Tried drilling a broken bolt. I work hardened it.

[AMCguy]

This is the front self tapping screw (one of three) that holds the plastic belt guard to the bottom of the swing arm on my 1996 Road King. I broke it off flush taking it out.

I'm not sure what size it is. It's a tad under 1/4''. I figured I'd just drill it out and tap a 1/4'' hole.

I got off to a good start. I centre punched it dead centre. Drilled all the way through about 3/4'' first with a 1/16'' then a 1/8''. So far so good, I'm dead centre. I then moved up to a 3/16''. It wasn't doing anything so I pushed a little harder. As soon as it screeched I stopped and looked at the bit with my magnifier. Sure enough, it was dull and damaged. I've now sent three new bits to hell and can't drill any further.

I figure I work hardened the screw.

Now what? Do I have to anneal it? What's the technique? I have torches but I've never done anything like this. And I don't want to screw my bike up any more than I already have.

Thanks, Glenn

 

[cvairwerks]

Die grinder with a small burr to knock the hardened areas off. Return to drilling with a quality bit, lube, correct rpm’s and drill pressure.

 

[dogdog]

Use cutting fluids ?

Usually if I already drilled through, I don't have problem with work hardening.... probably needed a bit larger next size drill bits...

 

[driftpin]

Die grinder with a small burr to knock the hardened areas off. Return to drilling with a quality bit, lube, correct rpm’s and drill pressure.

I'm no machinist, but this sounds like a good procedure to follow. I've used a diamond-coated bit to do something similar.

Here's one that gave me a bit of a workout. It's a bolt for a caliper on the front of a SOHC Honda 750 which I was disassembling for overhaul. The allen hex was worn-out, and instead of hammering-into the space an SAE-sized allen and trying to bust it out with an impact, I decided to drill it out. I did it on the drill press so I had more-control over the removal. You probably don't want to face removal of the swingarm just to do this, putting it onto a drill press.

Give cvairwerks' suggestion a try. Dremel has a diamond-covered conical bit for not much-money.

 

[DFB]

Can you maybe get an extractor in the drilled thru hole now?

 

[McFarmer]

Use left hand bits ?

 

[bullnerd]

Die grinder with a small burr to knock the hardened areas off. Return to drilling with a quality bit, lube, correct rpm’s and drill pressure.

Im with CV, unless .....was the drill still in reverse from changing the bit? It happens! Odd the 1/16" made it through but not the larger drill.

When you get it out, put anti seize on the new bolt and any others you take out.

 

[rsanter]

Use a solid carbide die grinder bit like a drill bit

 

[MattT]

You may be dealing with a case hardened screw. Pretty common with self tappers. Carbide drill bit or burr should work.

 

[Milton Shaw]

Self drilling and tapping bolts are hardened steel to be able to drill and thread. Soft center that was soft enough to drill and you ran into the hardened outer shell. Diamond or abrasive is about the only chance to get the rest out. I have seen those self drilling screws drill better than cheap HF drill sets.

 

[AMCguy]

Self drilling and tapping bolts are hardened steel to be able to drill and thread. Soft center that was soft enough to drill and you ran into the hardened outer shell. Diamond or abrasive is about the only chance to get the rest out. I have seen those self drilling screws drill better than cheap HF drill sets.

I never thought of that. Maybe it dulled my bit.

Glenn

 

[NZGarage]

Hi, we use cobalt drills to drill out broken titanium screws and hilocks works well no problems.

 

[gorilla]

You can grind it out with a small carbide burr but will you leave enough metal in the swing arm to tap 1/4-20? Tap drill for that is .205" I think. Do you really need all the screws to hold om a plastic guard?