Simple 4th Axis

A (relatively) simple 4th axis design for a milling machine. Based around a mounted angular contact bearing (typically used for a ballscrew) and an ER32 straight shank collet chuck. Allows for up to 3/4" round stock directly in the collets. The belt is tensionable via pivoting the motor (in this case, a NEMA 34 clearpath motor). Designed to mount to the table slots of a Bridgeport mill. I had originally intended to thread the straight shank and use a locking nut, but instead went with a shaft locking collar after slightly preloading the whole stack. Some other parts you'll need: NEMA 34 motor ER32 straight shank collet chuck (https://ebay.to/2E15JAL) Tail bearing (like https://amzn.to/2BtGFRf) 20mm Angular contact bearing (http://www.automation4less.com/store/proddetail.asp?prod=WBK20) 4:1 Pulley reduction (https://amzn.to/2RSIJri) 20mm shaft clamp (https://amzn.to/2TH3WXh)