A lot of people associate the acronym HTD with synchronous belts. While there is good reason for this, most take it a little too far, and believe that HTD refers to all synchronous belts. This is not the case. HTD stands for High Torque Drive, and calls out a specific tooth profile. This type of profile is called a curvilinear profile. An HTD tooth form looks like a half circle. Other curvilinear profiles are available today as well, including our GT profile. Here at Gates, we replaced our main 8mm and 14mm HTD belt lines with our GT tooth form quite a number of years back. HTD is still offered stock in 3mm, 5mm, and 20mm pitch belts, but not in our 8mm and 14mm lines.
Some of our competitors still offer off the shelf 8mm and 14mm pitch belts and sprockets. This causes questions about interchangeability. When we designed our GT tooth form for 8mm and 14mm pitch, we designed the belts to be able to drop into the old HTD sprockets. This is a one way replacement; you cannot drop an HTD belt into our GT sprockets. The HTD tooth is wider than that of our GT belts. Also, this drop in ability is only for the 8 and 14mm pitch belts, not for the smaller 3 and 5mm pitch.
There are reasons why one would still want to use HTD in 8mm and 14mm belts today, and it's possible with special order belts. Keep in mind though, special order means lead times and minimum order quantities. If you have a standard industrial application, it's likely it will be alright to switch to GT. If you have a specialty drive such as a supercharger on a car, you may want to call us to be sure.
For more interchange information, check out our Belt/Sprocket Interchange Guide. You can download your free copy at www.gates.com/drivedesign Click the link to Drive Design Manuals, and scroll down until you find it (you will have to register if you haven't previously done so).