Burnt blade corner -- what to do?

[Steven Mikes]

I finally bough a bench grinder and set about trying to put a camber on my LA BU Jack plane blade. I was also regrinding the primary bevel to 25 degrees at the same time. It was going great, I ground the camber first at 90 degrees with no issues, then adjusted the angle and started on the bevel. I was getting close to being done when I got too aggressive with the grinding and burned one of the corners. I know this is bad somehow, but what will the effect be? Can I keep using the blade? Is there a way to fix it?

[Jim Koepke]

It doesn't look that bad. You can either fret about your experience or learn from it. My tendency is to use the blade as is. The burnt area may be a bit softer than the rest of the blade. With a camber you may not even notice. Eventually you will hone past the burnt area and this will just be a memory.

Derek Cohen wrote a good piece on cambering Bevel Up Plane Blades:

http://www.inthewoodshop.com/Woodwor...aneBlades.html

You may find you need a bit more camber which will mean removing the burnt part.

My post on cambering is a bit nontraditional:

http://www.sawmillcreek.org/showthre...t-Finally-Came

jtk

[Philipp Jaindl]

As Jim already said what happens when you burn the steel is the heat treatment in that spot will be changed, in most cases the steel will be softened. Only 2 ways to fix that either grind past it, which is what you do in practice or in theory you can re-temper the whole blade which obviously is a silly thing to do, unless in whatever way half the blade lost its temper.

I'd just use it as is and either let it wear down over time or grind it down the next time you sharpen it.

[Patrick Chase]

I finally bough a bench grinder and set about trying to put a camber on my LA BU Jack plane blade. I was also regrinding the primary bevel to 25 degrees at the same time. It was going great, I ground the camber first at 90 degrees with no issues, then adjusted the angle and started on the bevel. I was getting close to being done when I got too aggressive with the grinding and burned one of the corners. I know this is bad somehow, but what will the effect be? Can I keep using the blade? Is there a way to fix it?

Which steel is the blade, and how would you describe the color immediately adjacent to the corner? It's hard to tell from the photo because the white balance is off, but I'm guessing somewhere between "purple" and "grey-blue"?

If it's PM-V11 I'd recommend grinding the edge back beyond the discoloration (looks like you need to take off a couple/few mm) and regrinding the bevel. LV's Rc62.5 default hardness for PM-V11 is achieved by tempering at 350-400F. The surface coloration suggests that the steel got up to 500-600F, which would cost you several points of hardness.

If it's O1 then it's a trickier call. LV's default hardness of Rc59 is achieved by tempering at 500F, which corresponds to reddish-brown surface color. If the iron didn't get much higher than that when you burned it then you can probably just use it.

[Normand Leblanc]

The corners on a camber blade hardly see any wood. Just use it like it is!

[Brandon Speaks]

Never done this with a plane blade but have on turning tools.

I would not retemper unless you are an expert. You could regrind.

I practice I would use as is, if that part of the blade saw much action it would likely dull more quickly, since it probably will not it should not dull much more quickly than the center. If you find useful portions of the blade are dulling too quickly you can always regrind at that time.

[Patrick Chase]

I would not retemper unless you are an expert. You could regrind.

Re-tempering doesn't buy you anything. You'd have to re-heat-treat, and *then* temper. Doing so isn't free though, as it can cause grain growth.

Also, if it's a PM-V11 iron the manufacturer of the steel recommends cryo treatment between HT and tempering.

[Pat Barry]

I'd use it as is and work to fix it the next time you need to regrind it.