Rotor set screw: What is the largest size drill bit to use t

[bobby in Derby City]

Rotors look like they been on the car for years. No torch to heat up set screws. They are going to strip so I am just going to go ahead and drill them out. What is the largest (appropriate) size drill bit that I should use? Should I look for a certain type other than metal drill bit? TIA

[Shawn D.]

I'm no machinist, but my technique has worked well for me. I used a cobalt bit that just fits into the hex hole (metric or English doesn't matter) to get a hole started going straight in, about 1/8" deeper than the hole bottom. Then I went 1/8" up in diameter and drilled to the same depth, and then 1/8" up in diameter again. The head came off cleanly. You could just skip the middle drill bit, but it worked best for me that way. HTH!

[bobby in Derby City]

Hmmm. I was thinking that one would be drilling out the entire screw and not just removing the hex-head portion. If that is the case, I will not be putting in another set screw when I put the new rotors on? I seem to remember a thread about the set screw not being an "essential" piece of this puzzle? Holla back Shawn and whomever else. TIA

[Shawn D.]

The point of this exercise is to remove the screw head, whereupon you can easily remove the rotor, and you're likely to discover that once the tension/rust is relieved from the bolt head, you can turn the remaining portion out with only your fingers. I just did the same on the pressure plate on the M30B35 I got -- from a corroded Canadian car, the bolts were stuck tight and stripped easily -- I couldn't get any of them out. However, once I cut the heads off with a die grinder, all except two came out with a twist of the fingers.

You're correct -- the screw is not "essential." If you put one back in, use anti-seize under the head.

[Edit by Shawn D. on [TIME]1111685432[/TIME]]

[rodpaine]

[QUOTE="bobby in Derby City"]Rotors look like they been on the car for years. No torch to heat up set screws. They are going to strip so I am just going to go ahead and drill them out. What is the largest (appropriate) size drill bit that I should use? Should I look for a certain type other than metal drill bit? TIA[/QUOTE]

If Shawn's process doesn't work for you, get a #3 Extractor from Sears and a high-quality 5/32 drill bit and take it out the old fashion way. Also, as Shawn says, don't forget anti-seize on a new screw and use very little torque when tightened.
-Rod

[JBort]

I've had good sucess with "left-handed" drill bits (available from Eastwood Automotive). These tend to "un-screw" as they turn and drill.

Like Shawn said, once the head is gone (or relieved), the remaining bolt usually comes out easily.

[a]

0 fer 2 using EZ outs. They are brittle and very hard. Snap one in a drilled out bolt and you've just turned a small PITA into a bigger one. Steel is elastic. when you drill its center out it relieves . When you wedge some into it it it expands outward. With a bolt stuck in in threads wedging it tighter is not what you want. P'rps I'm not explaining this clearly. I'm not an engineer. But I have worked with steel and stuck bolts for many yrs. Some things work and some dont. Ez outs dont. RE the rotor set screw. before drilling try this: hit the head dead on with a ball pein hammer. The shock will help break the screw free. Peining over the hex a little will help restore a little grip to the rounded out hex as well. tap the allen wrench into the hole and try it. Another thing to try is remove the lugs and rap the edge of the rotor with a board to move the rotor underneath the screw.

[spinedocab]

This has been said before, but may help a bit to repeat.

Before you attempt to remove via simple wrench turning, which may simply start the hex "boogering up process", get an old fashioned, hammer activated impact driver. Put your proper sized hex driver onto the 3/8 drive and set it to remove. Whack it solidly with the aforementioned hammer.

This does a couple of things. First, it provides an axial vibrational shock to the fastener which helps shake the rust loose. Second, the rotational force applied is also of the speedy variety. This can also crack it loose easier.

If you want to go all out, first spray a penetrating solvent into the fastener interfaces and then whack around it with a hammer a few times. More shock/vibration, plus penetrating oil can loosen it a lot.

HTH.
Andrew