newbie chisel sharpening question

[D_W]

...along with the daft mantra: "a sharp edge is the intersection of two flat planes" as often repeated, with variations. :roll:

How is this daft? That's exactly what a sharp edge is. If it's not then pray tell what is it?

...no more effective than the old freehand simple methods

While I'm a big supporter of freehand sharpening I'm not blind to how good it can be. You shouldn't be either.

Jigged sharpening, powered or by hand, can routinely create edges superior to those that the great majority of freehand sharpeners are capable of. That's a proven fact. The key point is however that freehand sharpening only done a reasonable standard is good enough for most people, for most jobs. But good enough is not the same as equally good.

I think there is a degree of subtlety in sharpening that many don't get. There's no reason that jigged sharpening would create a better edge than freehand except in the case where someone is not very good at freehand sharpening.

If it's an issue of beginners, that may be something entirely different.

The planes that intersect don't need to be flat, either, not even in an ideal sense. two curved surfaces meet at 30 degrees at the terminal point and two flat surfaces meet at 30 degrees, there isn't anything better about the flat bevels unless some area back from the curved bevels lacks strength.

(I recognize that before I had a good handle on freehand sharpening, it was easier to create a consistent edge with a guide, but that's just a matter of experience).

 

[Phil Pascoe]

The planes that intersect don't need to be flat, either ...
No, they don't. But they need to be parallel if the edge is to be straight - which you presumably want your chisel edge to be - so if one side is flat the other isn't the cutting edge won't be straight. Try honing a serrated edge.
I cannot see for the life of me how gringing a degree or two on the flat side is of any benefit - (we're not talking carving chisels) neither have I ever heard it suggested in 50 years of reading woodworking press.

 

[ED65]

I think there is a degree of subtlety in sharpening that many don't get.

If you'll pardon the emphasis, that's what I'm saying.

There's no reason that jigged sharpening would create a better edge than freehand except in the case where someone is not very good at freehand sharpening.

Yes, and most aren't.

The planes that intersect don't need to be flat, either, not even in an ideal sense. two curved surfaces meet at 30 degrees at the terminal point and two flat surfaces meet at 30 degrees, there isn't anything better about the flat bevels unless some area back from the curved bevels lacks strength.

In case it needs to be specified: I was referring to at the edge. All diagrammatic representations of edges show them as two flat planes, which they are at a small enough scale irrespective of the overall shape of the bevel – multi-flat, convex or concave (I know you know this, just specifying for anyone who doesn't).

 

[Jacob]

...along with the daft mantra: "a sharp edge is the intersection of two flat planes" as often repeated, with variations. :roll:

How is this daft? That's exactly what a sharp edge is. If it's not then pray tell what is it?

I can see it makes sense but a moments thought should tell you that a sharp edge is achievable with non flat bevels (rounded etc) - and a non straight edge (cambered etc). So it really isn't the only "exactly what a sharp edge is" and confuses a lot of people.

...no more effective than the old freehand simple methods

While I'm a big supporter of freehand sharpening I'm not blind to how good it can be. You shouldn't be either.

Jigged sharpening, powered or by hand, can routinely create edges superior to those that the great majority of freehand sharpeners are capable of. That's a proven fact. ....

Sorry - it isn't a proven fact at all - it all depends on the operative. Think of an old fashioned barber with his (occasional) stone and strop on a cut-throat - very sharp but with rounded bevels and non straight edge.

 

[D_W]

The planes that intersect don't need to be flat, either ...
No, they don't. But they need to be parallel if the edge is to be straight - which you presumably want your chisel edge to be - so if one side is flat the other isn't the cutting edge won't be straight. Try honing a serrated edge.
I cannot see for the life of me how gringing a degree or two on the flat side is of any benefit - (we're not talking carving chisels) neither have I ever heard it suggested in 50 years of reading woodworking press.

It's kind of hard to get those two points to meet using a relatively flat stone (or even one that's not flat) without the edge being straight.

If we're talking about chisels and plane irons, we lay the flat face of the iron on the stone to work the wire edge that we raised on the bevel. It's going to be flat or very close. For an iron that's a tiny bit defective, a very slight lift isn't going to cause much of a problem (by defective, I mean that you can't quite reach the wire edge laying it flat on a dead flat stone). It takes little bit of experience for someone to know when a little bit of a lift isn't going to cause a problem vs. just lifting without knowing what you're doing (which will exacerbate it). The conclusion that lacks subtlety and skill is to demand that such an iron can't be used, but that we have to stop work and break out machinist equipment until the back of the iron is optically flat. Not a horrible idea for people who are new.

So, at any rate, we're dealing with a flat or almost flat back. In order to raise a wire edge, the two surfaces are going to meet in a straight line. If they have a constant curve (perhaps one more than another) all the way up to the middle, there will be no inaccuracy, not even a thousandth or two, or we'd have a lot of trouble reaching the wire edge uniformly when working the back, and that would show up.

But we don't need to get into the dogma about two flat planes to describe sharpness. On the sharpest of tools that we need (carving tools) that are often finished by some sort of compound, it doesn't exist - they are slightly rounded all the way to the edge. Beginners generally don't carve, though, so they're not going to grasp that, either.

 

[Jacob]

The planes that intersect don't need to be flat, either ...
No, they don't. But they need to be parallel if the edge is to be straight - which you presumably want your chisel edge to be - so if one side is flat the other isn't the cutting edge won't be straight. Try honing a serrated edge.

Try cutting with a rounded bevel - flat on one side, rounded on the other. No problem

I cannot see for the life of me how gringing a degree or two on the flat side is of any benefit - (we're not talking carving chisels) neither have I ever heard it suggested in 50 years of reading woodworking press.

You wouldn't grind a degree or so but everybody free-handing tends to put more pressure towards the edge when removing the burr - obvious really otherwise you'd have to flatten the whole face every time you sharpened

 

[Jacob]

...
It's kind of hard to get those two points to meet using a relatively flat stone (or even one that's not flat) without the edge being straight.

Surely the other way round? Freehanded edges tend to end up slightly cambered with slightly rounded bevels and anyway it's really easy to apply a camber if that's what you want. Not hard at all - in fact almost unavoidable.

 

[Phil Pascoe]

Try cutting with a rounded bevel - flat on one side, rounded on the other. No problem.
Certainly - but not round from side to side. It could be wavy from top to bottom and not matter.

 

[Jacob]

Try cutting with a rounded bevel - flat on one side, rounded on the other. No problem.
Certainly - but not round from side to side. It could be wavy from top to bottom and not matter.

I've got a scrub plane very rounded bevel in two directions, but with a flattish face. Cuts well.

 

[D_W]

...
It's kind of hard to get those two points to meet using a relatively flat stone (or even one that's not flat) without the edge being straight.

Surely the other way round? Freehanded edges tend to end up slightly cambered with slightly rounded bevels and anyway it's really easy to apply a camber if that's what you want. Not hard at all - in fact almost unavoidable.

What I mean is that the edge is in a similar plane with the back of the iron, which is what is needed to create an acceptable surface. The bevel side can be cambered as needed, but the face/flat side of the iron needs to be straight across so that there is a good cap iron fit. That doesn't require two flat planes intersecting, though, nor one dead flat one with a bevel that is cambered but otherwise flat in the direction traveling away from the edge.

I don't round bevels on purpose like sellers does, but I don't confuse myself with the rhetoric that someone of the beginners teachers put out there such as "tools aren't properly sharpened unless..."

They're properly sharpened when they work sensibly for the user and provide good results. Narrowing it further from there is beginners' fare.

 

[Jacob]

...
I don't round bevels on purpose like sellers does,...

I don't think he does it on purpose - there's no particular value in a rounded bevel it's just that if you relax into a sensible and easy free hand honing routine rounded bevels are a by product, which is fine as long as the edge is actually near enough to 30º or other chosen angle, and sharp. it's extremely difficult to get a flat bevel free hand but it's pointless anyway.

 

[Phil Pascoe]

Try cutting with a rounded bevel - flat on one side, rounded on the other. No problem.
Certainly - but not round from side to side. It could be wavy from top to bottom and not matter.

I've got a scrub plane very rounded bevel in two directions, but with a flattish face. Cuts well.

Certainly - but the very point of a scrub plane is that it hasn't got a straight edge, unlike a chisel.

 

[RossJarvis]

I dare say we've lost the OP who opened this "can of worms" :shock: . I think it's actually hard to explain a lot of this by writing advice as we all can use terms differently and use jargon and principles not everyone is familiar with. Showing the poor chappy what we mean in person would be better.

Maybe what we all agree on is that common practice is to roughly grind the sharp end to 25 degrees (by "grind" I imply using flat stones and/or powered wheels).

Finely grind/hone the cutting edge to 30 degrees.

If the flat side is rough, it could be an idea to slightly lift the chisel to hone at the very cutting edge.(which is what I meant by grinding at a degree or two.). Having a dead flat and polished back may be ideal, but is very time consuming to achieve on Western chisels.

As an expedient, if the chisels weren't ideal, then it may be possible to finely hone the cutting edge slightly greater than 30degrees.

Any other discussions may well go beyond what a newbie may understand or need/want to know :roll: .

 

[sundaytrucker]

I have a chisel sharpening question and rather than start a new thread I figured I would throw it in here (I hope that is alright?).

Anyway, sharpening, here goes.

A few months back I bought a Record 6" grinder with the intention of using it solely for grinding the primary bevel on both chisels and plane irons but after having the grinder sit around for a couple of months I sort of realised that I have no real idea of how to accurately get a 25 degree grind on a blade. I only have the standard tool rests at the moment but would hope they would be serviceable for a primary bevel grind.

My first task is the put a nice camber on to an old Record no5 before adding the 25 degree primary bevel, my intention was to use an angle cube on the tool rest hit 25 degrees and voila, only I don't think that will work? Am I over thinking this? Any advice would be appreciated.

Once I am satisfied with how the Record iron is looking I aim to regrind the irons of my Veritas planes but my only experience is with a Tormek basically creating a smoothing plane profiles, I plan to experiment with the camber on the LAJ to have it function as a traditional jack plane rather than a longer smoother.

Sorry for the thread hijack and the rambling nature of my post.

 

[sploo]

I have a chisel sharpening question and rather than start a new thread I figured I would throw it in here (I hope that is alright?).

Anyway, sharpening, here goes.

A few months back I bought a Record 6" grinder with the intention of using it solely for grinding the primary bevel on both chisels and plane irons but after having the grinder sit around for a couple of months I sort of realised that I have no real idea of how to accurately get a 25 degree grind on a blade. I only have the standard tool rests at the moment but would hope they would be serviceable for a primary bevel grind.

My first task is the put a nice camber on to an old Record no5 before adding the 25 degree primary bevel, my intention was to use an angle cube on the tool rest hit 25 degrees and voila, only I don't think that will work? Am I over thinking this? Any advice would be appreciated.

Once I am satisfied with how the Record iron is looking I aim to regrind the irons of my Veritas planes but my only experience is with a Tormek basically creating a smoothing plane profiles, I plan to experiment with the camber on the LAJ to have it function as a traditional jack plane rather than a longer smoother.

Sorry for the thread hijack and the rambling nature of my post.

Because a grinder wheel is... a wheel, it's always going to be a slightly inexact science.

I tend to find a tool (chisel, plane iron) that I know has a correct bevel angle, and use that to set up the grinder tool rest. If you don't have anything then you could cut a cardboard template - remembering that you only need to be around the right angle for a few mm of contact area (the thickness of the chisel or plane iron).

With a 6" wheel you will get a concave bevel, which isn't my preference, but I do use it occasionally to grind out a really rough old blade, before hand sharpening to a gentle convex bevel (or a flat bevel + microbevel with a sharpening jig) - both on diamond plates, stones, or sandpaper on glass/granite.

 

[sundaytrucker]

Because a grinder wheel is... a wheel, it's always going to be a slightly inexact science.

I tend to find a tool (chisel, plane iron) that I know has a correct bevel angle, and use that to set up the grinder tool rest. If you don't have anything then you could cut a cardboard template - remembering that you only need to be around the right angle for a few mm of contact area (the thickness of the chisel or plane iron).

With a 6" wheel you will get a concave bevel, which isn't my preference, but I do use it occasionally to grind out a really rough old blade, before hand sharpening to a gentle convex bevel (or a flat bevel + microbevel with a sharpening jig) - both on diamond plates, stones, or sandpaper on glass/granite.

Thanks Sploo.

I am not too fussed over super accuracy as long as it is roughly there that will do. The Record plane is practice for using the grinder.

Once the primary bevel is there I will hone using the remaining scary sharp abrasives I have knocking about. Once they have been used up it will be time to see whether to continue with SS (I like the cutting efficiency for honing but not so much having to replenish the stock every so often) or find an alternative medium but that is for another day. thanks for your advice.

 

[swagman]

sundaytrucker; your on the right track. That's what I used to set my bench grinder tool rests at 25*

Stewie;

 

[Derek Cohen (Perth Oz)]

I sort of realised that I have no real idea of how to accurately get a 25 degree grind on a blade.

You have two choices.

The first is to simply ignore getting an exact angle. Place the bevel against the wheel, run the wheel by hand to scratch the bevel. If it leaves scratches in the centre of the bevel, you are close enough. Or just adjust the tool rest until the wheel scratches where you want it to.

The second method is to use a jig to set up any angle you want ...

The grinder in the following set up is an 8” half-speed machine with the Veritas tool rest. The wheel is a 46 grit Norton 3X.

Adjusting the tool rest for a specific angle needs to take into account two factors, the diameter of the wheel and the thickness of the blade.

As the diameter of the wheel becomes significantly smaller, it will be necessary to make a fresh jig (I emphasise “significantly” smaller since a little bit here-or-there is not important in the grand scheme of things). The only jig I am aware of that adjusts for different diameter wheels is the Tormek. However the is not enough room to use one on a dry grinder with wheel guards.

Each time the jig is used, it must account for the thickness of the blade. This is done by placing the blade on the tool rest, and then the jig on top of the blade.

Tighten the tool rest setting once it is set up as in the above picture.

The Jig ...

Making the Jig ...

The dimensions are not relevant and may be made any size you please. The jig in the picture will grind a 25-degree hollow.

1. Use a blade with a known bevel angle (say 25 degrees).

2. Set this up to grind such that it will create a hollow at the middle of the bevel. To test this, use a felt tip marker (texta, magic marker) and colour the bevel. Place the blade on the rest and – with the power off – move the wheel back-and-forth to create a slight scratch pattern. Adjust the rest until the scratch is in the centre of the thickness of the bevel.

3.Retract the blade on the rest until it no longer touches the wheel (you may want to clamp it here so that it does not move).
Place a block of wood on top of the blade and hollow grind that. This will give you a template to reproduce that angle.

Do another for 30 degrees (and any other angle you wish).

Regards from Perth

Derek

 

[sundaytrucker]

Thanks Derek.

I have earmarked the post on your website about cambering the Veritas LAJ iron when I am conversant with the grinder.

 

[swagman]

sundaytrucker; if your wanting to use that method, you should have been given the link that information was sourced from.

Stewie;

http://www3.telus.net/BrentBeach/Sharpe ... grinderset