Woodworking Lathe Headstock Spindle Adapter 3/4In x 10TPI to 1In x 8TPI, 3/4In x 10TPI to 1In x 8TPI Dimensions: 4.45 x 2.4 x 2.24 inches Convert a 3/4" x 10TPI lathe headstock spindle to 1" x 8TPI. Install the internal thread of the spindle: 3/4" x 10TPI. Install the external thread of the chuck: 1" x 8 TPI. The adapter body is made of hard steel. Greatly extend the service life. The weight of the adapter is 0.77LB. The length is 2.3" and the width is 2". This will extend the spindle length by approximately 1-1/2".