1. ADVANCED MECHANICAL DRAFTING
LECTURE #6

2. MMC & LMC MMC = Maximum Material Condition
Largest shaft diameter
Smallest hole diameter
Worst case in most assembly situations
LMC = Least Material Condition
Smallest shaft diameter
Largest hole diameter
Certain uncommon situations only

3. FITS CLEARANCE FIT HOLE SHAFT 1.505 Ø 1.500 1.494 Ø 1.490
CLEARANCE AT MMC = – = .006
CLEARANCE AT LMC = – = .015

4. FITS INFERFERENCE FIT HOLE SHAFT 2.747 Ø 2.741 2.756 Ø 2.752
INTERFERENCE AT MMC = – = .015
INTERFERENCE AT LMC = – = .005

5. INTERFERENCE AT MMC = 3.321 – 3.319 = .002
FITS
HOLE
SHAFT Ø
3.321
3.315
3.328
3.319 Ø
TRANSITION FIT
INTERFERENCE AT MMC = – = .002
CLEARANCE AT LMC = – = .013

6. MMC= LMC= GENERAL FIT CONCEPT
MAXIMUM INTERFERENCE or MINIMUM CLEARANCE
LMC=
MAXIMUM CLEARANCE or MINIMUM INTERFERENCE

7. FITS IN THE MHB Five Major Fit Classes
RC – running or sliding clearance fits
LC – locational clearance fits
LT – locational transition fits
LN – locational interference fits
FN – force or shrink interference fits
Each fit class contains several subclasses
All values in fit tables must be multiplied by 1000 before using them in calculations

8. EXAMPLE
Calculate Shaft and Hole diameters and clearances or interferences for a Ø1.50” basic mating shaft and hole in the following fit conditions:
RC-7
FN-4
LT-3

9. SHAFT
HOLE
CLEARANCE = = = =
MMC
LMC

10. SHAFT
HOLE
INTERFERENCE = =
= 1.501
= 1.500
MMC
LMC

11. SHAFT
HOLE
CLR or INT = =
= 1.501
= 1.500
.0007 MMC
.0009 LMC

12. GSH END DESIGN

13. CHANGING DIMENSION PROPERTIES
Left click on dimension to show grips
Right click to display change menu
Select PROPERTIES
Change or add prefix, suffix, precision, tolerances etc.

14. ADD PREFIX OR SUFFIX Prefixes: Suffixes: 2X, Ø (%%C), R, SØ, SR
TYP, MAX, MIN, etc.

15. CHANGE TO LIMIT .877 .872 Ø TYP EXAMPLE: Dimension .875
Lower limit .003
Upper limit .002
Precision 0.000

16. MOVE DIMENSION OUTSIDE OF EXTENSION LINES
1.505
1.497