Team Camaro Tech banner

Drill Bits, cobalt, HSS, Black oxide, titanium ???

10K views 18 replies 11 participants last post by  dragon0123 
#1 ·
Ok faced with the difficult task now of trying to drill out a lower fender bolt that snaped on me, Whats teh differences of all of the bits noted above. Actully which one is the BEST one for steel, bolts, stuff that I would use on my Camaro... preferably not for use on my tile floor or drilling though wood.

Im a little peaved as last night when my High quality harborfreight (sacasam) titanium bits seamed to be attempting to drill though diamond instead of a rusty bolt. 3 hours later I gave up..
 
#2 ·
It's a speed and feed question. The answer will be different for a hand drill, than a drill press, using a vertical mill? Once again a different response.

High speed steel bits will work best for a B&D 3/8th inch chuck hand drill. Make sure the bit is sharp with steady even pressure; and spray a little WD-40 every now and then to clear the chips, cool the bit and keep everything lubed.


Larger Dave
 
#3 ·
A good quality cobalt drill should do the job using cutting oil and a slower drill speed(do you have a variable speed drill motor?). Did you center punch the offending broken bolt to keep the drill bit from wandering and giving it a good place to start; and every thing else that Larger Dave said.
 
#4 ·
Cobalt is harder than HSS, and is not too expensive. Carbide is harder yet, but very brittle. They make carbide tipped drills for drilling hardend steels, but a 1/4" drill will cost you about $15.00 for a quality US made tool.
Try a left hand spiral drill if you can find one.
So,
1st try HSS
2nd Left hand HSS
3rd Cobalt
4th Carbide tipped
(Any of them can have a titanium coating that will help a little.)
Use a cutting oil with all of them.
5th Plasma cutter

Brichead
Drill Bit Salesman
 
#5 ·
Have you considered welding a nut to what is left of the bolt. Some have had good luck removing bolts like this. My brother recently welded a washer to the bolt and then welded a nut to the washer (larger surface area). Give it a good long soak with PB Blaster or something like that before you try turning it.
 
#6 ·
Yes Unfortunatly this bolt just doesnt want to give up the ship and is taking several dril bits of mine with it. .. I soaked it for quite afew days.. no luck - - heated it up glowing red.. no luck, tried to weld a nut to it.. no luck and broke it off. So I ground it down to a square and used a cresant wrench on it (which actully worked the best but broke it off close to flush) so drilling is my current option.. started small and drilled up into quite a way with my HF bit and broke it off in the bolt. :( so now ive been slowly drilling up into it as well breaking more bits in the process.. :( ive only drilled about 1/2 in or so into the bolt. and it seems to have come to a crawl now. ( im probably hitting whats left of the first bit I broke. ) I only went about a 1/2 in. in about and hours worth of work.

Im not too confident about my drill bits currently so im going to pick at least 2 decent HSS or cobalt quality ones thatll hopefully zip thought the remainder of it.
 
#8 ·
If you got the bit broke off into the bolt, you are really in deep as the bit is gonna be harder to get out than the bolt...but you need the hole. IF you can grab any piece of the bolt and I am guessing you cant, grab the remainder bolt with vise grips and heat bolt , then quench with solvent or even water to shrink it.. maybe , just maybe you can contract the bolt enuff to turn it .. Save the HF drill bits for something like wood or plastic..

Sounds like you have the fender out of the way and are working on the body threaded hole? A last resort is to weld a bolt on top and use it as a stud? Slot the fender area and slide fender onto stud,, add shims and tighten nut? Cut off remainder of bolt thread? No? Too much southern engineeing?
 
#10 ·
I picked up a couple of cobalt bits up tonight and went to work. Maybe my 1/2 inch depth was a bit generous.. closer to 1/4 of an inch or so.. Anyway.. the blasted HF bit that I broke in it caused my coablts to wander to the side and egg shaped the hole. Still couldnt get what was left of the bolt and was way off center and cutting into the nut now as well.. Even my biggest ez out was no help and wouldnt extrract it.. I didnt want to press my luck so I gave up on that before it snaped.

Anyway.. i think im on to plan B now which would be to cut out the bottom 2x2 inch piece and make up a new one with attached nut. Anybody see any problems with this plan..?? its about all I got left.. that bolt just aint coming out.!!!
 
#13 ·
The best thing that I've used for stubborn bolts is to heat it up and melt candle wax on the thread. Any wax will work but I've had the best results with bee's wax. The melted wax wicks right into the thread and the bolt turns out easy. Unfortunately this only works when you got something left of the bolt to grab onto.
 
#14 ·
Hey Karl , we love the wax trick up here in farm country, works nice :beers:
Dragon , don't use carbide drill bits in a hand drill , it wont turn fast enough to be effective. Also the steel may seem to be hard to drill because of something called work hardening where not applying enough pressure causes the drill bit to rub on the metal and actually makes it harder. Steady even pressure with lots of cutting fluid works the best. I realize you are past that now. Do you have a small grinding stone you can put in a die grinder so you could grind that hard layer off and start over ? You could center punch it and then start with maybe an 1/8 " drill bit.
 
#15 ·
Well the hole is pretty mucked up right now.. it goes up at about a 15-20 deg angle instead of straight. Also remember that this is drilling up into the bottom of the car.. wax and dril oil is a bit more difficult to work with.... Il have to remember the wax trick next time.

My only other thought now would be to tap it at its current size and use it like that.. ill have to check the angle of the dangle to see if it would work or not. but im thinking that probably my best option is cutting the whole piece out and forming a new one. Thatll be tonights project..
 
#17 ·
I dont have a convertable so Im knida guessing as to your situation.. I ended up cutting out the piece last night and am going to weld up a replacement piece with a nut attached.. Dont know if that is an option for you..
 
#18 ·
If it's not too late for a suggestion, here is what I did for several! broken bolts and it worked beautifully-

I used a handheld high rpm Dremel tool, with small diamond tip bits. Slowly, but surely, I just ground the bolt hollow, getting wider and deeper, stopping just shy of the threads in the hole. I then used a regular thread tap and 'chased' the threads, which removed the rest of the bolt and cleaned the threads out nicely.

It has worked flawlessly everytime I did it, but it takes a LOT of patience. I too tried a drill and I even broke off an EZ-out in a bolt (it was that rear fender mount bolt - very cumbesome to work on) and the small diamond tipped dremel bit worked. On one I cut a bit too deep and mashed up the threads, but a heli-coil repair worked there nicely.

I hope this helps
 
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Top