Drilling hardened steel?

[zedhead]

I have a gearbox output shaft that I need to drill,in order to fit a speed sensor. I tried a ti HSS 6mm bit that managed nicely to start with, but gave up after getting about 5mm in... I tried a smaller bit but that didn't touch it.
Using low speed, with cutting fluid, and the bits aren't dulling.
What do I do next?

 

[Pete.]

Carbide stub drill or slot drill?

Is this a suzuki-type four-quadrant sensor as fitted to GSXR etc? You don't need that particular trigger you could mount the sensor furter off-axis tot he shaft and make a trigger which doubles as a sprocket washer, or even better - machine castellations in the nut itself.

 

[rtbcomp]

Are you using a pillar drill?

 

[zedhead]

Pete - yup, Suzuki 4-bit castle washer thingy. Could be a bit awkward moving the sensor I think, as using a Bandit cable clutch cover. Probably try a carbide bit first I fink.

Rtbcomp - drilling it in situ, so using handheld drill.

 

[rtbcomp]

Right - so you're not hitting the depth stop then!

 

[h3rman]

Cobalt drill bit, worked wonders when I had to drill out an M12 hardened steel bolt.

 

[tigler]

Cobalt or carbide tipped drill, nothing else will touch it.

 

[zedhead]

Just ordered some cobalt bits off ebygum, so will give them a go... and then I have to tap it...

 

[tigler]

Tapping WILL be a problem !!

 

[Drains]

Cobalt or carbide tipped drill, nothing else will touch it.

One of the old boys at work swears by stellite drills. You get them red hot to get them cutting properly!

 

[rich r]

Cobalt bits get my vote too. But you absolutely must use a pillar drill and take it slowly. I've snapped a couple trying to drill out broken bolts on cars with a cordless drill. And given the cost of cobalt drill bits, it really hurts when you do that!

 

[PhillipM]

Nothing wrong with good old HSS, but I'm guessing with a hand drill you didn't have enough feed on and have work hardened the surface now. So it's gonna be a bitch.
Carbide and go slow.

 

[Epicyclic]

Probably a bit late now, but at work we use a spark eroding outfit in Redditch to make holes and cut threads in Nitrided parts. Could give you the add. but Cheshires a bit far? Maybe there is someone local if all else fails.....
Good luck!

 

[Pete.]

One of the old boys at work swears by stellite drills. You get them red hot to get them cutting properly!

I've got some round stellite stock, might try grinding up a drill just for kicks.

I was also going to ask about tapping.

I still vote for the custom sprocket nut.

 

[zedhead]

I still vote for the custom sprocket nut.

You voting to machine it for me Pete?

 

[zedhead]

Well, I failed on drilling the output shaft... using cobalt drills, with plenty of cooling and slow speed - didn't touch it. At all.
So, welded the speedo 'castle' nut to a washer, and that to the output shaft. Bit messy but seems to do the job...

 

[Pete.]

Damn, I missed your last post Dave, been working away and not keeping up with events. I would happily have machined you a fitting. If your shaft doesn't like the welding you did and the end snaps off, let me know and I'll do it.