plane blade's edge turning blue during use

[jorgoz]

I recently noticed the edges of a couple of O1 plane blades turning blue during planing. Is this normal ?

The one pictured was mainly used on soft maple and walnut. I rarely plane exotics. I also have the impession the edge retention is quite low, haven't recorded exact time but a guestimate would be about 10 minutes actual use. I never use a power grinder to grind plane blades, if i do i use a tormek, so no heating problems there. Sharpening sequence : king 800, cerax 3000 and naniwa 8000, all flattened with a well used atoma 400 (so i presume it's more going towards 600).

Back of blade

 

[Racers]

Hi,

Looks like overheating, you must be working a a high rate :shock:

Any chance of doing a bit of plaining and whipping the blade out to feel if its getting hot?

What make blades are they?


Pete

 

[bugbear]

Wow - your cap iron's a long way back!

I suspect this is just chemical/patina style "blue" as opposed to "it got very hot" blue.

I often have plane blades go black, when planing oak.

BugBear

 

[Karl]

I often have plane blades go black, when planing oak.

BugBear

Same here.

 

[Scouse]

I often have plane blades go black, when planing oak.

I never use oak, but I seem to remember someone, could have been Rob Cosman, noting that the tannic acid in oak causes discolouration and ultimately corrosion on hand tools.

As usual, I can't find the link... :roll:

 

[jorgoz]

Wow - your cap iron's a long way back!

These are single blade planes, no chipbreakers. I presume you mean this with cap iron.

What make blades are they?

Philly blades.

 

[bugbear]

Wow - your cap iron's a long way back!

These are single blade planes, no chipbreakers. I presume you mean this with cap iron.

The term chipbreaker is contentious in some circles. Cap iron (which refers to the same component) is less so.

BugBear

 

[jorgoz]

Just had a resharpen. About 5 to 6 minutes actual use, although i'm planing end-grain at the moment. It took about 2'30" on the 800 grit king to get a burr again. Now i know this is not the quickest cutting stone, but this seems a fair amount to get re-establish a burr. Total sharpening time about 8 mins, which included a flattening of the 800 in use and re-flattening everything for the next round.

I didn't take the blade out of the plane to feel how warm it was getting, but touched the blade bevel with a very sensitive part of my anatomy, and i do mean my upperlip :mrgreen: and it was pleasantly warm but not hot.

Bugbear, i'm not a native English speaker. I thought most of the time the lever-cap is meant when mentioning the cap-iron.

 

[bugbear]

Bugbear, i'm not a native English speaker. I thought most of the time the lever-cap is meant when mentioning the cap-iron.

A few people do that, but it's a mistake.

The lever cap (on an infill or Bailey) is quite a different thing, equivalent to the wedge in a wooden plane.

BugBear

 

[Henry Disston]

I have had scrub plane irons get hot enough in use to discolor. Quick strokes while edge jointing a long board can get an iron pretty hot in the center.

 

[Derek Cohen (Perth Oz)]

...I didn't take the blade out of the plane to feel how warm it was getting, but touched the blade bevel with a very sensitive part of my anatomy, and i do mean my upperlip :mrgreen: and it was pleasantly warm but not hot....-iron.

Hi Jorgoz

Mate, if you could get the blade hot enough to alter the temper just from planning, then you are indeed a superman! There is no way that this is possible ... friction heat would need to get the blade red hot ... literally.

All that is occurring is that the blade is being discoloured by the chemicals in the wood. I often see my blades turning a brown-rusty colour after a session of planing (of course they can go a rusty-rusty colour if left out wet, but that is another matter ). It is removed as soon as I re-hone the blade front-and-back, but often remains in the hollow grind.

Regards from Perth

Derek

 

[paulm]

I get the same effect on my turning gouges when turning oak, sweet chestnut or walnut, where the woods are high in tannin, more so if they are unseasoned with a bit of moisture in them still. Shavings will discolour the lathe bed too, or anything steel or iron.....

Cheers, Paul

 

[jorgoz]

Mate, if you could get the blade hot enough to alter the temper just from planning, then you are indeed a superman! There is no way that this is possible ... friction heat would need to get the blade red hot ... literally.
Derek

Derek, when grinding a blade on a high speed grinder, overheating and losing tempering doesn't turn a blade red hot, or am i wrong ? Forgive me guys if this seems obvious to some of you but i'm no metallurgist. And as mentioned earlier i don't power grind.

My main concern is that i'm losing my edge rather quickly, or again is this normal for O1 steel on soft maple, less than 15 minutes use and having to go through my complete sharpening sequence ?

 

[David C]

I would say that fifteen minutes of continuous planing on soft maple would be as much as you could expect.

David

 

[Richard T]

Maple isn't that soft - I'd say 15 minutes was about right too.

One way to check how hard the iron is is to gently run a file over the flat face not far from the end. Ideally it will just skate smoothly over without making any scratches at all. This is usually the case with old blades like the Marples I bought last week - it's like trying to file glass.

More modern blades may not be so hard. This is why I started with "gently". A new Stanley may just be hard - to - file, but you will make an impression if you try too much.
And a blade that has been over heated to the point where it has had its temper adjusted or lost its hardness will be soft - usually in patches; to thoroughly normalise a blade takes a very even heating. So a blade that has been ground too hot may still pass the file test in some places but not others.

Have you been planing oak or chestnut or something else with high tannin, or is the maple turning it blue? If the latter, it's very surprising to me. :arrow: :shock:

Ps people can and have got the ends of blades red hot with bench grinders in a matter of seconds. You can usually tell by the tell - tale blue/straw tempering further up. Your bluing doesn't look like that.

 

[Derek Cohen (Perth Oz)]

Hi Jorgoz

Let me describe it another way ..

If you were grinding a blade, and and edge went blue, then you would know the temper had been affected (to soften the steel). If you attempted to touch the steel, you would burn yourself as it would be very, very hot. One of the usual recommendations when grinding is to keep a finger close to the edge of the blade, and remove the blade from the wheel before it gets too hot to hold.

I very much doubt that one could generate this level of heat by just planning. I work doing some vigouros planning this afternoon, and after a session of 30 minutes continuos planning the plane was a little warm - nothing that made me want to drop it and run my hands under cold water.

Regards from Perth

Derek

 

[bugbear]

Mate, if you could get the blade hot enough to alter the temper just from planning, then you are indeed a superman! There is no way that this is possible ... friction heat would need to get the blade red hot ... literally.
Derek

Derek, when grinding a blade on a high speed grinder, overheating and losing tempering doesn't turn a blade red hot, or am i wrong ? ?

No, you're right, and I'm afraid Derek has slightly over stated things. Temper can be altered (specifically, in this case, "lost") at temperatures well below red heat.

Indeed, normal heat treatment involves exactly this - steel starts to glow red around 600c, but tempering is done at 200-300.

But (to agree with Derek) I think you'd struggle to get a plane blade up to "temper altering" temperatures by planing.

BugBear

 

[Derek Cohen (Perth Oz)]

Hi BB

Absolutely.

I was deliberately overstating the "red hot" side, and then forgot to clarify that when I posted later. :roll:

Bottom line is that friction on wood is never going to get the steel hot enough to affect the temper.

Regards from Perth

Derek

 

[jorgoz]

Thanks for clarifying this.

Richard, i used walnut, which contains tannins, i've got my dirty hands to show for it