Now the 7mm outside diameter insert requires a hole of 6.75mm to give a nice tight fit, that is unless you are using ebony or something equally as dense. This wood has no give and a trial fit as suggested simply split the wood. So the only choice was to drill a 7mm hole and glue it in with a dab of epoxy resin. The rather nice knurled nuts I'm using were made by Phil Edwards of Philly Planes. Phil can make various sizes and the prices are very reasonable even for small orders.
Here are the inserts installed, they look very neat although in use they are hidden, shame!
With the blade prepared and honed here is the finished gauge, sorry about to poor picture! The concave notches on each side are not just for show, they are there for your second finger to drop into and provide lateral pressure keeping the head agianst the work. The left hand notch is for lefties.