Moderatore: Moderatore Area Tecnica
- Messaggi: 1
- Iscritto il: 08/11/2012, 21:26
I recently purchased a straight razor on ebay from the ukranian razor maker LEZCHA. Unfortunately, after paying a premium price for that blade, I found it completely dull and with an “usual” geometry. So, I asked a team of local experts of this forum (Franzkleber&Aldebaran) for an independent opinion. I found their analyses of very high quality and of possible general interest. Therefore, I am submitting them to you and ask whether they might be of some use for the largest community of the straight razor enthusiasts.
On a personal note, the lack of a returning policy for such razors should be (very) carefully considered by a potential buyer…
Enjoy the reading (while, unfortunately, I won’t enjoy the razor)!
“This is a step-by-step analysis of a straight razor which was sent us by a customer for an independent evaluation. The customer was unsatisfied of the shaving quality of this razor and asked us to undertake a number of tests to evaluate its metallurgic properties.
VISUAL INSPECTION: the blade of the razor is about ¼ hollow with a nice mirror polish finish. Pin backs are well riveted; the blade is symmetrical, well centered and opens with the correct effort.
Acrylic scales are of good quality, with a nice polish finish. The red acrylic wedge is well proportioned. The razor has an overall good balance.
At this level of analysis, my only concern is the shape of the blade which is a rather extreme, but aesthetically pleasant, smile.
Therefore, a number of measurements were taken with a centesimal caliper and the detected values are displayed in the picture below. As you may notice, the theoretical sharpening angle is about 10°, which is an extremely narrow angle. To ensure a good balance between high sharpness and durability, the bevel angle of a straight razor should be between 16° to 18°.
In the recent past, we analyzed a custom razor with a bevel angle of 13° but the durability and quality of the edge was poor, although the hardening of the blade was optimal (see below). Therefore, we expect that an even narrower bevel angle could negatively impact on the sharpening of the razor and produce microchipping and microbending/nicking of its cutting edge.
MICROSCOPIC INSPECTION. We examined the cutting edge of the razor and took pictures of it at about 100x. Results are visible in the following sequence of images, which are taken from the heel of the blade to the tip.
As it is clearly visible, the edge suffers microchipping and microbending/nicking with a progressive increase of these defects from the heel to the tip.
Two hypotheses can be formulated to explain this phenomenon:
HYPOTHESIS # 1 The hardness of the cutting edge is extremely high with an increased austenite grain size. This condition will result in a fragility of the cutting edge with consequent microchipping.
HYPOTHESIS # 2 The hardness of the cutting edge is too low. This condition will result in a highly deformable edge, which can explain the microchipping and the tiny nicks observed in this blade.
HARDNESS TESTING. To test these hypotheses, we undertook extensive Rockwell hardness testing (HRC method). In the following picture, the scheme used for blade sampling is showed together with the relative HRC values.
As you can notice, the tang has a correct hardness (57HRC), while this parameter decreases toward the tip where it reaches an extremely low value of 37HRC (which is usuitable for sharpening of most cutting instruments). This value indicates a possible major defect in the hardening/tempering procedure for this type of steel. By the way, according to manufacturer’s information, the blade is made of Steel 65G from Metal Ravne (http://www.metalravne.com/selector/steels/65G.html) which is a sort of an AISI 1070 plain carbon steel whose tempering/hardening procedures are very well-known and highly reproducible, even at a hobbyist’s level.
CONCLUDING REMARKS. The razor has an overall good manufacturing quality but it is plagued by designing and construction flaws that are making it unsuitable for normal shaving. In particular, the cutting edge is damaged by extensive microchipping and nicking; this condition most certainly results from insufficient hardening of the steel (37HRC on the blade) and by a too narrow bevel angle (around 10°). To our experience, it is not possible to fix these defects, since “framebacking” of the blade to increase the thickness of its spine would certainly correct the geometry, but it would be of no use due to relative softness of the blade. It is difficult to conceive a re-hardening of this razor, since it looks too thin to withstand a heat treatment without cracking or warping.”
FINALLY, SOME IMAGES OF THE SETUP USED FOR THE MEASUREMENTS
THE SETUP FOR THE MICROSCOPIC
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They forgotten that this thread was started and writed from seller.................