Another lesson learned! EN1A vs EN3B

I have now learned there is a difference between machining EN1A & EN3B steel!

I want a 1.5mm wide slot, 6mm long 3mm deep in the end of a 12mm bar with a 6mm hole through. It's to insert a key to make a D hole so that the flat on an electric motor shaft will drive the rod. Eventually it will be a dog clutch.

Made the piece from a very short length of EN1A steel I had lying about. Very pleased, made the slot first attempt with no trouble.

Then I messed up the other end, and had to start again. The only 12mm I had was EN3B.

Three (admittedly cheap) 1.5mm carbide milling cutters later I had the new slot. The first broke (my fault) because I took too big a cut (1mm depth), The second grabbed where the slot breaks through into the central bore. The third just broke!!

EN3B does not machine as well as EN1A, at least at my skill level!! Now I know that.

Indeed not! EN1A is made to be free-cutting in exchange for slightly lower tensile strength.

Most EN1A contains a trace of lead for that, but there is also a steel grade using tellurium that is even more cleanly-cutting, designed for high-speed automatic production machines.

Welcome to the club.

In my experience EN3B can be finicky with regards to speeds and feeds versus surface finish and doesn't like fine cuts when turning with insert tooling. The material is slightly "gooey" and has a propensity to tear if speeds and feeds aren't correct.

On the plus side it is less prone to rust. I've machined EN1A, cleaned it and left it on the hall table and the darn stuff has gone rusty overnight; EN3B seems better mannered in that respect.

Andrew

I'm sure I've seen a thread previously on here of someone else who had problems machining EN3B; I was a bit mystified by this at the time. I use a lot of this material because it welds better (especially with TIG) than the (unleaded) En1A I have bought in the past. Are you machining it 'dry'? I use flood coolant on pretty much all the work I do here, and have always achieved an OK finish.

Just to add, although there's a HSS woodruff cutter in use here, i do most of my machining with carbide insert tooling. I also use HSS, but mostly where I've needed a form tool or similar.

Edited By Stueeee on 24/05/2021 23:32:36