The size of back plates's D1 should be a little bit smaller than the size of Chuck's D1. Because the gap between back plate and chuck is smaller, chuck's TIR is better. No gap is the best. You would not need to drill any mounting holes but you will need to turn the shoulder down.
040 to match the back of the lathe chuck to make the chuck & back plate more concentric with the lathe spindle. When turning the shoulder of the backing plate, ONLY TURN THE SHOULDER OF THE BACKING PLATE WHEN ATTACHED TO THE LATHE SPINDLE. If you use a chuck to clamp the backing plate and then turn it, the backing plate will not be true to the lathe spindle and will have more runout than specified when the chuck and back plate are put together.6 pcs of studs for mounting into the cam lock on lathe spindle. If you need to speak to a sales person feel free to call. We are open Monday through friday 8:30 to 5:00 est. The item "10 D1-5 Back Plate For 10 3 and 6 Jaw Zero-Set Lathe Chucks Need Machine D1 R" is in sale since Tuesday, November 26, 2019.
This item is in the category "Business & Industrial\CNC, Metalworking & Manufacturing\Workholding & Toolholding\Workholding\Chucks\Lathe Chuck Adapter Back Plates". The seller is "discount_machine" and is located in Saint Charles, Illinois. This item can be shipped to United States, Canada.