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The Great Rigid Blade Experiment

Chan Eil Whiskers

Fumbling about.
Ok gents, this is the basic setup that I came up with.
View attachment 1263743
BTW, the only new items in this picture are the razor and the surface plate. I got both of them for Christmas last year. The guys at Standridge lapped it to .00005" for me at no extra cost because I picked it up myself. The adjustable height stand in the back was my Grandfather's, it has the patent date Mar 17, 1896 stamped on it.
View attachment 1263758

The Fiddlestick itself weighs 7.4 grams.
The scale looks like this.
1) 10 grams
2) 30 grams
3) 60 grams
4) 90 grams
5) 120 grams
6) 150 grams
7) 180 grams

A few close-ups to show the positioning of the indicator tip and the Sonic Fiddlestick probe. The test indicator reads out in .0001" increments.
View attachment 1263744View attachment 1263746View attachment 1263747View attachment 1263748


This is totally amazing.

I'm glad Mike @Esox posted, in another thread, the link to your post because I had been unable to find it.

There's been considerable progress since we - Mike and Joel and others - were "measuring" rigidity with the naked eye and a pencil.

Great work.

Happy shaves,

Jim
 
This is the cool vise I got to hold my razors and my USB camera setup.
View attachment 1263056
@Dovo1695 sent me to this thread and I am happy to finally see the setup you put together. I can see why he is using your photos for his measurements. It appears you could adapt it to use just about any imaging device. The only thing I would suggest is controlling ambient light by building a box the whole thing could sit in. You could make one side openable for setup and omit the top. Or use opaque fabric and make a curtain.:thumbup1:
 
I wonder ...
Since there are quite a few different
martensitic and ferritic grades of
stainless steel used in today’s DE/SE
razor blades production ...
And since each factory may apply
different heat treatments for hardening...
Or even different models from the same factory maybe differently heat treated ...
And since there are different blade
thicknesses ( thick 0.125 mm , medium : 0.1 mm ,thin : 0.075 mm ) ...

Maybe the apparatus can be used
to measure the rigidity of various different blades .
Quite useful to know which blades
have higher rigidity than the rest.

Side note : I bet that Nacets and GSBs will
definitely be amongst the most rigid ones!
The different hardening methods used for different blades does not change much with respect to the blade rigidity.
As the hardness increase due to different tempering methods the young's modulus does change, but not by much.

1623934822377.png

The thickness of the blade on the other hand does have an effect. And then you have the different head designs, but that is different subject.
As you see from the calculation below the thickness of the blade is raised to the power of three. So even if the elastic properties change a fraction, the blade rigidity does not change much. The edge retention is a more important factor here.
1623935174858.png
 
The different hardening methods used for different blades does not change much with respect to the blade rigidity.
As the hardness increase due to different tempering methods the young's modulus does change, but not by much.

View attachment 1282939
The thickness of the blade on the other hand does have an effect. And then you have the different head designs, but that is different subject.
As you see from the calculation below the thickness of the blade is raised to the power of three. So even if the elastic properties change a fraction, the blade rigidity does not change much. The edge retention is a more important factor here.
View attachment 1282944
Hmm any theory why the Kai is perceived as a particularly rigid blade despite not being an outlier in thickness? You don't hear folks going gaga over Astra or Derby blades which measure the same.

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The Kai blade is also wider, which should give a more flexible blade feel. Rember that the blade cantilever i one of the most important factors.
Exactly. Makes it all the more curious why so many report it "feels thicker" ie less flexible.

FWIW blades which have been measured to be equal or greater in thickness to the Kai:

0.00450� 0.114mm Gillette Nacet Stainless
0.00450� 0.114mm Shaverboy Super Stainless

0.00425� 0.108mm Gillette 7 O'Clock Super Stainless (0.089mm*)
0.00425� 0.108mm Lord Platinum

0.00410� 0.104mm Feather

0.00400� 0.102mm Astra Superior Stainless
0.00400� 0.102mm BIC Chrome Platinum
0.00400� 0.102mm Croma Diamant Stainless
0.00400� 0.102mm Derby Extra (pre 2016, current blade 0.089mm*)
0.00400� 0.102mm Gillette Sword
0.00400� 0.102mm Kai*
0.00400� 0.102mm Personna Med Prep
0.00400� 0.102mm Personna Platinum Chrome (Personna Red)
0.00400� 0.102mm Polsilver SI
0.00400� 0.102mm Rapira Platinum Lux
0.00400� 0.102mm Sharp Star
0.00400� 0.102mm Super Max Blue Diamond
0.00400� 0.102mm Super Max Platinum
0.00400� 0.102mm Voskhod




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Maybe i need to try the blade, but the numbers does not support it.
How anyone can feel the difference is strange to me. There might be more blade feel because it is wider.
 
Maybe i need to try the blade, but the numbers does not support it.
How anyone can feel the difference is strange to me. There might be more blade feel because it is wider.
The judgements are not based on how it shaves but how it yields to pressure in hand or in the razor. I'm not one who has so experimented. Do a search for "are Kai blades thicker" and you'll find a large group who once believed in the affirmative.

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Is it possibly because it is claimed to be uncoated therefore having a thicker actual blade, but similar total thickness? I think someone quoted 0.01 for the coating which would yield a 10% thicker blade portion. I agree they feel stiffer, more like a machined piece of marine stainless than a spring. Hmmm
 
The different hardening methods used for different blades does not change much with respect to the blade rigidity.
As the hardness increase due to different tempering methods the young's modulus does change, but not by much.

View attachment 1282939
The thickness of the blade on the other hand does have an effect. And then you have the different head designs, but that is different subject.
As you see from the calculation below the thickness of the blade is raised to the power of three. So even if the elastic properties change a fraction, the blade rigidity does not change much. The edge retention is a more important factor here.
View attachment 1282944

I love this. This could be a great proxy for rigidity. It's certainly cheaper than buying dial indicators, durometers, and test stands. In it's current incarnation, it's set up for comparing different blades of different thicknesses. Seems like it would be more useful for comparing razors.

Could you make this "wiki ready" so that there is less extraneous info. For example, use Astra blade to replace variables as constants, and enlarge the razor diagram with only relevant variables labeled? Basically, the only variables should be L and X.

Speaking of which, where does x come from again?
 
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