Recovering scrap for usable material.

[freeclimbmtb]

Good morning all, I am involved with a local makerspace, specifically I have been leading the buildout of a dedicated machine shop within the space with our grand opening scheduled in the next few weeks. The space provides the community with access to manual machines (as well as a Sharp CNC knee mill) and the experience of a few local machine shop owners that provide oversight and some classes.

With our opening approaching I am on the hunt for stock to help members get started with projects, I plan to ask a few local shops to donate scrap, drops, and otherwise unused material.

Now for the real question. I have a small pile of car parts like axle shafts, and HD sway bars etc. While probably not especially usable as is due to heat treating, is it worth approaching a local heat treater about annealing or normalizing these parts so they could be available as bar stock for folks to use? Knowing full well that the specific grade of steel is not known, but if the machinability could be improved, they could be helpful to folks for practice or even non-critical projects.

Thanks in advance.

 

[M.B. Naegle]

I can't see it being viable to even consider universally annealing random scrap metal as it's not always necessary for what is being made, and sometimes the annealing process will warp or otherwise change a materials properties. Not to mention, half of the scrap getting annealed might never be useful anyway. How you anneal something often depends on what kind of material it is and how hard it is to begin with. It would be much better it keep an oven on site and let the 'makers' learn to anneal and heat treat their own stuff.

We have ovens in our shop and it totally changes the way you do things for the better. I think many shops see ovens as a pre or post op thing that's easy to farm out, but in reality heat treating metals is often an op that needs to be closely tied to the other ops. You sometimes have to fixture parts so they don't move and always have to measure and test pieces before and after heat treating to see what your next step will be.

Nothing is truly "free" and it might be good for the makers to learn that if they want to repurpose something, they'll need to invest the time and resources to do so... or just let the melting pot do the annealing and buy some material that's exactly what they need.

 

[bigjon61]

I've never really understood the whole "makers space" thing. I know how shared machinery turned out in HS/College, and there is no way equipment in such spaces wouldn't turn out the exact same. Where does the funding come from? What incentives are there to area businesses to donate raw materials and tooling? It seems counterproductive for businesses to do such a thing. "Here, let me donate the tools and the materials to make your parts, rather than me charging you $90/hr to make your parts." I don't think I can even print at the local library without being charged $.25 a sheet of paper, and that is funded with MY TAX dollars.

 

[freeclimbmtb]

All good points. An oven may be in our future, though not in the short term. In the makerspace world (at least in this one), repurposing is 90% of what these folks are looking to do. I'm sure there will be a project or two where someone will buy a 2"x24" piece of 4140, but for nearly everyone else its going to be either a piece of CR out of the bulk metals rack at tractor supply, or whatever they find that technically qualifies as "steel".

 

[freeclimbmtb]

I've never really understood the whole "makers space" thing. I know how shared machinery turned out in HS/College, and there is no way equipment in such spaces wouldn't turn out the exact same. Where does the funding come from? What incentives are there to area businesses to donate raw materials and tooling? It seems counterproductive for businesses to do such a thing. "Here, let me donate the tools and the materials to make your parts, rather than me charging you $90/hr to make your parts." I don't think I can even print at the local library without being charged $.25 a sheet of paper, and that is funded with MY TAX dollars.

In this case, the shops are monitored by camera, and access controlled with RFID. In order to use a machine, you have to have that machine enabled on your fob and have taken some base training on its care an operation. Funding comes from local business that have an interest in giving back to the community, from members that may have an interest and some money to donate, but not the space to set up a shop of their own. My area hasn't had a trade school in decades, so for some people that might be interested in a trade, it also provides them the opportunity to learn a new skill.

And as for why businesses would donate material, here's an example:
A piece of 3"x4"x12" 6061T6 bar from onlinemetals.com is $141 at 14.1lbs, or $10/lb. The scrap price of aluminum is what? $0.80/lb on the high end? So you can either take your scrap bin and get $0.80/lb for it, or you could donate it to a 501(c)(3) tax exempt company and then write off the value of it at what you paid...$10/lb. (Before you say it, this is an example, I'm not saying I'm going to find a shop to give me a perfectly usable slab of 6061.)

 

[reboots]

Find your local scrap metal recycler, and ask if you can pick through their steel and aluminum. Occasionally very nice stock material at per-pound prices. They might trade for e-waste, which tends to accumulate at makerspaces.

 

[HWooldridge]

The amount of work you put in to recover a usable piece of scrap material for machining purposes will be several times higher than the cost to buy new bar stock of a known grade/alloy, although bar drops might be useful if the CoC pedigree is available.

Scrap recovery seems to work better for blacksmithing and fab work where the material properties may not be as important. A blacksmith can cut off a piece of axle and immediately forge it into a set tool or cutoff hardy that will work just fine for the intended purpose, but annealing that same piece of axle for machining purposes can be an exercise in frustration, unless you have low expectations for the final results.

 

[freeclimbmtb]

The amount of work you put in to recover a usable piece of scrap material for machining purposes will be several times higher than the cost to buy new bar stock of a known grade/alloy, although bar drops might be useful if the CoC pedigree is available.

Scrap recovery seems to work better for blacksmithing and fab work where the material properties may not be as important. A blacksmith can cut off a piece of axle and immediately forge it into a set tool or cutoff hardy that will work just fine for the intended purpose, but annealing that same piece of axle for machining purposes can be an exercise in frustration, unless you have low expectations for the final results.

That's very helpful, we have a few members that do some smithing work, I'll set that material aside for them. They already have a horde of saw blades and leaf springs that they use for knife projects.

 

[Doozer]

A buildout ?

Re-using scrap metal after having it annealed ?
Like buying used underwear at the Goodwill
and washing it out, and being OK with it.
Never!

-D

 

[freeclimbmtb]

A buildout ?

-D

In the space's infancy we had a combined metal/machine shop. This was effectively a welding/fabrication room with an old and tired Bridgeport and lathe in the corner. The machines were in poor condition to begin with, and this was compounded by the welding and grinding grit in the room. As interest grew in a better equipped and cared for dedicated machine shop, I led the effort to convert warehouse space in the building by erecting partition walls and having twist lock drops and lighting installed to support the machine tools. With this we received grant money and donations to purchase a near-new condition Bridgeport, surface grinder, and one of our members donated the Sharp CNC knee mill. We are still on the hunt for a replacement for the 103 year old SB 14.5 lathe.

 

[M.B. Naegle]

To be fare, lots of machinists and fabricators repurpose material, but it's not common as a business endeavor. IOW, if you were quoting a job, you would quote new stock and not hope you had something in the pile to fit the bill. On the other hand, if you were making something like a tool or fixture in house, IMO scrap and drops is often preferred so it doesn't throw off inventory and often you can save time not having to carve out the thing from a solid. Kitchen staff don't mind eating leftovers out of Tupperware, but wouldn't send it out to the dining area.

It sounds to me like this is a bit of a grey area because most of these makers are not producing marketed parts and would prefer scraps, but with how your makerspace markets itself it might get hard to quantify things. Other spaces I know of will sell time on machines and you have to bring your own materials, because that keeps things fare and easy to bill. Even if there was someone like a high school shop teacher to play referee, I would think it would be hard to dance that line between educational, hobby, and job shop and keep everyone happy. Someone might be doing a job educationally, but does the makerspace see it that way on their own books? Even in my own business's shop, the side jobs that friends and family bring in are be far most frustrating activities that go on in the shop.

However you do it, IMO you have to see all materials processing as an operation (cleaning sandblasting, saw cutting, annealing, etc.) and if it's a communal pile of material, it's best to hold all that work until there's more details about the individual jobs the material is getting used on.

 

[henrya]

OP could probably search this forum for unknown mystery scrap metal projects gone bad and why they went bad. While I will admit to doing it from time to time, I will also say that I stay away from obvious screwups based on my having learned the hard way. And if it matters even a bit, I always buy new suitable material.

Some people learn by other’s experience and those can be helped with a few stories about wasted time and money from fooling with unsuitable scrap.

Simple things like “no you can’t make a nice high strength wheel spindle for your kids go kart from that foot long piece of rebar”.

What finally got me was a gift of a 4.5” round bar of aluminum about a foot and a half long. I had hit the jack pot for making adapter rings for big camera lenses. After half an hour I learned that nothing could make a nice finish on this crap and no way to cut a fine thread in it. No more useful than a rock.

 

[MrStretch]

Seems to me that random scrap could lead to lots of frustration, especially for beginners. How does one learn if you don't know what material you are using?
Is it normal for these kinds of places to supply all the material? I suppose you could cause people to want to bring their own by providing mystery metal.

 

[tdmidget]

Seems to me that random scrap could lead to lots of frustration, especially for beginners. How does one learn if you don't know what material you are using?
Is it normal for these kinds of places to supply all the material? I suppose you could cause people to want to bring their own by providing mystery metal.

Shouldn't one of the first lessons be to use the appropriate material?

 

[john.k]

I always save certain bits from trucks ,as when you need a bit of HT steel ,a few cents is a lot better than $100 from a steel supplier.

 

[john.k]

From two speed Eaton diffs .........save the four bronze planetary pins .......the four pins equal length to a bit of bronze that cost $200+ ,and big Eatons #4&#5 the pins are around 2" dia ,total length maybe 24"..........see what a bronze bar that size costs.

 

[john.k]

RWD axles ,sway bars ,torsion bars ,leaf springs,heavy coil springs .....save !

 

[jccaclimber]

Some maker spaces are non-profits. I've seen at least one machine shop use donated material as a tax write-off. Another charged for it at a price above scrap but below new cost. If you have a lot of drops you want gone it's convenient and they paid in cash.

Having the general population have slightly more machining knowledge/experience isn't a bad thing for shops. If nothing else it's a place to tell the inventor types to go when they come knocking.
Is it an 8 year apprenticeship? No, but nobody else seems to be exposing genpop to this sort of thing.

As for the OP, no, it's not cost effective. Leave it as a pile of scrap in the corner, maybe teach people to try to file stuff before they use it so they don't break new tools on hard stuff, assuming you're using carbide and not HSS.

I've repurposed a decent amount of stuff, but generally it's soft steel for times I need something to be not aluminum and don't really care past that. For a lot of maker projects where there isn't any real engineering to begin with and people are just experimenting at QTY=1 this is fine.

 

[Doozer]

Hearing about living the poor scavenger lifestyle is so annoying.
I have been known to dumpster dive things of value too,
but I do not go on an on about a hunk of brass that can be had
deep in some assembly to get it. And the blacksmith and knife
makers are the worst. They have piles of springs and axle
shafts and their shop looks like a scrap yard. When they die
it all will go in the dumpster their kids rent to cart it all away.
I have unknown steel pieces for non critical shop and home
projects. Yes for sure. But there is a limit before your shop
becomes a junk pile. More and more I find myself working
on projects that need to be out of some steel more durable
than 1018 or A36 soft as soft can be steel. If I am making
a shaft for a transmission or to fix a machine, it usually has
to be half hard Rc20 to 40, or full hard Rc 50 or 60. This
means 4140, 1144, A2, O1, 8620, you get it. Something
hard or that can be hardened. I even have Wilson Rockwell
C scale and N scale testers to verify heat treat before final
hard turning or grind. You just have to buy the material
you need to be sure of the specs. No way around it.
But to re-process axles or a shaft from the junkyard,
even for a maker space of non critical projects, is really
a bunch of messing around. It may put off the new people
from machining for all the fuss it involves. But you do you.
I just have my view of things that seems to be practical.
You may have different experiences. Best of luck.

-Doozer