Brian- thanks for that detailed explanation. I get it now- it actually makes sense to me.
But wow, that's pretty amazing.
Giving this more thought, especially the idea you only flatten the back of a western plane blade once. My bevel up blades at 38 degrees develop a roughness on the back directly behind the edge. This is clearly visible when working hardwoods. It means you need to flatten the back on a fine stone each time you sharpen the blade for a very fine edge. My bevel down blades function just with sharpening the bevel and burr removal on the flat.
The conclusion; bevel up blades are more work, not just because they are thicker but the backs do require constant attention.
Any one else reached the same conclusion?
I've seen the odd post with people using a ruler trick to add a small micro bevel to the back of the bevel up blade. Is this an attempt to remove the 'rough edge' I've described? It does seem counter productive as it would seem to encourage more 'roughness' to develop.
Last edited by William Fretwell; 01-18-2017 at 1:59 PM.
Having no Japanese plane blades does this mean they expect to work both sides of the blade routinely? Given the 'roughness' on my bevel up blades behind the edge on the flat that requires work are we fooling ourselves with the big flat back?
I can see flattening a chisel back once but my bevel up plane blade backs do require constant attention and the big flat back makes that more difficult.
So if a Japanese plane is in my future do I go Jack or Smoother?
Hira Kanna (smoother) would be the place most people start, also where most see the majority of the benefit. The other parts of your post, I sort understand what you're saying, but a bit confused?
Bumbling forward into the unknown.
Lets see if I can clarify a bit. Both sides of an edge should be 'flat' at the very edge for optimal cutting. It was suggested that some of LV backs are remarkably flat at purchase (grey flat) and that 'polishing' will be detrimental. This ties in with the convention of finishing the back of a plane blade once. My bevel down blades fit this model but my bevel up blades do not, they develop a pitting roughness immediately behind the edge on the flat side. This detracts from the achievable edge.
Maintaining the flat side frequently becomes essential beyond burr removal. This is a lot of work due to the large area to maintain.
I wonder if others have this issue with bevel up (38 degree) blades. I also wonder if the Japanese plane blade with it's much smaller back area is a solution to this issue.
Last edited by William Fretwell; 01-18-2017 at 4:49 PM.
I'm not so certain that it is a solution to that, but I've enjoyed the fact that there is a hollow and an iron which can be worked by tapping out rather than having to work the back to the degree required to flatten many of my western plane blades.
I would imagine one fix is to grind the edge back at each honing (bevel up)
I always hone away the wear bevel, in my case I'm usually doing so with a 1k stone.
Bumbling forward into the unknown.
I'm not sure I understand something William - Are you saying that it is your belief that the non bevel side of BD irons basically only require work on a stone once and then remain in a useable shape from that point on? And that the non bevel sides of your our BU irons require work every sharpening session due to some noticed pitting roughness? I have always worked the non bevel side (small portion near to the cutting edge only) every sharpening session on all (BD or BU) of my plane irons, but then again I have never looked at any blade through any type of magnification so I could be all wrong.
David
Hi Brian, I don't see any advantage to the tapping out process. I do however see the potential advantage of a hollow back. It seems the tapping out is a process invented from the necessity dictated by the hollow back. Certainly, if there were no hollow back then there would be no tapping out. Tapping out also seems very tedious and finicky and much more difficult than honing the bevel and back alone. certainly some western users would have invented the same process themselves if it were advantageous. God only knows how many forum threads would have been spawned by the tapping method if it did exist for western tools. Perhaps there are as many tapping out threads as sharpening threads on Japanese forums??
Hi Pat, They're part and parcel, so can't have one without the other. If western blades were hardened to the same degree, they would need also be laminated to soft iron to support the edge and a hollow would need to be cut to allow one to back to be flattened with success, so it is not simple enough to conclude that because western blades aren't done that way that it is unnecessary since western blades do not share the same characteristics entirely.
One problem aside, owed to a very curious circumstance, but I've tapped out practically every Japanese tool in my shop so once you have the process down it's not so easy to fail.
It's a fairly regular topic on Japanese tool forums.
Bumbling forward into the unknown.
I tend to agree with William on the difference in wear patterns between a Bu and a Bd plane iron. That the leading primary surface of the iron will dominate within nominal wear.
This could no doubt be confirmed by someone prepared to spend the time to undertake an in-depth analysis on the difference in wear patterns between to the 2 types of plane iron set ups.
If one were to just focus on Bd planes irons, there is also scope to consider that the bed angle itself also has some primary impact on wear patterns.
One could also consider with regards the use of double irons, that the time difference within wear can also be tied to how close the front edge of the cap iron is set from the leading edge of the cutting iron.
Not something I would be overly keen to spend the time on, but I can think of a couple of guys that might take it on.
Patrick or Kees; an opportunity has arisen for an in-depth analysis by a Mech Engineer.
regards Stewie;
Last edited by Stewie Simpson; 01-18-2017 at 11:39 PM.
I said that polishing for the sole purpose of achieving a mirror finish would likely be detrimental. If you've got a serious wear bevel as you describe below then that's a different matter - the perfect grey finish is gone anyway at that point, so you have to do *something*.
It actually isn't much work, for two reasons:
1. You only need to achieve optimal finish on the part immediately behind the edge, so you don't need to maintain a large areas. Lots of people polish with pressure applied to the leading 1/2" or so, and some go further and use the "ruler trick" to focus polishing right up along the edge. Both strategies work.
2. If the blade has been flattened (or came flat as with LV) then it doesn't take much work at all to remove a bevel-up blade's wear bevel as you describe. Such bevels are O(microns) deep, and that amount of material is very easy to remove from a flat surface.