Method and tool for reconditioning a damaged thread

1. A method for reconditioning a damaged thread ( 8 ) of a transmission ( 1 ) of a hover-capable aircraft; said damaged thread ( 8 ) being arranged inside a first hole ( 23 a ) of said transmission ( 1 );

said method comprising the following steps:

i) centering a tool ( 20 ) on said first hole ( 23 a );

ii) inserting a first tool ( 25 ) inside said tool ( 20 ) centred on said first hole ( 23 a ) and removing the damaged thread ( 8 ) by means of said first tool ( 25 );

iii) inserting a second tool ( 26 ) inside said tool ( 20 ) and creating a new thread ( 16 ) inside said first hole ( 23 a ) having a diameter larger than the one of said damaged thread ( 8 ); and

iv) screwing an insert ( 61 ) having a thread inside said new thread ( 16 ), so that said insert ( 61 ) engages said first hole ( 23 a ) and defines a reconditioned thread ( 8 ′); said step i) comprising the following steps:

v) inserting a pin ( 33 ) inside said tool ( 20 ) and inside said first hole ( 23 a ); and

vi) removing the pin ( 33 );

wherein said step i) comprises the steps of:

vii) screwing said pin ( 33 ) onto a further thread ( 30 ) of said tool ( 20 ); and

viii) arranging said pin ( 33 ) in abutment against an abutment surface ( 32 ) of said tool ( 20 );

said method further comprising the step of:

ix) keeping said transmission ( 1 ) mounted on the hover-capable aircraft during said steps i), ii), iii), vii).

2. The method according to claim 1 , wherein before said step i), the method comprises the following further steps:

x) removing a plurality of connecting elements ( 6 a , 6 b ) interposed between said casing ( 2 ) and said transmission ( 4 ), engaging respective said first hole ( 23 a ) and second holes ( 23 b ) of said transmission ( 1 ) and on which respective nuts ( 7 ) are screwed; said casing ( 2 ) defining said first hole ( 23 a ) and said second holes ( 23 b ); and

xi) removing said shell ( 4 ) from said casing ( 2 ) while maintaining said transmission ( 1 ) supported by said casing ( 2 ).

3. The method according to claim 2 , wherein after said steps x) and xi), the method comprises the following further steps:

xii) arranging a first bracket ( 21 ) of said tool ( 20 ) at said first hole ( 23 a ) before said step i); and

xiii) arranging a pair of additional brackets ( 22 ) of said tool ( 20 ) at respective second holes ( 23 b ) of said transmission ( 1 ) before said step i).

4. The method according to claim 3 , wherein the method further comprises the following steps:

xiv) screwing said nuts ( 7 ) onto the respective connecting elements ( 6 b ) engaging the respective said second holes ( 23 b ), during said step i).

5. The method according to claim 1 , wherein said step ii) comprises the following steps:

xv) inserting a first bush ( 40 ) inside said tool ( 24 );

xvi) arranging said first tool ( 25 ) inside a third hole ( 41 ) of said first bush ( 40 ) until a first operating end ( 70 ) of said first tool ( 25 ) is brought in correspondence with said thread to be removed ( 8 ) and inside said first hole ( 23 a ); and

xvii) actuating said first tool ( 25 ) so as to remove said damaged thread ( 8 ).

6. The method according to claim 1 , wherein said step iii) comprises the following steps:

xviii) inserting a second bush ( 50 ) inside said tool ( 20 ); and

xix) screwing said second tool ( 26 ) onto a nut screw ( 54 ) arranged inside a further fourth threaded hole ( 51 ) of said second bush ( 50 ) until a second operating end ( 71 ) of said second tool is brought ( 26 ) inside said first hole ( 23 a ).

7. The method according to claim 1 , wherein said step iii) comprises the further step xx) of screwing said insert ( 61 ) inside said new thread ( 16 ).

8. The method according to claim 1 , wherein said step ii) comprises the further step xxi) of arranging said first bush ( 40 ) against said abutment surface ( 32 ); and/or wherein said step iii) comprises the further step xxii) of arranging said second bush ( 50 ) against said abutment surface ( 32 ).