What's new

Do-It-Yourself - AGGRESSION measured to +/- 0.001 inch

good idea!

but...
woulnd it be easier to include a fine scale rule in the gap picture? less chance of lens distortion/cropfactors/calculation error.

Also: i think the about the blade "sticks out" also is an isue. (maybe because a different top piece for example). and than you have the angle of atack of the blade depending on the curvature ofsaid blade.

it's a start, but not all the data is factored in.
 
... Thanks ...

You're welcome.

... optical distortions ....

In order for the measurement to be accurate, you need to know that the lens does not distort the ultimate image. Unfortunately, even with the best macro lenses, you will get distortion and the measurements will be off. The more the magnification, the greater the problem will be magnified.

The (partial) solution is simple though. You need to correct the distortion. I suspect that the easiest way to do that is to measure the image of the ruler on the screen. If the measurements of the ruler are accurate, then the rest of the image in the same plane of critical focus as the ruler will also be accurate. Note that the correction will only work for items in the same plane of critical focus as the ruler. Accordingly, I suggest that you use as small an aperture as available, but even then, the ruler and the razor must be as close to one another as possible. For this, an accurate tripod and accurate measurements lens to subject will be crucial.


Your point is absolutely correct.

The solution you offer to "correct" for the error introduced is a very good one and I was delighted to see it.
Thanks for that.

The task (as I see it), however, is not dependent on particularly accurate measurements. What is required is a - number - of measurements.

If you have a reasonable number of data points (as long as they are - "in the ball park") you are able to calculate an "average" value that will be comparable to similar values established for other razors.

The very fact that different people with different approaches and hardware etc generate "s i m i l a r" numeric results that "cluster" around the true value enables us to get a value that is accurate enough for the purposes of comparison.

There is no single value even for a single razor. The variation over the span of the blade will be equal to +/- a setting on an adjustable razor - that is to say .025 in the middle and .021 at the ends etc.

but that is no reason to despair

If I have 10 values for razor model A manufactured over a period of 10 years to factory specifications that are outside the .001" limit I can "correct" for the variations by the volume of data collected.

If razor "A" gives "measured" values ranging from .018 - .023 with an average of .020 I know it's a "notch" milder than razor "B" that has values 10 ranging from .020 - .028 with an average gap of .024.

If the average gap were for "A" .022 and for "B" .023 they would be considered functional equivalents.

If all the measurements were done to the accuracy of 1/4 the wavelength of light the ranking would remain the same.


The fact that making measurements consistently to .001" is quite difficult is not a problem if you only need to determine the relative gap sizes.

Aggression:

less aggressive < - 0.002
same = +/- .001
more aggressive > +.002

In a different case ...

If you have dropped your razor and you need to determine the difference in aggression between the two sides and how it varies from end to end - for that "particular" razor - the data point method and averaging would be ineffective.

Then it would be electron microscope time. :biggrin:

Or you could just test both sides and stay away from the one that leaves raspberry jam tracks on your face. :tongue:

I measured a "problem" razor that was .034 in the middle and .000 at the ends and the blade was bow shaped like the letter "D". It was "unsafe at any speed" as you would press too hard for the middle and too light for the ends. All points of the blade were within the acceptable range.
In an undamaged razor of reasonable quality the blade is fairly straight and those razors with average gaps .002 - .004 greater than others feel/act a "little bit" more aggressive (all other factors being equal :lol: - of course).
 
Gillette Red tip - measured 25.5 thousandths of an inch

Slim Adj set to 7 - measured 36.1 thousandths of an inch

Aristocrat - measured 25.5 thousandths of an inch - exactly the same result as the red tip - which does not surprise me.
 
Gillette Red tip - measured 25.5 thousandths of an inch

Slim Adj set to 7 - measured 36.1 thousandths of an inch

Aristocrat - measured 25.5 thousandths of an inch - exactly the same result as the red tip - which does not surprise me.

! in under 20 hours from the start of the thread ! the first "NEW" data ! :biggrin:

Well done sir. :a50:

Thank you.

Your numbers have been added.
& the newest results are now at the start of the thread.
 
some metric conversions: top end en bottem end of scale only + red tip / slim 7

0,015 = 0,381 mm
0,040 = 1,016 mm

0,0255 inch = 0,6477 mm
0,0361 inch = 0,91694 mm

so that the metric folks have an idea.
 
some metric conversions: top end en bottem end of scale only + red tip / slim 7

0,015 = 0,381 mm
0,040 = 1,016 mm

0,0255 inch = 0,6477 mm
0,0361 inch = 0,91694 mm

so that the metric folks have an idea.

Thanks

mm units added to start of the thread
 
Top Bottom