well thats the question how many of them can u implanted on your character?, i ask this because i have reed that u can put one on your shoulder (so 2 in total ) and one in the sternum. ^^

The errata states that you can have as many mechadendrites as your Toughness Bonus (so if you have Toughness 36, and therefore your TB is 3, you can have 3 mechadendrites).

As MILLANDSON says, a tech-priests can have up to their toughness bonus in mechandendrites.

With the size of shoulders in 40k, I wouldn't be worried about multiple mechandendrites on each shoulder!

Out of curiosity:

As per RAW, I believe mechadendrites must be shoulder or sternum mounted. Has anyone allowed/had other locations in their games? I had one NPC with hip mounted mechadendrites that stowed in her bionic legs, for example.

The Boy Named Crow said:

Shoulders and upper torso is mostly where I picture them, and personally limit mountings to. Even with heavy cybernetic replacement I can't imagine it being too common for a mechadendrite to be mounted on the abdomen or lower portions of the body. Not impossible, just unlikely.

-=Brother Praetus=-

Shoulders and sternum are the places they'll usually be, but if a techpriest player wants them somewhere else they might conceivably fit (no manipulator 'dendrite on your little finger), more power to them.

I always envisioned some being mounted along the spine, in a sort of Doc Oct fashion. Your whole spinal structure has to be replaced in order to cope with that added weight, of not just yourself but the things you are likely moving and lifting. There is no way you would be able to lift the cars and/or tanks that you can with a Manipulator if you still had a "normal" spine. With the Servo-Arm now attached my Tech-Priest is at the 20 mark for lifting, which is 4500 kilos, or nearly 10,000 pounds (5000 pounds for "comfortably carrying"). There is no way I still have any sort of fully organic support structure left.