Metal identification and/or coating

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Metal Mickey

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Hello all, I was given a few bars of metal (see photo) and I don't know what to make of them. Do you?

millspiston008.jpg


At first thought, bearing in mind they are quite heavy, I was worried if they would machine up. However when building up courage, I faced off one bar and was pleasantly surprised at how easy it was machining.

millspiston007.jpg


So I am left with the question what is the coating, and is it Steel? and if really lucky.....what grade?

Anyway over to you..........
 
Hi Mike,

Are there any rust spots at all? Does a magnet stick to it?

Not infallible, but if the answer to both is no, then it could be stainless. Both are very quick checks for stainless steel.

Just looking at it, and as you say it machines OK, it could just be BMS (bright mild steel). If it machines very smoothly, it could be EN1a, a free cutting mild steel with a fair amount of lead in it.

It is almost impossible to detect exactly what it is without proper analysis. You can do a spark test with a grinder that might put you somewhere close.

Now ask yourself a couple of questions. Was it cheap or free? Can you machine it?

If the answer to both is yes, then why worry, just use it. For what we are making here it should do just fine. The purists will scream a little, but they will get over their passion for quoting numbers and letters, eventually.

If you were building a high stress crank, camshaft or something to be hardened, then you would purchase your specialised metal from a reputable metal supplier.

Otherwise just enjoy it.

John
 
From the photo it looks to me very like a zinc plated and passivated (ZPP) coating on a more-or-less mild steel.

reasons for thinking this:
The range of colours are what ZPP fades to after a few years, there also seems to be a slight white dusting, which would be zinc oxide.
ZPP is a minimum corrosion-resistant coating on parts which would otherwise corrode, so the base material is probably a low alloy steel

If the base metal is magnetic, and machines OK, it probably is Mild Steel - almost certainly free-cutting since these seem to be spindles of some sort with clip grooves at each end.

If you have pickling acid try dipping one end of one in it - ZPP will dissolve off leaving the base metal to be seen.

(The older corrosion treatment was cadmium plating and passivating - this is now considered very hazardous, but these are not Cad plated from what I can see. Cad plate has a glorious golden colour and does not form a white sheen - its also a much better protection so they would not be so varied and tarnished)

Sorry to ramble on when I usually just lurk
andrew

 
Don't want to "Tell my grandmother how to suck egs" BUT I would not face or turn with that much
length to diameter ratio protruding from the chuck.
FWIW.
...lew...
 
Are they magnetic?
Yup they are so I guess its BMS and suggested.
andrewh said:
From the photo it looks to me very like a zinc plated and passivated (ZPP) coating on a more-or-less mild steel.

reasons for thinking this:
The range of colours are what ZPP fades to after a few years, there also seems to be a slight white dusting, which would be zinc oxide.
ZPP is a minimum corrosion-resistant coating on parts which would otherwise corrode, so the base material is probably a low alloy steel

If the base metal is magnetic, and machines OK, it probably is Mild Steel - almost certainly free-cutting since these seem to be spindles of some sort with clip grooves at each end.

If you have pickling acid try dipping one end of one in it - ZPP will dissolve off leaving the base metal to be seen.

(The older corrosion treatment was cadmium plating and passivating - this is now considered very hazardous, but these are not Cad plated from what I can see. Cad plate has a glorious golden colour and does not form a white sheen - its also a much better protection so they would not be so varied and tarnished)

Sorry to ramble on when I usually just lurk
andrew


Thanks Andrew a very full answer for which I am gratefull
 
Lew Hartswick said:
Don't want to "Tell my grandmother how to suck egs" BUT I would not face or turn with that much
length to diameter ratio protruding from the chuck.
FWIW.
...lew...

I was just testing its machining ability rather than any project where any finish or tolerance is required. They are quite substantial bars and it seemed OK BUT I am here to learn, what have I one wrong? It seemed to turn OK to me so any guidance is appreciated. Mike
 
They are quite substantial bars and it seemed OK BUT I am here to learn, what have I one wrong? It seemed to turn OK to me so any guidance is appreciated. Mike

Mike you did not really do anything wrong since you and your machine are not damaged in any way.
excessive stick out can cause problems whether it is a turning /facing tool ,boring bar, or stock in the chuck .
The general rule of thumb for most materials is 2 1/2 times the diameter or tool size so a 1/2 inch diameter piece of stock should not stick out more than about 1 1/4 inches. Also be careful with stick out on the head stock a thin piece can bend, whip around and damage something like say a antique oak tool box for instance DAMHIKT .
With excessive stick out in the chuck if a piece bends it may catch the tool and grab. Then things happen so fast you can not stop quick enough.
The safe amount of stick out will vary with setup tooling material etc in most cases a stick out of 4-5 times the diameter will not cause problems but the 2 1/2 rule will keep you safe. when in doubt support on centers and/or with a steady rest or follow rest.
hope this helps
Tin
 
Many thanks, thats the sort of info that gets missed when your self taught.
 
They are quite substantial bars and it seemed OK BUT I am here to learn

at the risk of flogging the ailing horse, and beyond the safety issues Tin covered well, there are some basic engineering reasons for minimizing overhang in any setup - understanding this will make setups more intuitive.

When you cut metal, you are imposing force. force causes deflection. A fly landing on the tailstock imposes a force and twists the bed - not that we can measure or that would matter, but whenever a force is applied, deflection results. All steels have very close to the same module of elasticity - they will all deflect about the same under a force, so it doesn't matter what steel you are using. It also doesn;t matter dia (its the ratio that matters) - take a 2" dia piece with a foot sticking out of the chuck, put an indicator on it and lean on it. Then tell the missus you're so buff you can bend 2" dia bars. Point being, don't think of metal as rigid thing fixed in shape - its moving all over the place, albeit in small amounts, as forces are applied/removed

We want to minimize deflection and this is why you'll keep hearing people talk about rigidity and solid set ups. If the set up allows too much deflection it will be tough to maintain dimension accuracy and chatter will creep in. Its good practice to always keep set ups as strong as possible which means, among other tings, minimizing overhang. granted you weren't holding a dimension, but those, along with safety, are why its ingrained in us to do so
 
Mcgyver said:
at the risk of flogging the ailing horse, and beyond the safety issues Tin covered well, there are some basic engineering reasons for minimizing overhang in any setup - understanding this will make setups more intuitive.

When you cut metal, you are imposing force. force causes deflection. A fly landing on the tailstock imposes a force and twists the bed - not that we can measure or that would matter, but whenever a force is applied, deflection results. All steels have very close to the same module of elasticity - they will all deflect about the same under a force, so it doesn't matter what steel you are using. It also doesn;t matter dia (its the ratio that matters) - take a 2" dia piece with a foot sticking out of the chuck, put an indicator on it and lean on it. Then tell the missus you're so buff you can bend 2" dia bars. Point being, don't think of metal as rigid thing fixed in shape - its moving all over the place, albeit in small amounts, as forces are applied/removed

We want to minimize deflection and this is why you'll keep hearing people talk about rigidity and solid set ups. If the set up allows too much deflection it will be tough to maintain dimension accuracy and chatter will creep in. Its good practice to always keep set ups as strong as possible which means, among other tings, minimizing overhang. granted you weren't holding a dimension, but those, along with safety, are why its ingrained in us to do so

Many many thanks. I found that most informative.
 
Yes like McGiver said a lot of forces in various directions are applied when machining. For the sake of safety and quality we need to keep the amount of material and tooling that is not supported to a minimum. Also the speed and feed that is selected will influence quality and safety. A light cut will apply less force than a heavy cut. Also forces increase with tool wear tool wear increases with heavier feeds and speeds. Tis all related. A light hobby machine will have more flex than a sturdier commercial grade machine like a monarch.
In a money making shop the goal is to remove the most material in the least amount of time and keep quality/ finish and size to spec. But excesive tool wear wastes time with tool grinding or changes so it is all a bit of a find the happy medium trade off.
Tin
 
I learned this (again) this week when I needed to apply 4" of knurling on a 10.5" length of 1" round Al rod. The knurling tool applies a lot of lateral pressure. My first try I had the entire length between the chuck and the tailstock, and the force caused the center-drilled hole to warp a bit, messing up my knurls.

On a do-over, I chucked only about 4.5" and had much better results.
 
kvom said:
I learned this (again) this week when I needed to apply 4" of knurling on a 10.5" length of 1" round Al rod. The knurling tool applies a lot of lateral pressure. My first try I had the entire length between the chuck and the tailstock, and the force caused the center-drilled hole to warp a bit, messing up my knurls.

On a do-over, I chucked only about 4.5" and had much better results.

Haven't been well enough to do much in the workshop but did get to try turning a bar of aluminum just to face off and take a light skim. I remember now why I USED to leave so much out.....working near the chuck is a little disconcerting but I will use the system as the logic is beyond question. Its interesting to see your experience re messing up your knurls. I don't suppose supporting with a steady would work because of the pattern damage?
 

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