E.A. Berg chisels dull extremely quickly - what am I doing wrong?

So I'm trying my best cutting dovetails in 12mm (~1/2") shedua.

I remove most of the waste with my fret saw so there's only 1-2mm waste left for the chisel.

Using a 10mm E.A. Berg chisel and a small chisel hammer I make very light taps on the chisel to control the cut to remove the remaining waste in small increments, i.e. no one-time-heavy-cut that I would expect to damage the chisel quickly.
After just two or three cuts, the bevel is rolled over and the chisel is dull and useless.

I've sharpened the chisel using the Scary Sharp method, i.e. very very fine self-adhesive sandpaper fixed to a glass plate.
The back is flat and the single bevel is 25 degrees, both with a mirror finish and ensuring that any burr is removed completely.
The chisel is sharp enough to shave hairs from my arm if that tells anything....

So, is the chisel poor quality? Am I sharpening it incorrectly? Am I using the chisel incorrectly?

A couple of the smartest guys here have reported that some good chisels just don't get proper hardening and tempering treatment at the end ,and that grinding off a little gets you to the good steel.

Hone the chisel at 30 degrees. Your current 25 degree bevel is too low to cope with the impact.

I suggest a secondary bevel so that you do not remove much steel.

Regards from Perth

Derek

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Originally Posted by Derek Cohen

Hone the chisel at 30 degrees. Your current 25 degree bevel is too low to cope with the impact.

I suggest a secondary bevel so that you do not remove much steel.

Regards from Perth

Derek

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I'll try that and see if it helps any.

Thanks!

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Originally Posted by Mel Fulks

A couple of the smartest guys here have reported that some good chisels just don't get proper hardening and tempering treatment at the end ,and that grinding off a little gets you to the good steel.

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These are old, used chisels so I'm confident that whatever steel wasn't hardened has been ground off earlier in the chisels life.

i have heard complaints in the past about soft bergs. the 3 or 4 I have hold an edge fine, and I tend toward lower angle bevels on them, so it might just be your particular chisel. and yes, increasing the bevel is likely to fix it.

You're cutting shedua, you can expect a short edge life.

Until you are finished working with that material, I would put a 30 degree micro bevel on it.

My low angle chisels are for hand paring only. Even light use of a mallet will dull them quickly. As others have said, try a bit higher angle.

jtk

Ok, so tried a 30 degree bevel angle - 2 taps and the chisel was dead.
Tried another chisel also at 30 degrees - same story.

I agree shedua is tough, but should it really be so hard on my chisels that I can only tap twice before I have to re-sharpen?

Again, just to emphasize - we're talking very light cuts that requires tapping mainly for control.
I can pare with longer edge life, but I don't find that practical for removing waste between the tails etc.

That's pretty quick, but I'll be frank in that I'm not totally surprised. Diamonds and sandpaper are far too harsh an abrasive for a final edge on most chisel steels. I say this having chopped bubinga with white steel (HC steel) chisels. You need an abrasive that pairs well with these.

Until then, raise the cutting edge angle higher still, eventually the chisel will hold an edge.

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Originally Posted by Brian Holcombe

That's pretty quick, but I'll be frank in that I'm not totally surprised. Diamonds and sandpaper are far too harsh an abrasive for a final edge on most chisel steels. I say this having chopped bubinga with white steel (HC steel) chisels. You need an abrasive that pairs well with these.

Until then, raise the cutting edge angle higher still, eventually the chisel will hold an edge.

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I'm not sure I follow you. The sandpaper I'm using is not "normal" sandpaper, but abrasive made for polishing fiber cabling.
The final grit is 0.3 micron which as far as I can tell equates to something in the area of 75.000 grit.

Is that not fine enough?

If that's not your point can you elaborate on what you mean with "an abrasive that pairs well with these"?

A quick test with a file might indicate if your chisel is too soft.

jtk

0.3 micron is pretty fine, I agree, that should not be a problem. I show Green Chromium Compound and the Shapton Pro 30000 at about 0.5 micron.

If you went to 30 degrees, then that just seems odd unless someone overheated the chisels. Do you see similar behavior on other wood as well? And do you have any other chisel against which you can test; even a cheap one...

Quote:

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Originally Posted by Jim Koepke

A quick test with a file might indicate if your chisel is too soft.

jtk

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I kindly ask you to elaborate on how to perform such a test :-)

I suspect that you mean that the chisel should be hardened in such a way that it takes some effort to file away material from the chisel, but I'd like some details on what result I should expect in either a good or bad scenario.

Quote:

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Originally Posted by Andrew Pitonyak

0.3 micron is pretty fine, I agree, that should not be a problem. I show Green Chromium Compound and the Shapton Pro 30000 at about 0.5 micron.

If you went to 30 degrees, then that just seems odd unless someone overheated the chisels. Do you see similar behavior on other wood as well? And do you have any other chisel against which you can test; even a cheap one...

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As I wrote earlier I've tried two different 10mm chisels albeit both E.A. Bergs.

I have other chisels, but would it matter if the width is not the same?
I assume a chisel of smaller width would not see the same pressure on the edge, but I could be wrong?