HK500GT Tail Victim

I also experiment the same tail problem : M2 bolt broken... Simply buy an Align tail rotor and change all the bearings.
And now it's perfect!

Yep my screw broke blade went flying broke housing,belt,tail gear,mixer control arms waiting for the all alloy one to come into stock now!!

Guys.. Something I think you are all missing... The screw in the tail is plenty strong enough if you have no vibration. I noticed on spooling up that the tail boom and boom supports vibrate badly at certain throttle settings . When I investigated further, I noticed that the tail shaft bearings had some play in both the bearing and also on the shaft. When I replaced the $0.50 bearings for $2 ones from my local bearing shop. All the vibration was gone and problem solved. I have noticed that a number of the original bearings on the HK500 GT are very sloppy. This magnifies any vibration due to slight imbalances many times and will cause premature failure every time, due to fatigue. This also explains why high tensile screws are failing just as frequently. Beefing up the screws to 3mm will make them last longer but that is just treating the symptom, not the root cause of the issue. Further to this, everyone seems to rely very heavily on thread lock, but if you remove the source of vibration then your screws will not come loose. I'm not suggesting you don't use thread lock, just that you should take time to critically balance each rotating part of your heli before flying it and check for vibrations after any mod or crash.

I am another victim of the tail!!
First time with the belt drive the front gear striped and lost tail control, fixed it, did the mod to move the whole tail forward so the gears would mess closer.
Second time with the new Torque tube set up the tail rotor bolt on the tail snapped the head off and crashed again lucky not to far off the ground just busted up the landing skid and off course stripped the gears on the torque tube,
Third time ran again with the belt set up and ordered rotor to fix tail,
didn't even get the heli together the head snapped off during removal of the tail holder to lube the bearings,
I am right now sending a request for replacement of damaged parts during there assembly at HK or factory. I would say you all do the same.
I wish I would have just went with the Align Trex 500ESP kit at the start.
I would have been much happier and would be flying my 500 not my 450 right now.

i think this is the main issue. If the headspead is too high and you might have some unbalance, the tailrotor will snap off due weak bolds.
I also used a 1800kv motor with 13T pinon gear.
I will try it again with 12T gear and a copterX tailrotor (better then HK)

Align uses a 1600kV which is more adapted for the 500