strange bolt and nut (to me anyway)

[s19438]

two each of these were holding one fender on on my 35. what are they called?
now if anyone say's "fender bolt and nut" .......

 

[Ed H.-OH]

Inverted torx head and nut, Just a modern bolt,Hex head will do the same thing I would think.-ed
 

[2tractors]

Fender bolt, lock washer and nut.
 

[Richard L]

2tractors, you must have a lot better eyes than I, I cannot see a lock washer. LOL
 

[Bill Lisbon]

The last time I saw a bolt like that it was holding a jet engine onto an airplane. That is not the stock bolt for a tractor.
 

[jack bycraft]

Two of your respondent are correct it is an item of AN/MS hardware used primarily by aviation and military available in 1/8 increments by length, notice very short threaded length. You can use smaller lighter bolts if you always have solid shank in the bearing area. The head style allows the bolt to be installed in a narrower flange, again a weight reduction measure.
 

[2tractors]

I should not post after golf and beer! I think its a self locking nut.
 

[budbax]

Spline bolt, mostly used in A/C engines, and airframes... I"m an American Airlines aircraft mechanic.
 

[Bob (Aust)]

Similar to the bolts that hold Pratt & Whitney PT6 turbine and JT15 turbo jet engines into aircraft.

At least your fender won't fall off!