V-Belt Size Chart: How to Match Your Old Belt (A, B, M, SPZ, SPA, SPB) 三角帶尺寸對照
Replacing a V-belt starts with two questions: which section (the shape) and which length. This guide shows how to read your old belt and match it to a genuine Mitsuboshi belt (日本三星三角帶). All figures are from Mitsuboshi's V-belt design manual.
Step 1: read the markings
Most belts have letters and a number printed on the outside, such as A46 or SPZ 1000. The letters are the section. The number is the length. Classical belts (M, A, B) use inches. Narrow belts (SPZ, SPA, SPB) use millimetres.
Step 2: if the print has worn off, measure the top width
| Section | Type | Top width | Height |
|---|---|---|---|
| M | Classical | 10 mm | 6 mm |
| A | Classical | 13 mm | 9 mm |
| B | Classical | 17 mm | 11 mm |
| SPZ | Narrow | 9.7 mm | 8 mm |
| SPA | Narrow | 12.7 mm | 10 mm |
| SPB | Narrow | 16.3 mm | 13 mm |
Narrow belts are taller for their width than classical belts. An SPA belt (12.7 mm wide) looks close to an A belt (13 mm), but their grooves are different. Do not swap classical and narrow belts. Check the height as well as the width.
Step 3: understand the length number
- A and B belts: the number is the nominal length in inches, multiplied by 25.4 to get millimetres. A46 is 1168 mm and B52 is 1321 mm.
- M belts: the same inch system. M30 is 762 mm.
- SPZ, SPA, SPB: the number is the datum length in millimetres. The inside length is shorter than the datum length by 38 mm (SPZ), 45 mm (SPA) or 60 mm (SPB). The outside length is longer by 13, 18 or 22 mm.
Replacing belts on a multi-belt drive
Mitsuboshi standard V-belts are set-free: made to tight length tolerances so you don't need matched sets. You can replace one belt or all of them.
Old belt marked O-section?
O-section belts are about 10 mm wide, the same top width as the M section. The length numbers are on different systems, so send us the number on the old belt and we'll match the length.
Buy genuine Mitsuboshi in Fo Tan
Our Mitsuboshi belts are original products from the official channel, not the unbranded or fake belts common on online marketplaces. Shop by section:
- A-section, B-section and M-section classical V-belts
- SPZ, SPA and SPB narrow V-belts
- All Mitsuboshi belts we supply
Not sure what you have? WhatsApp us a photo of the old belt, or bring it to our shop, a 5-minute walk from Fo Tan MTR.
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