thanks for the advice and info, I appreciate it. I have a similar device to the spin lt, I prefer the swivels - they may just be "ok", but they get the job done. problem was uneven tension on the cores best I can tell. my raymo clamps will be here tomorrow, I'll be fine.I guess there's your problem, or at least one part of it. These swivels are "OK", but definitely not "great"... so grab something like a SpinLT or similar, as the ones you're using still add quite a bit more weight to the cores. The added weight is forcing you to use more tension on the drill in order to keep the cores snug. That's just because all the weight is pulling/swinging them away from being snug. So the tension you're adding onto the drill is causing the swivels to constantly grind themselves to dust instead of keep turning effortlessly smooth. They're not designed to withstand simultaneous high rpm and high tension, at least not in ways that they're capable to sustain for several minutes. Before your build is even half finished, they literally are turned to shit. If you pull on the drill hard enough whilst it is spinning at high rpm, you can actually make a ball bearing designed for skateboards wear out almost equally fast. The whole idea of using a SpinLT is not just the quality of the bearing, but also the fact that it will enable you to lower the tension on the drill, as the 3D printed part of the SpinLT supports the weight of the bearing.
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