Thread: My razor is too sharp???? I like a duller edge??

Interesting thread. Notice the injuction to use as thin a thread as possible

As the diameter gets larger it stops becoming a test of sharpness and starts to become significantly a test of cutting ability because enough of the edge will "see" the thread for geometry to be a factor

I think what he's saying is that for larger threads, the friction between the thread and bevel dominates the measurements.

Verhoeven makes a related statement on pg 11

Neither cut hair as easily, however, as a razor
blade. This later fact is probably due in large part to the much smaller edge angle of the
razor blades, 2β of 17o versus 40o.

In our case the whiskers aren't being put in tension by a fixture, and they supposedly have the tensile strength of copper, so it's reasonable to assume that they would show the same effect even more strongly than thread. That the commercial manufacturers coat their blades in teflon to improve cutting ability indicates that their testing also shows this to be a significant factor. What we don't know, however, is the degree to which a polished bevel performs the same function as teflon in reducing friction, and the degree to which this affects our perception of sharpness when we shave.

That was a pretty cool post alright...

I remember a similar contraption in hair salons back in the 80's, to show the condition of your hair by stretching it to breaking...
The more your hair stretched allegedly the better condition it was in..

I wonder if I could rig something like it using hair on one of my Digi Scales I have for reloading...

Not that it would be an exact test by any stretch of the imagination, but it might show some useful info, Maybe???

Originally Posted by gssixgun

That was a pretty cool post alright...

I remember a similar contraption in hair salons back in the 80's, to show the condition of your hair by stretching it to breaking...
The more your hair stretched allegedly the better condition it was in..

I wonder if I could rig something like it using hair on one of my Digi Scales I have for reloading...

Not that it would be an exact test by any stretch of the imagination, but it might show some useful info, Maybe???

Could well be useful. One thing I would say is to not stretch the hairs, because they're not stretched when we shave. Just hold them in the fixture with a bit of sag.

Originally Posted by mparker762

I think what he's saying is that for larger threads, the friction between the thread and bevel dominates the measurements.

I dunno, I think Cliff was usually one to dismiss the friction of the edge bevel and shoulder on thin objects. I know the durability is compromised easily on anything heavier. I noticed this myself with the first thread I purchased. I tried to use disposable Bics for a baseline, but the second cuts would be 100-120 grams. Looking at the edges under magnification, I saw the same damage as pictured. There is still a bit of argument over rope thickness and grind angle for cuts, some don't think it matters if the rope is not fixed from both ends, because the individual strands are cut and move away, so as not to side load the edge. The easy test would seem to be to cut some rope with a knife with one included angle, then resharpen to the same finish at a different angle, and see if the numbers change on force required to cut.

I really should get around to that.