Anyone have ideas about VFD spindles with MT/R8 bores?

I’d like to move to a VFD spindle. I’d also like to keep using my existing tooling: fly cutter, boring head, arbor for gear cutters, all of which are solid shank. Has anyone experience with spindles that are anything other than ERxx noses? I feel like some of my tooling needs a spindle with a through hole and drawbar to keep it secure.
A possibility is to use a VFD spindle to drive my existing spindle (just replace the motor) but that seems like goofy overkill and added weight to be using milling-grade spindle bearings on something that’s just a motor.

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What type of machine is this going on?

Is your current motor somehow integrated with your existing R8 spindle? If not, is there a reason you wouldn’t just use a three-phase motor driving your current spindle?

What power do you need?

Here’s an interesting thread that might be useful.

It suggests among other things AC servo motors like


Extremely belated reply, sorry. My previous laptop is… old, and no longer let me use makerforums because of issues with modern linux distros and a 32 bit system.

This is for a Sherline, which has a pretty easy to swap head/spindle unit. Motor is not tightly integrated. I could replace it with a different motor and have thought about buying a small spindle unit and replacing the spindle with a pulley to drive my current spindle. It’s frustrating having the motor hanging off to one side of the spindle. It’d be really nice to have an integrated unit so the weight is in line with the spindle. On a mill this light, that matters!

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Oh, I had no idea the sherline did that. For others like me, here’s a picture:

I don’t see how you do a drawbar spindle with the motor’s axis aligned with the spindle axis, unless, I guess, you give enough space to work the drawbar and use an idler pulley set to the side?

I was thinking about the ER type of spindle, where the motor is buried in the spindle housing.
But, with a hole through the spindle for a drawbar.

Want to gun drill an ER20 spindle and make up a custom collet that uses the same 8° taper? :grin::crazy_face: