Free Machining Stainless Steel

I just proved free machining stainless really exists. I carefully turned the end of a bit of 3/16" SS down to 0.125" to fit a crank, and cut a 5BA thread on the end using the tailstock die holder and mandrel handle.

I thought the thread looked a bit undersize, then discovered I had cut a perfect 6BA thread... no damage to the die as far as I can see!

Neil

Nice work...if you know where there is any free machining titanium I'd love to buy some - all mine is of the opposite variety

I'm guessing that you properly machined some 302 or 304 stainless bar as its relatively soft compared too  316, the latter is horrible to machine

Edited By Kevin Fenrich on 13/12/2012 23:08:43

Edited By Kevin Fenrich on 13/12/2012 23:09:43

Free machining is 303.

304 is like witches tits.

Free machining titanium is grade 2, grade 9 is like empty witches tits. Never come across grade 1, they always supply me grade 2, still tight when drilling and tapping though but with barbide turning tools and end mills it machines similar to 303 stainless.

Be aware that many grades of material are not available in certain sections unless you won't to pay setup prices. 303 isn't available in flat plate for instance, that's usually 304 or 316.

John S.

I've got quite a lot of 6AL4V - turns OK but it's nasty stuff to drill and tap. Got any tips on that score John ?

Hi John, I would like to learn more about witches tits.

Regards, Bear..

303 Grade SS is a pleasure to work with. I find it easier than free cutting MS, not a lot more expensive, and need no further finishing.

304 is not too bad to work, I'm surprised John S likens it to WTs, things that I've not heard of, maybe it because I dont get out often enough, or just lead a sheltered life.

Ian

Maybe WTs are a compliment, or would they have to be full then?

I'v found that even 316 is not too bad, apart from great streamers of swafe, made some hot ends for Stirling Engines from it, could only get solid bar at the time, had to bore it out to 1 3/4" x 3" deep, I'll admit it took time, but it's still in use 20 years later. Ian S C

Hi There

I seem to remember there were two types of 316.

316 AM, easy to machine

316 J just turns red hot when you try to cut it.

From memory of about 35 years ago.

regards David

I'd guess it was 303 then, I just bought it as free machining stainless to make some piston rods.

Neil

I am interested in all aspects of models; if you manage to turn a WT, does the W turn with it?

Only after 720 degree lag

Edited By jason udall on 17/12/2012 00:46:44

Btw worked with 1.6mm threads in 316S11 (L)..tapped 10X dia..1mm holes internaly deburred... polished to "mirror" finish (what ever that means)..

1mm holes through 20 degree included angle cone.316 is also know as surgical stainless..all worked in hardened form........Such fun yeild as low as 1 in 4..ie 1 completed part out of 5 started!...thouse taps argh!

Just taken apart a water pump and found that the shaft is worn (around 12mm by 100mm). Supplier says no longer able to get replacements. He says he thinks it is "hardened 316".

Machining isn't too complecated - just two flats on one end and a channel on the other.

Not sure about hardening this though - any thoughts?

Philip

Only if you pay close attention to the clamping

Regards,

Tony

Philip,

It is not possible to harden 316 using heat treatment. You have to use cold working methods instead, which may not be practical for a shaft. See this link:

**LINK**

Regards,

Andrew

Andrew

I wondered if heat hardening 316 was possible - thanks for confirming it isn't.

Not really sure hardening is required anyway - there are two rubber seals and three bearings, and no other metal contact.

Philip

316 work hardens with great ease.. the trick is doining it as required...in any case parts of spindle that are in contact would benifit from burnishing.. which will achive that end.

Year ago i came across free cutting stainless quite by accident. I was the machinist in a heavy industry factory.

One of my smaller jobs was to make SS nuts out of 2in bar, they had a tapped hole in the moddie and were anout 3/8 thick. I used to part them off using a parting off tool.

I decided to put the cross feed on auto one day and it worked perefectly. I only got one cut out of the tool and had to touch it up with a stone after every cut but it worked. The finish was like chrome, there was no juddering or tool bits snapping.

Witches Tits.. can't connect the analogy ??? Maybe my old grey matter is worse than I thought, enlightenment would be nice! or am I missing something?