1. COMPUTER AIDED DRAFTING ENGINEERING GRAPHICS II
KING ABDULAZIZ UNIVERSITY
FACULTY OF MECHANICAL
ENGINEERING
MENG 204
COMPUTER AIDED DRAFTING
ENGINEERING GRAPHICS II
Limits and Fits

2. Fundamental Deviation of Tolerance
The fundamental deviation is the deviation which is closest to the basic size and is used to locate the tolerance zone with respect to the basic size.

3. Fit
Fit is the general term used to signify the range of tightness or looseness that may result from the application of a specific combination of allowances and tolerances in mating parts

4. Bases of Fits
The hole basis
The shaft basis

5. Hole Basis
In this system, the basic diameter of the hole is constant while the shaft size varies according to the type of fit.

6. Shaft Basis
Here the hole size is varied to produce the required class of tit with a basic size shaft

7. Engineering fits between two mating parts can be divided into three types:
Clearance
Interference
Transition

8. Clearance fit
In which an internal member fits in an external member (as a shaft in a hole), and always leaves a space or clearance between the parts

9. Interference fit
In which the internal member is larger than the external member such that there is always an actual interference of metal

10. Transition fit
In which the fit might result in either a clearance or interference condition

11. Selection of Fits – Hole Basis System

12. Example

13. Example

14. Example

15. Example

16. Example