For what it's worth/it's not necessarily mainstream but i saw this cable splicer's knife while in the local electrical wholesalers the other day, and bought one to play with: http://www.kleintools.com/catalog/ca...plicers-knife#
Not sure how it will eventually work out, but it's got some features i seem to be gravitating towards for a marking knife for some jobs - a thick 2.25mm thick x 13.5mm wide x 42mm sharpened length blade in what feels like a nicely finished and decent piece of hardened and tempered steel ground in a single V from the cutting edge to the back edge, a straight cutting edge, and a square tip with a radiused corner. It not the cheapest ever...
Playing with various craft knives as a basis for marking knives suggests that they are too thin to grind in a nice flat single V as above so that they lie flat against a wood edge or a rule. (with just a small sharpening bevel both sides so it doesn't shave the wood or the rule) If ground that way the edge ends up being far too fragile and flexible, and anyway would cut a line so fine as to be almost invisible. Left stock the short sharpening bevel the makers put on steps the face of the blade too far away from the wood or the rule.
A thick knife can still be very sharp, but when the V angle is still large enough it means that pushing down a little harder significantly widens the line. Plus it's nice and rigid. It's probably not by accident that traditional marking knives are thick and sharpened to a single sided steep bevel.
I'm not a fan of the pointed shape of a traditional marking knife - after too many years of using an Xacto pattern point knife i prefer the way a straight cutting edge tracks as its drawn along the rule. The almost square tip/high back (I'll probably grind it to a slope of about 45deg to help with getting the tip right up against the end of a slot as in say a dovetail - what's sometimes called a lamb's foot shape) means that it's enough to show over 1/2 in stock...
PS should have said that it'll need a little bit of fine tuning of the shape of the blade, but nothing the waterstones won't handle..
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