Thread: How do not make it worst?

Originally Posted by straightrazorheaven

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.

I'm not sure how it is simpler - using arctan instead of arcsin is just changing a button on the calculator. Again, the formula Glen gave looks more complicated than it needs to be because it was a computational formula (I think) for use in something like Matlab, whose arcsin function returns angle in radians, not degrees. On a calculator you don't need the 180/pi conversion factor.

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

Sure. You lay the razor flat on a table (as if honing), put one point of your callipers at the edge, and the other on the part of the spine that would touch the hone - this point usually has a bit of hone wear to guide you. That is measuring the hypotenuse.

Edit: Here's a useful pictorial representation:

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.

Yes, that is true. There are all sorts of other problems too, like measuring only at one point and assuming the hypotenuse/spine width ratio is constant for the entire blade. Then there are the smiling blades that have varying spine widths etc etc.

There are a few interesting threads around about this. In particular, a post by an old member Mparker who mistakenly used arctan to calculate the angles, and subsequently fixed it up. The differences are not huge, but large enough.

James.

Originally Posted by sharptonn

Put a layer of tape on the spine and run it up and down a DMT 325 for 50 laps. Put another layer over that worn layer and go on the DMT until the runway diappears into oblivion.

50 laps on a DMT 325? I'll bet you your razor collection those chips will take 200 laps...maybe 300...maybe more. I'd be going at that edge with a belt sander, personally...

This is turning into a episode of Breaking Bad. I wish I could understand you Walt. Lesson learned - don't buy a razor with chips unless you plan to shave your face really carefully or plan to spend the rest of you life either learning to be an architect or astronaut/engineer/race car driver. All of these laps are making me dizzy

Originally Posted by sheffieldlover

50 laps on a DMT 325? I'll bet you your razor collection those chips will take 200 laps...maybe 300...maybe more. I'd be going at that edge with a belt sander, personally...

Methinks you ain't read it all!

[QUOTE=Jimbo;1055626]I'm not sure how it is simpler - using arctan instead of arcsin is just changing a button on the calculator. Again, the formula Glen gave looks more complicated than it needs to be because it was a computational formula (I think) for use in something like Matlab, whose arcsin function returns angle in radians, not degrees. On a calculator you don't need the 180/pi conversion factor.[QUOTE]


It was designed to plug straight into Google

In the link I provided is one with the values

(2 * asin(.181 / (2 * .620)) * 180) / pi =


Just copy and paste that into Google search and see what happens

Hello all good people,

Here is the end results of my work. Thank you for your help. Let me share few of my observations. I know you all did more razors (restoration) than I have hairs on my head however I have few thoughts I would like to share.

1. I used all this formulas you have provided, calculations and got little bit lost. Sorry it wasn`t for me or maybe I did wrong calculations. One formula said-can be done, other said... you miss the point where it can be done. I was little but confused so I decided to start with DMT.
2. It took a lot more than 400 breadkinifing moves to get this chips out. This thing is hard, hard, hard! However in some point steel become softer. This was actually almost point where I start setting a bevel.
3. Bevel setting was just tricky one. Without tape I basically couldn`t do it. I think one of comments said that this blade should be regrind and I think it is correct statement.
4. I had to improvise as 2-3 tape of black tape didn`t do the trick. Bevel was not there yet. I went looking for something else would help me. I founded some other electrical tape. It was a red tape, very thick. It was electrical tape but different size (thickens and width). I used two layers of this tape and this work out like a charm. Tape was thicker and stronger allowing me to do more passes on DMT and 1k stone.
5. I "almost" set bevel on DMT however I was worry that because I removed so much steel razor edge hardness will be different and bevel will be more delicate. I decide to finish it up on 1k Norton. This was good approach. Work out very well.
6. After 1K blade was already extremely sharp. According Glen theory and study I could shave it with it right away :-) But to be serious it was as sharp as finished shave ready razor.
6. Went thru 1k Norton, 4K natural stone, Belgium stone (I know this might surprise many of you that in this stage I did touch up on Belgium stone but I do have my reasons and theory), 6k King stone. 8k natural stone, Li and C12K.

Here are few pictures. Please notice that razor has "double bevel" but this s result of bradkinifing as this thing was hard, hard, hard:-)
Thank you everyone for help. I learn A LOT< LOT< LOT from you. Thank you for your help and willingness to educate me.

P.S. I have not shaved with it yet. I had no chance to shave with it yet as it was already late night when I was finishing up honing. Will tell you more about shaving experience pretty soon.

Plugged it into Google, all I have to say is ... very nice either somebody did a lot of work or Google is absolutely great!

[QUOTE=gssixgun;1055810][QUOTE=Jimbo;1055626]I'm not sure how it is simpler - using arctan instead of arcsin is just changing a button on the calculator. Again, the formula Glen gave looks more complicated than it needs to be because it was a computational formula (I think) for use in something like Matlab, whose arcsin function returns angle in radians, not degrees. On a calculator you don't need the 180/pi conversion factor.

It was designed to plug straight into Google

In the link I provided is one with the values

(2 * asin(.181 / (2 * .620)) * 180) / pi =


Just copy and paste that into Google search and see what happens

Yes. google's calculator by default uses radians and not degrees, although you can change that behaviour: the following gives the same result:

2 * asin(.181 / (2 * .620)) / degrees

I imagine this one would be better for most people who do not work with angles in radians.

James.

Math be damned, that must have taken forever! my fingers would be number than my brain is from all those equations. Nice work! Now for the shave test!

Originally Posted by Magpie

Math be damned, that must have taken forever! my fingers would be number than my brain is from all those equations. Nice work! Now for the shave test!

Anyone else remember the old SNL skit with Chevy Chase playing G.Ford? "It was my understanding there would be no math..." has been going through my head lately.

To the OP: that looks MUCH better! I have my fingers crossed for you that it works as well as it looks. Good luck.