Thread: How do not make it worst?

So, Professor Wullie (nice ring!) , Do this mean she will never shave again? Inquiring minds need to know!

Originally Posted by straightrazorheaven

An simpler formula to calculate your bevel angle is

a=2(tan({0.5x]/y})

a = bevel angle
x = spine width
y = blade width

tan() gives the ratio of two side lengths. That formula cannot output an angle. At the very least it should be arctan.

However, while the tan-based formula may be simpler to calculate in theory, it is not the simplest to calculate in practice. In practice you measure the hypotenuse - from the edge of the razor to where the hone would touch the spine.

Your assumption that y is the side adjacent to the half-bevel angle is fine, but basically impossible to measure since you would have to measure inside the spine itself. In reality the hypotenuse gets measured, hence arcsin is used for calculation.

I would also like to point out that in the original forumla given by Glen earlier in this thread, the assumption is that the resultant angle produced by the arcsin function is in radians, and is then converted to degrees via multiplication by 180/pi. If your calculator is in degrees mode, the formula should not include this conversion factor.

I'd also argue that you need to be very careful with definitions of variables: h is the hypotenuse - the distance from edge to honing flat on top of the spine - in that formula. If you take the actual height (back of spine to edge) for most razors you will be mis-measuring.

James.

Jimbo PLEASE! I thought I had put you scientists to bed! I digress!

Originally Posted by sharptonn

Jimbo PLEASE! I thought I had put you scientists to bed! I digress!

Scientist? I aint no stinkin' scientist!

Mathematics, rightly viewed, possesses not only truth, but supreme beauty - a beauty cold and austere, like that of sculpture, without appeal to any part of our weaker nature, without the gorgeous trapping of painting or music, yet sublimely pure, and capable of a stern perfection such as only the greatest art can show. The true spirit of delight, the exaltation, the sense of being more than man, which is the touchstone of the highest excellence, is to be found in mathematics as surely as in poetry.

Bertrand Russell.

James.

Jimbo, You and I graduated from the School of Hard Knocks! We should be tenured by now!

Correct, I missed the arc from the arctan, thank you Jimbo. While you are correct that measuring from the top of the spine isn't 100% precise, the mere fact that the range of angles is so large for a shaving edge, and not steadfast, the small inaccuracy in the measurement of the blade width makes the simpler calculation worthwhile.

Do you mind me asking how you measure the blade width from the top of the hone wear? I find doing this difficult. Thanks.

There is of course another problem with using any trigonometry to calculate the angle of the blade. we are assuming that the bevel is exactly half way between the spine width. What we are doing with both of these formulas is assuming that the bevel is central and multiplying the half of the bevel angle we calculate by 2.

Originally Posted by Jimbo

tan() gives the ratio of two side lengths. That formula cannot output an angle. At the very least it should be arctan.

However, while the tan-based formula may be simpler to calculate in theory, it is not the simplest to calculate in practice. In practice you measure the hypotenuse - from the edge of the razor to where the hone would touch the spine.

Your assumption that y is the side adjacent to the half-bevel angle is fine, but basically impossible to measure since you would have to measure inside the spine itself. In reality the hypotenuse gets measured, hence arcsin is used for calculation.

I would also like to point out that in the original forumla given by Glen earlier in this thread, the assumption is that the resultant angle produced by the arcsin function is in radians, and is then converted to degrees via multiplication by 180/pi. If your calculator is in degrees mode, the formula should not include this conversion factor.

I'd also argue that you need to be very careful with definitions of variables: h is the hypotenuse - the distance from edge to honing flat on top of the spine - in that formula. If you take the actual height (back of spine to edge) for most razors you will be mis-measuring.

James.

Originally Posted by sharptonn

So, Professor Wullie (nice ring!) , Do this mean she will never shave again? Inquiring minds need to know!

Personally, I think that razor will shave wonderfully.

Originally Posted by Wullie

Personally, I think that razor will shave wonderfully.

HERE HERE!!

Originally Posted by straightrazorheaven

HERE HERE!!

They don't call him "Professor" for nuthin! Wullie "professes" it all!
Awesome Dude, ol Wullie!

Originally Posted by sharptonn

They don't call him "Professor" for nuthin! Wullie "professes" it all!
Awesome Dude, ol Wullie!

I graduated Magna Cum Loudly from the School of Hard Knockage.

Padre Willie at your service.
Founder and owner of Padre Willie's Tooth Emporium, Tonsorial Parlor, and Shelter for Wayward Young Ladies of the Night.
Lettuce SPRAY!