How to sharpen a plane blade

[adrian]

But getting the burr at 45 deg takes about 50 strokes (which I then have to do in 5 positions to get all along my cambered edge.)

I don't understand this at all. I simply can't visualise what you're doing.

50 strokes is a LOT. To me it means you're either removing too much metal, or using too fine an abrasive.

The stone is a 1000 grit shapton stone.

How cambered is your edge? (i.e. what's the "sagitta" of the curved edge).

My goal was to get the equivalent of the 0.25 mm camber recommended by David C. But because of the 12 degree bed angle, this translates to a 0.8 mm camber. This number is the distance the outside edge of the blade would rest above a straight edge. I am not sure how well I accomplished this goal. One issue is that the corners tend to curve more than the rest of the blade---I don't have a uniform circular arc.

When you say "5 positions", are you trying to approximate a curve by multiple straight lines?

Right. Is there some other method? (Other than the curved diamond plates?) In David's video he shows that you apply pressure in the center, then at various other positions left and right of center to establish and maintain the camber. That's what I'm doing.

Are you using a honing guide?

Yes, Veritas mk 2 with the curved roller.

Are you re-locating the blade in the guide (if used) for each "position"?

Uh, to compensate for the varying blade projection along the camber? No, I use a fixed honing guide configuration for all projections. (So my bevel angle will get higher as I go away from the blade center.)

 

[bugbear]

OK. That's all very elaborate. Why not use a continuous motion, sothat as you push the blade along the stone, you "rotate" it so that the abrasion is over the full width (or is it length?) of the cutting edge.

If you then find the burr is developing faster in one area than the rest, just go through that area a little faster (or with less pressure).

An explicitly "faceted" approach seems both more complex and less "ideal" than a continuous approach.

I still haven't worked out your high stroke counts though.

BugBear

 

[adrian]

I agree that a continuous motion sounds like it would work better in theory in terms of producing the desired curved edge. But in practice it seems difficult for me to produce a continuous motion with confidence that I'm really working across the edge uniformly. Rather than being able to focus on moving back and forth and holding steady pressure I'm now trying to rock side to side at the same time. My expectation is that this would tend to wear the least in the center, which is precisely the spot of the blade that is the most dull.

Is this in practice a simpler method? If I want to sharpen evenly I have to now be able to judge the size of the burr across the edge so I can figure out how to adjust for nonuniformity. And this would be complicated by the fact that the blade is not uniformly worn. It will take more work in the center to produce a burr than at the edge, because the center will be more worn.

With the faceted approach I can take N strokes in each position and presumably I have removed (close to) the same amount of material everywhere, so I should get a reasonably uniform result. I can pick N to be the number of strokes required to raise a burr in the center. Presumably slop in how I apply pressure and hold the tool avoids getting a truly faceted result.

In David's videos he does show a continuous approach, but it seems to be presented as a sort of game, not as the primary technique to use to do the job. All the other sources I've encountered recommend the "facet" method as well.

 

[pedder]

Adrian, do you work with microbevels or second bevels?

Cheers
Pedder

 

[David C]

Adrian,

Where do you live?

David

 

[bugbear]

Adrian, do you work with microbevels or second bevels?

Cheers
Pedder

Careful! Jargon in this area varies so much that everyone needs to be VERY explicit in their language.

Despite his noble contributions to knowledge on sharpening, I feel Leonard Lee did a massive disservice to use all by calling what had been fairly universally called "secondary bevel" "microbevel" in his book.

BugBear

 

[adrian]

I live in the Eastern USA.

The blade that launched this discussion has 3 bevels at about 33 deg, 45 deg and 47 deg. Someone asked me how big my bevel was, and I took a look and realized it was kind of big---3 mm. So I ground the primary bevel and reduced the size of the secondary bevel to under 1 mm. The 47 deg bevel is applied by just a few strokes on the polishing stone.

In the other thread someone was saying that hollow grinding is essential for speedy sharpening. Do others agree?

 

[pedder]

The blade that launched this discussion has 3 bevels at about 33 deg, 45 deg and 47 deg. Someone asked me how big my bevel was, and I took a look and realized it was kind of big---3 mm. So I ground the primary bevel and reduced the size of the secondary bevel to under 1 mm. The 47 deg bevel is applied by just a few strokes on the polishing stone.

In the other thread someone was saying that hollow grinding is essential for speedy sharpening. Do others agree?

Hi Adrian,

I'm really glad you understood my carless question. May I carefully ask you, on wich of your three bevel you hone until you feel a burr? I think it would be enough, if you do that on the tertiary bevel (47°). Sorry if I musunderstood you way.

Cheers
Pedder

 

[adrian]

I have been attempting to follow the method described by David Charlesworth wherein I hone the secondary bevel at 45 deg until I feel the burr. Then I remove the burr on the polishing stone, and then I hone at 47 on the polishing stone 5 strokes in each position which creates a new tertiary bevel. The tertiary bevel is thus quite small and is removed each time I hone.

 

[David C]

Adrian,

So you won't be able to drop round to my workshop in the near future!

I find it helpful to keep that secondary bevel fairly narrow. When I regrind, a minute sliver of the previous honing is left behind.

On the first sharpening (1000 grit) it may only take two or three strokes to raise a wire edge.
On the second sharpening it will take more strokes say 4 or five, and so on. After a number of sharpenings it may be taking 15 strokes to get a wire edge. My patience gives up and I regrind, starting the whole cycle again.

Best wishes,
David Charlesworth

 

[pedder]

I have been attempting to follow the method described by David Charlesworth wherein I hone the secondary bevel at 45 deg until I feel the burr. Then I remove the burr on the polishing stone, and then I hone at 47 on the polishing stone 5 strokes in each position which creates a new tertiary bevel. The tertiary bevel is thus quite small and is removed each time I hone.

If the 3rd bevel ist just so small why, does it take you 5*45 strokes to remove it. Maybee you should take a coarser stone for that task?

I don think you need to feel the burr, but watch if the 3rd bevel is gone.

Cheers
Pedder

Edit: Forget it, I think David's answer is better. I just wrote too slow.

 

[adrian]

I agree that my secondary bevel was too wide. I've ground it back and will see tonight how many strokes it takes.

Regarding the question of when to stop, it seems conceivable that the back of the blade could be worn so that removing the tertiary bevel isn't sufficient. Checking for the burr ought to be a more reliable way of determining that I've done enough.

 

[Ikisumu]

Hello Adrian,

In the other thread someone was saying that hollow grinding is essential for speedy sharpening. Do others agree?

For freehand sharpening it is mostly helpful, for the stability.

With hollow grinding, there is also less surface area to be processed. This means that with coarse mediums the difference in time consumption is not that significant, but with finer and finer honing mediums the gap will increase more and more.

If you really have been honing the entire bevel area of a thick and wide plane iron, possibly high on chromium, tungsten and vanadium carbides and done it only with a fine honing medium, it is no wonder that it will take an unreasonable amount of time. Is this the case here?

Have you visited Leif Hanson's web pages?

Samu

 

[adrian]

As I noted above, I use what Leif Hanson is calling the microbevel approach. I am definitely not trying to hone the entire bevel. My secondary bevel had grown kind of large, though. I ground it back. But it's flat, not hollow.

Since I've never had anything hollow ground I don't know how a hollow ground tool would behave differently in terms of how fast the microbevel grows and how long before you have to resharpen.

The advantage for hand sharpening is clear.

 

[Ikisumu]

Adrian,

I went through your posts but failed to spot how many different kind of stones you are using in total? Also I wonder (due to described inefficiency) in what kind of condition the stone surfaces actually are.

Also, I did not catch who is the maker of your plane, and with what kind of iron it is equipped. Advanced modern tool steels can be quite "interesting" to hone with conventional stones.

****

So many people say they love sharpening. I do not at all. It is just something like a necessary evil to stop me for having my fun against my own will, and I hate it.

Therefore I have acquired the tools and methods I believe to be most effective and speedy, just to get back to my whittlings as soon as possible. I use both jigs and freehand.

I have a large electric bench grinder AND a proper wheel opener/conditioner. There is a hard felt wheel installed AND trued. It is installed in the other end of the grinder. I make my own waxes for it.

I have quite a selection of stones for both water and oil (some of those stones I have made myself), and both commercial and self-made pastes for metal polishing.

Then I have Buehler and Struers metallographic sandpapers up to 4000 grit. They can be used with water or oil. For stropping I like to use Buehler MetaDi diamond particles down to 0.2 micron in a special suspension, applied from a spray bottle. They have a very narrow particle size distribution, and are very effective in what they do.

I also have a jar of Buehler 0.05 micron gamma-alumina, just to scare the **** out of my woodworking pals. Otherwise I find no particular use for it.

However they wlll not solve the biggest problem, though.

Samu

 

[adrian]

My planes are Veritas. The irons are A2. I have Shapton Professional ceramic stones. I flatten them regularly on a DMT diamond plate (45 micron).

I have a 1000, 5000 and 8000. In following Charlesworth's method I have not been using the 5000, though. I've been working the secondary bevel on the 1000 and then the tertiary bevel on the 8000. (Note that the stone below 1000 in this series is the 320. There is no 800, for example.)

I have a large electric bench grinder AND a proper wheel opener/conditioner. There is a hard felt wheel installed AND trued. It is installed in the other end of the grinder. I make my own waxes for it.

What is the function of the hard felt wheel?

 

[Ikisumu]

A step from approximately 15 micron straight down to approximately 1 micron sounds to be quite much, however I will not argue here.

AISI A2 does not regularly belong in my arsenal. I usually use either classic carbon steels or O-1, and then I have HSS-Co for them extremely tough cases like for some aussie hardcore woods and for some african species. Carbon steels will be sharpened easily with conventional stones no matter how hard they are, and HSS-Co like M42 in HRc 66-67 will usually obey only diamond.

A2 is a cold work steel with reasonably good wear resistance, so unless you establish your bevel properly with some coarser medium and then use some medium grit in the middle, there is a lot of work ahead, because your fine grit has to attack directly those reasonably abundant special carbides.

It's not yet like fighting with let's say D2 or even D3 (dear God), but tedious at least. I would say the slurry of your 8000 will partly evade the ridges left by 1000 scratch pattern and rather be accumulated in the grooves left by the previous coarse medium, just because of the natural wear resistance of the steel.

This is very common phenomen with higher tool steels if grit steps are too large. Sure, they will be polished in the end, but it takes unnecessary amount of time. In the case of any true tool steel, I would personally use something between the steps of 1000 and 8000.

What is the function of the hard felt wheel?

In my application, it serves as a high speed edge polishing device. The wheel is made of natural sheep wool called "industrial wool" and compacted into 0,6 g/cm³ of bulk density. The size of the wheel is 250mm x 25mm, running at 3000 rpm. It is well trued and runs smoothly. In this form it is very fast edge polishing tool with a suitable polishing wax. It can burn the edge if not careful.

I use mainly homemade waxes made of natural solid vegetable fatty acids combined with fused reactive alpha-alumina. The brand and type of alumina is Almatis/Alcoa A 16 SG. The shape of the particle is not roundish like in most of the alumina sharpening and polishing mediums, but more like triangular or tetrahedron. It is very fast cutting particle type. A care must be taken when placing an edge on the wheel, it really eats the steel up very easily. The typical time of contact is 2-3 seconds at a time. That is enough to draw a 4" knifeblade once over the wheel.

An easier and perhaps more convenient way to use a hard felt wheel is to reduce the rpm down to for example 1000 rpm. Hard felt wheel is still needed, but could be easier to handle with almost the same performance.

I use this wheel mainly for my knifes, carving irons and other freehand operated woodworking tools in need of slightly convex edge.

For edges like plane irons, paring chisels etc I use hard stones, sandpapers and other harder substrates with pastes and fluids. Then I have a strop in pretty much the same role as Dr. Cohen presented in the other thread.

Samu

 

[bugbear]

I live in the Eastern USA.

The blade that launched this discussion has 3 bevels at about 33 deg, 45 deg and 47 deg. Someone asked me how big my bevel was, and I took a look and realized it was kind of big---3 mm. So I ground the primary bevel and reduced the size of the secondary bevel to under 1 mm. The 47 deg bevel is applied by just a few strokes on the polishing stone.

In the other thread someone was saying that hollow grinding is essential for speedy sharpening. Do others agree?

No.

As long as the bevel you're sharpening on your fine stones is small, sharpening is fast.

This is usually achieved by either hollow grinding, or multiple (relief) bevels.

What makes for slowness (fairly obviously) is working a large surface with a fine abrasive.

BugBear

 

[bugbear]

I think I've got it!

(can people please confirm/disagree).

Adrian is using a triple bevel 33º/45º/47º model.

As far as I can tell the 33º is just a pure relief bevel, presumably made with coarse techniques.

Adrian's also using a 8000 grit stone to put on his 47º "final" AKA "micro" AKA "tertiary" bevel.

Since the 45º bevel is taken all the way to a burr, the 47º is fully removed every time.

I suspect that Adrian, in a perfectly reasonable desire to do a good job of sharpening, may be taking a few extra strokes on the 47º bevel. Now, since the 45º bevel is taken all the way to the edge (forming a burr) the initial 47º bevel is pretty much zero size, and even an 8000 grit stone will enlarge it VERY quickly.

I suspect that, at the next sharpening, what's consuming the time on the 1000 grit stone is NOT removing the wear and bluntness from planing activity.

I think the effort is going into removing the 47º bevel.

BugBear

 

[adrian]

I think I've got it!

(can people please confirm/disagree).

Adrian is using a triple bevel 33º/45º/47º model.

As far as I can tell the 33º is just a pure relief bevel, presumably made with coarse techniques.

Adrian's also using a 8000 grit stone to put on his 47º "final" AKA "micro" AKA "tertiary" bevel.

Since the 45º bevel is taken all the way to a burr, the 47º is fully removed every time.

Yes, this is precisely correct. The 33 degree bevel I ground on 40 grit sand paper on a Worksharp. I work the 45 degree bevel on the 1000 grit stone each time until I detect a burr and observe that the previous 47 degree bevel is gone, and then I install the 47 deg bevel on the polishing stone. (This is based on the method taught by Charlesworth in his video.)

I suspect that Adrian, in a perfectly reasonable desire to do a good job of sharpening, may be taking a few extra strokes on the 47º bevel. Now, since the 45º bevel is taken all the way to the edge (forming a burr) the initial 47º bevel is pretty much zero size, and even an 8000 grit stone will enlarge it VERY quickly.

I suspect that, at the next sharpening, what's consuming the time on the 1000 grit stone is NOT removing the wear and bluntness from planing activity.

I think the effort is going into removing the 47º bevel.

This may also be correct. I'm not sure since I don't know how big those wear bevels are. I have been establishing the 47 degree bevel with 5 stokes in each position on the stone. Can I get away with less? How can I tell what's enough?

A step from approximately 15 micron straight down to approximately 1 micron sounds to be quite much, however I will not argue here.

Since I raise the bevel when I switch stones if I were to use a coarser grit, say the 5000, then that last 47 degree bevel would grow even faster and bigger, and I'd end up having a harder time removing it the next time back at 45 degrees.

Note that I sharpened the blade last night and took 20 strokes in each position on the 1000 grit stone at which point the microbevel was gone. It's possible I took more strokes than necessary because I, uh, checked for the burr on the wrong side the first time.

Total sharpening time was 10 minutes, and I did some 10X loupe inspections for wear bevels that probably took a couple extra minutes.