Drilling Hardened Steel

[Doc Sprocket]

I've drilled through hardened steel before, without too many problems. I've even drilled through tempered glass. But the sprocket pictured below- I don't know what Yamaha (or their supplier) did to it, but DAMMIT it was hard!!! Maybe they offer a lifetime warranty on their drive sprockets?

My usual bits wouldn't even put a ding in it. My first hint was when I flattened my centrepunch just trying to mark the holes! I fried multiple HSS and Titanium coated HSS. Even a 1/8" Cobalt died very quickly, hardly making a scratch in the material.

So I hit the 'net, and researched my brains out. I read all kinds of stuff about cobalt bits, spot-annealing, re-tempering...

Nevermind all that. I found a sweet and simple answer, and If I hadn't seen it, I wouldn't have believed it. Masonry bits. That's right, carbide-tipped drill bits used for boring holes in concrete. Since I already had some, I gave it a shot. Worked VERY well, and faster than I expected.

So, the next time you have to drill the un-drillable, go get some masonry bits. Low speed on the drill press, moderate pressure, and plenty of oil. Cheers!

 

[devino246]

Cool! Is it against mod code to sticky his own post?

 

[Doc Sprocket]

I wouldn't just do it, but with enough support...

All I know is that I was totally blown away by this solution to a common problem!

 

[Badot]

+1 for carbide tooling... cuts just about anything

 

[mckutzy]

If you have a diamond bit for a dremel mototool, you will be able to put on a better edge to it. Nothing much will touch carbide. look like you took care of what needed to be done though.

 

[DCProductions]

Interesting. I wouldn't think that masonry bits would be stronger, but I guess that carbide makes all the difference. Did it drill to the correct bore? I would be worried that the wide blades on the tips would be inconsistent.

 

[Doc Sprocket]

I haven't "finish" drilled yet, that waits until I select my fasteners and make sure I have a corresponding tap drill. That, AND- only the coupling's getting tapped- the sprocket holes can be slightly oversized. I had originally planned to tap through both, but now I'm afraid of ruining a tap in that sprocket material.

 

[B man]

carbide is always a better drilling bit. allows for higher drilling speed. it runs cooler and is way better than any HSS. this i should know because i have a shop test tomorrow!

oh and thats kinda what carbide bits where built to do.lol

 

[landuse]

I also wouldn't think that masonary bits would be stronger than HSS. Who would have thunk.......

Do they have to be carbide tipped though, or just ordinary masonary bits? I am assuming carbide tipped.....

 

[Simon Thomas]

This has reminded me of the trouble when drilling the bearing inner race recently. Good tips!

 

[devino246]

I also wouldn't think that masonary bits would be stronger than HSS. Who would have thunk........

Why? The hardness of a knife blade 5.5 on the Mohs scale. Quartz: 7. Feldspar: 6. Window glass: 5.5

 

[Doc Sprocket]

I just wouldn't have thought of it because of the type of tip not exactly the drill point one pictures when one is setting up to drill holes in steel. Sure as s**t, carbide's hard, but I didn't know that shape would work.

 

[redsox985]

I never would have thought it would work either. Since they're usually used with impact drills, I've assumed they were more dull and don't cut as much as accurately chip away at the surface. I could've used one a while back...

 

[fowler]

that is one rubbish drill bit to have it unsrew like that

iv known aout his foor some time it helps if u grind off the ears? or what ever they are on the outside of the tip
and sharpen it to a metal type point

i cant take credit for this by any means but i rea it on a buggy website
trying to drill into brake discs

 

[sexyvicta]

i have a question...

how do i drill out or extract a broken drill bit? lol

i slipped and the tip snapped off in a grub screw i was trying to drill out

 

[redsox985]

i have a question...

how do i drill out or extract a broken drill bit? lol

i slipped and the tip snapped off in a grub screw i was trying to drill out

Try to slot the top of it? Maybe. All I know for sure is that drill bits and other hardened things like Easy Outs are a b**** to drill out and remove.

 

[Banditz]

Good luck, snapped bits are a pain. Easy out or another type of puller would be your best bet.


OP, I JUSt used a masonary bit today to drill out my new axle sprocket! man oh man did it make short work of the metal!

 

[Doc Sprocket]

OP, I JUSt used a masonary bit today to drill out my new axle sprocket! man oh man did it make short work of the metal!

Good on ya!

 

[Banditz]

Gotta say, she is working beautifully!

 

[Rustydog2010]

Try to slot the top of it? Maybe. All I know for sure is that drill bits and other hardened things like Easy Outs are a b**** to drill out and remove.

You wont drill it out. Trust me I had it happen just the other day. We just drilled down beside it and used the gas to cut it out. That was in a digger pin where the retainer bolt had seized in. So probably wont work for you.