# Hard areas in steel



## GrahamRounce (17 Apr 2018)

I've bought various small amounts of cheap steel, mainly flats and bars. I'm plagued with finding areas that even a newish drill (eg 3mm) under pressure won't touch. 
Even tool steel (?) in the form of a lathe chisel drilled fairy easily.

I take it that the super-hard spots are where there is a localised excess of carbon due to the steel not being mixed thoroughly when molten?

I'm thinking that there must be different grades of steel, where the better ones don't exhibit this problem? If so, what sort of grade should I be looking for?
Thanks,


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## t8hants (17 Apr 2018)

You don't say what sort of lengths you are after, but assuming you only want small pieces, then the 'bright' range of steels would probably serve you better.
The 'black' constructional steels can indeed have hard spots, although 'new' drills can also need sharpening. 
It all comes down to what level of quality control the manufacturers employ.
Since we decimated our own steel industry to import cheaper foreign made, we get what we pay for..........Carp!


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## J-G (17 Apr 2018)

Even if you are using 'Black Bar' (unlikely), I doubt that what you are experiencing is 'Hard spots'.

I suggest that the most likely scenario is 'Work hardening'.

This can be caused by too high a speed, too slow a feed, blunt tool - among other reasons . I can't say I've come across it using a drill though, any size never mind 3mm!

What happens is that the tool 'rubs' and this causes a localized 'hardening' of the material due to heating through friction, often causing the cutting edge to be worn away since the tool is now 'softer' than the material. 

I've got around this in the past by changing to a carbide tool rather than HSS or HSS instead of Carbon Steel - even filing can sometimes get the hard spot removed.

I recently experienced this using EN1a !! --- I had my speed up as if I was wood-turning


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## CHJ (17 Apr 2018)

GrahamRounce":30liug48 said:


> I'm thinking that there must be different grades of steel, where the better ones don't exhibit this problem? If so, what sort of grade should I be looking for?
> Thanks,


Some Simplified information

I've not come across 'Hard Spots' in recent years, as said by others more likely over heating of drill bit by excessive speed and inadiquate feed.

In the 50's it was not unusual to get hold of cheap stocks that had loads of rubbish in it such as HSS or High Carbon tool tips etc. presume relics of wartime production short cuts, but have not seen such for many years.


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## hawkeyefxr (17 Apr 2018)

A big thing in drilling is the quality of the drill, like most people i have bought the set of drills, these are ok for real general work but will blunt quite easy.
I drilled a 1/2 stainless octagon bar with these and it was awful, horrible gritty sounds and a shiny blind hold. I bought a "good drill and 5mm tap" cost me £11.00 but wow the difference, no problem with the stainless at all nor with the tapping either. 
Dormer drills are good but a small set will set you back £60.00, bit for that Silverline or Aldi.

Black bar can be tough on the outside but generally the clean inside is ok. Bright mild steel is good easy material to work on as has been said above but it's not that strong in certain instances.

On another note, i used to make the steel melting furnaces, these were induction types where the magnetic fields would swirl the molten steel about so it was all mixed up ok. Just before they pour the steel they put various minerals in there that causes the steel to clean up and get rid of impurities. The biggest furnace we made was a 25 ton drum furnace, thats 25 tons of molten steel. It is hot and very dirty work but interesting to see.


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## sunnybob (17 Apr 2018)

Like already said. we can be sure your drills are sub standard (are they gold coloured aluminium? throw them away). Black steel coloured HSS is the only good colour for a drill bit.

And if you are using a battery hand drill the speed is too fast, even on slow speed.
I have cut many holes in stainless steel plate, up to 1/4" thick by using a good quality drill bit, and a slow steady pressure. Slow enough that you can see the flute rotating. pressure just enough to cut, but NOT by leaning on the drill.


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## AES (17 Apr 2018)

+1 for all the above comments. I also agree that hard spots, unless due to local work hardening, are unlikely. If the steel was bought "new", even from your local DIY place, it should be OK, whether bright (silvery looking) or the more common slightly rough dull black finish. With the black stuff it IS possible, very just now and then, to get a hard bit of lumpy scale on the surface, but a quick stoke with a file will soon remove that.

It's far more likely that your drill is blunt (causing friction rather than cutting properly, so causing local heating, leading work-hardening). But sorry I do not agree with sunnybob that for drilling a 3 mm dia hole a typical electric drill on top speed is too fast (typically about 2,500 rpm?). On the contrary, when I want such a small hole I set my pillar drill at it's fastest speed (in my case that's 3,200 rpm - and if smaller dia than that, I use a Dremel in a drill stand set at about 5,000 rpm). The basic trick is "the smaller the drill the faster you go, the bigger the drill the slower you go" - I drill half inch holes on my pillar drill set at either 210 or 280 rpm.

The next thing is "feed" - i.e. how hard are you pressing down on the pistol (or "leaning" on the pillar drill handle)?The downwards pressure needs to be "steady" but by no means "leaning hard"! Hard to put into exact words, but a skill of hand soon learnt - usually by pressing down too hard on a pistol drill with a small diameter drill which then quickly ends up broken! (Don't worry, it happens to us all when we first start out, but you soon get the hang of it)  

But that feed pressure is actually a very good indicator of when you do have a blunt drill (after you've got the knack). You'll feel immediately if you're needing to press down too hard - and you may even see a little smoke coming off the job!

Which brings us to lubrication. IMO ALWAYS a good idea, whatever the size of the drill, unless the steel you're cutting is very thin - say less than an eighth inch (roughly 3 mm). There are many good cutting fluids about, and they're especially useful for tapping threads, and also cutting on the lathe, but can be expensive, and some are quite poisonous. For "just" the infrequent drilling of mild steel you'll find ordinary 3 in 1 domestic oil is fine (and paraffin or WD 40 for drilling aluminium).

Finally drills. I basically agree with sunnybob, the "good old English" dull black drills are generally very good if they come from a known name like Dormer. But IMO he's not correct when he says "only" such drills. For example I bought a metric set from my local DIY place, bright silver, no name on them and they've had YEARS of service (with only the odd touch up now and then) and they're BRILLIANT (and weren't too expensive either). OTOH, I bought another set from another DIY place, they're that funny orangey/gold colour and they're "not too bad", whereas yet another set (black this time) someone bought for me are absolute carp - I think the cheese they're made of is not even of Swiss quality!

In other words, it's a bit of a mine field and without having a well known name it's all a bit hit and miss.

If you're just starting out it is worth getting a set (metric in 0.5 mm steps, 3 mm to 10 or 12 mm - or Imperial in sixteenth steps up to half inch say) but as above, you may have to buy a couple of sets to find a really good set. 

But once you've got that good set you just replace any breakages with singles, and/or learn to sharpen, either free hand on a grinder (again NOT easy until you get the knack) or one of the drill sharpener jigs that are around. I've found the couple of jigs I've tried "not bad/better than nothing", but if you can get the knack of it, hand sharpening is the way to go - BUT unless you've got better eyesight and a steadier hand than me, forget about sharpening anything under about say, 3 or 4 mm dia (say eighth inch) - when they get blunt just check 'em away and if you do a lot of small hole drilling, you can buy single sizes in 5 off quite cheaply. Ditto if you want smaller than say 3 mm - just buy them singly (or in five packs).

I short, the answer to your problem is MOST PROBABLY a blunt or a poor quality "cheesy" drill rather than the metal. Try a bit of 3 in 1 oil by all means before you give up with the present drill, but IMO you probably need to buy a new 3mm drill (or a pack of 5), by a good well-known name (like Dormer, or Patience & Nicholson - if they still make drills, I haven't bought tools in the UK for many years now, sorry).

Finally, if you don't want to risk loosing money in your DIY place, look on line - there's a list of suppliers in the sticky right at the top of this Metal Working section.

Hope this is not too long, and hope it helps.

Good luck mate.


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## chaoticbob (17 Apr 2018)

+ another for comments so far - but I agree with AES re speeds - 2000 rpm or so is not excessive for 3mm in steel , and TiN coating (I think - the gold stuff) isn't necessarily bad. I have a set of TiN coated Dormers which seem to chomp through anything. There are quite a lot of cheap TiN coated drills out there where the coating is there more for marketing than engineering purposes though , and I guess it's those that sunnybob is warning against. There really is a world of difference between 'proper' industrial drills and DIY shed offerings, in my experience at least. Other than Dormer, Guhring are very good - Sherwood (Cromwell tools) and Presto also perform well at a lower price.

Re steel grades, EN1A seems to be the 'stock in trade' of many home metalmanglers, - it machines well and is a good general purpose mild steel. It might be worth getting hold of a lump and seeing how the drilling goes with that. If there are still problems it's either the drill or technique. Eliminate one variable at a time I suppose!
Rob.


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## GrahamRounce (9 May 2018)

Hi - I don't generally have any problem drilling steel. My drill press is set to 500rpm, the slowest.
I suspect a "hard spot" because at school, late 60's, the turret drill refused to cut, and the teacher said, "You've hit a hard spot." That's all I know. I was just guessing about the carbon.
I'm enclosing a pic of the metal in question. It's about 4" long. You can see the failed holes, as well as some successful ones. 
I'd be happy to post it for investigation to anyone interested. 
I'd just taken it as an annoying but unavoidable thing with cheap metal - I didn't know it wasn't supposed to happen!
Thanks, 
Graham


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## CHJ (9 May 2018)

Try heating it to light red, ( hotter than cherry red) and let it cool as slowly as possible.
It should then be soft enough to drill with a sharp drill at sensible speed.

If you need it harder for use you must then harden and temper as required.


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## sunnybob (9 May 2018)

Seeing as its now scrap, hacksaw through the hard part, and then hacksaw through the soft part. See if you can feel any difference.


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## AES (9 May 2018)

Good advice there from both the above. As said originally "I" (several of us actually DOUBT - but of course don't know for sure) that it's actually a hard spot or not - far more likely to be a blunt (or "Chinese cheese") drill IMO.

But assuming the piece is scrap (I assume you have another piece to make whatever it is you want) I for one would be interested to know if it IS a hard spot. Any idea where that piece came from - out of a scrap bin (my favourite) or did you buy it "new" somewhere?

There's one other thing you could do if you have a grinder - grind one end (only gently) and see what the sparks look like (see under). It's an old fashioned but quite good test though not always conclusive (some sparks are difficult to see properly).






I see the spark descriptions on the RH page side didn't scan too well, sorry. From the top they are:

1. Short streaks, small leaves, sparks
2. Small leaf, larger spark nearer
3. Dull streaks, no leaf, profuse sparks very close
4. Forked and streaked sparking
5. Yellow streaks, points at ends
6. Very faint red streaks, forked end
7. Faint red streak, yellow bush spark at ends
8.Shoirt faint red streak
9.Long yellow steak, leaf fading away.

As you can tell from the above descriptions, this is NOT always easy (helps if you're shown the different effects, as we were as apprentices). But it's better than nothing and a couple of them are usually easy to spot - suggest you have a go.

HTH


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## novocaine (9 May 2018)

flip it over. 
center punch (automatic one would be good as it keeps the same pressure on it) a line down the middle using consistent hammer blows, if the hole is shallower where you had issues drilling, it's a hard spot, if they all look about the same it's a dead bit or you work hardened the steel by applying to much pressure with a dull bit (we've all done it). 

A rockwell test kit does something similar but with a ball and a press.

grinder trick works well too.


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