Alf":mvqvi9nh said:
Confused neanderthal alert! That is to say, I'm confused. Is that on bevel-up or bevel-down? Either way there seems to be a back bevel involved...?
Bevel down. If you draw a standard plane bed/iron
in cross section it is clear that the back (i.e. face down aspect) of the plane requires that the iron is ground with at least a 45° angle main bevel (measured from its front face) in order to be able to cut
at all. The clearance angle is, I believe, a way to achieve this with a margin of error and the actual angle is probably fairly inconsequential, so long as it is less than 45°. In machine woodworking we normally allow 5° to 10° clearance behind any cutting edge depending on cutterblock diameter, rotation speed, steel type, species, etc. because it makes for a cleaner machining operation. As machine practice originated from bench practice I see no reason to question the logic of what works well. So what that in turn means is that the expensive honing jig that so many people use to
grind an edge is probably completely unnecessary for a standard bench plane.
The secondary bevel, also on the back as you well know, is to allow an iron to be honed quickly to achieve a cutting angle. It is a lot quicker to hone a 0.5 to 1mm wide cutting edge than a 6mm wide one (the length of a 30° bevel on a 3mm thick iron).
In practice a 30° angle has been found to work well for a wide variety of timbers, retains a fair amount of strength in the cutting edge and coincidentally is about the angle you are looking for on a block plane.
Alf":mvqvi9nh said:
If you're using mainly hardwoods, 50° is nice, but not necessarily as easy to achieve on classic bench planes.
Agreed, but even Norris and Spiers planes came with a 47.5° bed angle and 45° was used on a lot of other "standard" planes like rounds and hollows, with 50° pitch available to special order - and how many of them do you see with a 50° pitch? I feel that this is indicative of the relatively high volumes of softwoods and soft hardwoods (such as poplar, lime, etc.) which were being worked from the Victorian period onwards by the trade. In any case if you need a 50° bed angle on a Stanley or Record bench plane this
can be achieved
at a pinch by adding a 5° front bevel to the iron - but this is now getting just a little bit away from the original subject, IMHO. :lol:
Scrit
I put it together ready for a play and the blade fits in back to front :shock: The honed edge is facing away from the cut . Its been a few years since i've used hand planes but i don't remember this . Is it normal ? It works fine .
