german planes

[Trafalgar]

There most certainly is not enough heat being generated to affect the properties of tool steel.

Are you sure, even at a microscopic level? ever seen sparks from a powered waterstone?

http://www.youtube.com/watch?v=K0BtDfJCNL8

Pete

That's all well and good but I'm sure that the only thing that happens with respect to this issue when one uses a waterstone in the vigorous manner described by Odate is that a lot of steel is removed, and in the instant case steel that wasn't heat treated properly. The bad steel is simply honed away back to the good stuff. There is no annealing going on or re-hardening or whatever it is Mr. Odate surmises may be happening.

 

[Cheshirechappie]

I think it is possible to alter the heat-treatment state of a tool edge whilst grinding it. We are all familiar with the phenomenon of softening - over-tempering - that can occur on a small bench grinder if the tool is allowed to dwell too long. The grindstones used by the old Sheffield makers were far larger, and were of two types. The first, large water-cooled stones running far faster (wheel peripheral speed, not RPM) than most bench grinders run today, used for rough shaping of the forged and heat-treated blanks, and the second a smaller (about 24" diameter) wooden wheel faced with leather and dressed with emery, run fast and uncooled, and used for 'glazing' or finish grinding.

It is quite possible for the heat generated by either wheel to raise the thin section at the cutting edge of the tool being ground to hardening temperature, and for the tool edge to 'quench' fast enough for hardening to occur as the cooler bulk of the tool sucks away the heat when the tool leaves the stone surface. (If anybody doubts that sufficient heat could arise, consider the sparks from grinding, some of which come off white. That indicates particles at close to or above the melting point of the steel.) As others have noted, the hard part is seldom more than a few thou thick, and can fairly easily be ground away to properly hardened and tempered metal - the hardening happens only very close to the cutting edge.

 

[woodbrains]

I think it is possible to alter the heat-treatment state of a tool edge whilst grinding it. We are all familiar with the phenomenon of softening - over-tempering - that can occur on a small bench grinder if the tool is allowed to dwell too long. The grindstones used by the old Sheffield makers were far larger, and were of two types. The first, large water-cooled stones running far faster (wheel peripheral speed, not RPM) than most bench grinders run today, used for rough shaping of the forged and heat-treated blanks, and the second a smaller (about 24" diameter) wooden wheel faced with leather and dressed with emery, run fast and uncooled, and used for 'glazing' or finish grinding.

It is quite possible for the heat generated by either wheel to raise the thin section at the cutting edge of the tool being ground to hardening temperature, and for the tool edge to 'quench' fast enough for hardening to occur as the cooler bulk of the tool sucks away the heat when the tool leaves the stone surface. (If anybody doubts that sufficient heat could arise, consider the sparks from grinding, some of which come off white. That indicates particles at close to or above the melting point of the steel.) As others have noted, the hard part is seldom more than a few thou thick, and can fairly easily be ground away to properly hardened and tempered metal - the hardening happens only very close to the cutting edge.

Hello,

The melting point of steel can and is reached by grinders, which is why diamond dry grinders are never used and CBN must be used instead. If the heat generated is that great, I doubt water will prevent it at the extreme, ultra fine tip of the tool. I recall that Jim Kingshott even commented that wet grinding only helped with not drawing temper, but not prevent it entirely, if used carelessly.

Mike.

 

[Trafalgar]

I think it is possible to alter the heat-treatment state of a tool edge whilst grinding it. We are all familiar with the phenomenon of softening - over-tempering - that can occur on a small bench grinder if the tool is allowed to dwell too long. The grindstones used by the old Sheffield makers were far larger, and were of two types. The first, large water-cooled stones running far faster (wheel peripheral speed, not RPM) than most bench grinders run today, used for rough shaping of the forged and heat-treated blanks, and the second a smaller (about 24" diameter) wooden wheel faced with leather and dressed with emery, run fast and uncooled, and used for 'glazing' or finish grinding.

It is quite possible for the heat generated by either wheel to raise the thin section at the cutting edge of the tool being ground to hardening temperature, and for the tool edge to 'quench' fast enough for hardening to occur as the cooler bulk of the tool sucks away the heat when the tool leaves the stone surface. (If anybody doubts that sufficient heat could arise, consider the sparks from grinding, some of which come off white. That indicates particles at close to or above the melting point of the steel.) As others have noted, the hard part is seldom more than a few thou thick, and can fairly easily be ground away to properly hardened and tempered metal - the hardening happens only very close to the cutting edge.

Well, yes, but apparently Odate is asserting that this can be accomplished when honing on a waterstone, by hand.

 

[Cheshirechappie]

Well, yes, but apparently Odate is asserting that this can be accomplished when honing on a waterstone, by hand.

Well - that's not how I interpreted it.

I read it that if Odate came across a tool that was brittle - too hard - his solution was to get it to tempering temperature, either on a hot ti roof (maybe just about possible on a very hot day) or by getting enough heat into the edge by friction on a sharpening stone to temper it back a bit (probably just about possible with a lot of energy exerted). He wasn't suggesting that friction on a hand hone would cause enough heat to bring the tool edge to hardening temperature.

What I was suggesting is a possible cause for the phenomenon noted by various people that some Sheffield-made plane irons (and also noted more recently with Ashley Iles chisels) are very hard and brittle at the cutting edge when brand new, but perform perfectly once the 'bad steel' is ground or honed back. That may also explain why Odate's tools were brittle when new, too - overheating local to the cutting edge on the manufacturer's grindstone.

 

[Trafalgar]

Chisels can certainly come with a small brittle portion at the end. In fact a lot do. Any treatment of this problem on one's honing stone (regardless of what kind) is not tempering this portion but simply removing it. The easiest thing to do is ignore the problem and continue to use and hone the chisel and soon enough all will be put right. If used only in paring and light chopping, the extra hardness isn't necessarily a drawback. At any rate, it'll be gone before you know it.

People run to the grinder too fast just because they notice a little nick. Just keep honing and using the chisel. Most of the time the nick won't even be a factor during use. No need to panic and no need to do a lot of grinding.

 

[Racers]

Chisels can certainly come with a small brittle portion at the end. In fact a lot do.

Well that statement seems to go against everything I have read or experienced making my own blades. Decarburization is something I have found when heat treating blades in either the BBQ or MAPP torch.

http://en.wikipedia.org/wiki/Decarburization

Pete

 

[Trafalgar]

I should say that people often complain of this problem over the years on the boards (perhaps not this one though) -- chipping at the end of a new chisel. Seems to be a common enough complaint. The standard, and good advice received, is to just grind it back a little or tolerate it until the small portion of brittle steel is honed away.

If it means anything, Odate has apparently experienced it enough times to have his pet remedies for it as well.

 

[Corneel]

Just an idea. Maybe a bit of case hardening going on? When the iron is heated in a coal furnace, I could imagine that some of the carbon migrates into the steel, carbonising the surface, and thus making the tip too highly carbonised to be usefull as a chisel. Grind it back abit and this area is quickly removed.

 

[Sheffield Tony]

According to our local smith Magnus ... placing the steel close to the air blast in the forge, where there was excess oxygen, tends to deplete the carbon from the steel. Whereas placing it to the side, away from the air where the fuel is burning with barely sufficient oxygen, allows carbon to be incorporated into the steel. This may of course be just an old blacksmiths tale.

Since the tempering temperatures for O1 or similar carbon steel are around 200C and hardening about 800C, compared to the boiling point of water at 100C, I cannot see a waterstone having a tempering or hardening effect - unless it is not wet ! Neither, to be honest, do I think that a hot tin roof is likely to make much difference. A domestic oven cranked to max will.

 

[bugbear]

According to our local smith Magnus ... placing the steel close to the air blast in the forge, where there was excess oxygen, tends to deplete the carbon from the steel. Whereas placing it to the side, away from the air where the fuel is burning with barely sufficient oxygen, allows carbon to be incorporated into the steel. This may of course be just an old blacksmiths tale.

Managing and controlling the distinction between an oxidising fire and a reducing fire is all part of the craft of the smith, where steel is concerned. No myth.

BugBear

 

[Cheshirechappie]

I think there may be a bit of confusion between faults occurring during heat treatment, and faults occurring during grinding.

The phenomenon of brittle cutting edges might (I emphasise might) be down to heat generated during grinding being sufficient to re-harden metal close to the edge. If the tool was properly hardened in the first place, it's unlikely to be a failure of tempering, because the problem can be solved by grinding away a small amount of metal at the edge. That wouldn't be the case if hardening hadn't occurred properly.

I've never seen any report of small workshop grinders being able to generate enough heat for this to occur - usually any problems they cause are softening due to reaching the higher tempering heats. However, the bigger grinders, running faster, used by Sheffield grinders may have been capable of bringing localised parts of tools to hardening heat - every picture I've seen of them in use showed bright sparks thrown from the job, so there was heat, water-cooled or not.

I don't know whether it IS the explaination, but all sorts of odd things happen to metal surfaces when being ground - it can be a very (locally) hot process.

 

[G S Haydon]

The only edge tools so far that have chipped in my hands during normal use are the Narex chisels. Both a mortice and the 8105's have brittle tips when brand new. I seem to recall it being down to heat treatment after grinding? In this case a few honings removed the issue.

 

[Silas Gull]

I have a 1938 Focke-Wulfe.

 

[Phil Pascoe]

One of those Fokkers that aren't Messerschmitts?

 

[dm65]

Oh, the good old days when Jim Davidson was funny

 

[Phil Pascoe]

No, it's older than that, even.

 

[Carl P]

Wasn't there a film...

 

[AndyT]

Nice bench, can you post photos of it if you have time?

Thanks! I will try and do a separate thread some time soon, but just at the moment my workshop has a lot of wood in it which is normally stored elsewhere and so although I can manage close-ups, I can't actually see across the room or take good pictures. The bench is strictly utilitarian but may help encourage others by its simplicity. Meanwhile there must be some views of it in earlier posts of mine!

- Update - see pictures in the Projects section - https://www.ukworkshop.co.uk/forums/my-old-cheap-easy-bench-t82290.html

 

[Trafalgar]

Fantastic... thanks....