CHAPTER 20 
STANDARD PRACTICES - AIRFRAME
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TABLE OF CONTENTS 
CHAPTER 20 
STANDARD PRACTICES - AIRFRAME
1. 
General ..............................................1
2. 
Bolt and Nut Types Used in the Airplane .....................1
3. 
Standard Torque Values .................................2
4. 
Special Torque Values...................................3
5. 
Torque Measurement....................................4
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CHAPTER 20 
STANDARD PRACTICES - AIRFRAME
1. General 
There are no maintenance practices which apply to the DA 40 airframe and its systems in general. This Chapter only has data about standard threaded fasteners. 
Always tighten the nut or bolt to the torque shown in the tables below. Always use the correct locking device with the nut or bolt. 
CAUTION:  DISCARD SELF-LOCKING NUTS AFTER REMOVAL. THE FRICTION TORQUE REDUCES WITH USE. 
2. Bolt and Nut Types Used in the Airplane 
The DA 40 uses 3 types of standard bolts: DIN 931 and LN9037 metric specifications and AN3 through AN20 American specifications. You can identify the bolt type by the marking on the head and the surface treatment. 
Bolt Type  Marking on Head Surface Treatment 
AN-Bolt 
Corrosion resistant
Non-corrosion steel bolts have a dash 
resistant steel Cadmium bolts have an X 
DIN-Bolt
Manufacturer 
Zink coated 
Property class 
The DA 40 uses these types of standard nuts: DIN 934, DIN 985, AN364, AN365, MS21042, MS21044. 
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3. Standard Torque Values 
These tables show the correct torque values for bolts and nuts to AN and DIN specifications. Use the following torque values for all bolts, nuts and screws which meet the specifications unless they are in the list of special torque values below. 
A. AN Fine Thread Series 
Bolt Size  Torque (Nm)  Torque (ft.lb)  
10 - 32  1.6  1.2  
1/4 - 28  6.2  4.6  
5/16 - 24  13.6  10  
3/8 - 24  20.7  15.3  
7/16 - 20  37.7  27.8  
1/2 - 20  54.2  40  
9/16 - 18  90.4  66.7  
5/8 - 18  124.3  91.7 
B. AN Coarse Thread Series 
Bolt Size  Torque (Nm)  Torque (ft.lb)  
10 - 24  1.6  1.2  
1/4 - 20  5.7  4.2  
5/16 - 18  10.2  7.5  
3/8 - 16  20.9  15.4  
7/16 - 14  28.9  21.3  
1/2 - 13  54.2  40  
9/16 - 12  79  58.3  
5/8 - 11  101.6  75 
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C. DIN and LN Specifications 
Metric Thread  Torque (Nm)  Torque (ft.lb)  
M4  1.8  1.3  
M5  3.6  2.7  
M6  6.4  4.7  
 
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