Drilling hardened steel

[Jackimus]

Hi all,

So, tried to drill through some car pedals with standard metal bits, not realising they're either hardened, or I've managed to work-harden them spinning the bit... I've just got polished craters where I'm meant to be cutting through.

Went up to cobalt bits, which also didn't touch it, could this be because the metal itself is too hard or just the part I think I have work-hardened?

I managed to snap the smaller cobalt bits I tried to make pilot holes with, seemingly by side-loading them (hand drilling an unstable object in a very awkward position) so I assume trying to move up to tungsten carbide bits is a non-starter unless I can get the pedals out of the car and into a drill press (don't have the space or money for one, would like one very much but can't justify it for this one thing)

Maybe one of those little presses you strap a hand drill into would be 'good enough?

Otherwise option two seems to be a rotary tool with a tungsten carbide bit, to shave away the potentially-work-hardened top and then try again with cobalt...?

Any thoughts appreciated. Thank you!

 

[bricol]

I assume you're trying to fit pedal covers/extensions? Block the pedal up so it can't move. I've never noticed any issues with drilling or cutting pedals - but I've not chopped anything modern about.

 

[Kram]

What bits are you using? sounds like you may have got the rubbish cobalt coated multicolour types? Coatings dont do much.

Decent cobalt HSSE m35-m42 should have no problems with that. You dont want to tickle the work at high speed, drills need enough pressure to make them cut. Perhaps hold the pedal fully down with a block of wood or someones foot...

Photo of the drills and the pedal?

TC bits can be brittle, particually if the underside of the part is not flat, they will catch and snap, and need a lot of care. I've often used them 1/8" sized in a hand drill, not too expensive if they snap.

Carbide burr in a die grinder would likely make quick work of it but not the most accurate.

Drill presses are a bit over rated - a lathe will do far more.. the smaller press attachements are rubbish.

 

[—Tom—]

Can always sharpen a masonry drill in a pinch to get the hole made will need high pressure and a lower speed.

 

[roofman]

Can always sharpen a masonry drill in a pinch to get the hole made will need high pressure and a lower speed.

just going to say the same myself...also used for drilling stainless steel.

 

[Kram]

You can, but those who only have masonary drills dont generally have diamond wheels for sharpening them with.

 

[Dapph2]

You can, but those who only have masonary drills dont generally have diamond wheels for sharpening them with.

A blue grade flap on an angle grinder when might be used as could a red aluminium oxide sanding belt or disc by dabbing the Tungsten for a second at a time on the abrasive.

I put my grinder wheel face up in a soft block grip of wood in the vice, get it running with one hand and sharpen the drill using the other hand .

 

[Jackimus]

What bits are you using? sounds like you may have got the rubbish cobalt coated multicolour types? Coatings dont do much.

Decent cobalt HSSE m35-m42 should have no problems with that. You dont want to tickle the work at high speed, drills need enough pressure to make them cut. Perhaps hold the pedal fully down with a block of wood or someones foot...

Photo of the drills and the pedal?

TC bits can be brittle, particually if the underside of the part is not flat, they will catch and snap, and need a lot of care. I've often used them 1/8" sized in a hand drill, not too expensive if they snap.

Carbide burr in a die grinder would likely make quick work of it but not the most accurate.

Drill presses are a bit over rated - a lathe will do far more.. the smaller press attachements are rubbish.

Will be able to get a pic of the pedals in a bit, I'm using these cobalt bits:

Supposed to be M35. I was using them in my Makita DHP486 cordless in its low speed gear (max 550rpm off top of my head?) I found that even at lower speeds and with all the weight I could put onto it, it was just spinning and not biting at all.

Can always sharpen a masonry drill in a pinch to get the hole made will need high pressure and a lower speed.

If a sharpened masonry bit would serve me better than these cobalts, I've got a diamond stone I could do that on?

 

[Jackimus]

And here is one of the two identical pedals in question.

That little divot on the bottom is all I've been able to manage...

 

[Dapph2]

And here is one of the two identical pedals in question.

View attachment 531886

That little divot on the bottom is all I've been able to manage...

Have you got any lathe center point drills? Use the biggest point you dare to make the start hole then follow up using small center point drills ..they are pretty hard drill points.

 

[Kram]

Have you got any lathe center point drills? Use the biggest point you dare to make the start hole then follow up using small center point drills ..they are pretty hard drill points.

Unless your buying special centre drills they will be plain HSS and no better than a standard drill.

Will be able to get a pic of the pedals in a bit, I'm using these cobalt bits:

View attachment 531873

Supposed to be M35. I was using them in my Makita DHP486 cordless in its low speed gear (max 550rpm off top of my head?) I found that even at lower speeds and with all the weight I could put onto it, it was just spinning and not biting at all.



If a sharpened masonry bit would serve me better than these cobalts, I've got a diamond stone I could do that on?

Never used them but I imagine they are chinesium, particually if they dont actually say m35 or hss-co anywhere.
From the looks of them they have sold you cobalt plated rubbish?
Normal cobalt is the same shade and appearance as plain hss, rather than that dark bronze colour.

 

[brightspark]

Can always sharpen a masonry drill in a pinch to get the hole made will need high pressure and a lower speed.

bosch tipped multidrills have a proper cutting edge for metal and concrete

 

[bricol]

And here is one of the two identical pedals in question.

View attachment 531886

That little divot on the bottom is all I've been able to manage...

Pedal looks like it's been battered about a bit?

Also looks like you are drilling into the area where it might be welded on the rear - and possible not far enough to the left of the lever part of the pedal to actually get a clear hole?

According to Rennie Amazon they are split point above 3mm, so shouldn't need pilot drills. Block the pedal from sinking, a bit of cutting lube, maybe a 3 or 4mm to start - but away from the middle and the weld.