Mild Steel Problems

I have recently been trying to drill small holes (5/16) in mild steel.

I have had 2 occasions where I have attempted to drill, but then hit a patch of steel that is so hard that nothing will touch it. I have tried Carbide drill bits, bur even these have difficulty.

Is the available steel rubbish or what am I not doing.

It is becomig expensive !!!

Any tips to assist me ?

Many thanks Malcolm Farrant

Sounds like the metal is work hardening like stainless does .

Slow the drill down , use cutting fluid and once the drill starts cutting don’t back off the pressure .

Why do you think it is "mild steel"? If it's bought as such from a reliable supplier then return it. If "scrap", be aware that material that has been (for example) welded, or odd bar ends, can be unexpectedly hard. Also it may have been a structural steel with a significant carbon content that has got hardened (e.g. through welding), rather than "mild".

As far as I'm aware, proper "mild steel" does not work harden.

Edited By John Haine on 25/08/2020 12:00:51

had it a couple of times in what looke dlike perfectly normal bar, tool suddenly hits a small patch that takes the edge straight off and even carbide struggles. Possibly an inclusion of something hard like an old carbide tip in teh scrap that was melted down

Malcom

Join the club!

There is some right rubbish out there sold either as plain mild steel or "what we give you as EN something". Even from suppliers to industrial customers.

Getting to the point where you need to ask for certificates and use the proper modern designations rather than EN equivalents if you need to be certain that what you get is exactly what you want. If the bar finishes with its natural end rather than being cut its usually prudent to dump the last couple of inches.

What cured me of EN number substitutes was 4 full lengths of "what we give you as EN 3B" that were all clearly different. OK I got a bargain 4 for 3 deal as they were the last 4 in the rack but I'd ordered under the proper number 070M20, got told "ah, we have EN 3B which is same thing". Pretty certain I actually got 080A15 supplied under composition, not mechanical properties, as the mix overlaps with 070M20. Actual mechanical properties can vary considerably if the material is supplied by composition. The paperwork said 080A15 which is commonly what you get if you ask for a basic mild steel bright bar.

6 digit designations with an A in it like the aforementioned 080A15 mean its supplied by composition. M as in 070M20 means it supplied against mechanical properties and composition. Materials with an M in the code will behave much more consistently than those with A. Composition of 080A15 overlaps 070M20 and EN3B but if supplied as 070M20 it will be certificated as having appropriate mechanical properties. So you can guess where the good stuff goes! Cynical folk would say that 080A15 is the rejects that don't test well enough to be 070M20.

Bottom line is if it hasn't got an M in the number you may get a surprise.

Clive

Edited By Clive Foster on 25/08/2020 12:36:13

I don't believe it's a new problem. When I was an apprentice in the late sixties one of our tasks was to make and heat treat a lathe tool from 1" x 1/2" carbon steel and try out its performance on mild steel. Mine behaved beautifully, and I took deeper and deeper cuts with more and more feed until it hit a hard spot and stopped cutting.

I tried all sorts to get through the hard spot, without success, and it actually tuyrned the end off my lathe tool as a boring bar might. At this point it became something of a game, and eventuall the tool tip became red hot. I then tried with a tool from tool stores (probably HSS in those days) , and that wouldn't touch it either, neither was it improved in the attempt, so I sneaked it back in the store while nobody was looking and binned the mild steel bar.

A pity, because up till then mine was a very efficient lathe tool.

George B.

Regarding the expense - it might appear that you need to sharpen your blunted drills. Lose time, yes, but as hobbyists we are not in any particular hurry, generally. Perhaps another skill to learn/practise?

How about a pilot hole, might help things out ?

Pete

Steel with hard inclusions is not worth bothering about,throw it in your dustbin,you have hit a hard spot under the drill it might be worse in other areas.

British machinists have often caused themselves grief by refusing to move with the times! Metrication is one example and EN numbers are another.

Problem with buying steels as specified in BS970:1955 is that no one makes them because the system was replaced in 1970. Anyone buying EN3B today will always be given a substitute. And which substitute is in the lap of the gods because the whole system is confused. As my local supplier's customers all ask for steel by obsolete EN numbers, he orders the same from the wholesaler, and the fiction goes a long way up the supply chain. I blame experienced oldsters for blocking progress. Young chaps burbling nonsense about BS970:1970 were soon sorted out. The old ways are the best...

However, a back-office purchaser eventually breaks the fantasy by ordering a real world steel to meet these sloppy orders. Structural steels in the EN3B class aren't challenging, so he'll probably buy whatever is cheapest at the time. Could be from anywhere - European, Indian, American, Russian, Japan, or China etc. As these guys make at least 18 different steels similar to EN3B, who knows what will end up in your workshop!

For most structural purposes the difference between EN3B-like steels like 080M15, 080A15 and SAE1018 probably doesn't matter. Machining them is a different story.

Given tradition has successfully maintained obsolete EN numbers 50 years past their use by date, I'm not sure there's a cure other than asking for a certificate. Nonetheless I've done OK ordering EN1A and EN1A-Pb because the modern equivalents are also formulated to improve machinability. Otherwise buying metal I always check what's said in the spec about machinability and avoid anything described as poor or average.

Dave

I must have been lucky these days, not encountered any hard bits as I can recall since making go - carts out of bed iron over 50 years ago.

Pete

Now that brings back memories of making a trailer for my brother out of the bed irons that he provides. All varied from easy to downright horrible to drill. But the arc welder had no problems!

And so, back to the thread!

Howard