Design of Gauges

mqc

1. Matoshri College of Engineering and Research Center Nashik Department of Mechanical Engineering Subject:- Metrology And Quality Control Class:-TE Mechanical Unit: I Measurement Standards and Design of gauges Semester:-V 2020-21 By Prof R.S.Patil (Assistant Professor MCOERC )

2. Contents(Session 3) Unit – I Measurement standards and Design of gauges Design of Gauges Tolerances Limits and Fits Taylor’s principle Types of gauges Wear allowance on gauges Matoshri College of Engineering and Research Center

3. Interchangeable Manufacture The interchangeable manufacture implies that, the parts that are for practical purposes identical. They are made to specifications by processes that ensure that they are so nearly identical that they will fit into any device of the same type Matoshri College of Engineering and Research Center

4. Matoshri College of Engineering and Research Center

5. Advantages For Interchangeable Manufacture Replacement: One such part can freely replace another, without any custom fitting (such as filling). Easy to Assembly: This interchangeability allows easy assembly of new devices Repairing: Easier repair of existing devices. Minimizing time and cost :Minimizing both the time and skill required of the person doing the assembly or repair. Rapid Manufacturing :Machine tool enables the components to be manufactured more rapidly Matoshri College of Engineering and Research Center

6. Terminology for LIMITS & FITS Size :- It is a number expressed in a particular unit in the measurement of length. Basic Size :- It is the size based on which the dimensional deviations are given. Actual Size :- It is the size of the component by actual measurement after it is manufactured. It should lie between the two limits of size . Matoshri College of Engineering and Research Center

7. Terminology for LIMITS & FITS(cont.) Limits of size :- These are the maximum and minimum permissible sizes of the part. Maximum limit :- Is the maximum size permitted for the part. Minimum limit :- it is the minimum size permitted for the part limit of size. Hole :-Refers to diameter of a circular hole as well as to any internal dimension of component .it is referred as “female” Shaft :-Limits and fits, all external features of a component including those which are not cylindrical are designated as ‘Shaft'. It is referred as “male”

8. Deviations Actual Deviation:- It is the algebraic difference between actual size and its corresponding basic size. Deviation :- It is the algebraic difference between a size, to its corresponding basic size. It may be positive, negative or zero. Upper Deviation :- It is the algebraic difference between maximum limit of size and its corresponding basic size. Lower Deviation:- It is the algebraic difference between minimum limit of size and its corresponding basic size. Matoshri College of Engineering and Research Center

9. Terminology for Limits and Fits Cont . Tolerance :Tolerance is the difference between maximum limit of size and minimum limit of size. Matoshri College of Engineering and Research Center

10. Different Types of Tolerance Unilateral Tolerance: In this method of presenting the limits, both the limits of size are on the same side of the zero line. Bilateral Tolerance: Here one of the limits is on one side of the zero line And the other limit of size is on the other side of the line. Matoshri College of Engineering and Research Center

11. Allowance It is an intentional difference between the maximum material limits of mating parts, For shaft, the maximum material will be it’s high limit and for hole, it will it’s low limit The positive allowance is clearance and negative allowance is interference.

12. Fit Fit is the relationship that exists between two mating parts, a hole and shaft with respect to their dimensional difference before assembly. Three types of fit are given here under 1) Clearance Fit : In clearance Fit shaft is always smaller than the hole. A positive allowance exists between the largest possible shaft and smallest possible hole. Minimum Clearance : It is the difference between the maximum size of shaft and minimum size of hole. Maximum clearance : It is the difference between the minimum size of the shaft and the maximum size of hole Matoshri College of Engineering and Research Center

13. Fit(cont .) Hole basis Shaft Basis Matoshri College of Engineering and Research Center

14. Fit(cont.) 2)Interference Fit: It is also called Press or force fit, In this fit shaft is always larger than the hole Minimum interference: it is the difference between the maximum size of hole and the minimum size of shaft prior to assembly Maximum Interference : It is the difference between the minimum size of the hole and the maximum size of the shaft prior to assembly. Matoshri College of Engineering and Research Center

15. Fit(cont.) 3)Transition Fit : it is called sliding Fit . It occurs when the resulting fit due to the variations in size of the male and female components due to their tolerance, varies between clearance and interference fits. The tolerance zones of shaft and hole overlap Matoshri College of Engineering and Research Center

16. Matoshri College of Engineering and Research Center

17. Matoshri College of Engineering and Research Center

18. Fundamental deviation There are 25 fundamental deviations in the B.I.S. system represented by letter, symbols (Capital letters for Holes and small letters for Shaft) Matoshri College of Engineering and Research Center

19. Grades of Tolerance In the Indian Standard System, there are 18 grades represented by number symbols, both for hole and shaft denoted as IT01, IT0, IT1, IT2.....IT16 Matoshri College of Engineering and Research Center

20. Example 30 H8 f7 30= Value of basic size H= type of hole(Hole basis system) 8= IT 8 grade of tolerance of hole f= Type of shaft 7= IT 7 grade of tolerance of shaft Matoshri College of Engineering and Research Center

21. Assignment 3 Q1) What is mean by Fundamental Deviation. Q2) Short notes on Interference Fit Transition Fit Clearance Fit Deviation Q3) Any Question p [email protected] Matoshri College of Engineering and Reserch Center