Through axle (thru-axle) - typical/minimum number of turns of active tread engagement On opening the cam lever of a 15mm through-axle, I have noticed it is possible to slide the axle out after only two whole turns.  When installing the axle, more that two turns results in a cam tension that is too tight, less than two turns then the cam tension is too loose.  I am concerned about safety and durability.

Does anyone know the minimum turns that a through axle should have in order to retain the wheel?  Otherwise what is the typical number of turns from your experience?  The bike in question is a cyclocross (if that makes any difference).

The image shows the threaded hole from the inside of the fork.

The length of the bolt that goes into this whole matches the outside distance of the fork, however the bolt is tapered at the end so the thread at the very end is not used.  The partially threaded hole seems to by typical of thru-axle designs to allow the bolt to pass into the fork for alignment purposes before threading begins.  In this case however I believe there is insufficient thread.

This is a new bike and I have concerns over safety and long term durability.
Sounds weird and wrong. Usually you indeed have a lot more thread engagement, I think 5-6 turns or more on the road/cross forks I have my hands on all the time. If there are a lot of threads present on the fork and nothing filling them up, I agree it sounds unsafe.

One easy possibility is that the bike ended up with an axle that isn't a correct match for its fork, and someone either didn't notice or care. To be really right it must be the axle intended to go with the fork in question, and they can require some work to track down, particularly if it's an OEM fork as opposed to a named aftermarket one.