Quick answer: a readable modular belt code has four fields: a series number that fixes the pitch and the sprocket family, a surface abbreviation such as FT, FG, PFT, RR or NT, a width figure, and suffixes for material and the bottom guide. Read in that order the string describes a physical belt. A string shaped like 0-9xx-xx-xxx-x is a different animal. It is a machine builder's material code, an accounting key inside one company's system, and nobody outside can turn it into a pitch.
Two kinds of number are in circulation
Every replacement enquiry carries a number of some kind, and the first job is working out which of the two you hold. They look alike on a purchase order and behave nothing alike.
| Belt specification code | Machine builder material code | |
|---|---|---|
| Shape | Digits plus letters: series, surface, width, suffix | Digit groups separated by dashes or dots, such as 0-9xx-xx-xxx-x |
| Who issued it | The belt maker | The company that built or bought the line |
| What it encodes | Geometry: pitch, surface, width, material | A purchasing record, a stock location |
| Decodable by a third party | Yes, field by field | No, at any price |
| Useful in an enquiry | Names the product | Lets your store find the record when the belt arrives |
Send both if your system exports both. We quote against the belt code and print the material code on the packing list so the goods land in the right bin. What we cannot do is reverse a material code, and any supplier who claims otherwise is guessing.
One quick test. Letter groups like FT, FG or RR mean a belt code. Digits only, in dashed or dotted groups, means an accounting key, so go and measure the belt instead. Series number plus surface style is covered in our note on modular belt naming conventions; this article takes the fields that note leaves out.
The series number fixes more than the pitch
The leading digits are the series. They set the pitch, the hinge geometry, the rod diameter and the sprocket tooth form, which is why a 900 flat top and a 900 flush grid run on the same drive shaft. Swapping surface inside one series is a stock decision. Swapping series is a project. Pitch alone will not get you to a single series, because the 25.4 mm family is crowded, so shortlist here and then separate the candidates by module thickness.
| Pitch | Straight running series | Radius series |
|---|---|---|
| 12.7 mm | 926 | |
| 15.24 mm | 1100 | |
| 19.05 mm | 5935 | |
| 25.4 mm | 966, 976, 986, 1000, 7200, 7705 | 916, 2400, 7100 |
| 27.2 mm | 900 | |
| 38.1 mm | 936, 4802 | |
| 46 mm | 300 | |
| 50.8 mm | 400, 956, OPB, battery plate | |
| 57.15 mm | 4809, 5997 |
The full range with strengths and open areas sits in the series index.
Surface letters
The letters after the series are the surface. Five abbreviations cover most of what arrives in enquiries, and each is a separate mould rather than a finish on a common module.
| Abbreviation | Surface | What it does | Open area in our range |
|---|---|---|---|
| FT | Flat top | Closed surface, contains crumbs and drips, supports small footprints | 0% |
| FG | Flush grid | Open lattice level with the surface, drains and lets air through | 7.7% to 37.7% depending on series |
| PFT | Perforated flat top | Closed surface with moulded holes, drains while still carrying small items | 7.7% to 31.7% |
| RR | Raised rib | Ribs above the hinge line so finger transfer plates can reach between them | 23.8% to 31.7% |
| NT | Nub top | Small nubs cut contact area for sticky or wet product | 0% to 25% |
Two points catch people out. Open area belongs to the series and the surface together, not to the surface alone, so an FG belt runs anywhere from 7.7% to 37.7% open in our own range. And RR changes thickness a lot: the 966 series is 9.5 mm as a flat top and 14.5 mm as a raised rib. If your code ends in RR, check frame clearance before you order.
Width notation, and why it lies to you
Width causes the most reordering. Modular belts are built by bricking modules across the frame, so a series is only made in steps, and the step is what the notation describes.
| Series | Width rule |
|---|---|
| 400 | Multiples of 50.8 mm |
| OPB | Multiples of 152.4 mm, increments of 16.9 mm |
| 7705 | Multiples of 76.2 mm, increments of 38.1 mm |
| 4809 and 5997 | From 304.8 mm, increments of 76.2 mm |
| 916 | Multiples of 152.4 mm |
| Battery plate | Multiples of 457.2 mm, increments of 25.4 mm |
| 900, 926, 936, 956, 966, 976, 986, 1000, 1100, 5935 and others | Custom widths on request |
Notice how many of those numbers are inches wearing millimetre clothing. 50.8 is 2 in, 76.2 is 3 in, 152.4 is 6 in, 304.8 is 12 in. A width printed in a code is a nominal figure derived from an inch dimension, so it will not match your caliper to the tenth of a millimetre. Send the width you measured and say that it is measured. We can work back to the nominal figure. We cannot work forwards from a nominal figure to a frame nobody has looked at.
Material suffixes
The material field is short and it moves belt strength by a factor of two or more. Our range is built in PP, PE and POM, and the same mould in a different material is a different product on paper.
| Material | Behaviour | Example from our range |
|---|---|---|
| PP (polypropylene) | The default. Good chemical resistance, light, lower strength | 986 series at 18,056 N/m |
| POM (acetal) | Stiffer, better wear and low temperature behaviour, higher strength | 986 series at 30,851 N/m |
| PE (polyethylene) | Low friction and low temperature work | Offered on 400, 956, 976, 1000, OPB and 5935 |
The gap is real. On the 1000 series the same 8.7 mm module reads 16,700 N/m in PP and 39,300 N/m in POM. Size a long centre distance from the wrong one and you are out by more than a safety factor.
Some makers spell the material out, some use a two or three letter grade suffix defined only inside their own catalogue, carrying colour and additive as well as base polymer. If your code ends in letters you cannot place, do not guess at the polymer. Tell us the line conditions instead: temperature, wash chemistry, rails or rollers. We will name the material from the duty, using the same comparison of PP, PE and POM that decides strength and chemical resistance.
The field almost nobody records
The last field of a belt code describes the underside. A belt can be moulded flat underneath, or with guide strips that run inside a slot in the conveyor frame. No shared notation for this exists across makers, which is exactly why it goes missing in transcription, and it is the field that decides whether the new belt tracks straight or walks off the sprockets in the first shift.
Do not try to recover it from the string. Turn a module over and photograph the back. That photo settles the field faster than any decoding exercise, and it shows whether the strips are single or double and where they sit across the width.
Reading a code end to end
Take a code of the shape 900 FG 1200 PP. The 900 gives 27.2 mm pitch and the 900 sprocket family. FG gives a flush grid at 31.7% open area and a 9 mm module. 1200 is a nominal width. PP sets belt strength at 17,500 N/m rather than the 40,300 N/m the same series reaches in POM. The underside is still missing. Four fields out of five come off the string, and the fifth comes off a photograph.
What to send with the enquiry
- Every number you hold, belt code and material code both, copied exactly including dashes
- One photo of the top surface and one of the underside of a module
- Measured belt width in millimetres, stated as measured rather than nominal
- Pitch measured across ten hinges and divided by ten, if the line can be opened
- Metres required and the number of belts
- What the belt carries, and the working temperature if the line runs hot or cold
Photographs move faster over WhatsApp than over email, and a ruler laid in the frame makes any photo worth several measurements. The contact form takes the same set. To browse by geometry rather than by code, the straight running modular belt range lists pitch, thickness and open area on every product page.
