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EN3B Machinability

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Jon Gibbs11/06/2014 14:57:55
739 forum posts

This is a very dumb question....

I have just bought some EN3B bar for general machining rather than the EN1A I have been using.

I'm using HSS tooling.

Am I going to regret buying it or notice little or no difference?

Any thoughts gratefully received - thanks


colin hawes11/06/2014 16:48:00
515 forum posts
18 photos

En 3B does not cut quite as easily to a high finish as EN1A which is why EN1A is known as free cutting mild steel. However, it is still easy to machine and is generally cheaper. A small radius on the tools' tip should give the best results.Colin

Jon Gibbs12/06/2014 08:26:37
739 forum posts

Hi Colin,

Thank you for the reassurance - phew! I have to admit I got a bit carried away and bought rather a lot.

It certainly seems a bit tougher than EN1A but seems to machine ok.

Many thanks


lancelot16/08/2014 12:03:58
63 forum posts
4 photos

Hi Colin and Jon...I recently obtained some 3/8''by 1/2'' I was told EN38 flat barfirstly my hacksaw with a new blad had trouble cutting it ended up cutting it with a chop saw......tidying up the ends of the bar for centering the linisher buff gave off a stream of small very bright golden yellow the lathe bar set up true ...tooling Glanz with circular tip... lathe sherline...( I know dont be surprised it has cut bigger ) anywaywhen toolapplied to metal it tore rather than cut speed was ok as was feed tried a HSS tool basically the sam...I do not think there was any problem with set up or tooling but I am not so sure of the material

any ideas on this,


Keith Long16/08/2014 12:22:40
846 forum posts
11 photos


Do you mean EN38 or EN3B - they're different materials - both exist. EN3B is a low carbon "mild steel" EN38 is a 5% nickel, case hardening grade.

Steve Withnell16/08/2014 13:16:20
819 forum posts
217 photos

"Free machining mild steel" isn't that the one the Consultants recommend as a cost cutting opportunity?




Edited By Steve Withnell on 16/08/2014 13:17:07

lancelot16/08/2014 14:38:05
63 forum posts
4 photos

Good afternoon Steve I need to trust the dealer i got it from so when told it was free cutting steel and fairly cerrtain EN38 results as described for ''Consultants'' Nuff said...

Hi Keith...I am reasonably certain EN 38 was mentioned along the rather crackly phone...what grade of steel would react like that to machining and give off that kind of spark..


John Durrant16/08/2014 20:53:52
44 forum posts
4 photos

I have a mix of EN1A and EN3B to work with. I much prefer the EN1A.

EN1A is, as already stated, free cutting and is easy to get a good finish. EN3B, though not Hard, takes a bit more power and does not finish as well.

That said, if you want to weld or heat treat then go for EN3B.

Chris Denton17/08/2014 01:21:10
275 forum posts

I've used a brazed carbide tool very sharp at 2000rpm (40mm diameter from memory) , light cut with very fine feed to get a good finish on it.

Andrew Johnston17/08/2014 08:06:38
5670 forum posts
656 photos

EN3B can be tricky stuff, see here for some ideas:


In some ways I prefer EN3B to EN1A, if only because it seems less prone to rust. I've had EN1A get rust spots within hours of machining even though the part was cleaned and was sitting in the nice warm hall in the house.



Nigel McBurney 117/08/2014 10:18:50
743 forum posts
3 photos

I use a lot of en1a f/c and en1a leaded I never get corrosion in regular use and can leave parts in the worshop for a long time without any surface problems, one thing that can cause corrosion is the modern soluble oils going "off" and bacteria in the solution turning acidic, I find that after a time the bacteria eats the solution and the solution turns from milky white to a grey clearer liquid which is acidic.I asked castrol if the problem could be solved ,they said no and suggested that the lathe pump is run every day to aerate the solution ,I tried cleaning the system ,flushing with Jeyes fluid and adding Jeyes fluid to the soluble oil with little success .

EN3b is a cheaper general engineering steel suitable for shafts and axles where there is a limited amount of machining ,it welds easily thought it is difficult to get good consistent machined finishes, it is also recomended for for boiler stays on full size steam engines. If you want machined all over parts with an execellent finish then use en1a leaded but it is not suitable for welding.

lancelot17/08/2014 10:56:03
63 forum posts
4 photos

Hi Folks, thank you all for this information...I will give brazed tips a go ...if i can unearth them may just change the design of the part all together '

All the best for now,


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