I ordered some diamond sharpening stones like these:- https://www.ebay.com.au/itm/203122872225?hash=item2f4b110fa1:g:70gAAOSwfCtfdEhd (Actual stone size is 155 x 67 x 6.5mm but there is sufficient wiggle room to accommodate a slightly larger stone.) so I thought I would make a honing guide to suit them for my chisels. I didn't like the homing guides that ride on the surface of the stone as they quite easily mar the surface of the stone so this design uses a running guide style chisel holder. One side of the carriage is set at 25° for the primary bevel, the other side is set to 30° for the secondary bevel. EDIT: I have added some alternate bases to suit the most common whetstones. See: https://www.thingiverse.com/thing:4678840 for details and files. They are designed to work with the same carriage as this design so you can just print the appropriate base to suit your stone.