Does steel have 'knots' in it

[JimM]

Evening all

I was trying to drill some lat bar earlier this evening and the drill was having none of it. It was a couple of pieces if 8mm tacked together but the drill bit only went in a mm or two and then refused to go any further, tried again a cm further along and it went through no problem. Flipped the piece over tried in the same spot as the first attempt and it went most of the way through before hitting the problem again. It's almost like the steel has a knot in it like you get with wood. Is this a common problem or is it a flaw in the manufacturing.

Cheers

Jim

 

[snowcat]

Any idea of the grade of steel, something like EN3b will "temper" if heated ie tacked...

 

[JimM]

No idea of the grade unfortunately and can't remember if the tack was at the point where I was drilling. The tack was very light though and the hole was 15mm in from the edge, would tempering still be possible ?

Thanks

Jim

 

[snowcat]

yes, actually could be tool tempering, if the work's got hot whilst drilling (often down to too faster drill speed) then, its very posible that the drill tempered its own pilot, EN3 can become imposible to work if its been flame cut as can over grades........

 

[JimM]

Thanks Snowy, sounds like that could be it then

Cheers

Jim

 

[piman]

Hello Jim,

I occasionally experience that when drilling stainless, and it is worse using a portable drill.

You said that you went to another spot and it drilled OK, I'm assuming with the same drill? When it stopped on the first hole it will have taken the edge off the drill. I would re-sharpen the drill then try again. If it is still a struggle using a pilot drill often works and then lets you open up the hole to the desired size. Good quality drills also are better.

Alec

 

[^neo^]

If the steel is relatively new (past year or so) we have noticed there is a hell of alot of crap being supplied at the moment with hard lumps in it.
Going through chop saw blades like theyre going out of fashion

 

[Stuggi]

The really nasty stuff is the acid-proof stuff (better than stainless, no clue what's it called in english, has a dull silver finish from the factory). It self-tempers when you drill it, and turns really hard. You need to use a carbide drill bit, and heat it with a torch every 2 mm

 

[Master-of-none]

-self hardening

Once had a talk from a specialist metal fabricator, he mentioned that a new young tool rep offered to demonstrate the quality of his hacksaw blades.
Unknown to him, they gave him a piece of Hastelloy which work hardens. The cut started but each blade only lasted a few stokes much to the rep's increasing constenation.
They had to stop him using the entire stock of demo blades!

 

[Hitch]

Occasionally find small hard bits in larger sections and heavy plates, especially if its Indian or similar.

And it does have a grain aswell.

 

[aametalmaster]

I thought i hit a car bumper turning a piece a piece of China cast iron on my lathe ...Bob