Pulled the trigger on the bt30 upgrade. Ordered a 14k rpm continuous bt30 cartridge and a dmm servo to drive it. They have a special motor that is not listed in their store. Its a 1kw in a nema 34 frame that is capable of 5k rpm unlike their other larger motors that top out at 3k. Looking at the torque/speed graph, the 1kw rating seems a bit conservative. At 5k rpm it will do 1.8ft/lb continuous, 3.6ft/lb intermittent. At 0-3k rpm, 3ft/lb continuous, 9ft/lb intermittent. So roughly 2hp continuous, 4hp intermittent, which I believe is mostly limited to what it can handle thermally. With a fan or cooled servo mount, could probably push it harder than 2hp continuous, although it's more than enough power for me. I will need to gear it about 1 to 3 to reach my 14k rpm max which still gives me 3ft/lb for rigid tapping, plenty for what I'm doing, smaller threads in aluminum.

A couple challenges I want to discuss. This spindle is being installed on my mill turn machine which up until now just used a gang setup on the head next to the spindle for various static turning tools, but with this guy I'm going to try something different. Every tool will be held in the bt30, milling and turning. Access to all milling and turning tools in the carousel. Turning tools will utilize a secondary small taper built into the tool next to the main bt30 taper in order to give a very rigid rotational lock on the tool, as well as giving a path for through tool coolant. This setup won't be quite as fast at production as the gang setup, but much more versatile with basically no setup time between different parts. Just load the needed tools into the carousel. Which will already have all the offsets stored for the static tools. I've seen this done before on a doosan mill turn machine, but obviously not with a bt30. I have a couple ideas on how to achieve this. A bt30 f1 boring head shank looks to be a good platform for these static tools. It was a 1 1/2 diameter male thread and a concentric ground diameter above that. I will machine a steel plate that clamps around that ground diameter and reaches over to the side to hold my small secondary taper. The female end of that taper will be mounted to the spindle. Probably hard to picture all that but I will come back to that later with some cad drawings.

For now I want to address the gearing for the spindle. Like I mentioned, it's a bt30 that is capable of 14k max and I'm driving it with a 5k max servo. The spindle comes with a 45 tooth htd 5m pulley on it. As is, it would definitely require a 2 stage setup because a 135t pulley on the servo is just too huge. I asked the seller if it's possible to swap out the 45t pulley on the spindle for something smaller, but I'm still not very clear on how the existing pulley mates with the spindle shaft. The seller is ok at English compared to other aliexpress sellers, but still hard to communicate technical stuff. When I asked him what the diameter of the spindle is where the pulley attaches, he responded "35mm, double 6 key symmetry". Anyone know what that is? Another thing I'm curious about, even if I can swap the pulley out with something lower tooth count to make the gear up easier, how sensitive is the balance going to be? With 14k capability, I imagine it needs to be pretty good and wonder if it's been dynamically balanced with the pulley installed. If it's likely that i will lose balance by trying to swap that pulley, I would rather leave it alone. Thoughts on that?
If I do leave the 45t on the spindle and go 2 stage, there's a couple options. An exactly 1:3 ratio would be convenient because it allows me to index the spindle for tool changes using the encoder that's already on the servo. If I don't have exactly 1:3, I'll need to add a sensor to the spindle. Problem is, it's not mathematically possible to get exactly 1:3 with a 2 stage and a 45t on the spindle. One option is to do 2 stage, but the first stage just being 45t to 45t, and a 24t is joined to that intermediate shaft with the 45t, and a 72t is mounted to the spindle. Downside to that would be that a 5m belt wrapping around a 24t at 14k rpm and 4hp peak might be a weak point. Another option is to forget about getting exactly 1:3 and just add an optical sensor to spindle for indexing. If i go this route, I can use more manageable size pulleys. I'm thinking 64t on the servo, and 32t/64t on the intermediate shaft, 45t stays on spindle. So first stage 64:32, second stage 64:45. This gives a total ratio of 1:2.84, max rpm of 14,200 with servo at 5k. Im leaning towards this option as it gives a more optimal belt situation and also gives a slight torque advantage over the exact 1:3 ratio. Only downside is that I can't use the servo encoder for tool orientation, I will have to add a sensor.

So for starters I would just like to get some opinions on the gearing setup and what my best option is, what challenges I might face, if balance will be an issue, etc