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 .

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

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.

How about a pilot hole, might help things out ?

Pete

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

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