Bits for hand drilling hardened steel

[Achilleus]

Greetings.

I'm looking for a set of drill bits 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)?

 

[dclassical]

They may not be the best or even the right kind of drill bit for the application. I do not have much experience.

However when a regular drill bit (HHS) broke on me while I tried to drill out a broken bolt, I looked for information online and decided to buy a solid carbide drill bit. I believe it was 4mm. I put it in the drill press and it was very easy to drill out the piece of broken drill bit and the rest of the bolt.

But they are quite pricey. I remember they each came in an individual plastic tube. I think I paid around $15 for the 4mm.

I hope this helps.

 

[Achilleus]

Yes that is what I heard someone else do. What about using them in a hand drill, rather than a press? Are they very brittle?

 

[dclassical]

I do believe that they are brittle, which is why I used the drill press... I did not want to take any chances with a hand drill (plus I am only a DIY so my experience is limited). Especially with it being a 4mm!

 

[Achilleus]

Could be a pain to break a carbide bit! How do you drill that one out? lol

 

[dclassical]

I believe there is a process called "electrical discharge ...." for such a case or to remove broken taps or such... I am sure it is not the exact name as I cannot remember it for sure.

 

[rodm1]

I believe there is a process called "electrical discharge ...." for such a case or to remove broken taps or such... I am sure it is not the exact name as I cannot remember it for sure.

Yep EDM for short pricey.

 

[Achilleus]

Good stuff! Thanks for the info.

So anyway back to my wallet's capacity, I did a little more reading and it seems people often use cobalt drills, usually in left hand rotation format. Irwin makes a set of 5 for not too much. Cheaper than one single carbide bit. Comments would be welcomed if there is something better for a reasonable price.

 

[Ford12508]

Those are probably carbide coated, much different than actually having a carbide bit.

 

[Lump]

My buddy works in a tool-n-die shop, and he uses EDM to remove broken studs from rare and expensive muscle car exhaust manifolds.

The way he explains the process to me, is that the EDM machine takes a piece of carbon (like pencil lead, sorta), and uses electricity to super heat the carbon. Then the carbon is pressed into the metal, and burns its way through. The tool-maker first shapes the carbon to whatever shape and size they need, and then put it in the EDM machine. So my buddy takes a piece of carbon shaped exactly like a specific allen key size, and burns a hole completely through the broken exhaust stud (and any drill bit, EZ Out, tap, or etc which may be in the broken stud). When the hole has been burned through the stud, he quickly inserts the correct allen key, while the broken stud is still very hot, and turns it out easily. He specifically looks for rare and expensive exhaust manifolds with broken studs and broken bits in them, because he can buy them cheaper, and it is easy for him to fix them.

But of course, you must take the engine component out of the car, and mount it carefully on an EDM machine in a tool-and-die shop somewhere. It's no help in the field.

 

[Marfark]

I had to drill out three hardened 5mm bolts that were broken off in an aluminum chainsaw engine housing. My MAC titanium bits wouldn't bite at all. I ended up buying a 1/8" Bosch tungsten carbide glass and tile bit. I think it was about $10 at Home Depot. It looks kind of like a tiny spoon bit. It drilled into the bolts easily.

 

[Achilleus]

Marfark - thanks for that, great idea and I have some of those somewhere.

 

[A_Pmech]

I usually use a one flute carbide die drill in such circumstances.

Being that they have one flute and no helix they are fairly strong and resistant to snapping. Die drills are specifically designed for drilling very hard materials. Drilling though a file is no big deal with one.

 

[Busted Bolts]

I use the Irwin cobalt bits for hardened and stainless drilling. Other than heating up and making the temper higher, I haven't had much problems dilling out studs with these bits

 

[ricleh]

These work pretty good. They will drill right through a file like it was a piece of plastic.

Rodman drill bits

 

[Lockman1]

Greetings.

I'm looking for a set of drill bits 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)?

Yes the solid carbide bits are worth every penny. They will drill just about anything.

RHC - Rockwell Hardness C

HSS Drill Bits - Work well up to the 50ish RHC
Drill - Mild steel, Some tool steel, Some Spring Steel
No Drill - Hard Plate, Anti Drill Plate, 404c Stainless Steel
Pro - Good in Hand Drills and most drilling applications
Con - Has limitations in hardened steels

Cobalt - Works up to 58ish RHC
Drill - Mild Steel, Some Spring Steel, Some Tool Steel
No Drill - Hard Plate, Anti Drill Plate, 440C Stainless Steel
Pro - Good for hand drills and most drilling applications
Con - Has limits with hardened steel

Carbide Tipped - Will drill almost any steel, Hard, Stainless or Mild.
Pro - Drills all steel
Con- Blunt tip requires extreme pressure to produce cuttings. Drill bit is hard to start on all steels.

Diamond Coated Drill Bit - Cuts on most steels(Not Hard Plate) just not for long.
Pro - Will Drill most steels (Not Hard Plate)
Con - Cutting stops quickly after diamond grit has warn off, Then behaves like HSS bit

Solid Carbide Drill Bit - Cuts all steels.
Pro - Sharpened points wont "walk" like carbide tipped bit. Cuts all steel
Con - Sharp tip and fine edges can chip easily and ruin drill bit. Not for hand drills. Expensive!

For more information enter “The Ultimate Guide To Drill Bits” ____ Tube video into your favorite search engine and watch the video.

 

[spotco2]

I've used a lot of Strong Arm, Mr Twister, ITW Ramset and Butter bits for hardened steel. They are carbide and work very well with a press but can also be used with just a regular drill.

Strong Arm are my go to bits for hard stuff and always use cutting oil with them.

 

[netgypsy]

Where can the strong arm bits be purchased? I'm north/nw of Atlanta

 

[fourjeepin]

For removing broken bolts or studs, my favorite tool is a welder. One time I had to weld the nut on twice. It works that well.

 

[jeremy v]

If you want to experiment with carbide drilling on the cheap, buy a carbide tipped masonry drill bit set. They are about $20 a set new, but I find them at garage sales for about $1 for the set all the time and that's why I use them. They don't look pretty or high quality, but even ugly looking carbide is better than no carbide at all. They don't have the variety of sizes that true drill bits have, but for many purposes the most common basic sizes work just fine.

They usually work right out of the box for me, but I have sharpened them by hand with a diamond wheel (harbor freight ~$5 and come in a 5 pack) in a Dremel tool. Sometimes it helps if they grab a bit more or less depending on the situation, so it is nice to be able to have a way to sharpen and/or profile them somehow.

They should work fine for you in a hand drill, that's how I usually use them. They probably actually work better in a hand drill than in a press, because they are cheaply made, so some of them have a little bit of wobble that the hand drill can compensate for and absorb easily so your hole still remains true.

http://www.sears.com/craftsman-7-pc-masonry-drill-bit-set/p-00967441000P

EDIT- I guess I should mention that I do realize the OP is asking about drilling in hardened steel and not masonry. I am talking about using the masonry bits for drilling steel. I use them when I drill steels that are too hard for my HSS bits. Things like hardened tool steels, cast iron, etc.

 

[kenburkholz]

Solid carbide,single flute bits, are very expensive, but yes they are very expensive, about $40 for a 1/4" bit. They should only be used in a drill press or mill, for stability, as they are extremely brittle. I have never seen them in sets. They are available from industrial suppliers like McMaster Carr, Grainger, or M.S.C. Masonry bits, which have brazed carbide tips are not made for drilling precision holes in metal. Ken.

 

[kenburkholz]

Solid Carbide, single flute bits are good for drilling in most hard metals. they are very expensive, and also very brittle, so they should only be used in a drill press or a mill for stability. Masonry bits with brazed, or cemented carbide tips should not be used to drill holes in metal. Ken.

 

[Steinmetz]

I believe there is a process called "electrical discharge ...." for such a case or to remove broken taps or such... I am sure it is not the exact name as I cannot remember it for sure.

Electrical Discharge Machining was our method for removing broken drills and taps back in the day...