Objectifying edge quality

[Doug Hepler]

Patrick,

It is very crude, but it distinguishes very clearly between an almost sharp edge and a sharp enough edge. For purposes of this project, sharp enough means taking an intact (albeit small) shaving off pine end grain. Yes, I push slowly because I want to see how much deflection I get before the thread breaks. Its main deficiency is not the lack of a peak reading, it's the need for me to hold the blade steady so that I don't slice. This is great fun to think about, but so far it won't replace the copy paper test. And, like Andrew, I will try to resist another $150 toy.

What I really want, BTW, is a way to quantify how much steel worn abrasive film can remove

Doug

[Steve Kang]

For me it's electrostatic shavings, the type that stick to you straight out of the plane. There's something neat about cutting so fine one force of physics takes over for another.

[Patrick Chase]

Patrick,

It is very crude, but it distinguishes very clearly between an almost sharp edge and a sharp enough edge. For purposes of this project, sharp enough means taking an intact (albeit small) shaving off pine end grain. Yes, I push slowly because I want to see how much deflection I get before the thread breaks. Its main deficiency is not the lack of a peak reading, it's the need for me to hold the blade steady so that I don't slice. This is great fun to think about, but so far it won't replace the copy paper test. And, like Andrew, I will try to resist another $150 toy.

What I really want, BTW, is a way to quantify how much steel worn abrasive film can remove

Doug

Yeah, your implied point that one can easily go overboard with this stuff is right on the money. If I were going to measure sharpness (I probably won't) I'd go with something like the $80 peak-reading Mitutoyo tension gauge that I linked in an earlier post. It's about as precise as the EdgeOnUp, and it actually has other useful applications. As you say you have to be careful not to slice, but that's an easily engineerable problem (I can think of a couple ways to fixture the tool and/or the thread to prevent it).

[Patrick Chase]

For me it's electrostatic shavings, the type that stick to you straight out of the plane. There's something neat about cutting so fine one force of physics takes over for another.

So fundamentally pointless, though. At <1 mil per shaving you can spend all day being mesmerized without ever making notable progress towards building something out of wood.

[Jim Koepke]

For me it's electrostatic shavings, the type that stick to you straight out of the plane. There's something neat about cutting so fine one force of physics takes over for another.

For me sharp is when only one row of angles are able to dance on the edge. When it gets a bit dull they can dance in two rows or more.

jtk

[ken hatch]

For me sharp is when only one row of angles are able to dance on the edge. When it gets a bit dull they can dance in two rows or more.

jtk

Jim,

It has been too many years but I'm Sure Patrick can correct me the number you are looking for is 6.02X10 to the 23 power.. My guess on a dull iron it would be X2

ken

P.S. If it feels sharp and looks sharp it is sharp

[David Ragan]

As an aside: one thing about folks who make shavings on YouTube (I know, I know...), is that they all hold up calipers and say "well...that is....0.001"...."

I just don't believe it. My skills arent that great, but my equipment is-and a strict one thou shaving is exceedingly thin-my planes are never set up for than thin for actual work.

I havent seen them "Gee, that only 3 thou, let me see about an adjustment" it's always Bam---one thou.

And, for the Mitutoyo gage, how do you translate 0.15N into Grams for resolution (just in case I need another toy)?

[Patrick Chase]

Jim,

It has been too many years but I'm Sure Patrick can correct me the number you are looking for is 6.02X10 to the 23 power.. My guess on a dull iron it would be X2

ken

P.S. If it feels sharp and looks sharp it is sharp

6.022 * 10^23, yes. By my time in high school they taught Avogadro's number to *four* significant digits :-).

[Patrick Chase]

As an aside: one thing about folks who make shavings on YouTube (I know, I know...), is that they all hold up calipers and say "well...that is....0.001"...."

I just don't believe it. My skills arent that great, but my equipment is-and a strict one thou shaving is exceedingly thin-my planes are never set up for than thin for actual work.

I havent seen them "Gee, that only 3 thou, let me see about an adjustment" it's always Bam---one thou.

It's called "editing" :-).

And, for the Mitutoyo gage, how do you translate 0.15N into Grams for resolution (just in case I need another toy)?

The one I linked has 0.05N resolution (0.15 is the bottom of the range, not the precision).

On Earth 9.81 N = 1000 grams force, so 0.05N = 1000*0.05/9.81 g = 5.1 g. Same resolution as the $150 EdgeOnUp.

[David Ragan]

Right.

Thanks.

[Mike Holbrook]

I use the paper test Jim Koepke mentioned early on. One can certainly argue that paper comes in all sorts of thicknesses/sriffnesses....but then so do fingernails, end grain, hair....I find that I learn to feel how a sharp blade, pushed straight into a piece of paper, should feel as it cuts, which reduces my reliance on the kind of paper. Paper is just about always around. With my thin skin, I am not a fan of skin tests.

[Andrew Pitonyak]

Andrew

Thanks for this tip. I had not heard of edgeonup. I had seen Steve Ellis thread test, which is the basis of edgeonup. I got inspired and today I made a thread tester out of sewing thread and a piece of UHMW plastic. I "calibrated" it by finding a weight for the thread that would almost but not quite allow the thread to flex without being cut by a new single-edge razor blade. Maybe you can satisfy your engineering impulses by making one for yourself. If you do, let me know how you make out.

I will run out of arm hair or calluses long before I run out of thread.

Doug

Very cool..... would love to see some pictures of the device. I would love to make one, but, I know that I lack the time.....

The primary advantage to a tool such as this is that it is repeatable and not as subjective (as in your don't need to learn what sharp feels like on your nail). One disadvantage, of course, is that you are testing at a single point on the blade.... nothing is perfect.

[Patrick Chase]

V
The primary advantage to a tool such as this is that it is repeatable and not as subjective (as in your don't need to learn what sharp feels like on your nail). One disadvantage, of course, is that you are testing at a single point on the blade.... nothing is perfect.

The usual way to deal with that is by repetition. IIRC Steve Elliott always did 5 thread loops at each condition. That could get expensive with the EdgeOnUp, of course.

[David Ragan]

Yesterday I was stropping blade (dry), left cap iron on. Then ran edge side to side through end grain-to remove burr. That is the correct scenario for that maneuver, right?

[Jim Koepke]

Yesterday I was stropping blade (dry), left cap iron on. Then ran edge side to side through end grain-to remove burr. That is the correct scenario for that maneuver, right?

There a million correct scenarios in the world of edge sharpening.

jtk