Which Drill Bit for Steel

[wdchyd]

Belzington, think cooling when using anything on the drill bits.....I use flood cooling on my equipment when drilling, milling and turning ......the coolant is 5-10% oil and the rest water
The only reason for the oil is to keep the machine tools from rusting

When drilling with water handy, try running a garden hose and have someone trickle it on the bit while you are drilling, you'd be amazed how well it drills.....no messy oil to clean up, just do it outside and drill at slow rpm

I routinely drill in excess of 1", use only HHS and use the drill doctor also for touching up drill bits

 

[wdchyd]

Also a squirt bottle of water works too, just keep spraying never letting the bit get too hot to anneal the bit

 

[CNC Dan]

If possable, drill a pilot hole first.
About 3/32" for 1/4" drill.
That will greatly reduce feed pressure required.

And use stubby bits.

 

[Shield Arc]

For the last 25-years I've been using cheap imports drill bits. 90% of them need to be sharpened before use. I hand sharpen my bits on a bench grinder. I sharpen one way to drill aluminum, another way for drilling stainless steel, and another way for steel. Very, very seldom do I break a bit. But one time I broke a bit by tightening it in the Jacob chuck of my mill:shocked:. Just like the bit was made of glass!

 

[kencunningham]

It has been my experience that cheap bits are the way to go if you can sharpen them, by hand or using a drill doctor. We had to drill out some exhaust bolts once that were very hard. The bit would cut for a few seconds and then it was pretty much useless after that. I would just hand the guy running the drill a freshly sharpened one, and he would take out the dull one and i would resharpen it. Rinse Repeat Etc. Didn't really take all that long to drill em out using that method.

 

[BKBoiss]

I too go for the cheap ones and sharpen very often . I just drilled a couple holes in 1/4 stainless (my first time with stainless) I left the bench grinder running used a drop of cutting fluid and VERY slow speed, drilled till it didn't bite anymore popped the bit out touched it up and back in again. I sharpened 4-5 times per hole but to me the bit if extra time isn't a huge deal. I think a freshly sharpened bit is the difference of night and day.

 

[davrow]

I just mounted a Piranha tooth bar to my bucket. Happens that on a Kioti the hole goes half through the bucket and half through the hardened steel reinforcement plate.

Very awkward doing by hand, got the 1/2 inch holes fine but then needed to up that to 3/4. Just went to Home Depot and bought a bit there. No name that I know of. Expensive, though (over $20). Not concentric enough in my Milwaukee Hole-Shooter. so when I went to Ababa Bolt to get #8 bolts (I needed more length than the #5 bolts included) I picked up a bit from them.

Looked really nice, spun nice and smooth. First break through chipped the cutting edges on both sides. Finally had to finish with the Home Depot bit, even though it wasn't straight, it finally finished the job.

Wish I knew about the water - I could have had my wife out there with a hose. The little oil I used didn't seem to matter much.

Drill press would have worked much better, but I couldn't fit the bucket in one (also don't happen to have a drill press )

 

[Shield Arc]

davrow one of these is what you need for a project like that.

 

[davrow]

Shield Arc, you sure have lots of fun toys... er, tools! :laughing: I didn't even know those things existed.

 

[Arc weld]

1/4" holes would be better done with a higher speed drill than a 1/2". The smaller the drill bit, the faster they need to turn. Any decent sharp drill bit should make childs play out of 12 1/4" holes in mild steel. Did you use a centre punch before drilling? This makes a big difference too as the bit can wander around when trying to start the hole which could be a factor in the bit breaking. The combination of too slow a speed and too much force on the bit will make matters worse. Cutting fluid helps but even dry, a properly sharpened bit should drill pretty easy. Should have 2 flutes when cutting properly. I've drilled a bunch of holes dry and if the bit is cutting properly, it doesn't overheat.