Interesting observation of two M42 Cobalt drill bits today

[Wamsutta]

The plan was to drill 3 holes into a .040'' x 12'' feeler gauge. I was going to bolt it to a broken toilet lever arm.

After finding out that feeler leafs are made out of high carbon steel, I went out and bought the highest quality cobalt drill bit known to man.

A Viking part# 08090 to be exact. It's a 3/16'' M42 cobalt drill bit from the local industrial supply.

The cobalt drill bit was able to make a nice dimple into the feeler gauge leaf, but that's it.

Being that I assumed the drill bit was made dull by the high carbon steel, I tried a 2nd brand new Viking cobalt bit. Same exact story with the 2nd drill bit. At that point I thought both new drill bits were toast, so to find out for sure, I grabbed a piece of 1/8'' thick mild steel.

Both drill bits cut through the mild steel plate like butter. I was sure they were going to be wiped out.

That's the part that amazes me. How could the high carbon feeler gauge leaf laugh at the prized cobalt industrial drill bits, but not dull them?

BTW, if anybody is wondering what the difference is between M35 and M42 cobalt drill bits, the M35 has 5% cobalt and the M42 has 8% cobalt.

 

[Cruzan80]

Guessing this had a backing, so it was supported? What happens if you try and drill the top of the dimple?

 

[Wamsutta]

I had the feeler leaf clamped to a piece of 4x4. Drill the top of the dimple? I don't understand you on that one.

 

[Cruzan80]

When I heard "dimple" I thought it made a V shape in the metal, and possibly pushed it "proud" on the other side. I was suggesting flipping it over and trying to hit the top of the V on the other side.

 

[Wamsutta]

I should've used the word crater instead of dimple. The other side is flat like nothing happened.

It basically looks like a countersink hole without the hole.

 

[whateg01]

Did you look at the cutting edges or just assume it was dull? You can see a reflection on the edge of it's actually dull

 

[Cruzan80]

Maybe try something like a Whitney punch instead? Now I understand what the "scar" looks like.

 

[American Locomotive]

You need a more rigid backer. The wood offers no support and compresses easily. So I think what is happening, is the feeler gauges are just deforming and conforming to the drill, rather than cutting.

Usually the trick to drilling thin, hard metal is to make a sandwich. Clamp the feeler gauges between two thick pieces of aluminum or steel, and drill through the whole stack.

 

[Wamsutta]

Did you look at the cutting edges or just assume it was dull? You can see a reflection on the edge of it's actually dull

The tips of both drill bits that did the cutting still feel very sharp. Color me perplexed for sure.

 

[Wamsutta]

You need a more rigid backer. The wood offers no support and compresses easily. So I think what is happening, is the feeler gauges are just deforming and conforming to the drill, rather than cutting.

Usually the trick to drilling thin, hard metal is to make a sandwich. Clamp the feeler gauges between two thick pieces of aluminum or steel, and drill through the whole stack.

I took your suggestion and immediately went out and clamped the feeler leaf to a plate of 3/4'' mild steel.

I didn't clamp the leaf directly to my workbench because I didn't want to drill through the workbench in case you were right.

Same story. Feeler leaf is impervious to the cobalt drill bit even with a steel plate backing.

 

[whateg01]

Viking part# 08090

Does not say anything about a split point. Is the feeler gauge stainless?

I took your suggestion and immediately went out and clamped the feeler leaf to a plate of 3/4'' mild steel.

I didn't clamp the leaf directly to my workbench because I didn't want to drill through the workbench in case you were right.

Same story. Feeler leaf is impervious to the cobalt drill bit even with a steel plate backing.

So, you are drilling with a hand drill? If the feeler gauge is stainless, it could be hard now and the drill is just skating over it. Combined with a chisel point, which just rubs and tries to push the material out of the way, all you are getting is heat. Do that long enough and you'll dull the edge of the drill. I would guess that the chisel point is rubbing and the flutes are still cutting air, so they won't dull. In mild steel, the chisel point is still able to push enough material out of the way for it to start drilling. A split point might have started cutting right away and allowed the drill to get through it before hardening anything.

 

[Wamsutta]

Does not say anything about a split point. Is the feeler gauge stainless?


So, you are drilling with a hand drill? If the feeler gauge is stainless, it could be hard now and the drill is just skating over it. Combined with a chisel point, which just rubs and tries to push the material out of the way, all you are getting is heat. Do that long enough and you'll dull the edge of the drill. I would guess that the chisel point is rubbing and the flutes are still cutting air, so they won't dull. In mild steel, the chisel point is still able to push enough material out of the way for it to start drilling. A split point might have started cutting right away and allowed the drill to get through it before hardening anything.

I don't think the feeler gauge is stainless. It has rust on it in some places from being left out in the rain. I think it has a plating on it of some kind or it's polished. I'm not sure which. Hand drill? I hold it in my hand yes. A drill press is probably what you're insinuating as being far superior.

Google A/I says the Viking 08090 is a 135 degree split point drill.

 

[whateg01]

Google A/I says the Viking 08090 is a 135 degree split point drill.

You had the drill in your hand. Is it split point or not?

 

[RoninB4]

That's the part that amazes me. How could the high carbon feeler gauge leaf laugh at the prized cobalt industrial drill bits, but not dull them?

-Beyond a certain level of material hardness (Rc) the twist drill won't do much even if it's a cobalt twist drill. Dull? Where exactly? The chisel point of the tip geometry isn't the same as a real cutting edge. While the chisel point tip may not look/feel dull it can be but still work well for plain (lower) carbon steel. You may have even work-hardened the feeler gauge through rubbing instead of cutting. If you know what to look for an evaluation under magnification should reveal what happened. There's far more to drilling than just poking holes in something. Most feeler leaf gauges aren't coated/plated. The appearance is a result of how they were made.

 

[5ubtle]

https://www.homedepot.com/p/Everbilt-Front-Mount-Toilet-Tank-Lever-in-Chrome-224115-CP/205213947

$6 - You must be emotionally attached to this toilet lever arm.

https://www.homedepot.com/p/Milwaukee-3-16-in-x-4-in-x-6-in-SHOCKWAVE-Carbide-Multi-Material-Drill-Bit-48-20-8884/313176644

Try a carbide drill bit.

 

[American Locomotive]

I took your suggestion and immediately went out and clamped the feeler leaf to a plate of 3/4'' mild steel.

I didn't clamp the leaf directly to my workbench because I didn't want to drill through the workbench in case you were right.

Same story. Feeler leaf is impervious to the cobalt drill bit even with a steel plate backing.

The metal is probably too hard, and your drills are probably not quite hard enough. You'd probably need carbide with a lot of tool pressure. It's pretty easy to get a lot of tool pressure with a drill press. It's much harder to do the same with a hand drill.

 

[1982fxr]

Off the top of my head this idea just seems like it would be problematic. I can't intelligently elaborate.

 

[cannuck]

I would never try to do this with a twist drill. It is a punch job.

 

[cbracer]

3/16" might be too big. I would start with 1/16" and see if you can get a small hold into it, then go bigger

 

[Wamsutta]

https://www.homedepot.com/p/Everbilt-Front-Mount-Toilet-Tank-Lever-in-Chrome-224115-CP/205213947

$6 - You must be emotionally attached to this toilet lever arm.

I was waiting for someone to mention that.

I just like the handle shape of the original Eljer toilet lever handle.

I wish they'd let us disconnect the handle from the lever so that we can just replace the lever.

 

[whateg01]

3/16" might be too big. I would start with 1/16" and see if you can get a small hold into it, then go bigger

I would never suggest that to somebody using a hand drill who is already having trouble making a hole. If the 1/16" drill doesn't cut, he'll lean into it and it'll snap.

 

[5ubtle]

... A drill press is probably what you're insinuating as being far superior.

I would never suggest that to somebody using a hand drill who is already having trouble making a hole. If the 1/16" drill doesn't cut, he'll lean into it and it'll snap.

I assume that he's ashamed, and is out buying a drill press now.

 

[paulsomlo]

The drill bit is indeed split point - I had to wade through the catalog on Viking's website to ascertain that.

 

[cbracer]

I would never suggest that to somebody using a hand drill who is already having trouble making a hole. If the 1/16" drill doesn't cut, he'll lean into it and it'll snap.

Yes very easy to snap, but he needs a bit that will bite into it and from my experience a smaller drill bit can bite into something easier.

 

[Beerhippie]

You need a more rigid backer. The wood offers no support and compresses easily. So I think what is happening, is the feeler gauges are just deforming and conforming to the drill, rather than cutting.

Usually the trick to drilling thin, hard metal is to make a sandwich. Clamp the feeler gauges between two thick pieces of aluminum or steel, and drill through the whole stack.

That's exactly what I would suggest.

Also making a starter hole with a much smaller bit.

But without a drill press... buenos suerte.