# Metal unknown?



## fast204 (Apr 12, 2017)

So let me first say, Thank you to all those that have provided some insight and experience to getting my hand me down lathe up and operating. As of now I have made a few pins for my tractor, a couple of axels for my pit bike and various parts and pieces for a couple gun builds I'm well into.
I was given a 5gal bucket of some misc metal over this last weekend and it has me scratching my head.... I separated it into what I could best tell. There is a few small rounds of aluminum, a few very nice pieces of brass hex stock, some misc larger hex stock and a lot of 1.5" - 2.0" rounds of material unknown. It is steel of some grade, covered in rust from sitting in a water saturated bucket.

I cleaned up a piece the unknown and wanted to make a few practice passes on the lathe. What I got was chatter, terrible surface finish and frustration. I am using hand ground HSS. I thought it must be the tool so I chucked a piece of material, 304ss. I was able to take a .030" doc advancing freehand with the carriage and got a very respectable finish. I then took a cut on a  piece of 1018 and aluminum 6061 just to make sure I was not fighting an improperly ground tool as this is something I'm new at. I decided to try with my carbide inserts and was unable to cut either the 304ss or the mystery steel?? Am I missing something or are the clearance angles on the hand ground HSS allowing me to cut the stainless but not this mystery material?

Any thoughts are welcome.


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## ghostdncr (Apr 12, 2017)

I don't know of any way to positively identify "mystery metal" but there are a couple of tests I do on the (frequent) occasions I run across some. You may already be familiar with these tests, but I'll post it it just on the chance it proves helpful. Foremost, you say it's rusted so we should be able to conclude it's some grade of either iron or steel.

I start out by addressing an edge of the material with a good file. If I get a good, sticky cut with a decent output of shavings, it's safe to call it unhardened. Steel will produce slivers, whereas iron filing tend to be more like a powder.  Pre-hardened materials (like 4140, P20, etc.) will resist the file, require considerably more pressure and produce far fewer shavings per cut, but the file will cut them. Full-hard steels like heat treated A2, D2, H13, or even Thomson shafting, will have nothing to do with a file, squealing at the file stroke and producing no shavings.

The third test I'll do is touching the material in question to a grinding wheel. Different materials produce different spark patterns when ground and by comparing the shower of sparks to any number of charts illustrating these patterns, a fairly close identification can usually be determined.  https://en.wikipedia.org/wiki/Spark_testing

I've usually been able to get pretty close to accurate identification using these methods and once the material is ID'd, it's much easier to develop a machining strategy that will produce accurate cuts and a good surface finish.


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## Silverbullet (Apr 12, 2017)

The steel if hardened sometimes can be annealed to a point that machining is possible. About forty years ago I ordered a piece of 4140 steel in a three inch square x 8' long. When it arrived at the shop it had been flame cut from a large plate. Guess what no tool in the shop would touch it , hard it was super hard. So we sent it back to the seller he sent it to a treating plant and annealed it. We made hold downs for our open sided hydraulic planer. I turned the pins on one end to fit the table , machined the squares to size , then I set them up on a thirty degree angle drilled and tapped on the angle , 3/4 - 16 . Using drill rod fully threaded turned long taper points to lock down the work to the table. Turned out to work so well our boss paid me to make a dozen total in my home shop at the time. My old Sheldon and m head mill worked great made those and lots more in a little one car garage back in 1976. Still have a couple small pieces of the steel in my shop now. Made jacks for using on the planer and VBM. Out of them.


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## fast204 (Apr 20, 2017)

I have not had a ton of time to re visit this metal as work has picked up quite a bit but I did run a file across it the night I got your post and the cut produced shavings and not actual chips. leaning more towards iron of some grade?


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## Round in circles (Apr 26, 2017)

I get the impression that steel kept in changing wet & dry condition will kind of case harden over the a few years as water & nitrogen in the air get acting on it .

Story ...
During my apprenticeship 1966 tp 1969 we were told during engine design studies that top of the range engines with cast iron steel heads & / or bodies at BMW used to be stacked along the side of the engineering shed where the beery workers use to nip out the fire doors for a quick pee . They used to pee on th castings .

This led to some interesting results for which the reason was not at first evident ,  once the outer skin had been cut off the rest of the metal cut like a dream & was stress free to an amazing degree.
  This led to supercharger blocks also intentionally being given the same treatment .

I have quite a lot of steel off cuts & rejected parts that came out of a closed down engineering works dumpster /rubbish area  . It has been there outside slightly shaded in all weathers for at least three years , similar to yours some of the pits are a good 1/5 " deep & some rusticles stand out almost the same distance .

 I ended up having to use a big meaty one inch shanked high speed tool steel cutter with quite a point on it to slowly & finely take off the crust at normal steel cutting speeds taking off only 5 to 6 thou at a time using the lathe in powered carriage feed at about 800 tpi it took ages as you can imagine .  They were turned them dry after using a flap disc on the stubs ( that I'd left to go bone dry )  whilst I'd got them in the bench vice to take off any really loose crud .  Bits of rust & muck were chucked all over the lathe but the end result on the steels was fantastic once I'd removed all craters & then used a little cutting oil to assist the fine final finish .

 I've also used my home made electrolytic de rusting tank & an old fashioned 40 year old battery trickle charger & a small hand full of washing soda in 25 gallons of water  to try & strip off the rust at about 1 amp for a couple of days . 
Any longer & you have to take out the item & the electrodes , wire brush & power wash them clean & restart the cleaning session .
 The resulting iron oxide on the metal is fine , slimy &  black , it marks skin & clothing better than any permanent marker pen .

  After a few days in the tank I've power washed off the oxide  , then  used a battery drill fitted with a cup wire brush & taken off a lot of muck .. there was no rust left to speak of but plenty of black .Once dried on a clean dry rag  I turned them down whilst they were still slightly damp .   That gave me far less flying crud & was a lot quicker as I could take about 8 to 10 thou off at a time .

 I tried heavier cuts  & faster speeds but they soon blunted the stoned cutting edge . I tried indexable TCT's & brazed on TCT's . None of them really wanted to play till the whole stub was well cleaned of everything , then it was magic as I suspect all the steels were quality engineering steels .

 That heavy old 1 " square shank cutter also helped I'm sure , for all my other cutting tips are on flimsy 1/2 " square shanks


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