Drill bits that cut steel???

[Bob B.]

Hi all,

I drilled out some broken-off Grade 5 bolts about a year ago and now I need to drill out some rivets and a broken-off Grade 8 bolt. I can't find what I used and what I am trying just makes a tiny impression on the rivets, which are certainly not Grade 8. I tried the Cobalt bits and they just spin and make a tiny impression. What kind of drill bit do I need to cut through steel???

Thanks,

Bob

PS: I have some C1 drums and some C3 rotors from which to remove the hubs. Can anyone tell me why in the world brake drums or disk rotors were ever riveted on in the first place???

[Joe L.]

Re: Drill bits that cut steel???

Hi all,

I drilled out some broken-off Grade 5 bolts about a year ago and now I need to drill out some rivets and a broken-off Grade 8 bolt. I can't find what I used and what I am trying just makes a tiny impression on the rivets, which are certainly not Grade 8. I tried the Cobalt bits and they just spin and make a tiny impression. What kind of drill bit do I need to cut through steel???

Thanks,

Bob

PS: I have some C1 drums and some C3 rotors from which to remove the hubs. Can anyone tell me why in the world brake drums or disk rotors were ever riveted on in the first place???

Bob------


My recommendation: Heavy duty carbide tipped drill bits. For this type of application I also recommend using the short type.

Why are disc brake hubs/spindles riveted to the rotors? The hubs and rotors are riveted so that the hubs/spindles and unfinished rotors are firmly attached. Then, the unfinished rotors were machined so that the rotor surface was perfectly perpendicular to the centerline of the hubs or spindles. This minimizes runout on the rotors which is especially critical in applications with non-floating calipers (like 65-82 Corvettes). By having the hub/spindle firmly riveted to the rotor the minimal runout condition is maintained.

[Russ S.]

Re: Drill bits that cut steel???

To add to Joe's response, you should mark the rotors to the spindles so that they get put back on the correct spindle in the correct location that they came off of. Of course if you replace or have them turned separate from the spindle than it's a mute point.a (12484);736318]Bob------


My recommendation: Heavy duty carbide tipped drill bits. For this type of application I also recommend using the short type.

Why are disc brake hubs/spindles riveted to the rotors? The hubs and rotors are riveted so that the hubs/spindles and unfinished rotors are firmly attached. Then, the unfinished rotors were machined so that the rotor surface was perfectly perpendicular to the centerline of the hubs or spindles. This minimizes runout on the rotors which is especially critical in applications with non-floating calipers (like 65-82 Corvettes). By having the hub/spindle firmly riveted to the rotor the minimal runout condition is maintained.[/QUOTE]

[Steven S.]

Re: Drill bits that cut steel???

Bob, you shouldn't need more than a high speed steel bit for this. If you are working with one rivit in particular you may have created a hard spot with a dull bit, if that were the case take a dremel or whatever tool you can get in there and try and grind some off the top and try again.

[Ed S.]

Re: Drill bits that cut steel???

If you have a very pointy / sharp center punch consider whacking a dimple into the center of the rivet to serve as a guide and center point for the drill bit - the dimple will also break through a hard spot that Steven refers to.

[Donald O.]

Re: Drill bits that cut steel???

The Dremel is a good idea, so is the center punch. Hopefully you did that first for all of the rivets.

Make sure your drill bit is sharp, a good high speed should suffice.
Use a little cutting oil. This is a lubricant for cutting, drilling, machining, etc. DO NOT USE ENGINE OIL! It will make things more difficult.
If need be, try a much smaller drill bit for the first 1/8" inch depth, then switch to the larger drill bit.
Set your drill to a LOW speed and use a low to moderate pressure. The drill should be making curled ribbons of metal, not chips.

DonO

[Gene M.]

Re: Drill bits that cut steel???

A carbide tip drill is generally of a bigger size causing difficult starting. Suggest a solid carbide drill bit as they are available in smaller sizes to get started.

[Gary R.]

Re: Drill bits that cut steel???

I use USA made High speed steel, (HSS), drill bits. Those should cut into a rivet and grade 8 bolt without much effort. I would make sure the edges are sharp, as a freshman in trade school were were taught to sharpen them by hand, maybe cut down on the RPM, give the drill a chance to cut and toss a chip out.

Spindle rivets are pretty soft and you don't have to drill through them to separate the rotor from a front hub or rear spindle. Center punch, center drill, 1/4" bit down about 5/16", then a 5/16" bit down the same, chisel across the rivet face and a hard shot with a hammer and the rivet heads will split and come out. Do all 5 and remove the rotor, then you can drive out the bodies with a punch.

[Gary J.]

Re: Drill bits that cut steel???

When drilling bolts out I have good luck using left hands drill bits, drill must be used in reverse. It may sound crazy but once the drill bites it usually brings the bolt out as you drill deeper into the bolt.

[Frank P.]

Re: Drill bits that cut steel???

Agree with Gary. Most people do not know about "left hand drill bits". Any time you are drilling out studs or bolt these work the best. If you can find them in 135 degree split point they work the best. Remember, run your drill in reverse.

[Joe C.]

Re: Drill bits that cut steel???

Use cutting oil which contains sulfur, lower the drill speed, and sharpen the drill bit yourself.

[Dan P.]

Re: Drill bits that cut steel???

make sure the head of the nail that pops off is gone . If it is still in the rivet you will not be able to drill it out.Use a small punch to drive it out . There are special drill bits mad for rivets. Sears had them years ago .

[Ray G.]

Re: Drill bits that cut steel???

Have been told this works, but have not experienced this process personally.

https://www.youtube.com/watch?v=YbeKxFBZrF8

my.02

[David H.]

Re: Drill bits that cut steel???

Have been told this works, but have not experienced this process personally.

https://www.youtube.com/watch?v=YbeKxFBZrF8

my.02

Ray,

I had a machine shop remove a 12mm rear spring retainer bolt using this process from the aluminum differential carrier on my 1980. The bolt head was snapped off leaving the bolt shaft insided (happened before I got the car). After they got the bolt out, I had them helicoil all three spring retainer bolt holes. To answer your question, it worked fine.