Does PMV11 burn easily?

[chris carter]

My wife asked me to fix a door. I made the classic mistake of not paying enough attention to nails and absolutely destroyed the irons in my cheap block plane and the PMV11 in my Veritas LAJ (thank goodness I didn't grab a third or fourth plane!). I did the block plane iron on the grinder first without issue. The PMV11 blade however was a different story. This is my only PMV11 iron and just a couple months old. It has seen a diamond stone once and otherwise only a strop. Right away I noticed it getting a straw color. I was doing everything just like I normally do and have never burned an iron except once the first time I used a grinder on an iron when I didn’t know what I was doing – but never after that. I was dipping in water after each pass and after noticing the straw color I started DIPPING like extended amounts to time. The edge NEVER got too hot to actually hold with my fingers. When I say hold I don’t mean half a second. I mean like hold indefinitely quite comfortably. And the color got worse, as you can see in the pic.

By my eye, this looks like it’s burned. Unless there’s something I don’t know???? I’m no metallurgist by any stretch. Is there something about PMV11 that would cause it to discolor without getting too hot? Is there something about it that would make it burn at such low temps? I’m at a loss here. But there’s no denying how it looks. It is what it is so I’ll use it and see what happens – maybe it isn’t bad enough to affect the iron noticeably…. If it’s trashed I figure I’ll find out soon enough and just order a new one. But I’m baffled at how easily it discolored (which I’m assuming is overheating, even though it never felt very hot). Are grinders a no-go for PMV11?

Someone explain this to me!
454131

[Mel Fulks]

It’s possible that the dark line is just dust and glue from the grinder . Is the dark line on both sides? If not ,then I’m guessing that it is indeed
the glue that made that line.

[Tim Best]

From David Weaver on WC forum:

I see a comment on the blue forum about whether or not V11 generates a lot of heat in grinding. If someone could do the poster a favor (They're trying to grind out a whole bunch of damage) and let them know, yes, it grinds much hotter if you're going to do any significant amount of removal.

To do heavier work or grinding with pressure, the OP should lay a wet paper towel on the back of their iron.

If it's just refreshed for hollows, no big deal. But if removing a lot of damage or adjusting the primary bevel, it's very easy to draw tempering on it - far far easier than something that doesn't have a lot of wear resistant carbides.

[Jason Martin Winnipeg]

Hmm. This is good to know.

[chris carter]

Mel: It’s only on the back, although I didn’t thoroughly check before I moved to the 1000 grit diamond stone. But it seems to only be on the back. That said, I did try lapping the back and it didn’t come off, so I don’t think it’s discoloration from glue.

Tim: thanks for that info!

I will admit I’m a little disheartened. I’m not about to try and grind out that 1/8” or whatever it is as I believe I’d just wind up back in the same place. It’s a freakin’ thick blade and trying to go slow enough to not overheat the edge would take half a day – it was never too hot to touch. It makes me wary of going with PMV11 again if this is what I will have to deal with if I change a primary bevel or have to remove a chip. I’m not about to buy a Tormek. I’m inclined to just leave it alone and see what happens; it might be much ado about nothing. If it is problematic I’ll toss it and buy on 01 blade.

[michael langman]

Ceramic grinding wheels will cut powdered metal much cooler then aluminum oxide wheels. Powdered metals take more patience then regular tool steels.

[Derek Cohen]

I use a 180 grit CBN 8” wheel on a half speed bench grinder to hollow grind PM-V11. I have never burned or discoloured a blade, and I have ground many, many. In my experience, PM-V11 does not pose any more difficulty than O1 or A2, whether grinding or honing.

Chris, no need to get paranoid. You are just new to this steel. Use it and grind again when it needs. I would be surprised that the brown colouring is more than superficial. In any event, brown is not a dangerous colour when tempering or hardening steel.

Regards from Perth

Derek

[James Pallas]

I have 17 PMV11 irons. I’ve ground at least a third of them on a 6” high speed grinder with a 36 grit grey wheel. I have not seen any color changes period. I have done a lot of grinding over the years and don’t have problems grinding anything. I did purchase a CBN wheel last year to get a little better finish but still use the grey to start. Since it appears that the color runs almost straight across the end of your iron it may be something on the iron.
Jim

[chris carter]

Chris, no need to get paranoid. You are just new to this steel. Use it and grind again when it needs. I would be surprised that the brown colouring is more than superficial. In any event, brown is not a dangerous colour when tempering or hardening steel.
Derek

Thanks for talking me down from the ledge!

James: Your experience is what has me so perplexed. I feel like if I were actually burning the edge (mostly brown, but there is a smidge of blue dead center) that I would have "ouch!" when touching the iron. I really don't think my temps got that high unless I was undergoing spontaneous and temporary acute numbness in my fingers at that very moment. I also was under the impression that it is easier to burn the corners because there's less steel (only on one side) to act as a heat sink. But my "burn" mark is the opposite: Nothing on the edges and it is worst at the center. I did try and lap the back pretty aggressively on the 1000grit diamond stone to see if I could wear off the color and it stayed. The color is also only on the back side - there is no discoloration on the bevel side (although after grinding I did put the final edge on it, but it's small due to being hollow ground).

Regardless, I'll just use the iron and see what happens. Probably nothing! If it chips easy, I'll get a new one. The LAJ is not a heavy user so it may take a while to find out (although I am liking it more and more so maybe it will replace my wooden jack for normal jack duties).

[michael langman]

I have 17 PMV11 irons. I’ve ground at least a third of them on a 6” high speed grinder with a 36 grit grey wheel. I have not seen any color changes period. I have done a lot of grinding over the years and don’t have problems grinding anything. I did purchase a CBN wheel last year to get a little better finish but still use the grey to start. Since it appears that the color runs almost straight across the end of your iron it may be something on the iron.
Jim


We used the Norton 32A 46 grit grey wheels for hogging off hard tool steel in the shops I worked in. Plunging through D2 and shooting sparks 2 feet off the grinding wheels. Sure would wake up the guy in front of me on the next grinder. Made the boss smile listening to all that noise. These were surface grinders.

[Curt Putnam]

Thanks for talking me down from the ledge!
Regardless, I'll just use the iron and see what happens. Probably nothing! If it chips easy, I'll get a new one. The LAJ is not a heavy user so it may take a while to find out (although I am liking it more and more so maybe it will replace my wooden jack for normal jack duties).

You have no risk in using the iron. You started out feeling that it was trashed. It apparently is not. Were I you, I would carefully polish the back to the highest grit you have and then use it. If it does chip, I would grind it back (on diamond) as far as you are willing to go, and then try again. I have not power ground my irons because they are a little too precious to subject to a novice grinder.

[Warren Mickley]

Thanks for talking me down from the ledge!.

Regardless, I'll just use the iron and see what happens. Probably nothing! If it chips easy, I'll get a new one. The LAJ is not a heavy user so it may take a while to find out (although I am liking it more and more so maybe it will replace my wooden jack for normal jack duties).

Tempering softens steel and makes it tougher. If you exceeded the original tempering temperature the iron will not be brittle, but it will be softer. It seems that you heated it to 500-600 degrees Fahrenheit.

[Andrew Pitonyak]

If you figure out that you did something to the blade, how far in is the damage likely to be?

Anyone near you with a Tormek or some other wet grinder?

If you get to the "throw it away" stage, send it to me. I will blunt on my regular grinder to see if it continues the trend when I try to take it back like 1/8" and then I will throw it on my Tormek, which will take a long time to grind back, but will not affect the blade negatively, just the stone.

I will return it with the same angle (or close) to what you send me unless you tell me to put on a different angle.

[Derek Cohen]

Tempering softens steel and makes it tougher. If you exceeded the original tempering temperature the iron will not be brittle, but it will be softer. It seems that you heated it to 500-600 degrees Fahrenheit.

Brown is formed on high carbon steels at 450 degrees F. A quick Google indicates that steels with high chromium content (since the assumption is that PM-V11 is a stainless steel) are good to up to 1600 degrees F.

Regards from Perth

Derek

[Lawrence Burkett]

Brown is formed on high carbon steels at 450 degrees F. A quick Google indicates that steels with high chromium content (since the assumption is that PM-V11 is a stainless steel) are good to up to 1600 degrees F.

Regards from Perth

Derek

Because I'm curious to learn more: is this true? I had the impression that if you exceeded the tempering temperature, you could have problems. When I google typical stainless steels, I see tempering in the range of 200 C - 350 C (350 F - 650 F). I'm not an expert, but I was using these sources:

https://www.materials.sandvik/en-us/products/strip-steel/strip-products/knife-steel/hardening-guide/hardening-programs/sandvik-12c27-piece-hardening/
https://www.materials.sandvik/en-us/products/strip-steel/strip-products/knife-steel/hardening-guide/hardening-programs/

[Warren Mickley]

Brown is formed on high carbon steels at 450 degrees F. A quick Google indicates that steels with high chromium content (since the assumption is that PM-V11 is a stainless steel) are good to up to 1600 degrees F.


Except that Chris said part of the iron turned blue, which indicates a higher temperature. I do not know what temperature was used for tempering. Maybe you have insider information.

[Rob Mahar]

One tip I picked up a while back for grinding out chips is to start with the tool rest at 90° until you are past the chip. Then reset to whatever bevel angle you usually use and grind the bevel until the flat end is almost gone. Finish on a stone for the last little bit. This keeps you from grinding on a very thin edge that overheats easier.

Being far from an expert I'm not sure how much difference it makes for the extra effort, but I've never managed burned a blade so I'll keep doing it. I suspect people with a better touch and feel probably don't need to do that.

[Charles Guest]

One tip I picked up a while back for grinding out chips is to start with the tool rest at 90° until you are past the chip. Then reset to whatever bevel angle you usually use and grind the bevel until the flat end is almost gone. Finish on a stone for the last little bit. This keeps you from grinding on a very thin edge that overheats easier.

Being far from an expert I'm not sure how much difference it makes for the extra effort, but I've never managed burned a blade so I'll keep doing it. I suspect people with a better touch and feel probably don't need to do that.

Absolutely, you should never grind on the hollow until the chip is gone. Blunt the end past the chip, then put the hollow back in to just near the edge leaving the honing stone to take you all the way there.

[James Pallas]

I have my own theories about grinding or abrading in general. After watching beginners I think everyone starts out thinking it’s a task that takes great force. It’s actually very delicate. Coarser abrasive quicker removal finer abrasive slower removal longer contact more heat. CBN and diamond, sharper finer abrasive. If you’re burning too much pressure not enough movement. What was it that guy used to talk about, baby bird or something? Ease up relax let the wheel do the work, keep in touch with the work so you know when it’s hot before you see the red glow and loose skin.