The manual is gone, the label has worn off, and the old belt is in shreds. You can still find the size: from what is printed on the old one, by measuring it, or for a bandsaw blade by working the length out from the machine. Each gives a figure to compare with the sizes actually sold, not a size to order on its own.
Look for a printed size first.
Most sanding belts have their size and grit printed on the back. Bandsaw blades usually come with a tag or a box label that gives the length, width and teeth per inch. The manufacturer’s figure for your machine is better than any measurement, so look up your machine before you reach for the tape. If it is documented here, you’re done.
Measuring a sanding belt.
- Width. Lay the belt flat and measure straight across, from edge to edge.
- Length, quick check. Flatten the belt on a bench so it folds at both ends, measure from fold to fold and double the figure.
- Length, a better figure. Draw a line across the back of the belt. Starting at the line, run a flexible tape along the back all the way round until you reach the line again.
- Match it to a real size. Expect your figure to be a few millimetres out. Compare it with the sizes on our size pages, then choose the one documented for your machine, which is not always the nearest number.
Measuring a bandsaw blade.
- A broken blade. Straighten it out on the floor and measure from end to end. That is the length of the loop.
- A blade in one piece. Put a piece of tape on the back of the blade. Stand the loop on the floor with the tape touching a mark, roll it along a straight line until the tape comes round to the floor again, and measure between the two marks.
- Width. Measure from the back edge of the blade to the tips of the teeth.
- Thickness. Use a caliper or micrometer on the flat body of the blade, away from the teeth. The teeth are bent outwards a little (the set), so measuring across them gives too large a figure.
- Teeth per inch. Count the tooth tips along one inch (25.4 mm). On a variable-pitch blade the spacing changes, so count along several inches and expect a pair of figures such as 10/14.
Working out blade length from the machine.
With no old blade to measure, you can calculate the length for a bandsaw with two wheels of the same size:
L = π × D + 2 × C
- D is the wheel diameter, measured across the tyre.
- C is the distance between the centres of the two wheel axles.
The blade wraps half of each wheel, which together make one full wheel circumference (π × D), and runs straight between the wheels twice (2 × C). Because the upper wheel moves to tension the blade, C changes too. Measure it with the old blade fitted and tensioned if you still have it; otherwise set the upper wheel about halfway along its travel.
Example. Wheels of 14 in with 24-3/4 in between centres give 3.1416 × 14 + 2 × 24.75 = 43.98 + 49.5 = 93.48 in, which points to the common 93-1/2 in blade. In millimetres: 355.6 mm wheels with 628.65 mm between centres give 1117.15 + 1257.3 = 2374.45 mm.
Round the result to a length that is actually sold, then check it against the manual or ask the manufacturer before you order. The calculation can be a little out: tyres differ in thickness, wheels wear, and the upper wheel may not sit where you think. Three-wheel bandsaws and machines with wheels of different sizes need a different calculation, so use the manual for those.
Keep the answer.
Once you have a size you trust, write it on the machine or save it to My Workshop, which keeps it on this device for next time.
Find machines by a size you measured ↗︎