Turning BDMS

[Martin DowingParticipant @martindowing58466]

[Martin DowingParticipant @martindowing58466]

Well, BDMS is not the nicest material to work with, nevertheless its mechanical strenght and some other properties are superior to F/C steel.

Screws made of BDMS, if there is a need to tighten them hard, are far more resilient than those made of F/C steel.

It can also be carburized and then hardened and of course it is very abundant and cheap.

However it can be quite a pig to turn. Perhaps one of the most difficult common materials to work with if good surface finish is required without grinding at least in my experience.

Any tricks to address this sad state of affairs?

[KWILParticipant @kwil]

Nice sharp HSS cutter, ground to the correct angles, (or a carbide tip if that suits you). However EN1A is OK but EN3B is crap. F/C steel is of course leaded and does not like to be silver soldered.

[Anonymous]

You need to specify the material more precisely. For instance EN1A (not free cutting) is very easy to turn and get a good finish. However, EN3B can be difficult; it tends to tear if things aren't right. I use insert carbide tooling and for EN3B the key is surface speed and depth of cut. See the first post in this thread:

**LINK**

Andrew

[Roderick JenkinsParticipant @roderickjenkins93242]

My understanding is that, unless specified otherwise, BDMS is en3b.

En1a is free cutting because of its sulphur content

En1aPb or en1a leaded has enhanced freecutting properties because of the lead content

En3b has a higher carbon content than en1a and for this reason is preferred for welding.

Cheers,

Rod

[Martin DowingParticipant @martindowing58466]

Thanks for comments.

Data from another thread linked by Andrew is interesting but unfortunately speeds suggested there are of no use for me, as I rarely use carbide inserts.

My ML7 does not run fast enough, hence no virtues of use of carbide inserts can be exploited.

Occasionally, when these *are* used there is no difference, albeit inserts in my posession are not of finishing grade. My BDMS is a continental equivalent of En3b (low sulfur mild steel with 0.3% C and below 0.5% Mn).

My personal findings are that the best finish is achieved with hardened high carbon steel. It get better polish than HSS. Nevertheless it is still not as good as on brass, aluminium or stainless of many grades.

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