This document discusses gear tooth profiles, specifically comparing involute and cycloidal teeth. It begins by stating that involute teeth have constant pressure angle throughout engagement, resulting in smooth running. It also notes that involute teeth can be manufactured simply and cheaply using basic rack tools. The document then lists advantages of cycloidal teeth, such as no interference, higher strength, and longer life due to mostly rolling contact. However, it also outlines disadvantages of cycloidal teeth, namely that they require a specific center distance and have more difficult hob manufacture. Applications of cycloidal gears include watches and paper mill machinery where strength is important.

1. Sanjivani Rural Education Society’s
Sanjivani College of Engineering, Kopargaon-423603
( An Autonomous Institute Affiliated to Savitribai Phule Pune University, Pune)
NAAC ‘A’ Grade Accredited, ISO 9001:2015 Certified
Subject :- Theory of Machines II
T.E. Mechanical (302043)
Unit 1
1.3 Gear Tooth Profile
By
Prof. K. N. Wakchaure(Asst Professor)
Department of Mechanical Engineering
Sanjivani College of Engineering
(An Autonomous Institute)
Kopargaon, Maharashtra
Email: wakchaurekiranmech@Sanjivani.org.in Mobile:- +91-7588025393

2. 1. Variation in centre distance does not affect the velocity ratio.
2. Pressure angle remains constant throughout the engagements which results in
smooth running.
3. Straight teeth of basic rack for involute admit simple tools. Hence,
manufacturing becomes simple and cheap.
INVOLUTE TEETH

3. CYCLOIDAL TEETH

4. Advantages of Cycloidal Gears
1. Cycloidal gears do not have interference.
2. Cycloidal tooth is generally stronger than an involute tooth owing to spreading flanks in contrast to the radial
flanks of an involute tooth.
3. Because of the spreading flanks, they have high strength and compact drives are achievable.
4. Cycloidal teeth have longer life since the contact is mostly rolling which results in low wear.
Disadvantages of Cycloidal Gears
1. For a pair of Cycloidal gears, there is only one theoretically correct center distance for which a constant angular-velocity
ratio is possible.
2. The hob of Cycloidal gear has curved teeth unlike involute rack teeth. Hence hob manufacture is difficult and costly.
3. Cycloidal gear will cost more.
Applications of Cycloidal Gears
1. Cycloidal gears are extensively used in watches, and instruments where strength and interference are prime
considerations.
2. Cast bull gears of paper mill machinery.
3. Crusher drives in sugar mills.
CYCLOIDAL TEETH

5. DIFFERENCE BETWEEN INVOLUTE AND CYCLOIDAL
TEETH

6. 6PROF. K N WAKCHAURE
Subject :- Theory of Machines II