Stamps and print
Check every face and both ends for a mill stamp, inkjet line or etched grade. On long bar it often repeats along the length, so a short drop may still carry part of it.
How we value · Unmarked stock · Solids only
How to identify unmarked metal drops
Every shop has a bin of drops nobody can name anymore. The marked end got cut off, the tag fell off, or two jobs got mixed. A few shop-floor checks can narrow a drop to a metal family. They usually can't give you the exact grade, and that difference decides whether a drop gets reviewed as reusable stock or sits in an ID hold.
Look before you test
The fastest ID is the one somebody already wrote down.
Tags and paperwork
Look for a bundle tag, a job traveler, a pack slip or the PO the stock came in on. A drop that matches a known job's material is a strong lead.
End paint
Painted ends help, but color codes differ from one supplier to the next. Treat paint as a clue that needs the supplier's own chart, not as proof of grade.
Shop-floor checks and their limits
Run them together. Each one rules things out more than it rules things in.
| Check | What it tells you | What it can't tell you | Tip |
|---|---|---|---|
| Magnet | Carbon and alloy steel, and 400-series and 17-4 PH stainless, pull hard. Aluminum, copper alloys, titanium and most austenitic stainless don't, or only barely. | 304 from 316, 6061 from 7075, or one steel grade from another. | Cold-worked 300-series can pull a little at cut edges. Test a flat face, not a burr. |
| Weight for size | Aluminum weighs about a third as much as steel for the same size. Titanium sits in between. Brass, bronze and copper feel heavier than steel. | Anything inside one family, like two aluminum alloys or two steels. | Weigh the drop, measure it, and compare against a density chart. It's quicker than it sounds. |
| Color and finish | Brass is yellow, copper is red, titanium is a duller gray than stainless, and aluminum scratches easily. | Grade. Plenty of different alloys look identical once they're machined. | Look at a fresh file mark, not the oxidized surface. |
| File test | Whether steel is soft or hardened. A file that skates instead of biting points to hardened stock. | Which tool steel it is, or how hard it actually is in numbers. | File a corner you don't care about. |
| Spark test | With practice and known reference pieces, it can separate low-carbon from high-carbon steel and flag titanium by its bright white sparks. | Exact grade. It won't tell 4140 from 4340. | Keep labeled reference pieces next to the grinder and compare side by side. |
These checks narrow the field so you don't mix families in the same tote. They are not an identification you can sell a grade on.
When a chemistry reading is worth it
An XRF reading helps when
- The drops look like specialty metal, like titanium, nickel alloys or tool steel, where getting the family wrong costs the most.
- The lot is big enough that one reading per group is worth the trouble.
- You need to split 304 from 316 or sort nickel alloys that look identical.
It still won't
- Read carbon reliably on a handheld gun, so steel grades that differ mainly in carbon stay uncertain.
- Give you a heat number or the mill's mechanical test results.
- Stand in for a cert on jobs that need traceable material. See mill certs.
Don't guess on the label
Unknown beats wrong
A drop marked "unknown steel, magnetic" is honest. A drop marked "4140" that turns out to be 1018 can ruin the next shop's job. Write down what you checked, not what you hope.
Keep families apart
Even if you can't name the grade, keep aluminum, stainless, steel, titanium and copper alloys in separate totes. One mystery piece can drag down a whole bin.
Mark it when you cut it
The cheapest fix is upstream. Paint-pen the grade on each drop at the saw, and cut from the unmarked end so the stamp stays on the bar.
How identity affects grading, from A to D and the ID hold, is on how we value. Unmarked titanium, nickel alloy and tool steel: specialty solids.
Unmarked drops FAQ
How can I tell what alloy an unmarked drop is?
Start with the cheap checks: look for any stamp, inkjet print or tag, try a magnet, weigh it against its size, and file a corner. Together they usually narrow a drop to a family, like aluminum, austenitic stainless, carbon or alloy steel, titanium or copper alloy. They rarely pin down the exact grade. For that you need chemistry from an XRF reading or the original mill cert.
Can a magnet tell 304 from 316 stainless?
No. Both are austenitic and read non-magnetic or only slightly magnetic, especially after cold work. What a magnet can do is separate them from magnetic stainless like 410, 416 or 17-4 PH, and from carbon and alloy steel. Telling 304 from 316 takes chemistry, because 316 carries molybdenum.
Is a spark test good enough to sell steel by grade?
Not on its own. A spark test on a grinder can help an experienced person separate low-carbon from high-carbon steel and flag titanium by its bright white sparks, but it needs known reference pieces and it cannot tell 4140 from 4340. Treat it as a sorting aid, not an identification.
Will you buy unmarked drops?
We review them. Unmarked, conflicting or uncertain material may get a lower offer, an ID hold until identity is clear, or a decline. We will not invent an alloy or grade. Send photos, sizes and anything you know about where the stock came from through the sell form or call/text 508-343-1219.
Does an XRF reading replace a mill cert?
No. A handheld XRF gun reads surface chemistry and can confirm a grade family, which can move an unmarked lot out of ID hold. It does not read carbon reliably, and it does not give you the heat number or the mill's mechanical test results, so it does not stand in for a cert on jobs that need traceability.