ill have to check out that planetary unit. As for preloading the bt30 dogs for the static turning tools, i considered that at one point, but with my latest design version i wont be relying on the spindle for rotational rigidity of these tools. I decided there was just too many limitations. First of all, the spindle would surely need some kind of disk brake to really lock it in place. The servo and belt definitely wouldnt be enough alone. Even with a brake, i think it would be difficult to get the kind of accurate rotational repeatability that i would want. Instead i have decided to use a secondary small taper that is built into the tool holder with an additional piece on the spindle to mate with it. heres a few pics of what i have so far, just a rough draft concept for now. For this version, the dogs are actually removed

This is a drilling/boring static holder. some of them may have a horizontal er20 built in for grabbing various diameters, or just leave it as a bigger bore with set screws and use sleeves to hold smaller diameters. That saves some horizontal room over the er20 version. The base piece with the bt30 taper is an f1 bt30 boring shank. The rest of the pieces will be custom made. Turning/facing/threading holders will be different. One option for those is to just use a more standard er collet bt30. still with the secondary taper pieces, but just grab a heavy duty boring bar vertically and use it for turning/facing. Another option is to custom make insert tools. the bottom peice shown in the pic will be swapped out for something that holds carbide inserts. Not hard to design exactly what i want. Might want to harden them and hard mill the final dimensions of the insert pocket.
The purpose of this secondary taper is to give very good rotational rigidity and also locational repeatability. An added benefit of this secondary taper is that it can be a path for coolant that can be plumbed into through coolant static tools. It could also be used as an electrical contact for a probe that can be picked out of the carousel and be used for probing cycles. I can also do some other creative things with that coolant channel like a coolant pressure powered bar puller. I do plan to use a high pressure diaphram pump for coolant so plenty of pressure there for a gripper. Lots of crazy ideas, hopefully some of it works the way i imagine it. Ive seen other mill turn machines that hold static tools in the milling spindle, but they use fancy modular holders like capto. I dont think ive seen any that use a secondary taper like i have for the static tools. One design issue that i do realize is that my secondary taper over constrains things and will require very precise machining of the piece with the 2 bores for locating my second taper pin perfectly coaxial and at a perfect distance away from the main taper. The depth will be adjustable. the bottom portion of the taper pin is cylindrical and can slide up and down in the bore for adjustment. The second taper constrains motion in 3 axis when it really only needs to constrain one, but i cant think of a good way to get a rigid rotational lock with less constraint without introducing other problems. For example it could be just a cylindrical pin joint that doesnt constrain depth, but that might try to bind when pushing in. could also be a pin sliding into a slot which removes a further constraint that i dont need, but i think it would be hard to design that with zero backlash and it would only have a very minimal amount of contact. For ease of machining something accurately that will give a rigid lock, the secondary taper seems to be my best option but im open to other suggestions. For now its all experimental and im sure it will be a while before i nail down a system that works.