How To Drill Through Steel and Other Metal

[Jason in DLH]

So after attempting to drill out broken and rusted bolts on my old car with several good bits breaking I did a bit of research and concluded the following:

1. Use Cobalt drill bits. Start small and progressively get larger. This set is what I use with fantastic results...


I would rate this set 5 stars as I’ve used them numerous times without issue.


2. Use cutting oil. I use this with great results...



3. Use slow speeds and have patience!

Note: if you’ve never used Cobalt bits, careful when handling as they are extremely sharp!


Hope this helps someone!

 

[OR VietVet]

Yea, learned that years ago in the shops I was at. Cobalt bits and oil and patience. If the bit is smoking when drilling, it is being damaged.

 

[George B]

If its really hard stuff you can use carbide drills. But they are pretty spensive.

 

[OR VietVet]

Yes they are. I went thru 3 different sets of carbide and cobalt bits over the years and they were not cheap, even back when I was in shops.

 

[drakon543]

drill bits also have varying pitches to the cutting head. so some non carbide bits will actually cut quite well with the same procedure. just because it says its for metal doesn't mean the mfg is sure thier pitch is actually the best. a good drill dr or patience and learning how to sharpen drill bits by hand you can actually change the pitch on a bit for varying uses. higher grade steel you want a meaty bit and slower speeds regardless. sharper the pitch is less metal at the contact point so heat will build faster and burn the bit.

 

[alpha_omega]

Another thing to mention for those less experienced with power tools, bits and drilling holes in metal is to start off using a center punch. An automatic center punch is a very handy tool for ensuring you have an indent for the bit so it doesn’t “walk” once you pull the trigger. As mentioned before, ensure to use cutting oil and a decent amount of pressure while going slow. Backing the bit out in reverse to clear the metal chips helps to keep the bit from binding and the oil from boiling.
For drilling larger holes you have a couple options. One is to start with a smaller bit and work your way up to the correct size that you need, whether you’re drilling just to make a hole or if you plan on “tapping” the hole so it has threads for securing a fastener into.
Option two and my preferred method, especially if the metal is very strong or you don’t have the ability to use multiple bits is to use what’s called a “step bit”. It’s a conical shaped bit that steps up the hole size the deeper you drill. As previously stated, OIL, clean the chips out and take it slow. *Milwaukee makes a great set

here’s a picture of the oil I use, the automatic center punch, and a step bit.

 

[ACM]

View attachment 264745

I would rate this set 5 stars as I’ve used them numerous times without issue.

I needed a bit to drill 7/64" pilot holes on Friday for some fender flares and the nice gal at the Ace Hardware across the street recommended this exact Milwaukee cobalt bit. +1 on the recommendation, they made the job easy even for this relative power tool novice.