The secret to cambering Bevel Up plane blades

[David C]

Brent,

I did not study the diagram properly, but think it is like the set up in my second book, used to produce blades for a hollowing plane, with curved sole..

The angle is controlled by a fixed sloping plane.

The radius is set from an adjustable but but finally fixed pivot point.

This produces exact repeatable curve without any skill input, or feel from the operator. It could be done with a blindfold on.....

best wishes,
David Charlesworth.

[bugbear]

[Paul Kierstead]

[MikeW]

I too fear the point is lost, BB.

What do we make of the scientist who doesn't try the solution to a problem choosing to rather rationalize why it won't work? Proving or disproving through trial and error is still the scientific method, eh?

In that vien, I went out and tried Derek's jiggy and a single-point version. Both work. The single-point requires more user intervention and changes the bevel angle as it moves to the outer edges. Which makes sense as that is how one produces a fingernail grind on a turning gouge. Derek's jiggy produces an even bevel angle.

The single-point changes the distance from the pivot-point to the edge. The other jiggy does not.

However, there is nothing in Derek's jiggy (or the other) to prevent one from over grinding and thus changing the desired camber. That part is user experience.

The solution to that "problem," it seems to me, is to first do what I have always done which is to grind the profile at 90 degrees and grind the bevel to nearly the edge and hone from that point on.

I look at the issue this way. A honing jig is just that--it is a holder to aid in fixing the bevel angle and desired shape. This is the same with the cambered roller on the LV MK.II honing jig, the Eclipse and its clones, the MF honing jig, the Stanley et al. All of them can produce/hone the desired camber (or straight) edge--and all of them require the user to be smarter than the jiggy. Some of them produce a more consistent result easier (less user thinking and acting). But they all require user intervention.

Derek's jiggy works the same way. It isn't automatic and foolproof. But hey, why not design, build and produce one? Or instead, you could simply tell people why one or another won't/can't work.

Take care, Mike
who recognizes you recognize Derek's works for him.

[Paul Kierstead]

Can we summarize by saying it isn't foolproof, but it sure helps?

As we say in my business; nothing is foolproof because fools are so ingenious.

[Derek Cohen (Perth, Oz)]

Thanks Mike .....

Regards from Perth

Derek

[BrentB]

Well, as one who has read a lot of results that worked in practise - that is, some one claimed to be able to do something - but were not reproducible, I have to take BugBear's side in this. In fact, in Mike's own (and several other people's, including mine) recommended solution, he explains exactly what is missing from Derek's approach.

When using the rod type tool rest, with no fixed angle guide, there is nothing to ensure correct angle. Chris adds that his jig had an angle plate. With an angle plate it will work for anyone, without an angle plate others trying this could easily foul up.

The alternative is a scribed arc on the back of the blade which gives the user a goal - grind to the scribe then stop (leaving the scribe just to be sure).

However, grinding the full bevel and attempting to reach the scribe both in the same operation can lead to overheating the edge - again, a problem with Derek's approach. Again, something Mike recommends against. First shape the iron, second grind the bevel.

In the grind the bevel part, if you don't have an angled plate, then a guide like Derek uses makes sense.

So, it works. It could work better with a couple of changes. Even with the changes it would not be my first choice.

Sharpening radiused blades
_________________
Brent
--
Victoria, BC, Canada

[Derek Cohen (Perth, Oz)]

[MikeW]

I think there are to separate arguments going back and forth.

One is establishing the camber. BB argues (it seems) that Derek's jiggy cannot do this as is and create the same camber on the iron as that of the jiggy. It does.

The second is producing the bevel proper. Derek is doing both at once.

I think that doing both at once is prone to the problem that Brent is pointing out, that is overheating the iron. That is an issue, but it is a procedural or best practices issue.

Creating camber on an iron that matches the jiggy is separate...or at least I separate them..issue.

As mentioned, there are procedural means to obviate overheating (do the operations separate) and or consistency in the bevel angle. The latter is easily done via experience, an angled rest in conjunction with the jiggy, a combination or [insert method here]. The former also has solutions. Water-based wheels (too slow), a light touch and coarse grits (mine and Derek's prefered means), or as mentioned, doing the grinding of the camber and shaping the bevel separately. However, doing them separately also introduces the possibility of overheating too.

This is where a modicum of understanding how fast heat is generated on the various mediums and especially what one person is using or has to use. It is also good practice to never grind to the very edge on bench grinders or belt sanders--unless with experience one knows how to keep the heat from tempering on their equipment (as much art as anything) and is using dressed coarse belts/wheels. Hand-cranked and water-based systems are also viable means but slow (and one can still overheat an iron with a hand-cranked system).

So what's the point to all my rambling? None, really. The important thing is to simply get the iron(s) into the shape desired, sharp, and make something.

Take care, Mike

[DaveL]

Hi Brent,

Welcome to the forum.

Your link has been caught by our spam trap, it will stop happening once you have a few more posts to your name.

[bugbear]

[Derek Cohen (Perth, Oz)]

[bugbear]

[ivan]

Provided you roll the template steadily from side to side, ensuring that all parts of the template's curve touch the tool rest, and don't linger too long in any one place, the camber will match that of the template about as well as a jig ground straight blade will match a square.

Don't forget a straight jig is grinding a camber of infinite radius....

[BrentB]

Ivan was a little ambiguous when he said