Global Stupid Questions

[Jammer Six]

We have a set of Global kitchen knives.

I've watched videos on Youtube, I've practiced.

I've sharpened them with waterstones and a Tormek.

Down in the shop, I can get them to shave hair off my arms.

But then I take them up to the kitchen, and scrub them down with a sponge to get the sharpening crap off, and that dulls them! No more shaving!

What's wrong with this?

 

[Thomas Linton]

One possibility is that you have a "tinned edge" - a flap of very thin steel at the extreme edge that is easily folded over. After that flap folds, and a sponge could to it, you no longer have a sharp edge.

 

[knives_in_nature]

^ exactly

 

[Jammer Six]

Huh. Thank you.

How does one polish (I assume it will be polishing...) the tinned edge off?

 

[Chris Larrikin]

I think from memory most Globals are hardened to the 56 to 58 HRC range. 56 is still on the softish side for such a thin blade. I have a set myself and found they often formed the edge as described. After sharpening them I have taken to giving them a few very light strokes each side on a ceramic rod and then stropping (in a fairly half arsed way) on some balsa with compound. Seems to produce good results.

 

[BenchCo Spydermade]

Maybe try more degrees per side. I don't think (though I'm no expert on this) that a steel at 56hrc will do well keeping an edge of 30 degrees inclusive or less. Maybe a 40+ degree microbevel would help.

 

[Obsessed with Edges]

Huh. Thank you.

How does one polish (I assume it will be polishing...) the tinned edge off?

Don't have any Global knives, but...

I'm sure the problem described is due to a burr/wire edge (a.k.a. 'tinned edge' as described earlier). Stropping on firmly-backed denim with some white rouge or similar AlOx compound is likely how I'd take care of that.


David

 

[Jammer Six]

Well, I have denim, but no balsa wood.

And for more stupid questions, buffing on a felt wheel with green polish from Home Depot was how I got them to shave. How do I strop on denim in such a way that it doesn't simply do the same thing?

 

[Obsessed with Edges]

Well, I have denim, but no balsa wood.

And for more stupid questions, buffing on a felt wheel with green polish from Home Depot was how I got them to shave. How do I strop on denim in such a way that it doesn't simply do the same thing?

The white rouge or similar AlOx compounds* do a LOT better with tenacious burrs on softish stainless steels (and many others). For the strop itself, a paint-stirring stick or similar piece of wood works well, with the denim attached with contact cement or other adhesive. Use it by hand only; no need for powered stropping.

Using the powered buffing wheel with green compound runs the risk of overheating a very thin edge (I've used that combination with a dremel; it gets HOT fast). This might've been part of what you experienced in seeing your edge fold over so quickly, as the temper of the steel at the thin edge might've been damaged.

( * = I've also liked Sears' #2 grey AlOx compound on a denim strop, and use it as much, or even more often than the white rouge. )


David

 

[Squashfan]

Well, I have denim, but no balsa wood.

And for more stupid questions, buffing on a felt wheel with green polish from Home Depot was how I got them to shave. How do I strop on denim in such a way that it doesn't simply do the same thing?

Much more control with the nonpowered strop. I feel I have a very tiny right to speak about stropping on buffing wheels because I am currently experimenting with it. You probably have a burr, even off of the felt wheel. I have to work hard to not have a burr when I come off of the powered wheels. Run the tip of your fingernail backwards from spine to edge. A burr would feel like a very tiny catch. But a sharp apex feels very similar. I don't know to explain it. Maybe someone better with words could explain it to you.

 

[Thomas Linton]

With help, the burr can be seen.

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[Jammer Six]

With this hand stropping, how much are we talking about, three or four strokes? A few minutes work? A hard hour on each side? And since it shaves with a tinned edge, how do I tell when I'm finished? What's the goal, and how is the goal different from shaving hair off your arm with a tinned edge?

This is a lot more complicated than chisels. Chisels are easy.

 

[Squashfan]

With this hand stropping, how much are we talking about, three or four strokes? A few minutes work? A hard hour on each side? And since it shaves with a tinned edge, how do I tell when I'm finished? What's the goal, and how is the goal different from shaving hair off your arm with a tinned edge?

This is a lot more complicated than chisels. Chisels are easy.

You strop until the burr is gone. If every thing was done right on the stone, it will only take a few strokes per side. A burr is sharp but because it is a sliver of metal hanging off the edge. For that same reason, the knife doesn't stay sharp because the sliver falls off or breaks off during use. You know you are done when the edge is durable and lasts.

 

[Jammer Six]

The way I understood this, I have a tinned edge, not a burr.

 

[Obsessed with Edges]

The way I understood this, I have a tinned edge, not a burr.

As described in the context of this thread, they're both the same thing: very thin & weakened steel at the edge, formed in the process of sharpening, when the steel at the edge is eventually made too thin to remain strong in use. Different name, but the same issue with the same solution (stropping or other burr-removal techniques).


David

 

[Obsessed with Edges]

With this hand stropping, how much are we talking about, three or four strokes? A few minutes work? A hard hour on each side? And since it shaves with a tinned edge, how do I tell when I'm finished? What's the goal, and how is the goal different from shaving hair off your arm with a tinned edge?

This is a lot more complicated than chisels. Chisels are easy.

If using white rouge or the other AlOx compound I mentioned (which are very aggressive, compared to green), it doesn't need many strokes. Best way to check progress is to cut some phonebook paper or other light & thin paper as you go, every couple of passes or so. While the burr is still there, you'll see the edge slipping over or snagging in the paper. As the burr gets diminished by stropping, you should see cutting becoming much easier & smoother, with lighter effort (assuming the edge is also fully apexed, of course). With these aggressive compounds, you could also refine & further sharpen the edge, if your technique is good, maintaining proper angle and pressure. Focus first on cleaning up the burr, and don't worry as much about trying to take it too much further, at this point.

It may seem complicated now, but it won't take long to realize just how simple it actually is. Don't be too intimidated by it.


David

 

[Thomas Linton]

If using white rouge or the other AlOx compound I mentioned (which are very aggressive, compared to green), it doesn't need many strokes. Best way to check progress is to cut some phonebook paper or other light & thin paper as you go, every couple of passes or so. While the burr is still there, you'll see the edge slipping over or snagging in the paper. As the burr gets diminished by stropping, you should see cutting becoming much easier & smoother, with lighter effort (assuming the edge is also fully apexed, of course). With these aggressive compounds, you could also refine & further sharpen the edge, if your technique is good, maintaining proper angle and pressure. Focus first on cleaning up the burr, and don't worry as much about trying to take it too much further, at this point.

It may seem complicated now, but it won't take long to realize just how simple it actually is. Don't be too intimidated by it.


David

One way to eliminate the burr or tinned edge is to place the blade at right angles to a piece of dowel (or similar) and use the knife to roll the dowel back and forth while bearing down. The burr breaks off. Then strop conservatively until the edge is "sharp enough."

Or avoid creating burrs in the first place. (I know. Not Knife Place PC, but I'm old enough not to care.)

 

[Obsessed with Edges]

One way to eliminate the burr or tinned edge is to place the blade at right angles to a piece of dowel (or similar) and use the knife to roll the dowel back and forth while bearing down. The burr breaks off. Then strop conservatively until the edge is "sharp enough."

Or avoid creating burrs in the first place. (I know. Not Knife Place PC, but I'm old enough not to care.)

Some very ductile steels won't shed their burrs by such means; especially high-chromium/low-carbon combinations like a lot of inexpensive kitchen knives, 420HC at lower hardness and others. Burrs on these steels will bend back & forth all day, but seldom break off. That's why I use white rouge & similar compounds on denim or linen, to abrade them away.


David