Metal quotes and certs are full of shorthand. Here are the terms small shops run into most, in plain language, grouped by where you will see them.
Quoting and ordering
RFQ
Request for quote. The list of material, sizes, quantities and requirements you send to get a price. Our RFQ guide shows what to put in one.
Lead time
The time between placing an order and the material being ready or delivered. For metal it depends on the material, the processing and where it is going.
Minimum order
The smallest order a supplier will accept, set by dollar value, weight or quantity. Small shops run into these often with large distributors.
Cut charge
A charge for cutting material to your size, often per cut. It covers setup and machine time, and it is separate from the material itself.
CWT
Hundredweight, meaning 100 pounds. Metal is often priced per CWT underneath, then converted to a price per piece or per foot on the quote.
Random length
Bar, tube or shapes supplied in lengths that vary within a range set by the producer, rather than one exact length. Fine when you are cutting parts from it anyway.
Cut length
Material cut to a specific length you order, within a stated tolerance, instead of a full or random length.
Full sheet
An uncut sheet in a standard size such as 48 x 96, 48 x 120 or 60 x 120 inches. Buying full sheets avoids cut charges if you can use the size.
Drop
The leftover piece after parts are cut from a bar, tube or plate. Drops can often be sold for less than new material if the size works.
Remnant
A leftover section of sheet or plate, usually irregular or odd-sized. Remnants are a good buy for small parts and one-offs.
Freight and delivery
FOB
Free on board. It names the point where ownership and risk pass from seller to buyer. FOB origin means at the shipping point; FOB destination means at your dock.
Freight prepaid
The seller pays the carrier. The cost may be built into the price or added to the invoice as a line, sometimes written prepaid and add.
Freight collect
The buyer pays the carrier directly, usually on delivery or through their own freight account.
Certs and traceability
Mill cert / MTR
A mill test report. It records the chemistry and tested mechanical properties of a specific heat of metal, tied to the material by heat number. See mill certs.
Heat number
An identifier for one batch of metal melted together. It is stamped or marked on the material and printed on the cert, which is what links the two.
Heat lot
Material that came from the same heat, and for heat-treated alloys often the same heat treatment batch. Traceable jobs may require all pieces from one heat lot.
ASTM
ASTM International, the body that publishes most of the material standards used in the US, such as A36, A500 and B209. The spec sets chemistry, properties and tolerances.
AMS
Aerospace Material Specifications, published by SAE. Aerospace and some defense work call for material to an AMS spec, which is stricter than the commercial equivalent.
Grades and specs
Temper
The condition of the metal from cold work or heat treatment, written after the alloy, as in 6061-T6 or 5052-H32. See the temper guide.
A36
The most common structural carbon steel spec for plate, shapes and bar, with a minimum yield of 36 ksi. See A36 steel.
A500
The ASTM spec for cold-formed structural tubing, round, square and rectangular. Most structural square and rectangular tube is A500 Grade B or C.
A513
The ASTM spec for electric-resistance-welded mechanical tubing. It holds tighter dimensions than A500 and is used for machined and precision parts rather than structure.
Pre-hard
Alloy steel, most often 4140, supplied already heat treated to a moderate hardness, roughly in the low 30s Rockwell C. You can machine it and skip heat treat. See 4140.
Stress relieved
Heated or stretched after processing to reduce internal stress, so the material moves less when you machine it. T651 aluminum plate is stretched for this reason.
Forms and processes
Hot rolled
Steel rolled at high temperature. It has a dark scale surface, looser tolerances and rounded edges, and it is the most economical form for structure and fabrication.
Cold rolled
Steel rolled further at room temperature after hot rolling. It is smoother, flatter, closer to size and a little stronger than hot rolled.
P&O
Pickled and oiled. Hot rolled steel with the scale removed in acid and a light oil applied to hold off rust. It paints and welds cleaner than plain hot rolled.
Galvanized / G90
Steel coated with zinc to resist rust. G90 is a coating weight of 0.90 ounces of zinc per square foot, total of both sides, and is common for outdoor sheet.
Cold finish
Bar that has been cold drawn or turned after hot rolling for a smooth surface and tight size. Cold finish bar like 1018 and 12L14 is the machine shop standard.
TGP
Turned, ground and polished. Round bar finished to a very close diameter and straightness, used for shafts and pins that go into bearings.
Extrusion
A shape made by pushing heated metal through a die, like squeezing toothpaste. Aluminum angle, channel, tube and custom profiles are usually extruded.
Pipe and tube
ERW
Electric resistance welded. Tube or pipe made by forming strip into a round and welding the seam. Most structural and mechanical tube is ERW.
DOM tube
Drawn over mandrel. ERW tube cold drawn over a mandrel for a uniform wall, tight tolerances and a clean inside. It covers most uses where people once specified seamless.
Seamless
Pipe or tube made from a pierced solid billet, with no weld seam. Called for in some pressure and high-temperature service.
NPS
Nominal pipe size. A name, not a measurement: 2 inch NPS pipe has an OD of 2.375 inches. From 14 inch NPS up, the OD matches the nominal size.
Schedule
The pipe wall thickness designation, such as Sch 10, 40 or 80. The actual wall for a schedule changes with pipe size, so always pair it with the NPS.
OD / ID
Outside diameter and inside diameter. Tube is usually ordered by OD and wall; pipe by NPS and schedule.
Wall
The thickness of a tube or pipe wall, given in inches, gauge or by schedule. OD minus twice the wall gives the ID.
Thickness, finish and protection
Gauge
A number system for sheet thickness where a higher number means thinner. The same gauge is a different thickness in steel, galvanized, stainless and aluminum. Check the gauge chart.
Sheet vs plate
Sheet is thin, plate is thick. In aluminum the line is usually 0.250 inch; in steel, material thicker than about 3/16 inch is generally called plate.
Mill finish
The surface as it comes from rolling or extruding, with no polishing or coating. Normal for material that will be painted, machined or hidden.
2B
The standard stainless sheet finish: cold rolled, annealed, pickled and given a light final pass. Smooth, moderately reflective and dull gray.
#4
A brushed stainless finish with fine directional grit lines. Used for appliances, kitchens and anything people see and touch. Grain direction matters on the order.
PVC film
A peel-off plastic film on finished stainless or aluminum sheet to protect it through cutting and forming. Laser-grade film is made to survive a laser cut.
Paper interleave
Paper placed between sheets to prevent scratching and water staining in transit. Common on aluminum and polished stainless.
Cutting and tolerances
Shear
A straight cut made with a blade, used on sheet and thinner plate. Fast, with no kerf loss, but it leaves a slight roll on one edge and a burr on the other.
Burn
A thermal cut by oxy-fuel, plasma or laser. "Burned" parts have a heat-affected edge that may need grinding before welding or bending.
Saw cut
A cut made with a band saw or cold saw. The usual way to cut bar, tube, shapes and thick plate to length. See saw cutting.
Kerf
The width of material removed by the cut. A saw or plasma kerf has to be allowed for when nesting parts from one piece.
Tolerance
How far a size can vary from what was ordered, written as plus or minus. Tighter tolerances usually mean a slower cut method and more cost.
Flatness
How far a sheet or plate deviates from a flat surface. Standard mill flatness is set by the ASTM spec; tighter flatness is a special request.
Camber
Edge curvature in the plane of a sheet, plate or bar, like a gentle banana shape when you sight down the edge. It matters on long pieces and slitted strip.
TIR
Total indicator reading. The total swing of a dial indicator as a round part turns. It measures runout and is used to specify straightness on shafting and TGP bar.