Thread: The Secret to The Secret to Cambering Bevel Up Plane Blades

In Modern Carpentry A Practical Manual by Fred T. Hodgson, 1902 He's pretty emphatic that "Geometry" is a positive skill for the tradesman ...

indeed, although the way i read it ,it seemed to me he was saying that the tradesman learns it, gradually, from performing the task(s) in a very proficient manner , rather that learning it (geometry) from books or the classroom first and then having to put it into practice anyway, which is almost like learning it all over again from the beginning i think...however like i said before i get that some people, as Pac Man mentioned just want to know, and explaining things with numbers is something we blokes love to do when all else is missing...as Ball Peen mentioned its a wise thing to use your intuition and i suspect that Pac Man more or less was when he picked up on some discrepancies or had problems from reading the article, which prompted his question

The books I had seen gave me the impression of a carpenter and his framing square like a samurai with his sword - inseparable.

that cracked me up, that paints a classic picture...i do love my roofing square and i am very protective and dare i say proud of it , the young guys have practically no idea how to make good use of it they just open a book with the answers, use a speed square or the calculator that short cuts them to the answer...they get off to a quick start but i can still beat em by the end of day ...i never thought of it as a samurai sword though, thats classic, i spin my hammer backwards and forwards and spin it into the hammer holster like a six gun, does that count? its funny because you always see the other guys ,especially the apprentices practising it when they think no ones looking, the hammer goes flying in all directions, sometimes nearly knocking themselves out with it, one day a guy lost it straight through a window lol


cheers
chippy

Thanks Chippy that was my feeling too there does seem to be something missing from DC's original article ( linked in the first post) which prompted my initial post . I was left thinking i should be able to repeat this method from the article but could not, this did not stop my work but did prompt me to ask the question what is the secret that i am missing.

I'm coming in late ... just been too busy to read the forums much recently.

Now I am not sure what is missing. One never sharpens by the numbers. The article was a description of a process, nothing more.

It may be helpful to understand the background as this has become shrouded in time (and I think I do need to edit the article in this regard as well).

At the end of the article I made a reference to a Knots discussion. For those unfamiliar with Knots, it is a woodworking forum attached to FWW magazine. I used to contribute there years ago. There was a time when it was one of "the" places to find spirited discussion (which could - and often did - go waaaay overboard ). The article here was taken from postings I made at Knots.

Briefly, what happened was that there was a heated debate on BU verses BD planes (hey, this was 2006 or so). Larry Williams (of Old Street Planes) strongly dislikes BU planes and one of his arguments was that they could not be cambered in the same way as a BD plane. His argument was that they could only be used with a straight blade, which made them incapable of taking thick shavings. This was not just for common angle jack planes, but especially for high angle smoothers.

Larry was partially correct - few, if any, users of a BU added a camber. They found this too difficult to do. Some would add a camber and it would have no effect. Of course this is only half the story. The reality is that the angles of BU and BD beds demand that the cambers are ground differently. The camber on a BU plane needs to be larger than the camber on a BD plane. This is due to geometry.

I decided to accept this as a challenge, and eventually posted images and content that is seen in the article. The aim was not to provide a cookbook approach but to offer a method and explanation what to do for BU planes. Demonstrating how much a radius one needed for a BU jack was the first part of the challenge, and became the first part of the article. At first I overcompensated with a 5 1/2" radius. This was later altered to a 8" radius. All this is in the article. Just keep in mind that there are no magic numbers - blade widths vary. The main point is that a camber for a BU plane is slightly less than for a BD plane.

The second part of the article focusses on the way one would camber a high cutting angle - for example, a 50 degree bevel (creating an included angle of 62 degrees) - needed to be done in the method I developed if you wished to be efficient. Done this way it becomes a doddle. Try and imitate the way you would do a BD blade, and it would be sheer frustration.

For BU smoothers the answer was to only camber the micro secondary bevel. The main point here is that you want to work on removing the least amount of steel. Cambering a thick primary bevel (which is what everyone was attempting to do up to the publication of this article) is a fools errand. Consequently I advised that one should only use the lowest primary bevel - 25 degrees - and add the higher secondary bevel to this. Note that Lee Valley continue to offer bevels at 25, 38 and 50 degrees. The latter two are fine if you do not plan to camber the blade. Rob Lee is aware of this and agrees with the method in the article - indeed, at the first WIA (Woodworking in America) show, he presented a talk (along with Thomas Lie-Niesen and Chris Schwarz) in which this method was a central part of the discussion.

I have not looked at the article for a long time. It is apparent that much gets taken for granted when one is fired up. Looking at it again there are elementary facts that need to be added in.

Regards from Perth

Derek

Thinking about the whole idea, Derek, if people were finding it a difficult task, isn't it partly a misconception (for want of a better term) of the problem?

If you change a normal chisel from a 25^o primary bevel to a 30^o or 35^o bevel, you would use a grinder - not a honing-related product, right?

So isn't the issue here of creating a full cambered bevel at 38^o or 50^o essentially the same situation?
(Aside from taking the approach that you described)

By definition - or perhaps logic - shouldn't a modification that requires a lot of material to be removed semi-automatically be a regarded as a grinding job? This would explain the frustration if people were trying to do it by honing.

?

Paul

Hi Paul

I suggest that you try grinding a 3/16" thick blade at 50 degrees, and then hone it. That will answer your question.

It is not hard to do if you keep the bevel edge straight but you cannot camber this on a grinder for a HA smoother (not a jack - you can lower the cutting angle for that). The camber on a smoother is too subtle for a grinder, but there is still too much steel to remove (on this blade) to do it by hand. Try it and see.

There are some users who actually do it that way, but the world always has a few who insist of doing things differently ...

Regards from Perth

Derek

Last night I drew a 8 1/2 inch radius on a piece of timber to get an idea of the camber for the scrub plane i needed to grind using a simple compass.I then drew it on the back of the blade.
IMG_0191[1].jpgAttachment 245684


Fast forward to this morning i then ground the camber profile using my hand grinder sneaking up on it.
IMG_0197[1].jpgIMG_0196[1].jpgIMG_0199[1].jpg
Then honed a 35 degree bevel on it and put it back in the plane
IMG_0200[1].jpgIMG_0202[2].jpg
The only thing i was not able to replicate was the shaving type or width on hardwood that was shown on ? pine in the article, experienced some tear out also. Tear out was deep and large in some patches.
IMG_0203[2].jpg

Will now go and grind the bevel to 52 degrees to minimise tearout.

Will now go and grind the bevel to 52 degrees to minimise tearout.

Did you forget the smiley face?

If not (and you are serious), save yourself the trouble. A jack plane is not about fine, tearout-free shavings. It is a coarse tool, removing waste, preparing a surface .... not finishing it.

The high angle secondary bevel goes on a smoother. The camber on that would be too slight to see in a picture unless you held a straight edge against it.

Regards from Perth

Derek

No didnt forget - didnt think about it! So I will now leave it as it is and work up from coarse to fine.

Thanks for the reminder.

To do the 52 i will do the David Charlesworth’s “cambering by the numbers”

I am the Leonard Hoffstader to your Sheldon Cooper. ( Leonard replicates the work of other scientists rather then undertaking his own experiments)

Originally Posted by derekcohen

Hi Paul
I suggest that you try grinding a 3/16" thick blade at 50 degrees, and then hone it. That will answer your question.

Well - it is either "great minds ..." or "fools seldom differ"

I thought Derek made a good point, so I decided to try it out ... also, as it turns out.

I missed the 3/16" part ... the old abused blade I got with my old abused #62 is 1/10" ... so 0.100" instead of 0.188"

Camber 005.jpg Camber 004.jpg

Time is damn short around here at the moment, so I made the world's dodgiest trammel (8")

Camber 006.jpg Camber 007.jpg

and like Pacman, marked out on the back of the blade, then ground that profile.

Camber 009.jpg Camber 013.jpg Camber 014.jpg

Unfortunately ... there being a previous standard bevel there beforehand, there wasn't the metal there to support a full 50^o bevel, and I had to do it again further in

Paul

I think that you misunderstood - or I did not explain well enough (probably the latter).

Try grinding the blade straight across at 50 degrees. Now try adding a fine camber (one for a smoother - which means you will remove about two shavings worth at each side). This is a blade for a smoother, not a jack. The camber on a jack is easy since it is large enough to do on a grinder. The bevel is at 25 degrees since a low cutting angle is good to have when you traverse a board. A camber for a smoother is another matter altogether. Because it is so fine it must be done by hand. That s when the fun begins.

Regards from Perth

Derek

Camber 015.jpg Camber 017.jpg Camber 020.jpg

I ground an old chisel to about 50^o to get a feel for it

Camber 021.jpg Camber 024.jpg

With that to compare against I roughed the vertical edge down to what looked to be 50^o

Camber 025.jpg Camber 028.jpg Camber 029.jpg Camber 030.jpg
Camber 031.jpg

I had planned to get it close, then make a 8" swinging jig to grind it properly ... but I could get close enough like this to go on to hone the edge. I'll try that tomorrow.

Cheers,
Paul

Originally Posted by derekcohen

Paul
I think that you misunderstood -

I think I understand your idea - a 25^o primary bevel, with a 50^o cambered bevel superimposed on it - capable of being formed by honing. Right?

I wanted to make a full-height cambered 50^o bevel off a grinder.
Seems do-able.
I don't know about a small camber being too subtle ... even if you don't do the vertical shaping on a grinder, you can do that part on a coarse stone.
Grinding a 50^o bevel to match the edge profile doesn't seem a problem, or the honing ...
so
... maybe I'm missing something ?? (it happens a lot)

Paul

What is the point of a jack-type camber with a 50 degree bevel? What type of plane would you use this on? None that I know of.

The thin blade that you are using is not a challenge - it is not the same as a 3/16" thick blade. Indeed, I developed a method of converting a 3/16" blade into one like yours so that I could freehand camber it on a 50 degree bevel: http://www.inthewoodshop.com/Woodwor...aneBlades.html

The issue at hand is to try and camber a 3/16" thick blade ground on the straight/square. Try that!

Regards from Perth

Derek

Originally Posted by pmcgee

I have often thought - wrt woodwork articles - that instead of trying to mark out (eg) a 12.5^o angle it could more accurately be done by measuring along 'x' cms and up 'y' cm. You can make it as accurate as you like by making the x and y larger.

The books I had seen gave me the impression of a carpenter and his framing square like a samurai with his sword - inseparable.

Further to rambling on about carpenters squares ... these little bits are on the Timbecon website ... great idea ... but $40!?!

Originally Posted by derekcohen

What is the point of a jack-type camber with a 50 degree bevel? What type of plane would you use this on? None that I know of.

The thin blade that you are using is not a challenge - it is not the same as a 3/16" thick blade. Indeed, I developed a method of converting a 3/16" blade into one like yours so that I could freehand camber it on a 50 degree bevel: http://www.inthewoodshop.com/Woodwor...aneBlades.html

The issue at hand is to try and camber a 3/16" thick blade ground on the straight/square. Try that!

Regards from Perth

Derek

I don't have anything in thick steel that I want to mess with, so I'll take your word for it Derek (of course).
On the plus side, I now have a 50o #62 blade - which I always wanted to try.

Friedrich Kollenrott has a saw-sharpening page in German ... and also a plane/chisel page:
Das Schärfen von Stecheisen und Hobeleisen

Halfway down - Figure 20 - I think he is talking about roughly your idea Derek.

But also, aside from the calculations at/near the start of the thread it had occurred to me that there are (infinitely?) many ways of cambering rather than forming the edge into a part of circle. I believe some people grind a bit of the vertical corner away. Friedrich seems to be describing something different but similar there with the chamfering ... but I haven't looked at it properly.

Cheers,
Paul