I used some close loop steppers on my lathe and I really like them. If you loose steps the program stops. Instead of going on cutting in the wrong spot. They are quite a bit more expensive unfortunately. Especially if you don’t go with the Chinese knockoffs. Spent about $1800 on these but they are nice and very strong. 1133 and 2800 oz/in.
I just got the spindle VFD speed range dialed in. I am able to get 50rpms to 5940rpms in vector speed mode. After I broke the new SDK bearings in I ran it for 20 min at 5940 rpms and it only got to about 90 deg. Should work really well. I usually tap at around 350 rpm. on my other mill I have to switch to a lower gear and I can still stop the spindle with my hand. Not this one!!! The difference being 2hp vs 1.1 hp and the vector mode VFD. Going to put one of these VFDs on my lathe too and see if it makes a difference.
By the way, I found out why my spindle got so hot before. The oil seal at the end of the spindle is too tight. If you run without it, no heat. Just though you should know. I ordered a new one that is slightly larger inner diameter. 47mm(45mm originally)x72mmx10mm. so if your spindle end is getting hot this is probably why. This amount of heat will cause bearing failure and tool longevity.