WHEN TO USE WORMS AND WORM GEARS
Worms and worm gears provide solutions to a wide range of drive problems,particularly when the following factors need to be considered:
• High ratio speed reduction
• Space limitations
• Right angle shafts
• Non-intersecting shafts
Now that you have been introduced to worms and worm gears, let’s take a closer look at each, starting with the worm.
WORMS - IDENTIFYING THE NUMBER OF THREADS
worms are cut with single, double, triple or quadruple threads. To determine the number of threads on a worm, look at an end view so you can see the “start” of each thread. One start means that you have a single thread, two starts a double thread, three starts a triple thread, and four starts, a quadruple thread. (See Figure right side)
DIAMETRAL AND CIRCULAR PITCH
As you learned from our lessons on spur gears and helical gears, diametral pitch and circular pitch are two systems used to designate the size of a gear’s teeth. Diametral pitch (also referred to as pitch) is the relationship between the number of teeth in a gear and each inch of the gear’s pitch diameter (PD). For example, a worm gear with 16 teeth (T) and a one-inch pitch diameter is a 16-diametral pitch (DP) gear.
DP = T ÷ PD or DP = 16 teeth ÷ 1 PD = 16 DP
Note: Diametral pitch can be measured using a gear gauge.
Important: Diametral pitch can also be determined using the following formula: DP = 3.1416 ÷ Circular (linear) pitch
