The Concave Cambered Blade

[adrian]

In another rather lengthy topic a couple months back, I noted that I have a problem with my Clifton #7. I cambered the blade and worked for a while planing edges and then I discover that the blade is not cambered any more but in fact has gone concave in the center.

Someone suggested that I should show a picture, but I was finishing up with the edge planing and the problem didn't recur...until now. (I'm trying to plane the glued up panels to all have exactly the same width, and preferably right angles at the corners.)

I found it rather challenging to take a picture of this but here's my best effort

You can see that light is shining through in the center and at the edges. The blade rests on two points on the straight edge and does not rock.

In the last discussion, the prevailing opinion seemed to be that my blade must be very soft for some reason ("made of cheese") and I should get a new blade. Is there any alternative explanation?

I'm thinking maybe the Veritas "Stanley #7" replacement. Is that a good choice?

 

[bugbear]

I found it rather challenging to take a picture of this but here's my best effort

That's very well taken - nice work.

Yes, it appears your blade is made of cheese.

BugBear

 

[hamburglar]

I had the same happen on a blade from a record 4 1/2. In my case I felt it could have been due to prolonged use on the shooting board with oak.

 

[Karl]

Adrian - nice photo.

Is the blade the original Clifton? If so, I would ask whoever you bought the plane from for a new blade.

Cheers

Karl

 

[MIGNAL]

Resharpen the blade and pare away at some Hardwood endgrain. Don't mount it in the Plane body, just use it chisel style. If the blade is soft the edge will blunt or turn over in no time.
If you bought it from new send it back to Clifton.
If that's not an option you could grind back 1 or 2 mm's and hope you hit on some hard Steel, that is if soft Steel is the problem.
I recently bought a New Old Stock Sheffield cast blade where the problem was the reverse i.e. the very tip was super hard and a pain to sharpen. After I ground back a little the blade stopped behaving like HSS and more like 01. Perhaps too much Carbon at the edge and it was effectively case hardened.

 

[Inspector]

Any chance the frog isn't quite flat forcing the center of the blade down more than the sides?

Always thought the blade was supposed to be ground straight to joint edges and cambered to plane faces. Did I get that mixed up somewhere along the way?

 

[adrian]

Any chance the frog isn't quite flat forcing the center of the blade down more than the sides?

So you're wondering if the frog is hollow in the center? I can inspect the frog and see if I notice anything odd...but how would this cause the problem I've observed? Wouldn't a frog problem cause chattering or some other sort of misbehavior? (Given that this is a bevel down plane the edge never gets near the frog.)

I considered that maybe the chip breaker is causing the problem somehow, but I haven't seen any evidence in support of this.

Always thought the blade was supposed to be ground straight to joint edges and cambered to plane faces. Did I get that mixed up somewhere along the way?

There are multiple approaches. Charlesworth in his planing DVD and book says to camber the blade for all work, actually. For edge jointing with a cambered blade you shift the blade side to side when the edge is not square to the face. Cosmon in his DVD shows the same job with a straight blade. He has you tilt the blade when you need to correct a non-square edge. I personally find it extremely hard to set the blade tilt accurately, so this seems more difficult to me. (And what do you do if the edge is twisted? Half a shaving with one setting and half a shaving with another?) I've found the Charlesworth method very effective.

 

[Handworkfan]

Always thought the blade was supposed to be ground straight to joint edges and cambered to plane faces. Did I get that mixed up somewhere along the way?

There are multiple approaches. Charlesworth in his planing DVD and book says to camber the blade for all work, actually. For edge jointing with a cambered blade you shift the blade side to side when the edge is not square to the face. Cosmon in his DVD shows the same job with a straight blade. He has you tilt the blade when you need to correct a non-square edge. I personally find it extremely hard to set the blade tilt accurately, so this seems more difficult to me. (And what do you do if the edge is twisted? Half a shaving with one setting and half a shaving with another?) I've found the Charlesworth method very effective.

In fact, edge jointing with a no 7 is the only task for which David Charlesworth uses a straight blade in a bench plane. The cambered edge is useful for truing an out-of-square edge, so great for a jack plane, but for jointing squareness isnt' an issue since if the two boards are planed together, then opened like a book, any angle will cancel out. It's the way I've always done it, and it's worked well - and on getting David's last DVD, 'Five Topics', I find he actually recommends it, which is nice!

 

[Karl]

Interesting - I had always understood that DC advocated the "wandering blade" method for jointing boards. I haven't yet seen his 5th DVD.

Cheers

Karl

 

[adrian]

Certainly in his first video on planing he focuses on the use of the cambered blade and the "wandering blade" method. In his book he goes so far as to write "If any reader can explain to me how a square edge is produced with a straight blade -- other than with a shooting board --- I would be most grateful."

 

[Wiley Horne]

Adrian,

Read no further if you do not use a sharpening jig....

If you do use a sharpening jig, it could be that the blade is being deformed while sharpening. Or that the blade has a concavity or convexity which is being pressed flat during sharpening. Or that the sharpening jig is exerting a different pressure pattern than the mounting assembly in the plane.

To test:

1. A typical card scraper will be Rc 50 or less. Will it score the back of your blade?

2. Examine the blade against the light for convexity or concavity of the back.

3. Sharpen the blade to the best of your ability and re-take the picture you show above, with the blade (a) still in the jig, and then (b) released from the jig. Do you get the same profile?

4. To check the plane, test the freshly sharpened blade in a different plane--same result or different?

Your answer should lie somewhere in the above. I apologize if this has all been covered in the previous thread you mention in your post.

Wiley

 

[Inspector]

So you're wondering if the frog is hollow in the center? I can inspect the frog and see if I notice anything odd...but how would this cause the problem I've observed? Wouldn't a frog problem cause chattering or some other sort of misbehavior? (Given that this is a bevel down plane the edge never gets near the frog.)

I considered that maybe the chip breaker is causing the problem somehow, but I haven't seen any evidence in support of this.

I was a little skeptical of the blade having a soft center (sounds like a chocolate) and was looking for another explanation. If the frog and chip breaker are good then that would leave the blade.

I suppose that the blade could have been locally overheated during the initial grinding resulting in a soft center area but I don't believe it was from the initial heat treating of the metal. If you were here I would put it on a hardness tester and check along the cutting edge and see if there was a drastic difference. Since the indentor needs to be back from the bevel to test, (at least 3 diameters of the indentor tip) it wouldn't read any differences at the cutting edge caused from bad grinding unless it was a major goof by the maker. You could try and take a fine file and try to lightly file the bevel. If the file "bites' in the middle and not the corners you have a soft center, but if it "skates" over evenly then it is approximately the same hardness.

Get a hold of Clifton and talk to them and see what they say, otherwise carefully grind the edge back 2 or 3mm and see if the blade holds its edge. If it doesn't then look at a different blade or play with re-tempering it yourself. You wouldn't have anything to loose if it's soft and won't hold an edge.

 

[adrian]

Adrian,

Read no further if you do not use a sharpening jig....

If you do use a sharpening jig, it could be that the blade is being deformed while sharpening. Or that the blade has a concavity or convexity which is being pressed flat during sharpening. Or that the sharpening jig is exerting a different pressure pattern than the mounting assembly in the plane.

I do use a jig, the Veritas Mk II. Why would this deformation, were it occuring, lead to the observed failure?

To test:

1. A typical card scraper will be Rc 50 or less. Will it score the back of your blade?

The corner of the plane very decisively scratches the scraper. The scraper does not scratch the bevel of the plane. I tried in the center about 1mm behind the edge.

2. Examine the blade against the light for convexity or concavity of the back.

The back is flat.

3. Sharpen the blade to the best of your ability and re-take the picture you show above, with the blade (a) still in the jig, and then (b) released from the jig. Do you get the same profile?

If the jig deforms the blade won't the deformation occur perpendicular to the blade? I would think it would be invisible in a picture like the one I posted. I'm holding off on resharpening this blade for now because it might eliminate evidence of how the failure occurred.

4. To check the plane, test the freshly sharpened blade in a different plane--same result or different?

My only other compatible plane is a Stanley #6 that I use as a fore plane to clean up rough stock (with an agressively cambered blade and a really heavy cut) and it's not a very good plane, so I'm not sure I can use this plane the same way as the jointer long enough to produce the problem. It takes a while to happen. Note that it also seems to happen suddenly, Everything is fine for a long time and then abruptly I notice that the plane is cutting at the edges rather than in the middle.

 

[Handworkfan]

Certainly in his first video on planing he focuses on the use of the cambered blade and the "wandering blade" method. In his book he goes so far as to write "If any reader can explain to me how a square edge is produced with a straight blade -- other than with a shooting board --- I would be most grateful."

Correct on both counts - and in both cases he's talking about squaring an edge relative to the face side of the board. However, in this instance he's discussing the straigtening of two boards prior to jointing, and the squareness of the edge isn't a prime concern. If both boards are placed face to face in teh vice and planed together, when they are aligned the angles will cancel one another out so squareness isn't an issue - it's all on the DVD.

 

[bugbear]

but for jointing squareness isnt' an issue since if the two boards are planed together, then opened like a book, any angle will cancel out.

This is often called "match planing" and works when the blade is wide enough to manage two workpieces at once.

BugBear

 

[adrian]

So based on the scratch tests it would appear that the problem is not that the Clifton blade is very soft. Is that right? Or is this test not conclusive?

I checked the frog. It appears to be reasonably flat.

Suppose I took a freshly sharpened plane and approached the edge I wanted to plan with the plane set for a shaving that is much too thick (say 1 mm). The blade just bashes into the edge of the work and doesn't take a shaving. Could doing this cause the failure I have observed? (I'm not saying I do that, but rarely I somehow approach the workpiece and something sort of like this happens.)

The one thing that makes me think the problem must somehow lie with the plane and not my technique is that this failure has happened 4 times to this plane and zero times to my other planes despite (presumably) no variation in technique.

Could it matter that my other planes blades have A2 vs who-knows-what for the Clifton blade? Could the bevel angle of my blade matter? I believe the Clifton is sharpened at a lower angle than my other planes (I think it was 28 degrees---but I think I've been raising it as I observe these problems, so I'm not sure where it is now. My other bevel down plane is sharpened at something like 32 degrees.)

Someone suggested contacting Clifton. I'm in North America and don't want to phone them. They don't seem to have an online presence. I have tried contacting the guy I bought the plane from (7 years ago) and he doesn't have any insight.

 

[Karl]

If you've had the plane for 7 years and only just found out about this problem, what the hell have you been doing with it all this time?????

Just ditch the blade, buy a replacement LN blade and get it back into working order.

I think it is pretty clear that the blade you have isn't going to work. Ever. So bin it and buy a new one.

Cheers

Karl

 

[adrian]

If you've had the plane for 7 years and only just found out about this problem, what the hell have you been doing with it all this time?????

This is a fair question. This was the first bench plane I ever bought. During that 7 years I've been learning how to sharpen, and learning planing technique. Since the cause of this problem remains unknown, it's hard to be very specific about why I never noticed the problem before, but when I started I was sharpening the blade straight, not cambered, so I couldn't very well notice a loss of camber. I was planing the face of the wood, not edges, so I wasn't working a limited area in the center of the blade. (My early efforts to plane edges were unsuccessful so I was using an electric router to joint edges instead.) Also note that I haven't had enormous amounts of time for my woodworking projects during the 7 years in question.

If this failure were to occur while planing a face with a straight blade it would appear as a generally dull edge---no reason to suspect anything funny. Once I intentionally cambered the blade (which I did about 8 months ago for the first time) the first thing I did was flatten a lot of lumber. I didn't notice the camber vanishing during this work. Apparently it doesn't cause the problem.

I returned to edge planing armed with the Charlesworth method only late last year. While edge planing, the tool switches from cutting in the center to cutting at the edges, so it's immediately apparent that something strange has happened. If the camber did start to vanish while face planing, it wouldn't be possible to tell because the symptom would be a more uniform shaving.

 

[ivan]

Why not just try a blade from one of your other planes in your Clifton?........

 

[adrian]

Why not just try a blade from one of your other planes in your Clifton?........

The only compatible blade I have is an old Stanley blade sharpened with an 8" radius for very rough work. I don't think I'd learn anything by putting that blade into the clifton. My other bevel down bench plane is a Veritas 5 1/4 and it has a much narrower blade.