Bits for hand drilling hardened steel

[Giurerana]

Greetings.

I'm looking for a set of drill bits, like this, for drilling out tough bolts, such as hardened exhaust studs. (Even with my favorite dewalt HSS drill bits I often have a really bad time getting anywhere.)

I've read a few sparse comments about solid carbide bits being great but I never used them, and I can't find sets of them anyway. Are they worth the price (like $25-40 a bit)?

[wingless]

Welcome to the forum.

 

My Irwin Hanson 11119 extractor w/ left hand Cobalt drill bits works really well on hard fasteners.

[paulengr]

With drills there are two issues. The first one is most people go WAY too fast. If you run the speed too fast in wood most of the time you just burn the wood. In steel you melt and dull the bit almost instantly. So find a drill speed chart and follow it religiously. In practice if it’s not on the edge of chattering it’s too fast. Second is pressure. If you got the first part right you don’t need much. You should get nice chips or ribbons. It will cut much faster.

Now for bits if you are in a store and all you see if gold colored bits, those are all junk. This is TiN costing. Real TiN does not cost $50 for a box. It costs more like $50 per drill. The reason TiN is used is it’s super cheap in thin coatings and makes dull, ordinary looking HSS bits bright gold color so it looks nice. Do not be fooled. You can’t sharpen these and you don’t want to because it’s just gold colored cheap Walmart grade bits. In fact they might even sell good bits but since they are selling cheap garbage just walk out. You can’t see all the pits and the fact that it’s low grade carbon steel, maybe not even high carbon tool steel. Just cheap Chinese high sulfur medium carbon garbage suitable only for wood peckers.

What you need is machinist grade. So here’s the secret trick. HSS is good for your job. You could get carbide but you need a drill press to control it because if it chatters or squeals at all it shatters. It’s completely unforgiving. At best maybe a little cobalt but that’s it, Your bits will be dull looking from the high carbon content. That’s good. Shiny is bad.

So go to either Reid or MSC or these days even Amazon. MSC is trying to be a Grainger clone so don’t bother unless you know where to look. Look for jobber length HSS drills. The word jobber is just a machinist term for standard length but this key word screens out non-machinist junk. You will easily find American made brands like Viking. Expect to pay around $100-200 and if you followed step 1 right they will last quite a while. In terms of metallurgy 90% of new high grade iron ore comes from American ir Canadian mines along the Mesabi range surrounding Lake Superior. It is mostly smelted here mostly using coke made from low sulfur and low phosphate Appalachian coke. You cannot add enough lime to get rid of the excessive sulfur in Chinese coke nor clean up the low grade steel, nor remove the high phosphate in German steels. This is one time where American made is important not just for some union flag waving but because quality drills start with quality ingredients. There is no way around the fact that Chinese and European steels are inferior because they don’t have access to quality iron ore and coke where it is mined,

Don’t bother with 135 degree points. In stainless the slower 118 degrees is a much better choice. Just hit it with a centering or prick punch first so your bit doesn’t wander to get started.

Follow this and you will have bits that easily cut stainless with little effort and last quite a while. Hand sharpening is best but if you don’t know how a drill doctor is inexpensive. A jobber set can last for years if you sharpen them.