Thread: Why are some straights heavily Magnatized?

I can recall seeing a razor in a local antique store with 'The amazing magnetic razor' written on it. I initially thought it meant there was a magnet in the scales to help keep it shut.

Originally Posted by Kingfish

Metal atom get together a little different on an atomic level. They form collectively a metalic bond where they share electrons. Remember electrons are the part of the atom where things happen chemically speaking. With so many woodworkers past and present claiming magnetized blades keep an edge better, should the idea itself be so easily dismissed?
Mike

As Khaos points out though, the edges of other tools are much thicker than that of a razor. Would the benefits be noticeable? Have to confess, I see no difference with mine. Shaves very well though, so no complaints. Also, what does Leonard Lee say on page 27 of his book on sharpening? Haven't got it unfortunately.

Just to further illustrate my point... Gravity is an attractive force, dependent on mass. More mass=stronger gravity. However... at the atomic level, gravity is negligible, because mass is negligible, instead EMF forces take over.

Magnetism depends on a variety of things, but in general, the amount of atoms lined up with each other controls the strength of the field. Ie, if all of them are perfectly aligned, you have a very nice dipole system, like a bar magnet. If every atom is arranged in a totally unique and chaotic direction, their fields will cancel. I believe this is why some steels are magnetic and others not, even though they are all largely iron, which is supposedly magnetic.

The other part of my point, is lets say you have a very "sturdy" edge- a broadsword or plane chisel. The edge on the that will be wider than say, a double hollow ground razor. Lets say that we even give them the same magnetic strength, so the "aligning" magnetic force on both edges is magnetic force B. Now, lets say you tried to shave with both blade. Your arm exerts a constant force F. Lets assume there is a perfect transfer of power through the lever system of your arm through the spine of both to the edge. Here's where the difference is. The principle that make a razor shave better than the sword (or knife or chisel) is also its downfall. The shearing force (v) placed on the hairs is proportional to the stress on the edge of the blade (sigma), which is relative to pressure, or force over cross-sectional area (F/A). We all know a thinner, finer edge cuts better, this is why- the thinner edge as a reduced cross sectional area, so with constant force, the lower your A the higher your P or sigma, which means the shearing force (cutting force) placed on the hair is higher.

HOWEVER. Higher P means higher compressive stress and therefore deformation on the blade edge. Deformation = (Force * Length)/(Area * Young's Modulus) or delta = FL/AE where F is the force from your arm, L is the blade width (from spine to edge) A is the cross section of the cutting edge and E is Young's modulus, ie, how elastic the steel is.
Thus a smaller A, while allowing you to cut better, subjects the blade to a higher deformation. If the stress placed on it exceeds the "yield" stress of that steel, you get plastic (permanent) deformation ie dulling of the edge.

So thats the physical forces grossly over simplified to show a point. Magnetic force B however, depends not on the edge, but on the field generated by the steel. This is a ***** to calculate and would make the earlier paragraph looks simple. So lets assume both blades generate the same magnetic field, and thus, at the blade edge, the magnetic force is constant.

SO IN CONCLUSION... Made from the same steel (therefore same Young's modulus, same yield stress, same magnetic properties) and generating the same magnetic field, because the razor has a thinner edge, the relative mechanical force on a razor's edge than on a thicker blades edge, while the magnetic force is relatively constant.

DISCLAIMERS: I know there are people who are gonna dispute this, so I'm gonna say this is a gross over simplification to show the priciple. In theory one would have to also account for blade geometry (the fact that it is a wedge) and therefore we would need to find an average value for sigma normal through integrating it and dividing by the area integral and that the blade edges are also subject to shear themselves (we only looked at buckling or normal compressive stress, in theory we can approximate sheer stress by (rad(2)/2)*sigma, but that is assumign that the sheer and normal stresses are perfectly normal to each other), etc etc etc, and that the magnetic field varies along the edge of the blade unless the blade were infinitely long, etc etc etc. Just as we assume that gravitational force is constant around the globe, doesn't mean it is (you weigh less on Mount Everest than in Holland for example). In every day life we can generalize a little because getting really really specific only changes the answer a little. I'm certain magnetism has an effect, but it is negligible in OUR case. (just as distance from the core of the earth influences satellites and the moon, but for us humans in every day life, we don't bother to recalibrate scales based on where we live)

Ya! And if you take enough Geratol your blood - with it's high iron content - will stay on the razor and not drip into the sink. <LOL>

Originally Posted by John Crowley

Ya! And if you take enough Geratol your blood - with it's high iron content - will stay on the razor and not drip into the sink. <LOL>

Isn't he arguing (something like) the opposite? Or have I just had too many beers?

Originally Posted by AlanII

As Khaos points out though, the edges of other tools are much thicker than that of a razor. Would the benefits be noticeable? Have to confess, I see no difference with mine. Shaves very well though, so no complaints. Also, what does Leonard Lee say on page 27 of his book on sharpening? Haven't got it unfortunately.

Hi Allen,
Lee basicaly elaborates on how magnetic induction work hardens steel to make it 30-200% more durable in edge durability. In the same article he points out how some woodworkers do simple methods of magnetizing plane blades to improve durability.
My main point was to point out where the best ores were located and still are. Historically, when carbon steel was the best alloy for tools and razors, methods of working raw material to finished product depended on the magnetite ore. Better razors throughout history started from magnetite ore. Sheffield Cutlers used this material, so did others and yes it may have had some ability to hold on and stay magnetized better than inferior steel derived from other inferior ores. Remember magnetite also called "Lodestone" because when hung on a string pointed at the Lode Star or North Star as we call it today. They melted earth magnets to make the best razors of history. Some gimics have some interesting facts that brought them to life. Thats all.
Mike

Well one thing is for certain this thread has sure brought out some interesting ideas. I'm just about convinced that there is a certain amount of marketing ploy and some who probably though it actually would be a benefit to the razor owner.
The Lauderjung picture I posted that was holding the other razor up easily is also one of my best shavers and holds and edge very well. I'll go so far as to say I've had to hone it less than any other razor I own. Is the quality of the steel used or does t have something to do with magnetizing the blade or a little of both. I'll probably never know for sure.
If you look at the picture it's holding the other razor by a very very small area. Not only that it will stay there even if you swing it around a bit.
Pretty amazing either way.

Originally Posted by Gunner777

If you look at the picture it's holding the other razor by a very very small area. Not only that it will stay there even if you swing it around a bit.
Pretty amazing either way.

Mine does the same thing. It was not magnetised by chance, IMO. Great thread by the way.

I'm glad your enjoying it Alan I sure am:-) I'm sure mine was done on purpose because it says it was. A couple of others are marked as such also but never as powerful as this one.

Didn't get the original box and nothing's marked on the razor. So I can't say for sure, but it's so strong (the magnetism) that I think it must have come out of the factory like that. Have to admit though, I still think it was a gimmick.