On 14/04/2012 09:37, Norman Billingham wrote:
On 14/04/2012 08:54, Nthkentman wrote:

"ss" wrote in message
...
When sharpening a wood chisel is there just one angle on the sharp end?
Or two?
I have one of those tools (for sharpening) that has embossed on the
side ...30mm=30 deg 40mm=25 deg

If it's the one with the roller underneath that clamps the chisel I've
always sharpened at the 30 deg then lightly finished off on a finer
stone to 25. Seems to do the job.


There are whole books on the subject and many views. The lower the
angle, the sharper the chisel but the more easily the edge breaks up
under load. For light paring cuts in soft woods a 25 degree angle is OK,
but 30 degree is better for harder woods or for end-grain cutting and is
the common choice. However, if you sharpen the whole bevel at 30 then
you have to remove metal over the whole area every time you re-sharpen.
Either way the edge won’t be sharp unless the back face of the chisel is
flat at the edge.
The way many woodworkers go is first to flatten the back of the chisel.
This can take a long time first time out - work with your coarse stone
until the back (at least the first inch or so) is completely uniform,
then change to finer stone and keep polishing. Once you’ve done this
once, the back is never touched by anything other than your finest stone.
Once the back is flat, set the guide to 25 degrees and sharpen the bevel
until it’s uniformly flat and smooth - once the edge is sharp you will
feel a slight burr if you slide your finger down the back of the chisel.
Now re-set the angle to 30 and give the edge just a few rubs on a medium
or fine stone - you should see a bright line of new 30 degree bevel
across the whole edge. Get this as polished as your stones will let you
then rub the back on the finest stone again and you’re done. Once the
edge is blunt you re-sharpen at 30 and that second bevel will get wider.
Every now and again you go back to 25 and use your coarse stone to get
back to the 25 degree bevel and re-hone at 30. That way you have to do a
lot less work than starting with a 30 degree bevel.
You need at least a couple of stones, one coarse and one fine - and they
must be flat. Some people use abrasive cloth glued to plate glass - look
up "scary sharp".

Thanks Norman, useful info. I will probably set something up with plate
glass at a later date as I have a couple of wider plane blades and the
stone I have is `not flat` anymore. My stone will do short term so that
I have a couple of sharp chisels to get on with some work I need to do.

Its strange when I think about it as I have been doing odd jobs in
woodwork for must be 30 years and my original set of chisels are only
now getting sharpened, that set lasted a few years and then my F in law
gave me an old set that was sharpened and they lasted me another few
yeras and then he moved to a flat and gave me some more that were sharp
so I have never had to sharpen any til now.