**** happens, but not me again! Drill bit advice please

[It'sNotWorthComplaining!]

I'm trying to remove 2 broken exhaust flange studs, Access underneath is not a problem, I've tried drilling and using an easy out, but after having one break years ago, I decided not to force it in case.
So I decided to drill the stud out, all was going well until I noticed a red Glow ( had it going too fast) and the bit end melted.
So now I have the problem where I can't drill it out as the drill bit steel is hard and the other drill bit goes blunt.

IS there a special drill bit that will drill out hard steel?
I'm pulling out the 2 strands of hair I have left on my head:(:(:(:(:(

[It'sNotWorthComplaining!]

I came across this, might see if I can acquire one.


Solid Carbide Drill-bit


Now this is a beast. It will drill and cut into a screw and stud extractor (also known as an "easy out") — an extractor tool for a broken stud/bolt, and these are made from quite hard steel in their own right.
There is also a fair chance that it could cut into any of the above drill-bits, if you could keep it on centre.

[Killer]

If you get hold of a masonary bit and sharpen it like a standard twist drill it should do the job. Only problem is you need the correct type of grinding wheel (green wheel) to sharpen them.

Cheers, Mick.

[GuyG]

I believe you can get a reverse drill bit, so in addition to drilling it out its trying to undo it also

[It'sNotWorthComplaining!]

I believe you can get a reverse drill bit, so in addition to drilling it out its trying to undo it also
It didn't beak in the hole, it melted itself in there, so the bottom of the hole is tipped with hard metal.

[nice1guv]

A carbide drill bit should do it, and most places should have them. :)

If not then my next step would be a diamond tipped drill bit, but they are expensive and hard to get. :p

[incisor]

not good juju

carbide tip, medium->slowish speed and some cutting compound or water to keep the heat down...

trick with carbide is not to let it chatter...

[Bigbjorn]

Sounds like you were using a blunt drill to start with. If you had used a reverse helix drill first you most likely would have unwound the offending stud. A tungsten carbide inserted drill or solid TC drill will do the job. Get a stub drill or a straight flute drill. You are less likely to break a stub drill. The grade of carbide used in masonry drills is not the same as used in hard steels but if sharpened correctly to 135 degree twist drill geometry on a silicon carbide or diamond wheel will do but will likely be stuffed afterwards. If available I would use a straight shank, straight flute TC inserted die drill. These normally use C2 carbide. go to a good engineers supplier.

[johnclv]

All suggestions are good especially the reverse drill bit

If you can leave your manifold on and use it as a guide to drill out the stud ( and then use a helicoil ) that works well

After my first bad experiience with snapping of a easyout, the next time I snapped a stud I found a guy in the yellow pages ( brisbane ) who does that for a job. Thats all he does, remove and replace studs.

Came out to my place and for $100 removed and replaced all my studs. He had all the gear and it was done in 15 mins ( I removed and replace the manifold myself etc )

For that price I could not be bothered doing myself

Just remember ( as I am sure you know anyway ) when drilling steel - slow and easy is the way to go. High speed and pressure is one way to killl drillbit

My Disco broke a stud or two on a yearly basis. POS!!

[rijidij]

A mate of mine had a similar problem on a prime mover, I think. He ended up buying a cobalt drill bit. It was then like drilling through butter apparently.

"8% Cobalt Content.

Suitable For Drilling Into High Alloy Content Steel and Metals with Tensile Strengths over 1000N/MM2."

Cheers, Murray

[Rudolf]

I'm trying to remove 2 broken exhaust flange studs, Access underneath is not a problem, I've tried drilling and using an easy out, but after having one break years ago, I decided not to force it in case.
So I decided to drill the stud out, all was going well until I noticed a red Glow ( had it going too fast) and the bit end melted.
So now I have the problem where I can't drill it out as the drill bit steel is hard and the other drill bit goes blunt.

IS there a special drill bit that will drill out hard steel?
I'm pulling out the 2 strands of hair I have left on my head:(:(:(:(:(
My total sympathies on this one.
The broken Easy out is the current problem and its past frustrating.

[Blknight.aus]

broken easy outs can be worked out with a pin punch and a small hammer with patients.

hit it with freeznrelease then start tapping it round clockwise with the pinpunch

you can also get them out with reams (if your lucky) and carefull die grinding but you are going to need to helicoil afterwards.

In stead of easy outs you can also use a rigid extractor which is essentially an allen key with fluked edges you hammer in then slide on a special nut to turn it.

BOL

[It'sNotWorthComplaining!]

Well I got both broken studs out. Ist as it had a good length of stud protruding, but gripping with multigrips , and trying 2 nuts locked together would not budge it. Patchespal loaned me an extractor tool that fits onto a socket wrench and as you unscrew it tightened more and more onto the stud shank and it unscrewed.( great tool if you have got something to grip on.)
The other was the one with the drill bit broken inside. I visited total tools to get a carbide or cobalt drill bit, the guy suggested I buy an easy out extractor set with various left hand cobalt drills bits included.
The drill bits didn't splice through the broken bit very well at all, but after an hour of persistence I managed to get the broken bit out with the easy out.

The other tool pics. I must get one. Great if you have enough to grab on to.
https://www.aulro.com/afvb/images/imported/2009/11/369.jpg

https://www.aulro.com/afvb/images/imported/2009/11/370.jpg

https://www.aulro.com/afvb/images/imported/2009/11/371.jpg

[banksdizzle]

Id definately go with good quality cobalt drill bits (eg sutton)to drill any kind of steel, high speed steel drills are allright though. Slow speed and lubricant is essential to avoid heating the cutting tip to a point where it starts to soften resulting in a blunt drill bit. Even a Cobalt drill bit will go blunt very quickly if you are drilling too fast.

[Bigbjorn]

Id definately go with good quality cobalt drill bits (eg sutton)to drill any kind of steel, high speed steel drills are allright though. Slow speed and lubricant is essential to avoid heating the cutting tip to a point where it starts to soften resulting in a blunt drill bit. Even a Cobalt drill bit will go blunt very quickly if you are drilling too fast.

"Cobalt" cutting tools are simply high speed steel with a higher alloying content of cobalt. You get tools in HSS, Cobalt HSS, Cobalt 5% HSS, Cobalt 8% HSS. Cobalt drills were developed for high performance drilling in tough materials like stainless steels and can be run up to 30% faster than same size HSS drills in the same material. They will also give better performance in hard short chipping materials than conventional HSS. Remember this, if you can file it, you can cut it with HSS.

HSS has good high temperature characteristics and retains "red" hardness. You are more likely to blunt a sharp HSS drill by continuing to drill in a hole with a work hardened bottom than by running the drill hot. In work-hardening steels you need to keep up a heavy feed so the drill's cutting edges are cutting in the original material below the work hardening zone created by the pressure and heat generated by the cutting action. Steels with a significant manganese content are the most common work-hardening steels.

[numpty]

Sounds like you were using a blunt drill to start with. If you had used a reverse helix drill first you most likely would have unwound the offending stud. A tungsten carbide inserted drill or solid TC drill will do the job. Get a stub drill or a straight flute drill. You are less likely to break a stub drill. The grade of carbide used in masonry drills is not the same as used in hard steels but if sharpened correctly to 135 degree twist drill geometry on a silicon carbide or diamond wheel will do but will likely be stuffed afterwards. If available I would use a straight shank, straight flute TC inserted die drill. These normally use C2 carbide. go to a good engineers supplier.

Maybe something I didn't know, but standard twist drills are sharpened to an angle of 118 degrees.

[Bigbjorn]

Maybe something I didn't know, but standard twist drills are sharpened to an angle of 118 degrees.

Yes, general purpose Jobber length drills are almost always 118 degrees with a 30 degree helix angle. Point angles and helix angles are available in a multitude of angles to suit different purposes and materials.

Cobalt HSS and tungsten carbides drills and drills intended for use on tougher and harder materials are usually supplied at 135 degrees. This gives a shorter cutting edge and thus more power is applied per linear measurement. In other words, a 135 degree drill will cut the difficult stuff easier.

Drills also come in a variety of surface finishes such as bright, blue, TiN TiCN, TiAlN. All have their application.

[Blknight.aus]

Well I got both broken studs out. Ist as it had a good length of stud protruding, but gripping with multigrips , and trying 2 nuts locked together would not budge it. Patchespal loaned me an extractor tool that fits onto a socket wrench and as you unscrew it tightened more and more onto the stud shank and it unscrewed.( great tool if you have got something to grip on.)
The other was the one with the drill bit broken inside. I visited total tools to get a carbide or cobalt drill bit, the guy suggested I buy an easy out extractor set with various left hand cobalt drills bits included.
The drill bits didn't splice through the broken bit very well at all, but after an hour of persistence I managed to get the broken bit out with the easy out.

The other tool pics. I must get one. Great if you have enough to grab on to.
https://www.aulro.com/afvb/images/imported/2009/11/369.jpg




https://www.aulro.com/afvb/images/imported/2009/11/370.jpg

https://www.aulro.com/afvb/images/imported/2009/11/371.jpg

I have several varients of that exact tool....

one of them was sold as the "nutf*R" (replace the * with 4 ####'s)

[Bigbjorn]

They are a very old tool. Were around when I was an apprentice. Work well if you have enough stud left to grip and it is not too badly glued in. Any decent tool shop has them in a variety of sizes.

[chazza]

Years ago I watched a demonstration of a stellite drill, drilling through a flat bastard file :eek:

I don't know if they are still available but they would be the ideal thing for exhaust studs :)

Heating the stud with an oxy, or by running the engine, has also got me out of trouble more than once.

Remember to use anti-seize on the new studs before you put them in,

Cheers Charlie

[clean32]

the easiest and quickest next step is what Killer posted. a Karob drill bit. basically it is a masonry bit re sharpened. on very slow speed and a lot of weight i used to drill out inner races of roller bearings. 1 hole = 1.5 drill bits. used to break as they came though.

[Bigbjorn]

Years ago I watched a demonstration of a stellite drill, drilling through a flat bastard file :eek:

I don't know if they are still available but they would be the ideal thing for exhaust studs :)

Heating the stud with an oxy, or by running the engine, has also got me out of trouble more than once.

Remember to use anti-seize on the new studs before you put them in,

Cheers Charlie

I haven't heard of "Stellite" or "J-Metal" being used as a cutting tool for yonks, but I have been retired a good while and "off the tools" some years before that. My 1959 Sixteenth Edition of Machinery's Handbook mentions it, but the 1976 20th. Edition does not. It is a non ferrous alloy of cobalt, chromium, and tungsten, hardness Rockwell C 60-62 and exhibits same hardness and increased toughness at elevated temperatures, so good "red hardness" as this is called. Gives good finish when run at high speeds, can be run dry or wet and can run up to 30% faster with coolant. Higher production rates and extended tool life appear to be the reasons for use as a cutting tool. Several grades with differing performance and applications are mentioned.

Probably been replaced by tungsten carbide tools except for specialist applications. It is still used for valve seats.

Edit:- My "Automobile Engineers Reference Book" by Molloy and Lanchester mentions "Stellite" only as a hard facing material for poppet valves and valve seats. One of the grades for this application contains a significant percentage of nickel. This book doesn't mention it at all as a cutting tool material, but does state that it is weldable and readily machinable. Hot strength and corrosion resistance are given as the reasons for use in this application.