[BIGBLOCK1965]

Here are a couple of low cost choices- The Chinese one in the box looks to be an air motor with air cylinder to drop it down. The one made in California is semi manual but low cost and adaptable to a lot of machines. I would go with the California unit.

Milling Machine Accessory Air Power Drawbar A T Ant 300V R8 NMTB30 or NMTB40 | eBay

Power Draw Bar Fits Bridgeport J Head Milling Machines | eBay

I am going to order the more expensive unit and give it a try. It has a nice set of controls and automatically raises and lowers the air motor to engage the drawbar. It looks like a pretty easy mount up, only needing to machine some standoffs to raise the mount up over the belt, and maybe a re-do of the spindle sensor bracket, then cutting away some of the top sheet metal cover. I will also make a new drawbar with a heavy duty 19 MM hex head, tapered to center in the spindle, and with a tapered pilot on the threaded end to center in the collets.