Best drill bits for broken stud

[cn90]

This is a generic question, when you guys deal with broken studs, what drill bit brands do you recommend?

I usually use metal drill bits from Home Depot (can't remember the name) but it takes forever to drill through steel stud.

Any tricks/tips will be appreciated: brand-name of the bits, any tips?

And yes I heated the stud way before but you know the "drill", these rusty nuts and bolts will break during removal.

[xHeart]

Occasional user. It is working for me.

left handed set

MVS_0244.jpg (379.42 KiB) Viewed 13007 times

[mecheng]

My weapon of choice: Craftsman bolt out. Works excellent

http://www.sears.com/craftsman-bolt-out ... 952060000P

[kahl]

last week I had to drill out the 10mm wheel sensor bolt on a spindal. I used a cobalt bit. I ground smooth the broken bolt, then with a punch tagged the center then drilled. kept the bit tip wet with WD40. tried an easy out with no success. kept going up in bit size then used a tap to clean up.

[deepsouth]

This is a good topic. I've broken more easy outs than I can recall attempting to extract snapped bolts and have also had the maddening experience of not being able to drill through high grade studs. Perhaps someone with a decent knowledge of drill bits can chime in regarding various metals. Cobalt, black-oxide, titanium?

[j-dawg]

can't comment on this particular application, but McMaster-Carr has a decent page with some general info about drill bits. i saved it as a PDF and attached it to this post. they also have good-quality tools that you will get the next day at a reasonable price.

generally if you're drilling hard materials you want a carbide-tipped tool or a tool with a TiN coating (that goldie-lookin' stuff). heat is the main killer of cutting tools. they get hot because they're insufficiently lubricated and/or/therefore chips can't be evacuated, causing friction, binding, chattering, etc. this gets them hot, and the hot tool pushing on a hard surface blunts the cutting edge.

to deal with this, use plenty of lubricant and "peck" at the part you're trying to drill. i usually use old motor oil for lubricant, but i'm usually not drilling into broken studs, so your results may vary. be liberal with it - oil is cheap, and it cools off the tool and part as well as removing chips.

"peck" at the part by repeatedly applying and removing pressure from the bit, which gives the bit a moment to cool off and gives some room to evacuate chips. if you're not getting results and you bear down hard on the bit, you're going to dull it out even more and make things worse.

[cn90]

xHeart,

Thanks for the "LH drill bit" but from what I understand, there are roughly 2 situations of broken stud:

1. Overtorque a bolt, the head or shank snapped off. This is the easy one because once the head is snapped off, all you have to do is turn the broken stud CCW with the LH drill bit and it should come out.

2. Studs that are seized from years of exposure to salt, rusty threads. These broken studs are one of the most difficult to remove w/o damaging the threads on the female side. This is because they seize in place, the LH drill bits won't do anything to turn them out.

- Heat, PB Blaster etc. may help

- Some people TIG weld something to the broken stud and hopefully spin it out.

- The worst case scenario is drilling straight into the steel stud, it is labor intensive and sometimes you may have to accept the fact that the female threads may be damaged during drilling. This is the scenario I am trying to get at. What is the best drill bit for this?

[kahl]

the best cost affective drill bit I have found for hardened steel is a cobalt drill bit.

[xHeart]

[...]
- The worst case scenario is drilling straight into the steel stud, it is labor intensive and sometimes you may have to accept the fact that the female threads may be damaged during drilling. This is the scenario I am trying to get at. What is the best drill bit for this?

One lesson is to slow it down. Let it soak longer, prepare well, and plenty of patience.
Getting a starter hole on a machined surface using hand-held in situation you describe is a risk.
But, before a drill bit, a good punch to mark the start point is key to successful start of drilling.

Starting the first hole with a new set of drill bit -- small size first, and then gradually increasing the hole 1/16" or 1/32", and little deeper each time. It goes quickly after the first hole with plenty of oil on the bit. It helps to use stopper.

The thread can be saved by stopping at a dia 1/32" or 1/64" smaller than the thread size.

My axle troubles here https://www.matthewsvolvosite.com/forums/viewtopic.php?f=9&t=62641

[Xeamar]

I apologize for bump an old topic from the dead, just have a few interesting observations from personal experience, maybe someone will need this information in the future.
Depending on the material that you are drilling, HSS is probably your best all-around choice.
For plastic, aluminum and light gauge steel, the price/longevity ratio is tough to beat. Between fabbing stuff 5-10 times a day for the trucks at work, and general use (drilling through firewalls, extracting stuck bolts, etc), I use my bits pretty much every day. From my experience:
1. Cobalt is best, but a good HSS bit is fine if it's from a quality source. I bought a set of bits (1/16 -> 1/2 by 64ths) off one of the tool trucks at work. Ran ~$180 for the set, but the bits are warrantied for breakage, so as long as you keep them sharp it's a reasonable investment.
2. Keep them sharp. Most drill bits aren't as sharp as they could be, even out of the packaging. Learn how to use a bench grinder, or even better, a drill doctor (but get one of the higher end ones that will do split points).
3. Split points for metal is the way to go. Keeps the bit from wandering.
4. Use cutting fluid. It keeps the bit cool and prolongs the life of the bit. Heat kills bits.
5. Let the bit do the cutting, not pressure. Apply just enough pressure for the bit to work, any more than that and you are dulling the cutting edge of the bit. It sounds simple, but most people don't do it. I used to drill quite a bit of stainless while working offshore (mostly 10 ga or less). I did not find any bits that would do it "easily", Cobalt bits Irwin https://mechanicguides.com/best-cobalt-drill-bit-sets/ tend to be better. Slow speed and heavy feed pressure with ample coolant will do the job, which means that you need a drill press with appropriate speeds. If you have to drill with a portable drill, keep the speed VERY slow and press HARD.
Stainless tends to work harden so you must keep cutting through the hardened layer every revolution, if you let up on the feed for an instant, the hardened layer will be too thick and will ruin your bit..I like to watch YouTube videos of a similar subject when I'm looking for information about the right product. I hope this helps someone in the future. Good luck!