My blade's better 'n your blade!

1afc · Post by **1afc** » Tue Nov 13, 2012 12:07 am

The human eye is actually quite a delicate instrument and when I was changing some blades recently I noticed some funny reflections (besides me in the mirror!).

One blade was the Astra Platinum and the other a Feather. I use both blades and my preference is for the Astra Platinum as it provides me with a much smoother feel when cutting. The Feather is very sharp and when used in a Tech it also provides a great shave. It is a bit too aggressive for me in an EJ DB89.

YFMV - Your Face May Vary (seeing as we're mostly talking about shaving faces)

What I noticed was that the reflection of the cutting edges of the two blades were different.

The Feather has a standard V type edge so the light reflection was basically nothing or full on.

However, the Astra has a convex edge so, as I tilted the blade, I could follow the line of light down the edge to the tip. This was confirmed with a 10x loupe.

I'm presuming we can link for reference on edges.
from http://zknives.com/knives/articles/knifeedgetypes.shtml

Flat (V)
- The simplest and most widespread in factory knives. The edge tapers from both sides of the blade. Gets sharp, sacrifices durability though. Induces extra drag, because of the sharp transition point.

Convex
- My favorite. Provides the most durable edge at a given angle and has less drag compared to other edge grind types due to smooth transition lines. Instead of tapering in a straight line, the edge is slightly curved outwards. Famous Japanese Samurai katanas featured this type of the edge.

I guess there is no reason why a razor blade should not "benefit" from the same geometry.

I had some other blades and it appeared that a Gilette Yellow had a similar convex grind but Personal and Gillette Super Thins appeared to have a flat grind.

So what are other blades like and has anyone got any other comments.

brothers · Post by **brothers** » Tue Nov 13, 2012 11:17 am

Alan, you've highlighted something I've not personally considered. I'm going to take a close look at the eges on the Personna hospital use; the "old" Super Iridium; the new Polsilver Super Iridium, and then maybe also a Gillette Swede. I want to see which grinds they have.

ShadowsDad · Post by **ShadowsDad** » Tue Nov 13, 2012 3:17 pm

Interesting.

bernards66 · Post by **bernards66** » Wed Nov 14, 2012 10:22 pm

Brian, Well, it is interesting....but it's not that easy to really tell. When Squire was doing his DE blade evaluations here he included highly magnified pictures of the edges, but even with that it was not that easy to visually discern the grinds used. FWIW, I am convinced that there is something unusual about the manner in which the Feather blades are ground. Everyone agrees that they are uber sharp, but a number of us ( like the original poster ) have found them to be irritating, including myself. In addition, even many who don't have that particular issue do admit that they don't hold up well compared with other higher end blades ( past or present ). So, I think that there is something 'different' about how they are made...most likely the grind angle/geometry.
Regards,
Gordon

ShadowsDad · Post by **ShadowsDad** » Wed Nov 14, 2012 11:17 pm

And I'm among those folks. They failed in my testing because they didn't hold up for even 3 shaves.

brothers · Post by **brothers** » Thu Nov 15, 2012 6:07 am

Effective (financially successful) disposable product. Sharp, not the cheapest, not the most expensive, and engineered to fail promptly so the satisfied repeat customer will replenish the product more often.

1afc · Post by **1afc** » Thu Nov 15, 2012 9:32 am

I agree that Squire did a great job with the photos but its hard to see the curvature if the light is not right.

Btw I'm still not saying I'm correct in my conclusions so if there is any corroborating evidence it would be good.

The other thing is that I think a convex grind is actually difficult to produce. Straight grinds and hollow grinds are a function of the grinding surface but the convex grind usually involves movement in more than one axis at the same time.

Anyway if anyone can identify the same thing at lease we know we're discussing something real.

Racso_MS · Post by **Racso_MS** » Thu Nov 15, 2012 7:04 pm

If it gives me a close shave...
And it lasts for a reasonably long time (3-5 shaves)...
Convex, concave, straight grind, hollow grind...
MACHT NICHTS...
I'll buy it and use it...

Have a great day an enjoy your shave...

Remember...Blades are a YMMV item. We all have different beards...

Merkurs Rule...

1afc · Post by **1afc** » Thu Nov 15, 2012 11:05 pm

Aw heck Rasco stop taking the fun out of this.

I agree with you that if it gives a close and smooth shave a person would use it but what many members seem to be interested in is why the performance is so.

For instance if others inspected blades that I don't have and they identified a convex grind then I'd really like to know so I could have a reasonable expectation that they might also work well for me.

Similarly, it has been suggested that Feathers are sharp but don't last long. I think I saw in Squire's blade reviews that they had a double bevel. It may be (not saying it is) that the two bevels make a type of hollow grind and the edge therefore suffers from lack of support.

Anyway that was the objective so lets see if any others kick in with some info.

Pauldog · Post by **Pauldog** » Fri Nov 16, 2012 3:11 am

Squire · Post by **Squire** » Mon Nov 19, 2012 8:03 pm

Alan the Feathers have a unique three step flat grind that creates a sharper edge than other blades. So sharp in fact it's not durable, so there's the tradeoff. You can have the sharpest edge that doesn't last or a lasting blade that isn't the sharpest.

Shave4Fun · Post by **Shave4Fun** » Mon Nov 19, 2012 8:23 pm

Squire wrote:Alan the Feathers have a unique three step flat grind that creates a sharper edge than other blades. So sharp in fact it's not durable, so there's the tradeoff. You can have the sharpest edge that doesn't last or a lasting blade that isn't the sharpest.

Agreed!

1afc · Post by **1afc** » Wed Nov 21, 2012 7:42 am

Thanks for the info Squire and Roger.

Squire did you notice anything like a convex or hollow grind edge when you were doing your reviews?

Squire · Post by **Squire** » Sat Nov 24, 2012 4:18 pm

None Alan, they were all flat ground. I expect cost is the main factor.