Walk into any plant that runs vibratory separators and you will find the same conversation in the maintenance shop: which wire cloth do we order this time? The wrong answer costs money in two directions. Order too heavy and throughput drops. Order too light and screens fail in days instead of months. The decision lives at the intersection of three industrial wire cloth grades — market grade, mill grade, and tensile bolting cloth — and most operators pick by habit rather than by spec.
This guide breaks down what actually distinguishes the three grades, what the published standards say, and how to choose for your application.
The Three Grades at a Glance
All three are typically woven as double-crimp square mesh and fall under ASTM E2016, Standard Specification for Industrial Woven Wire Cloth. ASTM E2016 covers the wire tolerances, mesh tolerances, and acceptance criteria for general-purpose industrial wire cloth used in particle separation. It explicitly does not cover testing-sieve cloth (that is ASTM E11), filter cloth, dutch weave, fourdrinier, hardware cloth, insect screening, spiral weave, or welded wire cloth — so be careful about cross-referencing those specs.
The three grades differ primarily in wire diameter. At any given mesh count, market grade uses the heaviest wire, tensile bolting cloth uses the thinnest, and mill grade falls in between. Wire diameter then drives everything else: opening size, open area percentage, weight, and wear life.
Market Grade
Market grade is the workhorse — the most common specification in industrial applications. Heavier wire, lower open area, longer life under abrasive load. Typical wire diameters in market grade run roughly:
- 12 mesh — 0.023" wire, 0.060" opening
- 20 mesh — 0.016" wire, 0.034" opening
- 100 mesh — 0.0045" wire, 0.0055" opening
Source: published market-grade specification tables compiled by industrial wire cloth suppliers. The pattern is clear — wire diameter is a substantial fraction of opening size, which is why open area lands lower than the other two grades.
Mill Grade
Mill grade sits in the middle. Wire is thinner than market grade but heavier than tensile bolting cloth. The grade exists because some applications need more open area than market grade delivers but cannot tolerate the wear life of TBC. Examples from published spec tables:
- 12 mesh — 0.018" wire, 0.065" opening
- 30 mesh — 0.0095" wire, 0.0238" opening
Compare that 12-mesh row to market grade: a smaller wire (0.018" vs 0.023") and a slightly larger opening (0.065" vs 0.060"). That delta is the entire point of mill grade — measurably more throughput at the same nominal mesh count, with a wire heavy enough to survive moderate-duty service.
Tensile Bolting Cloth (TBC)
Tensile bolting cloth is the lightweight, high-throughput specification. Per Newark Wire Cloth and CPI Wirecloth published data, TBC is produced in mesh counts from 16×16 through 230×230, with wire diameters ranging from 0.0090" at 16 mesh down to 0.0014" at 230 mesh. Open area on TBC sits in the 46–73% range across that span — substantially higher than mill or market grade at the same mesh count.
Standard material is 18-8 stainless steel (304/304L), with 316/316L, aluminum, copper, monel, hastelloy, and inconel available for corrosion or temperature-driven applications. The thinner wire is what makes TBC a "bolting" cloth — historically used for sifting flour and fine powders where every fraction of a percent of open area matters.
Open Area: Why It Matters More Than Mesh Count
Open area is the percentage of screen surface that is hole rather than wire. At a given mesh count, open area can swing dramatically depending on which grade you specify. The standard formula:
Open Area % = (Opening Size ÷ (Opening Size + Wire Diameter))² × 100
Plug in the numbers. A 30-mesh mill-grade screen with 0.0095" wire and 0.0238" opening lands near 51% open area. Move to TBC at the same nominal mesh count and you can pick up several percentage points by switching to a thinner wire. That sounds small until you remember that throughput on a vibratory screener scales roughly linearly with open area, so the difference between a 33% open screen and a 50% open screen is roughly a 1.5× capacity multiplier on the same machine.
That is why "specify by mesh count" is a beginner's mistake. Mesh count tells you how many openings per linear inch. It does not tell you how big those openings are or how much of the screen is open. Two 60-mesh screens can have meaningfully different cut points and capacity if one is woven in market grade and the other in TBC.
Wear Life: The Other Side of the Trade
The same wire diameter that hurts open area helps wear life. Heavier wire takes more abrasion, more flexure, and more impact before it fatigues and breaks. Industry guidance from multiple wire cloth suppliers is consistent: tensile bolting cloth handles higher volume, market grade lasts longer in service. Mill grade is the engineered compromise.
This is why you almost never see TBC in a hard-rock aggregate or high-abrasion mining application. The fines and angular particles will tear through the thin wire long before the cost-per-ton numbers work out. Conversely, you almost never see market grade in pharmaceutical or food sifting at fine mesh counts — the throughput penalty is too steep on free-flowing, non-abrasive product.
Material Selection: Beyond the Grade
Grade and material are independent decisions. Once you have picked a grade, you still need to specify the alloy:
- 304 / 304L stainless steel (18-8): Default for most industrial applications. Good corrosion resistance, food-contact suitable, widely stocked.
- 316 / 316L stainless steel: Higher chromium and added molybdenum for chloride and acid resistance. Standard for marine, pharma, and chemical applications.
- Hard-drawn carbon steel / T-430: Cheaper, magnetic, lower corrosion resistance. Used where economics dominate and the environment is dry.
- Monel, Hastelloy, Inconel: Specialty alloys for aggressive chemistry or high temperature. Expensive, long lead times.
How to Choose
Three questions, in order:
- How abrasive is the material? Hard-rock aggregate, frac sand, sintered ceramics, glass cullet — go market grade. Soft, free-flowing food powders, pharmaceutical excipients, plastic regrind — TBC is on the table.
- What is the throughput target? If you are running below capacity on the screener, mill grade or market grade is fine. If you are pushing the machine hard and capacity is the bottleneck, the open-area gain from TBC may pay for itself in shorter screen life.
- What is the cost-per-ton math? Calculate (screen cost ÷ tons screened before failure). The right grade is the one that minimizes that number for your specific feed. Not the cheapest screen. Not the longest-lasting screen. The one with the best ratio.
Common Mistakes
Specifying mesh count without grade. "Send me a 60-mesh screen" gets you whatever the supplier stocks. That may or may not match what was on the machine. Always specify grade.
Assuming finer mesh = better separation. If wire diameter grows faster than opening shrinks, you can buy a finer-mesh screen with worse separation efficiency. Look at open area and opening size, not just mesh count.
Treating wear life as fixed. Wear life is a function of feed, amplitude, frequency, tension, and grade together. Switching grade without revisiting screen tension and machine setup gives you a worse comparison than you think.
Using TBC where mill grade is needed. TBC's open-area advantage evaporates if it lasts a quarter as long. Run the cost-per-ton math.
FAQ
Is tensile bolting cloth the same as a "bolting cloth" used in flour milling?
The name comes from the historical use in flour bolting (sifting). Modern TBC is woven from stainless steel wire and used across food, pharma, chemical, and fine-particle industrial applications. The term is preserved by tradition.
What ASTM standard governs these grades?
ASTM E2016 covers industrial woven wire cloth, including double-crimp square mesh in all three grades. ASTM E11 covers testing-sieve cloth, which is a different specification with tighter tolerances. Do not cross-reference E11 numbers when ordering production screens.
Can I mix grades on a multi-deck screener?
Yes — and it is common. The top deck (scalping) often runs market grade for wear life, while the lower decks (finer separations) run mill grade or TBC for open area. Match each deck's grade to the loading on that deck, not to a single house standard.
Does the grade change for round separators vs rectangular vibratory screens?
The grade options are the same, but selection tendencies differ. Round separators in food, pharma, and chemical service lean toward TBC because the duty is gentler and capacity is the priority. Rectangular incline decks in aggregate and mining lean toward market grade for the same reasons in reverse.
How do I read the spec on a screen I already have?
The mesh count and wire diameter are usually stamped on the frame label or printed on the original packing slip. If those are gone, measure the wire diameter with calipers and count openings per linear inch — then match against a published mesh and wire sizing chart.
Will switching grades change my cut point?
Yes. A finer wire opens up the apertures even at the same nominal mesh count, so the d50 cut point shifts. If your specification is tight, validate the new screen with a sieve analysis before committing to a full replacement run.
The Bottom Line
Mesh count is a starting point, not an answer. Grade — market, mill, or tensile bolting cloth — is what determines whether your replacement screen will hit the throughput, the cut point, and the wear life you actually need. Specify the grade. Run the cost-per-ton math. And do not assume the screen you ordered last time is still the right answer if the feed, the rate, or the machine has changed.
Need Help Specifying?
ScreenerKing stocks round vibratory replacement screens in market grade, mill grade, and tensile bolting cloth across the full range of mesh counts and standard alloys. We also build custom screens when the standard catalog does not match your spec — see our mesh and wire sizing chart for the full grade and mesh range. If you are not sure which grade fits your application, send us your feed material, your machine, and your throughput target — we will work the math with you and quote what actually fits.
Contact ScreenerKing or call 866-265-1575.
Related Reading
304 vs 316 vs Duplex 2205: How to Pick the Right Stainless for Your Replacement Screens
Coil Springs vs Rubber Mounts: Vibration Isolation Selection for Round Separators
Market Grade vs Mill Grade vs Tensile Bolting Cloth: Choosing the Right Wire Mesh for Vibratory Screens
