About the headstock spacer
This riser can be used on both a mill and lathe. Having the option to extend the headstock further out on the mill can sometimes allow surfaces to be machined that could not otherwise be reached without breaking down the setup and re-clamping the part. The spacer moves the spindle out an additional 1-1/4″. In many cases, it is much easier to increase your machinable surface area by using this spacer than it is to re-clamp the part. Precisely machined keyways keep the headstock accurately aligned. A precision ground alignment key is included. The headstock spacer block increases the maximum working diameter of the lathe to 6″ (152mm)
NOTE: This part is the same as the lathe headstock spacer block, so you need not duplicate it if you already have the spacer block kit unless you wish to leave the spacer block in place on either the lathe or mill and don’t wish to deal with changing it back and forth between machines. Also, note that the Model 5400 mill comes with this spacer block as part of its standard equipment. The Model 2000 mill has ram in/out adjustment that, for the most part, eliminates the need for this accessory, so it is not included with that mill. There may still be special setups where you would find it useful on that machine as well.