Thread: Making a plane blade 1

Since the kitchen boss was home, I didn’t proceed to the tempering step in the interests of domestic harmony, but I decided to see what would happen if I used it as-is. I finished grinding the bevel (which I’d taken down about ¾ of the way while the steel was soft) and honed it up. The hard steel honed nicely, as it does, and I quickly had a keen edge. Into the plane it went, and produced some creditable shavings on Vic Oak. 11 Blade test 1.jpg

I then fed it some She-oak, which it cut ok, but I could feel it getting rougher as I planed. 12 Blade test 2.jpg

A look at the blade showed what you’d expect – lots of chips along the edge (too small to photograph, but very evident under mild magnification), indicating a too-brittle blade.

So the final result is going to have to wait until I can get a couple of hours alone in house & fire up the oven and temper the thing back. But I'm not sure I’ll try this stuff again, though. O1 gauge plate is not much more expensive and comes ground flat & clean. It’s just as easy to work in the annealed state (as it arrives) and involves far less effort to clean up after oil-quenching, at least, which has always worked for me in the past.

Again, any comments from those with more smithing experience??

Cheers,

Hi Ian,

Only point to contribute is that I've quenched 1084 in canola oil and it works beautifully.

Cheers,
Zac.

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Hi Ian. I like this thread! My experience has been the same as Fergi. Vegetable oil worked for me. I am running out of 1084 and going to try using some steel from the body of a big old circular saw blade for my next batch.

Ian,
Great write up, tho at one stage I thought he’s turned to drink, then realised it was a form.
What are you using to fire the forge with?

Cheers Matt.

So when you folks say the oil worked, how hard were your blades after quenching? Dd you try filing them?

It seems the sump oil wasn't doing the same job as Canola, then, but I've read that you can substitute sump oil, so since I had plenty of that on hand I thought it was worth a go. At least the brine quench confirmed that the steel had reached critical temperature (which the loss of magnetism also told me). I guess the best way to find out is to try another blade with Canola. I'll take a trip to the supermarket in the next day or two & stock up on some cheap Canola (or do I have to buy top quality?? )

This programme will resume shortly....

Cheers,

Originally Posted by Simplicity

....What are you using to fire the forge with?....

MAPP gas with a swirly-burner thingy. It got the blade nicely hot very quickly - in the past I've heated smaller pieces by just sitting the cylinder on the bench & holding the object in front of the flame (with tongs, of course!). It's hard to get the metal properly glowing over the whole area you want to harden, that way - a puff of wind through the door & you lose colour immediately. I would certainly not have been able to get 30mm of blade evenly red hot without the furnace.

That part of the experiment I rate a success.

Cheers,

Hi Ian,

My forge was far more primitive than yours, being just a brazier on the porch with my wife's hair dryer pumping in the O2. It's a few years ago now but I judged the temp by colour and quenched in a 4l container of canola oil that had been slightly warmed. Mine was black and gold, to me quality canola oil is an oxymoron. I tried a file which skated on the surface, and then promptly dropped the workpiece, which was a beautiful drop point knife, and cracked the tip off. So I proceeded to temper in the oven and re ground the tip to a slightly stubbier profile.

Cheers,
Zac.

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I have never done any of this yet,but I have followed a few on YouTube,
So take this with a pinch of salt.
An remember some saying to heat the quench medium slightly, so it has less of a shock to the metal when quenched!.

Cheers Matt.

Originally Posted by Simplicity

I have never done any of this yet,but I have followed a few on YouTube,
So take this with a pinch of salt.
An remember some saying to heat the quench medium slightly, so it has less of a shock to the metal when quenched!.

Cheers Matt.

I think the shock thing is claimed often, but the real gain with oil that's 150 degrees plus is that it flows better and the transition temperature is achieved faster. Same as brine vs. water, to increase the contact with the blade.

That said, I rarely preheat my oil, but use oil hardening steel and have made a few blades out of XHP (which is the likely V11 steel).

XHP needs to get to super bright orange bordering on dull yellow (which can only be achieved with a single torch inside of a paint can type forge or something insulating - the paint/coffee can type are nice because you have some lateral room to move and adjust rather than guessing in a longer thinner forge). that steel can't stay in open atmosphere for long and needs to be heated quickly and then quenched any number of ways (oil is a good choice for it, too - it's very stable - no preheated needed for that as the transition need to harden is 50 degrees F per minute.

Originally Posted by D.W.

..... I think the shock thing is claimed often, but the real gain with oil that's 150 degrees plus is that it flows better and the transition temperature is achieved faster. Same as brine vs. water, to increase the contact with the blade. ...

Yes, it did puzzle me how heating the oil by a fraction of the steel temperature did much to reduce the "shock".

In fact, it most likely increases the rate of thermal transfer. I just did a quick search to compare the specific heat of vegetable & mineral oils (i.e. the amount of heat it requires to increase the temperature of a given volume by 1 degree) and they are not radically different at room temperature. But what I did learn (or re-discovered; been over 50 years since I did chemistry & physics!) is that the specific heat of oils increases with temperature. This means the hotter the oil, the more heat it can absorb without getting much hotter itself. In my book, that ought to increase "thermal shock".
As usual, the more I learn, the more I realise the vast extent of my ignorance...

Ferg, I used the oil both at room temp and when it was quite hot. No difference. I am wondering if the way engine oils are made their thermal properties are wildly different from plain vegetable oil, and that may have a bearing on the matter. As I said, the sump oil seemed to work well enough on the O1 steel I hardened.

And if a file skated & the metal was brittle, that's convincing evidence you got it hard alright!

Cheers,

a soft ark or washita stone is also a great indicator of hardness after tempering. If a blade is around 62/63 hardness, it'll just barely be usable. If one is 60/61, it'll work quite well and create a fine edge and raise a wire edge. If a blade is 58 or so, the washita will cut it deeply and make a less fine edge.

I think the idea of less thermal shock was added by some folks along the way who knew that the oil works better warmed.

I've always used soy or peanut oil here, mostly unheated due to laziness. It does make sense that when the oil is warmer, it will flow to the surface of the blade faster, which is the explanation I've heard for brine - smaller bubbles, maybe fewer, don't know, but water stays in contact with the tool and transition happens faster.

I used to just swish the blade around in the oil and saw a video of a knifeman last year where the fellow mentioned sliding the blade through the oil thin side else using the blade like an oar may result in more warpage as one side gets faster cooling than another. No clue, though. I break lots of rules and figure that if I run into steels that don't allow it, I'll get more forgiving steels (e.g., I don't interrupt quenches even though some schedules request it, and I don't remove the iron from the oil early - just sort of leave it in there until it seems workable, then take it out and hustle it up to the kitchen oven for temper before it's lost it's malleability.

I went so far with XHP as to stroke test a blade in beech last year to see how close it was to V11 - it went about double my best O1 iron - over 4000 feet in the test wood, same as LV V11. A very forgiving steel if you can find it precision ground (The scale would be intolerable) and can drill and file by hand slowly so as not to heat it- it air hardens with the first sniff of heat and is very hard to deal with after that. Once you get it to the point that it can be quenched, it just needs a lot of fast heat and then a quench, and stays very flat.

O1 can be biased by partially cutting the bevel, and then the odds are in your favor that the warpage on the blade, if any, will make a hollow in the back instead of a belly.

Originally Posted by IanW

Yes, it did puzzle me how heating the oil by a fraction of the steel temperature did much to reduce the "shock".

In fact, it most likely increases the rate of thermal transfer. I just did a quick search to compare the specific heat of vegetable & mineral oils (i.e. the amount of heat it requires to increase the temperature of a given volume by 1 degree) and they are not radically different at room temperature. But what I did learn (or re-discovered; been over 50 years since I did chemistry & physics!) is that the specific heat of oils increases with temperature. This means the hotter the oil, the more heat it can absorb without getting much hotter itself. In my book, that ought to increase "thermal shock".
As usual, the more I learn, the more I realise the vast extent of my ignorance...

Ferg, I used the oil both at room temp and when it was quite hot. No difference. I am wondering if the way engine oils are made their thermal properties are wildly different from plain vegetable oil, and that may have a bearing on the matter. As I said, the sump oil seemed to work well enough on the O1 steel I hardened.

And if a file skated & the metal was brittle, that's convincing evidence you got it hard alright!

Cheers,

Ian,
Are you saying,if the oil is hotter it can draw the heat from the steel(Plane blade in your example) quicker.
Impacting more “shock”?

Cheers Matt.

Originally Posted by Simplicity

.... Are you saying,if the oil is hotter it can draw the heat from the steel(Plane blade in your example) quicker. Impacting more “shock”?

Matt, what I'm trying to say is that the quicker the heat goes from steel to quenching medium, the greater the thermal "shock" - that would be my definition of 'shock'.

Exactly how that happens, if it happens, and how much it 'matters' gets into territory beyond my present understanding - biology was my field, not engineering!

This is how I see it. As the oil gets hotter, it can absorb more heat with less of a rise in temperature. This could affect heat transfer in two ways:
1. Heat moves according to the temperature gradient, the greater the difference, the more rapidly it flows. If specific heat keeps rising with temperature, the oil closest to the hot metal maintains a steep gradient longer.

2. If the liquid in contact with the hot surface boils, the gaseous phase will have lower thermal conductivity & reduce the rate of heat transfer considerably. The more heat the liquid can absorb without boiling, the better it can maintain the gradient.

DW - I'm not too sure what you mean, exactly, by "improving flow". My understanding of the use of salt solutions is that it would increase the specific heat & increase the boiling point of the water, thus helping to reduce cavitation around the metal, which I guess could be loosely described as improving flow....

But I'm floundering in ignorance, & theorising on he basis of dimly-remembered lessons of long ago. I could easily be in the wrong damn bush & barking up the wrong type of tree....


Arrrgh! I'm going to the shed to play with some wood.....

Hi Ian. Not sure if this makes a difference but I didn't clean off the mill scale before annealling. I cut to shape, profiled the cutting edge and put it into the fire. First time I relied soley on colour, second time (as encouraged by Doug) I checked with a file when it was cherry red. File just raised some "sparks" but slid along steel. I don't have a magnet to run that test but so far so good. My advantage is I am only making moulding plane blades, so much smaller surface area. Obviously I am very new to this and am trying to follow others instructions. Paul and Doug have been a great help.