are you running your drill at a low speed?
Well for this stuff, it's quite small and I'm using a Dremel at about 60%? Tonight's Googling suggests 2500RPM is a good speed though.
Without knowing anything about your dremel I would suspect 60% is way too fast.
Even 2500rpm seems a bit fast to me unless you are drilling really tiny holes.
2500rpm on a drill press is for. .. 4mm Max iirc
sounds pretty close to me Alex.
Keep the load on the bit down and let the bit do the work.
2500 still sounds fast.
Hey I'll slow it right down then and see how I go. This is on the parcel shelf of the 244, so obviously the drill press won't fit there :P
I'm no expert, but a decent set of HSS drill bits is generally fine unless it's a large hole through thick steel. If you have to drill a large hole, start with smaller bits and work your way up.
I try to keep the speed down. I think the no load RPM on the slow setting of my drill is 1900, so while drilling it would probably be more like 1500. If you're seeing filings rather than swarf, the bit is probably blunt. Try to keep the tip of the bit relatively cool to help prevent blunting the bit. Even water helps.
I slowed it down and dialled the pressure back and have had good success with the cobalt bits now!
That's what she said!
HSS steel drills are all that is needed if speeds and technique is correct and of course use Rocol , Trefolex isn't for high speed drilling.
Learn to sharpen the drill bits from an expert and keep a pedestal grinding stone just for this purpose keeping it dressed well at all times.
Mind you , after too many years of drill sharpening I still can't get my hit rate above ....oooooh 25% I reckon. Bloody hopeless at it...
Good to have a half dozen of the ones you are using to change over as they blunt so you don't overheat the drill and/or lose the good form you have ground on it to make resharpening much easier.
Buy a good quality drill.
For big drills and holesaws I have a Metabo high torque one with 13mm HD chuck with key not twist lock. Bloody rip yer arms off...
Handles the pulse method for holesaws easily.
Good kit pays for itself.
From my fitting and turning days, the rough formula we used was rpm = 300 x cutting speed in metres/minute, divided by diameter.
Cutting speed for HSS tool on mild steel is 30 m/min so 300x30/D or 9000/drill diameter.
Use a lubricant!
Even a squirt of WD40 is good, a drop of proper cutting oil on the drill bit is amazing.....cuts so much faster and keeps cooler.
Big holes, start with a pilot hole quite small, no more than a quarter of the finished size, preferably smaller still. Big bits, run slow. Ease the pressure right back when you're nearly through or it will catch.
I have been using cutting oil also, it does make a big difference!
I have a small coke bottle of it from years ago when I worked in a workshop where it came in 200l drums....a small drop on the drill bit is all you need, I still have most of the bottle left about seven years later.....
Makes tapping threads so much easier too...I've never broken a tap and the threads are much cleaner and smoother.