Hybrid Profile for Freehand Sharpening BU Plane Blades

[Alf]

I'm old fashioned, Derek - grinding angle is always a little less than the honing angle. Secondary bevels are our friends and I personally see no virtue in honing across the whole face of a bevel, except apparently for bragging rights. (Damn! ) If I needed a 50° honing angle, I'd hollow grind a handful of degrees less. At a 62° EP, I think a few degrees here and there are probably a bit academic when it comes to the end result.

 

[Derek Cohen (Perth Oz)]

I'm old fashioned, Derek - grinding angle is always a little less than the honing angle. Secondary bevels are our friends and I personally see no virtue in honing across the whole face of a bevel, except apparently for bragging rights. (Damn! ) If I needed a 50° honing angle, I'd hollow grind a handful of degrees less. At a 62° EP, I think a few degrees here and there are probably a bit academic when it comes to the end result.

Hi Alf

We are describing something similar then. Neither of us wishes to hone a full bevel face. So we seek to create a secondary bevel at the desired angle. My definition of "accurate" for bevel angles is "in the ball park", a few degrees here-or-there are irrelevant. However I would like them repeatable - hence the secondary hollow grind (if I can call it that) on a lower primary bevel (in other words, the angle of the secondary hollow does not have to be spot-on 50 degrees, but the hollow allows for a repeatable honing angle). I think what you are doing - correct me here - is to eyeball the secondary bevel angle after grinding the primary bevel on that contraption of yours , sighting the secondary on the primary? If so, the difference between our methods is that I have a secondary hollow to return to for a repeatable honing angle, and you do not (and obviously not seeing a need for one).

Regards from Perth

Derek

 

[Jacob]

...

We are describing something similar then. Neither of us wishes to hone a full bevel face. So we seek to create a secondary bevel at the desired angle. My definition of "accurate" for bevel angles is "in the ball park", a few degrees here-or-there are irrelevant.

What happened to "precision" then. :lol:

However I would like them repeatable

Perfectly possible now you have abandoned precision.

.. I think what you are doing - correct me here - is to eyeball the secondary bevel angle

exactly - getting it "in the ball park". This sort of hand/eye skill is quite fundamental to woodworking an a lot of other things. Think of dart throwing. Anybody care to work out the geometry of the bulls-eye and the thrower? Much more precision compared to sharpening a chisel IMHO even if you only just hit the board!

.. sighting the secondary on the primary?...

Er, how would you do that? With mirrors or something? Crawl underneath? They are both out of sight.
No, you set the "secondary" by looking at the blade you are holding and its angle relative to the surface of the stone. Would a diagram help? :lol:
So its "in the ball park", "hand and eye skills", "looking" and you can start saying goodbye to SIDS ("Sharpening Is Difficult Syndrome" in case you have forgotten).

 

[Alf]

Think that's about it I think, Derek. I rest the grinding bevel on the stone, then tip it up "that much". Couldn't tell you how many degrees "that much" is, but I seem to have got into the habit of tipping it the same amount of "that much" from the primary bevel each time, so I suppose I end up with a repeatable secondary honing angle that way. So eyeballing it, but by feel. So, um, not really eyeballing, but, um, muscle twitching? Need to work on the terminology... Anyway, until it becomes too large to make sense, and back to the grindstone we go to knock it back again. If I was to grind the secondary angle, then I'd reckon it had become my primary angle and I'd be looking to tip it up "that much" from there. At which point, we find ourselves off down the rabbit hole, because from my perspective you're effectively honing the whole primary bevel again and it's not a secondary bevel as I think of it at all! I can see where you're coming from (I think), but I still can't see the advantage. Which is probably my fault, 'cos sharpening discussion always confuses me eventually; I should know better than to start. #-o

 

[Jacob]

... So eyeballing it, but by feel. So, um, not really eyeballing, but, um, muscle twitching? Need to work on the terminology... .....

:lol:
I think of it as "just doing it"

 

[Derek Cohen (Perth Oz)]

Jacob

If you think we're wrong and you're right, then say so. Don't hang back. :lol:

Regards from Perth

Derek

 

[Alf]

... So eyeballing it, but by feel. So, um, not really eyeballing, but, um, muscle twitching? Need to work on the terminology... .....

:lol:
I think of it as "just doing it"

Well so do I, Jacob, but find that conveys surprisingly little in a text-based discussion.

 

[hockeydad]

I'd have to buy a little thin ruler which I don't need!

Doesn't have to be a ruler, could be a piece of paper or thin card.

As we career towards an agreement that the important lesson is that polishing four square inches of blade back is a complete waste of time. The point of the ruler/card/bit of thin stuff is that by slipping something under the other end, someone without the skills to differentiate between one gnats and two can reliably produce the desired result without inadvertantly going beyond the 7 degrees where their bevel up plane stops working.

David teaches at all levels from 'what's a chisel' to time served carpenters switching to furnituremaking, he also teaches people all over the world via video / DVD - so his methods have to work for people who he can't be there to correct if they misjudge how big a gnats is.

Matthew,
It's been quite a few years since I posted in this forum, the last time being on this same subject. In response to David C's ruler trick, I suggested a piece of a pizza box which worked quite well. In the 10 to 15 year interim, I've switched to using either painters tape or duct tape. By varying the number of wraps i can vary the length/width of the back bevel and by using a specific distance from the end of the blade and marking it with an indelible marker, I achieve both precision and repeatability, which I find a comfort when freehanding. (Jacob, my 76 year old artheritic hands aren't as sensitive to elevation as they used to be).

Since the tape is stuck to the blade I don't have the problem of it sliding around on the ruler, I can use all or any portion of the stone/paper/plate and I can put it on or take it off in seconds. I have switched to diamond paste and cast iron plates to minimize the sharpening/honing mess and the couple of times I tried the ruler I found that the ruler was getting pretty well useless for what it was intended. Besides, I could never find it when I wanted it.

 

[bosshogg]

I'd have to buy a little thin ruler which I don't need!

Doesn't have to be a ruler, could be a piece of paper or thin card.

As we career towards an agreement that the important lesson is that polishing four square inches of blade back is a complete waste of time. The point of the ruler/card/bit of thin stuff is that by slipping something under the other end, someone without the skills to differentiate between one gnats and two can reliably produce the desired result without inadvertantly going beyond the 7 degrees where their bevel up plane stops working.

David teaches at all levels from 'what's a chisel' to time served carpenters switching to furnituremaking, he also teaches people all over the world via video / DVD - so his methods have to work for people who he can't be there to correct if they misjudge how big a gnats is.

Matthew,
It's been quite a few years since I posted in this forum, the last time being on this same subject. In response to David C's ruler trick, I suggested a piece of a pizza box which worked quite well. In the 10 to 15 year interim, I've switched to using either painters tape or duct tape. By varying the number of wraps i can vary the length/width of the back bevel and by using a specific distance from the end of the blade and marking it with an indelible marker, I achieve both precision and repeatability, which I find a comfort when freehanding. (Jacob, my 76 year old artheritic hands aren't as sensitive to elevation as they used to be).

Since the tape is stuck to the blade I don't have the problem of it sliding around on the ruler, I can use all or any portion of the stone/paper/plate and I can put it on or take it off in seconds. I have switched to diamond paste and cast iron plates to minimize the sharpening/honing mess and the couple of times I tried the ruler I found that the ruler was getting pretty well useless for what it was intended. Besides, I could never find it when I wanted it.

I use a piece of fine wet and dry, width of the stone/plate and about 1/2" wide. Just stick it to whatever stone your using (drop of Methuselah's glue) this gives a polish and sharpen all in one. Good for those those situations, not quite polishing the very end of the blade back, I have also found, once done with this the blade can be flattened on the stone surface within a few strokes with no wet and dry...bosshogg

Imagination is more important than knowledge...
Albert Einstein (hammer)