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Adrian Lopez

Can't get my knife sharp enough

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When I was at college, we had access to a digital kiln for heating steel, soaking it, and tempering. My tutor advised me to make the most of it. I made copies of four knives and a set of thumb plane irons. 

To this day, I've never found any blades to beat them. I’ve tried a lot since and only found one commercial type which came close.

Had I known at the time, I would have made many more. Hindsight is a wonderful thing.

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24 minutes ago, Melvin Goldsmith said:

I never managed to get a decent edge on this make of blank either

Me too,

I've got a box of old odd knife blades, I looked and these are no longer in there, and being that I would never give junk to another maker, I probably used them in a welding project or made curtain rod holders out of them or something useful. It is possible that I just threw them in the recycle, just don't remember.

What I do remember is,,,,, Junk.

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5 minutes ago, Dave Slight said:

When I was at college, we had access to a digital kiln for heating steel, soaking it, and tempering. My tutor advised me to make the most of it. I made copies of four knives and a set of thumb plane irons. 

To this day, I've never found any blades to beat them. I’ve tried a lot since and only found one commercial type which came close.

Had I known at the time, I would have made many more. Hindsight is a wonderful thing.

What kind of steel did you use?

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46 minutes ago, Melvin Goldsmith said:

I never managed to get a decent edge on this make of blank either

 

20 minutes ago, Michael Darnton said:

Based on my experience, recycled tin cans.

 

15 minutes ago, Evan Smith said:

Me too,

I've got a box of old odd knife blades, I looked and these are no longer in there, and being that I would never give junk to another maker, I probably used them in a welding project or made curtain rod holders out of them or something useful. It is possible that I just threw them in the recycle, just don't remember.

What I do remember is,,,,, Junk.

Well it's time to get myself a different blank, then. I think I'll get myself some HSS blanks like Michael uses, or maybe a Hock blank from Woodcraft (assuming they're any good).

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I wrote to Pfeil. Here is the reply:

Vielen Dank für Ihre Nachricht. Wir haben unseren Betrieb für zwei Wochen geschlossen. Ab dem 5. August 2019 sind wir wieder für Sie da.

Thank you for your message. We have closed our operation for two weeks. From 5 August 2019 we are back for you.

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56 minutes ago, Adrian Lopez said:

 

 

Well it's time to get myself a different blank, then. I think I'll get myself some HSS blanks like Michael uses, or maybe a Hock blank from Woodcraft (assuming they're any good).

Well, I guess it is time for my reply. I make excellent violinmakers knives of powder metallurgy steel PM-X. I believe they are the very best available.

contact me here: jpschmidt44(atsigngoeshere)gmail.com

http://jpschmidtviolins.com/mknife.html

 

 

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6 hours ago, JohnCockburn said:

I don’t know, John, but I have several and they take a good edge. Not as good as your knives, but perfectly serviceable....

I guess I must be hallucinating again.

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8 hours ago, violins88 said:

What kind of steel did you use?

It was a type of unhardened Sheffield tool steel, I don’t remember what the actual composition of the steel was. I shaped all of the blanks to a sharp edge before they went in the kiln.

My feeling is that the excellent kiln made the most of the steel, rather than the other way around, but I could be wrong.

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There is a whole philosophy of sharpening knifes for optimal cutting. There is a difference of cutting by sliding over the surface or cutting by pressing the blade on the surface. Additionally the properties of the material demand different blades in different shapes and different hardness. To learn what cuts best it takes years of experience. 

I use Pfeil steel on a multi purpose knife because it cuts well on most materials. It needs to be res hardened more often but that can be done pretty rapidly. 

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Just following the comments on this subject. I find that knife sharpening is a skill set which can be difficult to acquire and I am on the learning curve myself. But I do have a backround in metallurgy and heat treating which is helpful in selecting the right steel. The content of the steel is important as it sets the limits the steel can attain to,  but the heat treatment is all important and can make the difference between a piece of crap steel and something that is just wonderful. M2 steel has great potential but the heat treatment is difficult and needs a high temperature for both the pre-quench and temper treatments. Powder metal can be any type of steel, even M2. It simply refers to the method of manufacturing. Metal powder is compacted under high pressure and sintered to make the steel avoiding the segregation of alloy content that normal solidification causes; it is very uniform in content. I have seen very good steel make crap cutting tools because the Chinese forgot to heat treat it properly. Find out what your steel is and from the internet you can see the time and temperature needed to heat treat it properly. Problem is you need a protective atmosphere at higher temperatures. If you are a do it yourself person one thing you can do is double temper your steel. Simply do the temper twice and this, especially for some of the exotic steels, will take some of the brittleness out of the edge. As long as the temperature is controlled it will not hurt the steel and can only help. 

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I think that Pfeil tools are made with a chrome/vanadium alloy steel. My experience is that they tend to be a little soft and are difficult to sharpen, probably because of the chrome content. The biggest problem is that they develop a very flexible burr during sharpening which can be difficult to deal with. But marketing can overcome anything it seems.

 

 

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2 hours ago, Andreas Preuss said:

There is a whole philosophy of sharpening knifes for optimal cutting. There is a difference of cutting by sliding over the surface or cutting by pressing the blade on the surface. Additionally the properties of the material demand different blades in different shapes and different hardness. To learn what cuts best it takes years of experience. 

I use Pfeil steel on a multi purpose knife because it cuts well on most materials. It needs to be res hardened more often but that can be done pretty rapidly. 

Regarding cutting by pushing forward or using a slicing action, some electron microscope pics on this website show a sawtooth shape of a sharp edge: https://scienceofsharp.wordpress.com/2014/04/16/the-honing-progression/

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On 7/21/2019 at 1:28 PM, Davide Sora said:

1430884850_BridgeKnives1rid.thumb.jpg.eeaffeb19db55b0f1daa2ba33f220338.jpg

 

1 hour ago, Dennis J said:

I think that Pfeil tools are made with a chrome/vanadium alloy steel. My experience is that they tend to be a little soft and are difficult to sharpen, probably because of the chrome content. The biggest problem is that they develop a very flexible burr during sharpening which can be difficult to deal with. But marketing can overcome anything it seems.

I must confess that the first knife on the left of the photo is a Pfeil, but I confirm what was said by DennisJ. The steel is too soft and I can only use it for very fine, almost straight cuts.  For thicker cuts where more pushing action is needed, the sharpening will be ruined immediately, impossible to use in tight curves due to excessive flexibility that induces vibrations creating an unmanageable "saw-tooth" action.  Unthinkable to use it with a scraping action.

But I was sorry to throw it away.....so I use it only for light finishing cuts.

The other two are my favorites, very hard steel, the thin one in the middle is made from a circular saw blade, the one on the right is for bridge feet and it's an old blade of those with a gold coating, I don't remember the brand.  A whole other world compared to Pfeil.

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Well, I have to admit to being completely puzzled by this thread. I've never had any trouble at all with Pfeil knives or gouges. I have 4 of their gouges, 3 of which I use for scrolls, the other for rough arching. They get just as much use as the rest of my gouges (a mixture of henry taylor, ashley lies, and vintage marples) and I don't find them at all lacking in sharpness or in need of sharpening any more frequently than the others. 

I have a little pfeil knife with a very curved blade that I use pretty much exclusively for ebony work. Again, it works absolutely fine, holds an edge for a long time, and far from it being "unthinkable to use with a scraping action" I use it for scraping saddles and nuts on a regular basis.

So there ya go :D.

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Years ago, I purchased a lot of Pfeil tools from Fine Woodworking--mostly, they were too soft, and I sold them on ebay.  This is most likely a manufacturing issue in the head treatment shop since it is unlikely that Pfeil makes its' own steel.  More recently, Pfeil steel knife blanks have worked OK for me.

If you are going to intelligently comment on the best steel, it is vital to know what the steel is (composition).  

It is extremely difficult to sharpen thin steel blades without accidentally softening them from overheating, and then you blame the manufacturer for an error you made.  Thin blades must be sharpens either very very slowly using say a hand  rotated grind stone or ground under water.

This issue of the best steel never goes away.  The old steel gouges that everyone loves (and sell like hotcakes on ebay) were most likely O-1 steel.

Mike D

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The opening to this thread started with, "So I got a bench grinder..."  That may be the biggest problem if you werent careful, overheated the edge, and took the temper out of the steel.

Pfeil isn't the best steel to begin with and I find it difficult to form a nice burr when sharpening their chisels, especially on low angle edges. Too easy to just break the burr off and leave a rough edge, which is what the photos show.

 

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2 hours ago, Shunyata said:

The opening to this thread started with, "So I got a bench grinder..."  That may be the biggest problem if you werent careful, overheated the edge, and took the temper out of the steel.

Pfeil isn't the best steel to begin with and I find it difficult to form a nice burr when sharpening their chisels, especially on low angle edges. Too easy to just break the burr off and leave a rough edge, which is what the photos show.

 

Perhaps, but in my case I think the main issue is the angle of the bevel. I'll probably be getting rid of the Pfeil, if only because it makes no sense to try to make a silk purse out of a sow's ear, but I think I'l use it as my "sacrificial victim" as I learn to sharpen. I figure I should at least be able to get it to cut paper.

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I, too, cringe at the thought of using a bench grinder to shape a knife blade. I use diamond honing plates by "Dia-Sharp" and "DMT" to carry out those tasks. I have a 120 mesh (grit) that cuts so efficiently that it really is a practical substitute for a bench grinder for many tasks. And no burning tempers ever. At the other end of the spectrum is my 8000 mesh diamond plate which polishes an edge indistinguishable from my 8000 grit water stone, at least to my eyes, but cuts so much faster that it requires far fewer strokes, and therefore offers fewer opportunities to roll the edge over. My water stones seem increasingly impractical.

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On 7/21/2019 at 10:18 AM, Adrian Lopez said:

For the shape of the knife I've been going for something resembling the profile on one of Michael Darnton's bridge knives (see first picture). His knife is 18mm rather than 12mm and the angle of the picture might be throwing me off, but I don't think it's that far off.

The flatter section of the edge is so the knife can serve double duty for anything that might benefit from a flatter edge, though it's longer than I wanted as I wasn't watching the length of it too closely at first. The second picture shows what the knife looks like once placed inside its holder/handle.

On "rolling the edge," I suspect you're right, but I'm finding this very difficult to control. I can't catch myself doing it while I'm sharpening, but I must be doing it or the edge would not look rounded.

The consensus appears to be that 30 degrees on each side (60 inclusive) is too steep, so that's one of the first things I'm going to change. I had read here on Maestronet that a 30 degree bevel was a good target to aim for, but I realize now they must have meant 30 degrees total, so 15 degrees on each side. The strange thing is the width of the bevel has come out twice the thickness of the blade (2mm vs 1mm), which what you'd get with a 15 degree bevel each side -- even though I've been comparing against a 30 degree angle guide. I guess I'm not holding it right, in spite of my efforts.

Thank you all for your advice.

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I think the big confusion is beveling  both sides.  Save that for magic chief kitchen knive.

Backside flat. Then bevel from the one side only.  25 or 30, or as Darnton says making the bevel width double the blade thickness gives you 30 by geometry. A bit wider will give a lower angle.

Backside flat.  Grind straight surfaces coming together, then hone.  Do your real sharpening work (=shaping) with course grit.  Only then hone to make smooth and clean.

Until you get confidence sharpening I would recommend marking surfaces with something like a black marker, then looking under magnification to see that each stage of your work goes clean all the way to the edge.

Physical test: shave hair, bites finger nail, slices paper 

Also, for each stage of work, if good, a butt will form on opposite side. Should be able to feel.

 

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