Filter paper is the roll medium in belt, gravity and vacuum filters that clean coolants and process fluids in metalworking. We stock 7 series in viscose, polyester and polypropylene — 39 variants from 20 to 400 g/m², in standard widths from 0.39 to 1.0 m.
Most people start with the filtration grade ("I need something fine"). That is the last thing to lock in, not the first:
1. The system. Gravity filter systems let the fluid run through under its own weight — too dense a medium causes backflow and floods the belt. Vacuum systems pull the fluid through and can handle denser media and thus finer filtration.
2. The fluid. Standard fluid → viscose or polyester. Aggressive chemistry (acids, alkalis, solvents) → polypropylene.
3. The job. Only now come grade and weight — coarse for turning and drilling, fine for grinding, honing and lapping.
Choosing too fine "to be on the safe side". A denser paper than the job requires means a higher pressure drop, more frequent changes and poorer fluid flow. Finer is not better — the right grade is better.
Keeping the same paper when the process changes. If the machine switches from coarse turning to fine grinding, the requirement changes. Review the paper choice when the process moves.
If in doubt, the label on your current roll is the shortcut: it usually carries weight, material and dimensions. Send a photo of it and we will match the paper.
| Filtration grade | Typical processes | Gravity systems | Vacuum systems |
|---|---|---|---|
| Coarse (~150–200 µm) | Turning, drilling, milling, coarse wire drawing | UTV 20 · UTN 40 K1 | UTP 40 |
| Medium (~100–150 µm) | Drilling, milling, grinding, medium wire drawing | UTV 35 · UTV 50 · UTN 60 K1 · UTN 80 HF · UFusion 70 · UJet 70 | UTP 50 · UTP 70 · UTN 80 HF · UJet 70 · UFusion 70 |
| Fine (~50–100 µm) | Grinding, honing, lapping, fine wire drawing | UTV 60 · UTN 130 HF · UJet 100 · UFusion 100 · UTN 150 K1 | UPP 70 · UJet 100 · UTN 130 HF · UTN 150 K1 · UFusion 100 |
Belt filter paper is a depth-type medium: particles are captured inside the fibre structure, not only on the surface. And the particles already held in the medium help capture new ones — the so-called filter cake effect. A paper that is indexed too often therefore wastes both paper and money: the feed should be set to the actual load, not to habit.
The programme covers the three main materials — viscose, polyester and polypropylene — in five production methods. A full datasheet exists for every single weight.
Viscose, acrylic-binder bonded · 20–60 g/m²
Soft, dimensionally stable filter medium for coarse and medium filtration in both gravity and vacuum filter systems. The economical standard choice for common coolants.
Turning · Drilling · Milling · Wire drawing (coarse/medium)
Polyester spunbond, thermally bonded · 20–100 g/m²
Good dimensional stability and chemical resistance. A versatile series for medium and fine filtration — the broad choice for vacuum filter systems.
Drilling · Milling · Grinding · Vacuum filtration
Polyester spunbond, high density · 30–70 g/m²
Dense polyester spunbond for fine filtration. Low air permeability and small pore size give efficient particle capture in precision machining.
Grinding · Honing · Lapping · Fine wire drawing
Polyester, needle punched · 40–400 g/m²
Needle-punched polyester with a three-dimensional fibre structure. High load capacity and the widest weight range in the programme. Variants: K1 (standard fibre) and HF (finer fibre for finer filtration at the same weight).
Turning · Drilling · Milling · Grinding · Honing
Polyester spunlace (hydroentangled) · 50–150 g/m²
Produced by hydroentangling: a uniform, stable fibre structure with good filtration properties in both gravity and vacuum filter systems.
Grinding · Honing · Milling · Precision machining
Polyester, graded fibre structure (BICO fibre core) · 40–100 g/m²
Three-layer filter medium with a progressive fibre structure: coarse particles are captured in the open layers, fine ones in the dense layers. That increases capacity and extends service life — often with lower paper consumption than a single-layer medium for the same job.
Grinding · Honing · Lapping · Precision machining
Polypropylene spunbond, thermally bonded · 20–70 g/m²
High chemical resistance to acids, alkalis and organic solvents. The right choice for aggressive cutting fluids and special applications where viscose and polyester do not hold up.
Drilling · Milling · Grinding · Aggressive process fluids
Measured to DIN EN 29073 (weight, thickness, tensile strength, elongation) and EN ISO 9237 (air permeability). Pore size is stated as Bubblepoint/Meanflow.
| Variant | Weight g/m² | Thickness mm | Tensile strength N/5cm (MD/CD) | Elongation % (MD/CD) | Air permeability L/m²/s | Pore size µm (BP/MF) |
|---|---|---|---|---|---|---|
| UTV 20 | 20 | 0.19 | 45/8 | 4/25 | 5,700 | 190/85 |
| UTV 25 | 25 | 0.20 | 50/9 | 4/26 | 5,400 | 185/75 |
| UTV 30 | 30 | 0.23 | 75/9 | 8/35 | 5,000 | 125/70 |
| UTV 35 | 35 | 0.27 | 65/12 | 5/28 | 4,400 | 120/60 |
| UTV 40 | 40 | 0.33 | 95/10 | 7/32 | 3,500 | 120/60 |
| UTV 50 | 50 | 0.38 | 100/14 | 7/35 | 3,000 | 100/55 |
| UTV 60 | 60 | 0.45 | 120/17 | 7/38 | 2,500 | 95/50 |
| UTP 20 | 20 | 0.16 | 41/34 | 20/23 | 8,000 | 200/110 |
| UTP 30 | 30 | 0.15 | 70/60 | 20/20 | 6,000 | 190/100 |
| UTP 40 | 40 | 0.16 | 110/90 | 20/20 | 4,200 | 180/100 |
| UTP 50 | 50 | 0.18 | 140/120 | 20/20 | 3,300 | 150/70 |
| UTP 60 | 60 | 0.21 | 175/140 | 20/20 | 2,700 | 120/60 |
| UTP 70 | 70 | 0.30 | 170/130 | 20/20 | 3,400 | 140/70 |
| UTP 80 | 80 | 0.26 | 230/200 | 20/20 | 1,600 | 75/45 |
| UTP 100 | 100 | 0.32 | 280/260 | 20/20 | 1,300 | 60/45 |
| UTH 30 | 30 | 0.30 | 55/55 | 20/20 | 4,200 | 180/95 |
| UTH 50 P | 50 | 0.48 | 105/65 | 34/33 | 1,900 | 65/45 |
| UTH 70 P | 70 | 0.40 | 160/130 | 35/40 | 1,300 | 55/35 |
| UTN 40 K1 | 40 | 0.51 | 45/60 | 40/50 | 4,800 | 164/70 |
| UTN 60 K1 | 60 | 0.82 | 75/120 | 45/75 | 4,100 | 128/65 |
| UTN 80 HF | 80 | 0.88 | 125/130 | 40/75 | 3,500 | 105/65 |
| UTN 100 | 100 | 0.90 | 220/210 | 32/71 | 2,500 | 95/55 |
| UTN 130 HF | 110 | 1.14 | 130/170 | 50/95 | 3,000 | 105/54 |
| UTN 150 K1 | 150 | 1.10 | 330/340 | 45/55 | 1,700 | 89/50 |
| UTN 300 | 300 | 1.80 | 604/858 | 55/60 | 540 | 65/40 |
| UTN 400 | 400 | 2.30 | 900/900 | 45/65 | 320 | 55/30 |
| UJet 50 | 50 | 0.70 | 90/95 | 23/60 | 5,200 | 145/75 |
| UJet 70 | 70 | 0.80 | 99/60 | 23/60 | 4,400 | 110/70 |
| UJet 100 | 100 | 1.06 | 190/130 | 33/62 | 3,150 | 100/60 |
| UJet 150 | 150 | 1.31 | 370/360 | 45/75 | 2,000 | 95/54 |
| UFusion 40 | 40 | 0.45 | 90/75 | 25/25 | 5,700 | 190/80 |
| UFusion 70 | 70 | 0.85 | 170/150 | 35/30 | 4,200 | 165/60 |
| UFusion 100 | 100 | 1.12 | 250/220 | 35/30 | 3,200 | 95/55 |
| UPP 20 | 20 | 0.19 | 31/20 | 35/40 | >5,000 | 230/100 |
| UPP 30 | 30 | 0.25 | 75/40 | 80/90 | 3,500 | 140/70 |
| UPP 40 | 40 | 0.35 | 80/50 | 45/55 | 2,500 | 90/50 |
| UPP 50 | 50 | 0.37 | 120/70 | 80/90 | 1,800 | 100/55 |
| UPP 70 DP | 68 | 0.35 | 200/150 | 35/35 | 3,900 | 200/120 |
| UPP 70 | 70 | 0.45 | 150/100 | 90/100 | 1,300 | 95/60 |
The weight in g/m² is the weight of the medium per square metre and correlates with thickness and density. Higher weight typically means finer filtration and longer service life, but also a higher pressure drop. Our series cover 20–400 g/m² — the choice is always a balance between cleanliness, flow and price.
With the right paper, a standard paper bed filter typically retains particles down to around 5 microns. If you need to go lower, for example in fine grinding or lapping, it takes special media or supplementary filtration.
Grinding typically calls for fine filtration (~50–100 µm). On gravity systems that is often UTV 60, UTN 130 HF, UJet 100 or UFusion 100. On vacuum systems often UPP 70, UJet 100 or UTN 130 HF. The final choice depends on the fluid and the surface requirements.
Viscose is often the economical choice for ordinary jobs. Polyester has greater strength and chemical resistance and is used where the medium is heavily loaded. Polypropylene withstands acids, alkalis and organic solvents and is chosen for aggressive cutting fluids. The material is decided by fluid type, temperature and load.
Some series work in both system types, but not all weights are optimal in both. Vacuum systems pull the fluid through and can handle denser media, while gravity systems depend on the fluid flowing freely. Choose the weight to match the system, not just the filtration grade.
The particles already held in the medium help capture new ones — the so-called filter cake effect. A paper that is indexed too often is therefore not necessarily an advantage: it is about finding the right balance for your particular system.
Yes, usually. Belt filter paper is not tied to the machine brand — what matters is dimensions, material and weight. Many save money by switching from the original brand to an equivalent. Send us the data of your current paper and we will match it.
Both are needle-punched polyester in the UTN series. K1 is the standard fibre; HF is a finer fibre that gives finer filtration at the same weight. Choose HF when you need to capture smaller particles without going up in weight.
The width has to match your machine. We stock standard widths from 0.39 to 1.0 m; widths above 1 m are made to order. Send the machine type or the dimensions and we will find the right roll — width, length and core diameter.
Cleaner fluid means slower degradation of the emulsion, fewer bacteria problems and less wear on pumps and tools. The right paper therefore often pays for itself on fluid economy alone.
A filter list, a specification or a photo of the label on your current roll is enough. We compare it with the 7 series and come back with a recommendation and a price.
Or write to sales@unionoiltech.com