Toothed belt pulleys

The use of toothed belts in transmissions has led to special hobbing tools, such as cutters and reference hobs. The figure above shows us the 3 most common types:

• profile according to DIN7721
• toothed belts with upper and lower teeth to reverse the shaft rotation
• toothed belts type HTD (3M, 5M, 8M, 14M, 20M)
 Type MXL XL L H XH XXH T2,5 T5 T10 T20 Pitch (p) 2,032 5,08 9,525 12,7 22,225 31,75 2,5 5,0 10,0 20,0 Helix angle 40° 50° 40° 40° 40° 40° 40° 40° 40° 40° Tooth depth 0,51 1,27 1,91 2,29 6,35 9,53 0,7 1,2 2,5 5,0 Face width 1,14 2,57 4,65 6,12 12,57 19,05 1,5 2,65 5,3 10,15 Belt height 1,14 2,3 3,6 4,3 11,2 15,7 1,3 2,2 4,5 8,0 a 0,254 0,254 0,381 0,686 1,397 1,524 0,27 0,43 0,925 1,43 Type AT5 AT10 AT20 3M 5M 8M 14M 20M Pitch (p) 5,0 10,0 20,0 3 5 8 14 20 Helix angle 50° 50° 50° – – – – – Tooth depth 1,2 2,5 5,0 1,17 2,06 3,4 6,1 8,4 Face width 2,5 5,0 10 – – – – – Belt height 2,7 5 9 2,41 3,8 5,6 10 13,2 a 0,61 0,925 1,42 0,38 0,57 0,685 1,40 ?

The above table indicates the different belt characteristics for the most common toothed belts. In case the customer only wants to outsource the pulley, the pulley diameter can always be calculated using the following formula:

do = p·z/π – 2a

The table below lists the tolerances for the different diameters.

 Diameter Tolerance 0 – 25 0 / +0,05 25 – 50 0 / +0,08 50 – 100 0 / +0,1 100 – 175 0 / +0,13 175 – 300 0 / +0,18 300 – 500 0 / +0,15 500 – ….. 0 / +0,2

These pulleys can possibly be provided with flanges in steel or other material and upon request, according to the following figure.

The available hobbing tools you will find in the table below.

List of hobs for toothed belts

 Pitch in mm Pitch in inch Belt type Outer diameter 5,08 1/5″ XL -0 9,525 3/8″ L 83,8 12,7 1/2″ H 82,3 22,225 7/8″ XH 108,6 31,75 1″1/4 XXH 114,4 HTD3 – 3M – HTD5 – 5M – HTD8 – 8M – HTD14 – 14M – HTD20 – 20M – AT10 (16-20) – – – AT10 (46-144) – – –

List of cutters for toothed belts

 Pitch in mm Pitch in inch Belt type Pitch circle diameter 5,08 1/5″ XL 3″ 9,525 3/8″ L 3″ 12,7 1/2″ H 105 22,225 7/8″ XH 4″ 31,75 1″1/4 XXH 4″

Please consult us for other possibilities.