Which Drill Bit for Steel

[Beltzington]

What types of bits do you metal mavens typically use with your hand drills? Here is my recent experience drilling 12 1/4" holes in 3/8" mild steel:

Dewalt Cobalt ($$$) Cut well but broke three bits in 5 holes

Irwin Black Oxide ($) Dulled quickly but managed to complete the remaining 7 holes using four bits

Dewalt Titanium ($$) Did not try

Mineral oil (messy) and WD-40 improved the drilling I did not have actual cutting fluid. I am sure a drill press would prevent or reduce snapping the bit but this is not an option.

Appreciate your experiences

 

[Soundguy]

Good grief! if you are breaking bits, you are likely flexing or moving the bit while it is piloted in the hole.. that's the problem with using a hand drill.. you have to hold it steady.

1/4" mild steel 12 holes used 7 bits? WOW.

simple HSS and cutting oil should have done it with 1 bit. Manage heat,, oil is cheap...

 

[Beltzington]

Good grief! if you are breaking bits, you are likely flexing or moving the bit while it is piloted in the hole.. that's the problem with using a hand drill.. you have to hold it steady.

You think Capt. obvious?

How about some real advice? What is HSS High Speed Steel? Do you have a favored brand?

 

[Soundguy]

You think Capt. obvious?

How about some real advice? What is HSS High Speed Steel? Do you have a favored brand?

How about some real advice? Um.. I gave you real advice.. both on drill type and technique.... here's some more.. how about not being rude to those helping you?

I'm putting you on ignore now after that rude comment.

good luck with the 7 bits per 12 hole ratio... wish i owned a drill bit store.

 

[Raspy]

Soundguy has it right.

One HSS or titanium bit, or equivalent should have done them all with ease.

Hold the drill motor steady with both hands so it's not bending the drill bit or can't twist when it gets stuck. Apply enough pressure to get a curl of cut metal once the drill gets established and gets deep enough for full flute contact. Slow speed is better than a very high speed to prevent heat. Any handy oil will help. Motor oil is good, drill slow enough that it doesn't get slung away (if you don't have any, pull the dipstick on your tractor and touch the end on your mark). Ease the feed force as the drill begins to break through the other side to prevent getting stuck or breaking the drill.

The best way to do this is to put your steel on the floor on a piece of wood. Put both knees down on the floor and get a solid grip on the motor. A couple drops of oil on your mark. Feed with steady pressure and look for the curl. Not much pressure is required for 1/4". If the bit gets stuck, hit reverse to get it free, then come in again at full RPM and very little pressure.

If you are drilling stainless, you must have a curl or the metal will work harden and ruin the drill.

 

[Beltzington]

Sounds like Soundguy is a tad sensitive this morning. I know I broke the bits because of the poor control of the drill, very awkward position, I was drilling inside of a metal cabinet one handed at an angle with a 1/2" drill. That being explained I still managed to complete the remaining 7-holes with black oxide bits which did not snap. My assumption is some bits or much more brittle than others leading to my question. Which type drill bits (brand) have you folks had good experience with?

 

[SPYDERLK]

Do not push the drill motor using its handle. Use a hand on the back directly in line with the bit. If youre not good feeling imminent breakout try one of the clutch settings to prevent overtorque. If no clutch, moderate chuck tightness can be used at some cost to the bit shank.
larry

 

[sal64]

Jobber Length Drill Bits | MSCDirect.com

 

[varmint]

Wow... this can only get better. HHS bits and, perhaps, a bit of lubricating oil (motor oil will work if nothing better is available) and you should be good to go. If the bits are dull or mis-sharpened, then sure, there will be trouble. But a new bit- oughta be a piece of cake. Cobalt bits are intended for drilling into stainless steel. Like others observed, pushing straight into the hole is critical, and some pressure will be required to advance the bit. Mild steel should drill nicely.

 

[arrow]

Some of the best bits I've used are Milwaukee's. After they dull, the Drill Doctor does only a fair to middlin job for me getting them back in shape.

 

[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.