Elastic modulus, or Young's modulus or modulus of elasticity, is a material property. It varies little for steels. Stiffness that you feel when you bend a blade is a combination of a material's elasticity and the geometry (thickness and shape). Changing the material and/or the geometry changes the stiffness, which affects the forces or bending moments (force over distance) required to bend the blade, change the curvature, and cause deflections. Applying this to your neat question about the Probak blade, the elastic modulus would be the same for the same material, but the different shape would affect the stiffness, so the same forces applied to the edges would cause different deflections. Making the blade thinner in some spots would make the blade less stiff and easier to bend there, but making the blade thicker in other spots would make the blade stiffer and harder to bend at those spots.
Thin Blades?
- Thread starter mjclark
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Elastic modulus, or Young's modulus or modulus of elasticity, is a material property. It varies little for steels. Stiffness that you feel when you bend a blade is a combination of a material's elasticity and the geometry (thickness and shape). Changing the material and/or the geometry changes the stiffness, which affects the forces or bending moments (force over distance) required to bend the blade, change the curvature, and cause deflections. Applying this to your neat question about the Probak blade, the elastic modulus would be the same for the same material, but the different shape would affect the stiffness, so the same forces applied to the edges would cause different deflections. Making the blade thinner in some spots would make the blade less stiff and easier to bend there, but making the blade thicker in other spots would make the blade stiffer and harder to bend at those spots.
I don't have any vintage blades, but I'd like to measure some in the future. Some measurements have been done before (see this thread).
I think I know where this started. At a big website, Kai apparently sells their blades stating, "Made of a thicker gauge steel than other brands . . ." Now, it is true that Kai blades are thicker than other brands, but not thicker than ALL other brands according to my measurement. There are other blades that are just as thick, but the manufacturers of those blades do not make the statement that Kai apparently does.
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- #45
Aha! I'm going to test for myself whether there is less chatter in the 2011 R41 with the Kais.
So what other blades have the same slight extra thickness that the Kais have?
These could be blades of choice too fir the R41.
The cheapest I could get the Kais is £3.50 for 5(!!) so it will be good to have alternatives [emoji3]
You can see preliminary blade thickness results on the previous page here for the blades that I've measured so far. That might help you find another blade. Regarding the Kai blade, it would theoretically result in less chatter compared to thinner blades with respect to blade thickness, but chatter could be higher or increased because of the larger blade width with the Kai. So far, Kai is the widest blade that I've measured. The wider the blade, the more blade deflection. However, the thicker the blade, the less blade deflection. Which one would win out regarding chatter is unknown to me.
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- #47
You can see preliminary blade thickness results on the previous page here for the blades that I've measured so far. That might help you find another blade. Regarding the Kai blade, it would theoretically result in less chatter compared to thinner blades with respect to blade thickness, but chatter could be higher or increased because of the larger blade width with the Kai. So far, Kai is the widest blade that I've measured. The wider the blade, the more blade deflection. However, the thicker the blade, the less blade deflection. Which one would win out regarding chatter is unknown to me.
Brilliant! Yes it looks like the Bic Personna Feather and Voskhods could all be good bets.
This is fascinating - I never guessed that the blades were different widths either.
Do you have a table of blade widths too?
Blade width varies a lot, and this is very significant. I have preliminary results, but I'm not willing to share those. I need enough samples to form confident averages, and even then, I only want to publish those results for a blade after I get the user ratings. Sorry.
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- #49
Ok - I await further results with great interest.
This goes a long way to explaining why different blades give different results in different razors.
Your research is very exciting exploring the geometry of the blades themselves.
Exactly! Yes! Blade dimensions relate to blade performance, but no one has worked out the exact relations, so we're just shooting in the dark and saying "YMMV". Enough is enough.
I'm glad that you understand and look forward to seeing results. I look forward to getting them out there, too. Measurements take time. It's a slow process, but getting user ratings takes time, too, so I'm trying to do them at the same time. Blade geometry data is valuable, and when we put it all together with user ratings and other info, we have an even more powerful tool.
Forgive me for introducing apples into a thread about oranges, but when I first got my hands on a Mongoose and used the SE Feather Pro blade in it I did think that the added rigidity of the thicker, as well as narrower, SE blade contributed to the excellence of the shave. OTOH, the thinner DE blades are also beyond excellent so name your poison.
@ShavingByTheNumbers thanks for your comparison chart and input on this thread in general. Great to see someone mathematically minded apply their skills to this topic.
On the subject of Gillette blades, here are a few examples I picked up along the way ;
When I began shaving, with Gillette's DEs, in the early 1960s I used the Blue Blades and IME they were brutal. Maybe it was my technique, or the lack, but I remember being so happy when the Super Stainless, or maybe it was Platinum Plus, came out. A much better shaving experience. The older Gillette No Hone No Stopping is shown above on both sides. BTW the ten cents price difference in the thin blades and the blue blades is in a 5 pack of each. Believe it or not, ten cents was a fair amount of $ back in those days when fifty cents per hour was not an uncommon wage.
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I love your apples. 
Gillette made razors that reduce/eliminate chatter. For example: NEW SC, Postwar Tech, and all TTO's.
If thin blades came out around the same time as the SC and TTO's, then they may have realized that the thick blades wasn't necessary anymore.
If thin blades came out around the same time as the SC and TTO's, then they may have realized that the thick blades wasn't necessary anymore.
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- #56
Yes indeed - and conversely when we use modern blades in Single Rings and other DEs from the era of thick blades some people like to shim them to emulate the extra thickness and give the comfortable shave that Gillette intended.
Without it and with a thin blade,the geometry of those early razors means there's blade chatter and a tendency to bite but also a bit of a boost in efficiency.
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