Drilling steel.. You ever had this issue?

[Noods]

Hi..

Has anyone experienced this issue when drilling mild steel..

Drilling 2 x 8mm holes through 6mm thick mild steel..

Pilot holes drilled and first 8mm hole drilled through without any issue..

Hole 2 again pilot hole drilled first with coolant and get half way through with the 8 mm and the drill won’t go any further, so i sharpen the drill bit and try again but no, it does not want to know ( always sharpen my bits without issue normally) so, i get a brand new 8 mm drill bit HSS of high quality but no, it won’t touch it either..

All i can think of is perhaps the heat has case hardened the steel.. ? Or perhaps could there be impenetrable elements within the steel.. ?

Your thoughts… with thanks..

 

[Seadog]

Case hardening requires carbon. I suspect that, as you suggest, there's an inclusion in the metal that has work hardened.

 

[brightspark]

havent been welding anywhere near have you and cooled it with water

 

[hotponyshoes]

You can't harden mild steel to any noticeable extent.

Might be an inclusion in the steel.
Have you had a close look at the end of the first drill bit to see if a little piece of it has chipped off and got stuck in the hole?

Try flipping the sheet over and drilling from the other side.

 

[bricol]

8mm seems small to need a pilot - so won't help with cutting edge life.

Cutting lube and correct speed will help with life.

 

[Gritineye]

Sounds like the old bed frames used to be, one part drills fine, another part blunted the drill straight away, rubbish steel even before Chineesium reached these shores.

 

[Dcal]

I had the same problem on some 100mm 10mm wall S355 box.

I drilled lots of holes without issue, but one wouldn't cut.
Turned out it was on the flash weld along the box
It was as hard as glass.

I assumed it was cheap Chinese steel with a far higher carbon content than it should have had, or some other inclusion.
A new slugger bit wouldn't touch it.
I ended up burning a hole and taking it out to size with a burr.

 

[Seadog]

Sounds like the old bed frames used to be, one part drills fine, another part blunted the drill straight away, rubbish steel even before Chineesium reached these shores.

It wasn't rubbish. Popular lore has it that tram lines were recycled into bed frames. Tram lines are made from manganese steel which work hardens.

 

[anto44]

I was drilling some 40mm thick mild steel plate and hit a spot where it seemed to be a lot harder, all of the sudden the drill bit just flew about 10mm into the plate accompanied by a puff of black dust out of the hole. There was some sort of inclusion in the steel but I don't know what it was.

 

[Munkul]

It wasn't rubbish. Popular lore has it that tram lines were recycled into bed frames. Tram lines are made from manganese steel which work hardens.

The tram lines weren't the problem, it was the other pot metal they chucked into the mix...

 

[Noods]

havent been welding anywhere near have you and cooled it with water

Not on that actual piece no.. The weird thing is the two drill holes are approx only 50mm apart but, !

 

[Noods]

You can't harden mild steel to any noticeable extent.

Might be an inclusion in the steel.
Have you had a close look at the end of the first drill bit to see if a little piece of it has chipped off and got stuck in the hole?

Try flipping the sheet over and drilling from the other side.

Tried flipping it but no, no joy.. The only other thing that similarly happens i’ve noticed is sometimes when cutting the same material with a 1 mm disc on an angle grinder i get the same issue on occasion, like it’s cutting through beautifully and then comes to a complete halt for a bit before eventually it gets going again, not always but sometimes..

 

[Noods]

I had the same problem on some 100mm 10mm wall S355 box.

I drilled lots of holes without issue, but one wouldn't cut.
Turned out it was on the flash weld along the box
It was as hard as glass.

I assumed it was cheap Chinese steel with a far higher carbon content than it should have had, or some other inclusion.
A new slugger bit wouldn't touch it.
I ended up burning a hole and taking it out to size with a burr.

That sounds familiar …

 

[hotponyshoes]

Would be interesting to cut it in half and etch it

 

[arther dailey]

Sounds like the old bed frames used to be, one part drills fine, another part blunted the drill straight away, rubbish steel even before Chineesium reached these shores.

strange stuff the old bed frames, used outside with no paint they get just a few speckles of surface rust then thats it ,weatherproof it seems..so for some jobs its good !

 

[addjunkie]

Grind up an 8mm masonry drill….then try, plenty lube

 

[Chippie]

Time to get the gas axe out and burn it thru'.... or plasma cutter....last resort...lol.

 

[brightspark]

Sounds like the old bed frames used to be, one part drills fine, another part blunted the drill straight away, rubbish steel even before Chineesium reached these shores.

good stuff used to buy it it lengths from the scrappies 50 pence each

 

[brightspark]

strange stuff the old bed frames, used outside with no paint they get just a few speckles of surface rust then thats it ,weatherproof it seems..so for some jobs its good !

they were coated with something . it smoked and stunk when you welded it . was a type of spring steel

 

[Pigeon_Droppings2]

We had something similar at college with a "scrap" bar....dunno what it was but took the powered bandsaw ages to cut it....then it was a nightmare in the lathe....I seem to remember we gave up in the end.

Cobalt bit might work...I buy the odd size Dormer ones that turn up on evilbay just for pilot hole drilling. Don't think my hss-e ones have been defeated yet!