Derek Cohen (Perth Oz)
Established Member
Relax. The point made is that no bevel has to be ground or honed to an exact angle. With BU blades there is more reason to do so, but even then there is a little leeway. For a shooting board plane keeping the secondary bevel low (about 25 degrees) is desired. For high angle blades, a primary bevel of between 20 - 25 or so degrees is fine before adding the higher secondary bevel. It is the secondary bevel that needs to be exact for purposes of repeatibility (=efficiency and economy of honing).
The point I am making is that a low primary bevel is easier to grind than a high primary bevel when one plans to add a camber.
Be careful with hand grinders - it is easy enough to spin them fast and burn an edge. The old grey wheels they usually come with must be discarded. They need to be matched with an appropriate wheel - a coarse (46 grit) white Nortons wheel is good - and they need a decent tool rest to leave enough coordination over to feed the blade straight.
An alternative to a high speed grinder is a belt sander, again with coarse medium. I use a belt of 60 or 80 grit to remove lots of steel. These run cooler than a grinder but still need to be watched (and dunked frequently in water).
Here is the Mk I (wood version) jig I made for the belt sander:
http://www.woodworkforums.ubeaut.com.au/showthread.php?t=14908&page=1&pp=15
The Mk II (metal version) is here:
http://www.woodworkforums.ubeaut.com.au/showthread.php?t=16156
Regards from Perth
Derek
