Bevel up sharpening question

[ian maybury]

I'm just gearing up to do some Veritas bevel up sharpening on the new waterstones using a Veritas mk2 guide for the first time.

It's clear that when sharpening it's (despite most descriptions saying only that it's necessary to create a wire edge) necessary to keep on going until the wear bevels are removed to create the 'V' that comprises a truly sharp edge.

There's a fair degree of consensus to the effect that it makes sense to use three bevels to minimise the amount of material to be removed - the primary/ground bevel, a second sharpening bevel, and a third honed or polished bevel.

This makes sense, but doesn't seem all that practical in the case of the flat side of the blade on a 12deg bed/low angle bevel up plane. Specifically that it's not going to be possible to fit three bevels on the flat side within the available 12 deg, and still be left with enough clearance angle. (which some suggest shouldn't be much less than 10deg anyway)

The fix is presumably to rely on removing the metal almost entirely from the (in this case) top/primary bevel to eliminate both wear bevels, and to only give the flat back enough of a re-polish to remove the resulting wire edge.

Something along the lines of David Charlesworth's ruler trick for polishing the back sounds like it might be a good move - after flattening the back of the blade on say a 1000 grit stone. Provided that is it doesn't leave the blade unsupported over too much distance.

Does this make sense? Has anybody got any experience based angles/thoughts/solutions/methods that work well in this situation that they can describe?

Thanks

ian

[Derek Cohen]

Hi Ian

I'm going to keep my reply short as I have answered this so many times here.

Firstly, read this article for strategies on sharpening BU plane blades: http://www.inthewoodshop.com/WoodworkTechniques/TheSecretToCamberinBUPlaneBlades.html

Secondly, I have since added the Ruler Trick to my BU sharpening routine as it guards against the incursion of a wear bear.

Try and keep the sharpening routine as simple as possible. One primary bevel at 25 degrees, and a secondary bevel at the angle of choice. The low primary bevel enables a high angle with camber to be honed with the greatest efficiency. No need for more complication.

Regards from Perth

Derek

[Jim Koepke]

There are many opinions on this. This is just my opinion...

On the back side of the blade, my blades tend to be flat up to the cutting edge. No ruler trick for me on most of my blades. the exception is if there is some pitting on a bevel down blade the ruler trick might be used to get rid of the pits. Most of the time it is just used since eventually renewing the edge will eventually get past the small defect.

Most of the time my blades do not have a secondary bevel as my sharpening is usually done free hand and secondary bevels are easier to create with a blade holder.

Please note this is just my opinion based on what works for me. Just because it works in my shop is no claim that it is the right way to do something.

Though a wire edge can be created on a push stroke, mostly it is created on the stroke pulling the blade on the sharpening media. For the longest time it was my feeling that my sharpening was in the "Twilight Zone" because of only pushing on the stone and lifting the blades off the stone on the return stroke. It seemed to take forever to raise a wire edge.

On some thick blades, the one on my LN 62 is almost 1/4" thick, it is near impossible to keep the full bevel on the stone while sharpening. For these I will lift a little to create a secondary bevel.

On a bevel up blade, having a bevel on the back side for me doesn't make sense except at the edges.

Here is my explanation of that:

http://www.sawmillcreek.org/showthread.php?158373-My-Camber-Blade-Round-Tuit-Finally-Came

Hope this makes sense or helps, one of two isn't bad.

I noticed Derek's post after mine was sent. He has excellent advice in this area. His comment about using a bevel on the back of the blade to avoid accumulated wear is a good reason to have a back bevel.

My tendency is to sharpen often enough that renewing the primary bevel helps to avoid this condition.

Derek works on hardwoods I can only dream of. I work softwoods many people wouldn't use to build a dog house.

jtk

[ian maybury]

I'd been reading some material by Brent Beach who seems to suggest three bevels on both sides of a plane blade - basically because (a) it's necessary to remove the top and bottom wear bevels, and (b) to minimise the required amount of metal removal. i.e. i guess you can sharpen perfectly well using a single bevel and a flat back if you don't mind spending more time on it, or using two bevels, or whatever.

This seems reasonable enough, but as above three bevels on the flat/bottom of a bevel up blade isn't all that practical if a ten deg clearance angle is to be maintained - which is what prompted the question. On the basis that it's possible to remove both the top and the bottom wear bevels by cutting just the primary bevel back enough too. Which may take a little longer, but leaves the clearance angle on the flat side of the blade untouched. (leading to the likelihood that a bevel up blade is a little slower to sharpen than a bevel down - even before the cambering issue kicks in)

My reading of both your views is that the ruler method is also a good move, in that it reduces the possibility of any wear bevel being left on the flat side of the blade without reducing the clearance angle by too much.

It sounds reasonable that with the Veritas guide, starting with a low 25deg primary bevel and a fast cutting waterstone that two bevels are enough - that it's still a pretty fast route.

Time to get sharpening....

Thank you

ian

[Derek Cohen]

Hi again Ian

Please bear in mind that there are so many ways to skin a cat, that most of them work pretty well, and the longer one uses a particular method, the better it will become. At the end of the day you must find what works best for you. You will experiment with a few and this way gain the understanding to make this decision. There are no absolutes in this game, no Brent says this, Derek says that, Jim does it this way ...

I try and keep it simple .. KISS. :) I use two methods for honing blades, one for BD plane blades and chisels, and another for BU plane blades. I see the issues involved here as being different. BU planes bring along a few challenges that the other group do not encounter, but the results speak for themselves - BU planes are capable of an effortless superior performance, and this is the reason I use them. I use BD planes as much, possibly even more, and state this to indicate that I am trying to offer a balanced view.

As you are aware, BD planes achieve a cutting angle from the angle of the bed. The bevel angle is chosen to suit the steel type (e.g. 25 degrees for O1 and 30 degrees for A2). The bevel angle for a chisel is chosen for the purpose it will be used for - paring or chopping. For both these types I prefer to hollow grind the primary bevel at the desired bevel angle, and then freehand sharpen (on waterstones). This is the simplest way I know to hone an edge and be able to return to resharpen it just as easily. I cannot emphasise enough this latter point - sharpening once is easy. But can you re-sharpen the edge just as easily?

Now the BU blade takes its cutting angle from a combination of the bed (generally a low 12 degrees) and the bevel angle. This means that the bevel angle is usually quite high.

Complication #1: I add a camber to almost all plane blades. This is extremely difficult to do if the steel is thick. The steeper the bevel angle, the thicker the steel. My solution is to thin the steel so as to work with a low primary bevel - keep all primary bevels at 25 degrees and add a micro secondary bevel (this is the reason I only recommend purchasing blades with a 25 degree primary bevel). You need a honing guide to do this. Keep in mind that my BU planes have 50 degree secondary bevels - try cambering a 50 degree primary bevel! :)

How many micro secondary bevels? Brent and David Charlesworth use three. I use one. The reason for multiple secondaries is to reduce effort in polishing. A micro bevel is a teeny weeny little thing. Just a glint of steel. How much extra work is needed to polish it? One is enough for me. I do not need to alter the settings on the honing guide (which i generally dislike using - as in most things, I become knowledgable in order to pare the process down to its essence. I spent Saturday morning at an exhibition of Picasso, Mondrian, Miro, Warhol, etc. They spent their lives doing this - so we are in good company! :) )

The camber for a smoother is easier to achieve using the first stone - mine is a 1200 - on the initial secondary micro bevel.

Complication #2: Wear occurs on both sides of a blade. On a BD blade most (not all) gets grind off when sharpening. On a BU blade the wear bevel developes on the back of the blade, and extra effort is then required to remove it. Fortuunately there is a simple solution. The wear bevel occurs precisely where one can place a back bevel.

Complication #3: A back bevel will reduce the clearance angle. This needs to be a minimum of about 7 degrees, depending on the hardness and springback of the wood. We are starting with 12 degrees (the angle of the bed), so there is some leeway. In any event the amount removed by the Ruler Trick of David Charlesworth is 2/3 of a degree. Miniscule. And the RT takes seconds to do, and is repeatable with the same steel ruler. That is why I now use it.

Regards from Perth

Derek

[ian maybury]

Thank you Derek, that puts in words the conclusion I'd drawn from your material, and from the other material that's about. We're on the same hymn sheet.

Time will tell, but common sense suggests that if a little extra work on a free cutting stone can avoid the need for the guide adjustments required to set up to create an extra bevel that it makes sense - bearing in mind your point that starting with a 25deg primary bevel makes the job much easier.

The very fundamental point that emerges from all of this is as you say that it's not so much about finding a process that will give a sharp edge on a one time basis, it's to come up with one that does so on an ongoing basis when starting from a worn edge with top and bottom wear bevels. (these are the very minute bevels formed on the bottom of the cutting edge b as it slides on the work surface, and as a result of shavings rubbing on the top surface as they are peeled off)

One basic insight i seem to have picked up is that while there are different sharpening strategies that can deliver a result (and what works for BD isn't necessarily ideal for BU - because of the need to maintain enough clearance angle) - it's necessary to remove enough metal when (re-) sharpening to remove the wear bevels by whatever means. So that the new sharpening bevels form a cutting edge comprised of the required flat sided 'V'.

[Harry Goodwin]

Maybe one thing to consider is I would not buy a used plane that I knew the back of the blade was not flat. HG

[david charlesworth]

Hurrah for Derek !!!!!.....

I do a few more strokes for the ruler trick these days , to be sure of removing wear bevel. (Polishing stone only, say 8 or 10 thousand grit). It can be seen in good light. The ruler trick removes less metal when obliterating wear bevel than would be removed on a flat backed blade.

best wishes,
David Charlesworth

[Jim Koepke]

Maybe one thing to consider is I would not buy a used plane that I knew the back of the blade was not flat. HG

The other side of this is to expect every used plane to have trash for a blade. Occasionally one will be pleasantly surprised by a decent blade.

Having to flatten a lot of blade backs is what lead me to finding an alternate to cambering explained here:

http://www.sawmillcreek.org/showthread.php?158373-My-Camber-Blade-Round-Tuit-Finally-Came

For BU planes, this seems easier for me than trying to camber the bevel.

This method doesn't work well if one is trying to camber a blade for a scrub plane.

jtk

[ian maybury]

:) You never know who is looking in David. Ta for that. Here's hoping that your health has settled down again.

Since I'm just finding my way into serious sharpening i'm not an ideal person to comment Joe. But it makes sense that the removal of some metal to the outside of the flat back on a low angle bevel up blade should be a viable method of forming a camber as long as the angle was shallow enough that it didn't reduce the clearance angle too much. Better still if it was to be the means of removing pitting, and entailed removing less metal.

The latter is quite hard to judge. I know that Derek has posted some numbers for calculating the amount of metal it's required to remove for a variety of bevel angles - it's not the easiest to figure out on paper by other means....

ian