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View Full Version : Section 6-6, Sharpness Tests Vs. Edge Uniformity Tests - Bevel Creation Guide



heavydutysg135
12-08-2007, 09:47 AM
Introduction

I decided to make this thread to teach people how I assess the edge quality at the most important step in the honing process, the bevel creation stage. If you learn to use these tests well and together, then I am confident that the quality of your edges will improve, and it will take you a lot less time and experimentation/guessing to get a great shaving razor. As far as I am concerned there are only two main types of tests: edge thickness (sharpness) test and edge uniformity tests. Both are equally important and have their own strengths; however, both have their weaknesses as well. Therefore, they must be used together to produce the highest quality and most consistent edges in the least amount of time.


Edge Thickness (Sharpness) Tests

These are the tests that you probably hear a lot about: the thumbnail test (TNT), thumbpad test (TPT), and of course the famous hanging hair test (HHT) and its many variations (arm hair, badger hair, etc.). I am not going to go into detail on how to perform these tests because there are already many great threads from experienced members explaining how to perform these (at least over at the SRP), just use the search function and you will get as much information as you could ever want. I will give you a summary of how to perform each of the tests and then explain their strengths and limitations individually and as a whole (which are addressed with the edge uniformity tests).

The thumbnail test is performed by dragging the edge of the razor (from heal to toe) along your wet thumbnail. The feeling that you want is for the razor to have a smooth and even bite indicating that the bevel is sharp enough to cut into your nail. If the edge glides across your thumb nail easily without resistance then it means that the edge is too dull to bite into the nail and will need more work to get sharp. If you feel the edge bite in but it feels “rough” in certain areas then this indicates that there is roughness such as microchiping or overhoning in that portion of the edge that will need to be worked out before moving on to the polishing grits. Do not perform this test past the 4K stage because the edge will be damaged.

I perform the TPT by lightly pressing and dragging my wet thumb along (not across) a small portion of the edge. The feeling that I am looking for is a smooth sticky feeling caused by the edge slicing into my skin. I then lift my thumb off that portion of the edge and check the next portion in the same way going all the way from the heal to the toe. You will likely find that some areas are sharp and some others are not, indicating that blade will require more work to get uniform sharpness from heal to toe.

There are several different variations of the HHT. The standard test is to hold a hanging hair between your thumb and index finger and then bring it to your razors edge. The hair should be easily and cleanly cut in two pieces (not peeled down the center). The HHT should be performed along the entire blade from heal to toe in order to make sure that the entire edge is sharp. Another variation of the test (which I do not like as much) is to bring the edge across your arm hair and assess how easily it pops the hairs. In my opinion the major shortcoming of this test is the fact that it will not tell you which portions of the blade are actually very sharp and which are not because hairs will be popping all over; it gives you more of an idea of the average level of sharpness of your entire edge. If you are a perfectionist like me you will want the entire edge to be at its optimal level of sharpness. Another variation of this test is to pick one particular hair on your arm, and attempt to cut it with a particular portion of the edge. Different hairs can sometimes react somewhat differently in the HHT, and the general rule is the thinner the hair the sharper your edge will need to be to cut it cleanly.


Strengths:

All of these tests are fundamentally testing the same thing: the thickness of the edge (not width of the bevel) which is more or less the same as the sharpness. Many people say that the only real test is the shave test; however, I have NEVER had a great shaving razor that did not at least pass these sharpness tests very well. In fact I would go so far as to say that passing these tests well is a pre-condition to having a high quality edge; if your razor will not pass the sharpness tests and you think that you are getting good shaves then all I can say is that you don't know what you are missing because you are getting a great shave in spite of the edge; not because of it. Take the time effort to learn what these tests should feel like and correlate the results to your shaves and the quality and consistency of your edges will improve and it will take you a lot less test shaving to get there. If you can run your thumb along the edge without it cutting in, run the edge across a wet thumbnail with no drag, and/or the blade will not pop hairs suspended above your skin then I can guarantee that your blade is not sharp enough at this point and that you have at least a fair amount of work left to do on the 4K (or other bevel creation stone) if you want to finish with a quality edge.

Limitations:

These tests are more subjective than the Edge Uniformity Tests which I will explain in the next section; however there is definitely a proper way to perform the tests and a right and wrong way to interpret the results. The tests are not a pass fail thing, sharpness is more of a continuum or scale. What one person may perceive as a very sharp edge, another who is more experienced may perceive the same edge as dull based on the results and their experience using the tests. Personally, I think that I can get a lot more information about the thickness/sharpness of an edge by the results of the TPT or HHT than I can from the TNT; furthermore I think that there is a higher possibility for damaging an edge with a thumbnail so I stick with the thumbpad and HHT. It takes time and experimenting to interpret the information that these tests give, and someone with more experience will definitely be able to use these more effectively than someone just starting out; however, this does not mean that these tests should be ignored.

The main limitation with the sharpness tests is that they cannot detect a double bevel in the edge or even the places where the stone is not contacting the edge if that portion of the blade was already sharp (at a steeper angle); the edge uniformity tests are needed to detect this. In my experience, the most common times when this common problem shows up are when you are honing a factory sharpened razor for the first time, and when you establish a bevel with tape on the razor to protect the spine from the dreaded hone wear during the early stages and then try to finish honing the razor with the tape off the spine. Basically the problem of double bevels arise whenever a sharp bevel was set at one angle (steeper) and you are trying to hone the razor at another angle (shallower) When you perform the sharpness tests on the razors they will appear sharp as indicated by the sharpness tests, and they are indeed sharp at the 4K level. The problem is that when you try to improve the razor with the higher grit stones you will be doing absolutely nothing to the edge of the edge. The angle that the bevel and edge is set at is at one steeper angle (caused by the factory sharpening the razor with the spine lifted to avoid selling a razor with hone wear, or you setting the bevel on a razor with tape to protect the spine and then removing it for further polishing), and you are honing the razor at a shallower angle because the spine is now on the stone and only the back of the bevel is in contact with the stones. This means that the rough but fairly sharp factory edge or 4K edge will remain regardless of the amount of touch-ups or fine tuning that you do with the finishing stones because the edge that you are actually shaving with has never been in contact with the higher polishing grits. The razor will shave the same and you are absolutely wasting your time until you establish a uniform bevel. At this point I hope that you are asking yourself “how do I know when I have established a single uniform bevel?” Great question, the answer is that you assess this by using the Edge Uniformity Tests which are explained in the next section.


Edge Uniformity Tests

The edge uniformity tests are just as important as the edge sharpness tests because they address the important issues that the sharpness tests do not; however, they are unfortunately overlooked many times leaving people with sup-par edges that will not get any better (or worse) with any touch ups or fine tuning. There are only a few edge uniformity tests that I am aware of, and I have found that the easiest and most effective are the permanent marker test and the microscope test. The microscope can also be used to assess other problems such as micro-chipping and overhoned edges; however, it is not really talked about much in terms of assessing edge uniformity as I am going to explain now. The permanent marker test is a very easy test to perform and interpret; it is a pass fail thing. All that I do is mark the edge of the bevel with dots that go to the very edge of the edge all the way from heal to toe (yes you can use a line too if you want). Then when you hone the razor the marker should be completely removed with a few passes indicating that bevel is completely uniform and the stone is contacting it everywhere and all the way to the edge. If your razor passes this test and also passed the sharpness tests very well then you can be confident that you are ready to move on to the polishing stages, and you will have a razor that shaves great when you are done. On the other hand, it is very likely that the dots will not be completely removed, and you will know that your edge is not uniform and will not be sharpened any further with the higher grit stones. If the dots or line is removed toward the back of the bevel but marker remains at the edge of the edge then you have the very common and significant problem of a double bevel. You must hone on the 4K (or courser stone) until the marker is completely removed all the way to the very edge so that you know that the double bevel is removed. This will allow the fine stones to work their magic on the cutting edge and give you a very sharp, smooth, and great shaving edge.

You can also perform a very similar test with the microscope as I learned from Mr. Randy Tuttle. You will be able to see a double bevel in your edge if the edge is two different colors and has two different scratch patterns. The difference is because the light will reflect differently because of the slight difference in the angle, and the scratch pattern will be different because it will not be from the stone that you are currently working on, it is from the stone that set the first bevel angle. When you are done removing the double bevel, the bevel should only be one color (black) and should have only one scratch pattern from the stone that you are currently using that extends all the way to the very edge. You can also use these two edge uniformity tests together to ensure the best results.

Strengths

These tests allow you to see if the entire edge is contacting the hone, or if you have issues such as a double bevel that need to be worked out. If you attempt to use finishing stones when the edge of the edge is not contacting the hone as in the case of a double bevel then you will be doing nothing but wasting your time because the edge of the razor won’t see them. If you only have one even bevel then at least you know that the stone is working on the most important part of the bevel; the edge.

Limitations:

You cannot see the bevel thickness or sharpness with a microscope or the magic marker test, all you can see is how the side of the bevel is contacting the hone. You could have the prettiest, shiniest, and most even side of the bevel; however, that absolutely does not mean that the edge is sharp. You must use the sharpness tests to determine if the bevel actually meets at an edge.

Conclusion

I hope that after reading this short guide you have a better understanding of both the strengths and weaknesses of the two main types of tests and how to use them to assess the edge of a razor, especially during the very important bevel creation stage. The TPT, TNT, and HHT will tell you if your bevel is sharp but not uniform, and the marker test and/or the microscope will let you see if you have an edge that is contacting the stone uniformly and hopefully all the way to the edge, but it will not tell you the thickness/sharpness of the bevel. Both tests have their strengths and weaknesses, so the results are best when they are used together. Unfortunately we cannot see everything that is happening at the microscopic level of our razors edge; however, by using these various tests together we can give ourselves a very good idea of what is going on at the edge level. After a quality bevel as indicated by the tests is both sharp AND even then you just need to polish it carefully with your method of choice, strop it up, shave, and then fine tune it a little if you feel that it is necessary. If you like to use Belgian stones then I have found that using 50-100 passes on both the blue and yellow produces consistently superior results, as does a few light pyramids on the Norton 4K/8K (or even just a few passes on the 8K). Hopefully these tests can take some of the guess work out of the honing process for you, because whiskers only grow so fast.

PROCEED TO THE NEXT SECTION OF THE GUIDE - Section 7 - 1, What do you need and what's recommended? (http://www.badgerandblade.com/vb/showthread.php?t=28539)

BACK TO THE TABLE OF CONTENTS (http://badgerandblade.com/vb/showthread.php?t=28547)

heavydutysg135
12-08-2007, 09:55 AM
It is worth noting that when I posted this over at the SRP Lynn and several very experienced honers stated that they do not use these tests, they only use the shave test. I think that these tests are very helpful in determining what is happening to the edge at the microscopic level (otherwise I would not have taken the time to write this out and post it), but there are many different "correct" ways to put a great edge on a razor.

joel
12-08-2007, 10:32 AM
VERY cool post!! :thumbup:

Lots of great info for newbies!

gglockner
12-09-2007, 05:15 PM
While I don't consider myself a newbie, I do still find this post very informative. If I have honed 500+ razors I probably wouldn't need it as much. So until then I find information like this extremely useful.

Thanks Glen

Jim
12-09-2007, 05:20 PM
Thanks Heavy D'!

Sticky
01-20-2008, 03:16 PM
Thanks Heavy D'!
+1

randydance062449
01-21-2008, 02:50 AM
Well done!:thumbup:

heavydutysg135
01-21-2008, 11:09 AM
Well done!:thumbup:

Thanks Randy! I learned a lot of this information from our many phone conversations a while back and my experiments and experiences confirmed that you were absolutely right. The challenging part was organizing and presenting the information that I collected from you and from my experiences in an organized manner that would be fairly easy to understand. As I said before, many people do not use all or any of these tests and still can get great shaving razors; but they have really helped the consistency, speed, and quality of my edges. If this guide helps even one person improve their honing skills then it was more than worth the time that I put into it!

heavydutysg135
02-25-2008, 12:36 AM
One topic that I did not fully cover in this guide is honing a straight razor with a taped spine. As I said before, if one sets an edge with a taped spine (in order to remove chips in the edge or fix other “issues”) and then plans to finish the job without tape they will need to use the permanent marker test or microscope test to make sure that they completely re-establish the edge without the tape before moving on to the finishing stones. The other "correct" option that was not covered is to leave the tape on the spine throughout the entire honing process (you can replace the tape as you progress throughout your stone progression). This will save hone wear on the spine and also ensure that you polish the edge at the same angle that the bevel was originally established. I will sometimes use this technique on vintage NOS razors that I want to keep looking like new and also most wedges because they usually take a lot of hone wear to set a quality edge. The drawback to honing the razor with a taped spine is the fact that you will also have to tape the spine (with tape of the same thickness) every time that you touch up the razor on a stone in the future; otherwise the shaving edge will not be polished due to the double bevel.

If you are like me and have several razors that are honed with tape and several that are honed without then I would highly recommend listing how each razor in your collection is honed so that you can match up the bevel angle to your finishing stones for future touch-ups. If you purchase a razor from someone that is “shave ready” then I would recommend asking them if the razor was honed with or without tape so that you can match the angle on your stones in the future. Alternatively you could use the permanent marker test and a very high grit finishing stone to see which bevel angle the edge was set at and then record it for future reference. It is possible that the double bevel would not be as much of or any issue if you use pasted hanging or pasted paddle strops to touch up your razors because of the give in the leather but I have not tested this. You could easily perform your own test using the permanent marker test to see if the paste is properly abrading the shaving edge.

David

Philadelph
02-25-2008, 07:49 PM
Great explanation of the TPT in particular! I haven't heard it explained so well and will now start using it as well as the others since I know exactly what should be done! Thanks

eddie
03-01-2008, 03:21 PM
I'm not a newb by any stretch, but I have only recently become aware of such things as hone wear and honing with tape.
For over a decade, I've simply sharpened my blade and shaved with it.
So, in some ways, I guess I am a newb. So pardon my observations:

If you hone with tape, and always replace the tape as you hone, you will still not get a consistent angle of the bevel. If you think about the mechanics, the edge wears back as you hone, increasing the angle between the edge and the outer radius of the spine, who's thickness remains unchanged.

I've always honed without tape, and considered hone wear on the spine to be the way in which one maintains a consistent bevel. If you do not use tape, ever, you will wear the spine as you wear the edge, at about the same rate, and your bevel will be much more consistent than by any other method.

But, the payoff is you have hone wear. I never thought of it as an issue, but then my razors were just shavers and not collector's items. I'm rethinking this as I see many absolutely gorgeous razors out there.

So, if I had a beautiful razor from some of the custom people here, I'd use tape, I suppose. But for my $100 C-Mon, which will likely never be a collectible, and my $50 vintage K-Bar, I'll just wear the razor as I use it, and look to keep the most consistent bevel possible. Maybe my great grandson will not inherit a useable razor, but he can buy his own, I suppose. Maybe I'll buy a couple just to pass on.

But I see that no one here likes hone wear, and many here know much, much more than I about razor care and honing. So I'd welcome criticism.

Ed

heavydutysg135
03-01-2008, 05:31 PM
I'm not a newb by any stretch, but I have only recently become aware of such things as hone wear and honing with tape.
For over a decade, I've simply sharpened my blade and shaved with it.
So, in some ways, I guess I am a newb. So pardon my observations:

Honing a razor without tape is perfectly fine as I said, in fact that is what I would recommend.

If you hone with tape, and always replace the tape as you hone, you will still not get a consistent angle of the bevel. If you think about the mechanics, the edge wears back as you hone, increasing the angle between the edge and the outer radius of the spine, who's thickness remains unchanged.

That is true but you will always contact the shaving edge and it is much better to use an angle that is slightly steeper than not steep enough. Razors are not ground as perfectly as you think, there is a fair amount of variation among bevel angles and grinds so changing it a slight amount is absolutely not going to hurt anything. I have a question for you, have you ever worn through an entire razor or even close to that in the normal course of shaving and touching up your blade? It takes a LOT of work on course stones to significantly wear a razor down, with a finishing stone the hone wear is almost nothing. If a razor is properly maintained throughout its life then I would be very surprised if you changed the angle by more than a few degrees. This will not make a difference in the shave.


I've always honed without tape, and considered hone wear on the spine to be the way in which one maintains a consistent bevel. If you do not use tape, ever, you will wear the spine as you wear the edge, at about the same rate, and your bevel will be much more consistent than by any other method.

Many times the edge and the spine do not wear at the same rate because the thickness of the steel are different at the edge and at the spine because of the grind. As I said before honing without tape works very well and that is what I would recommend doing. The angle is not as perfectly scientific as you think though. I would recommend PM'ing Randy Tuttle (Randydance) and asking him about his experiments measuring bevel angles

But, the payoff is you have hone wear. I never thought of it as an issue, but then my razors were just shavers and not collector's items. I'm rethinking this as I see many absolutely gorgeous razors out there.

So, if I had a beautiful razor from some of the custom people here, I'd use tape, I suppose. But for my $100 C-Mon, which will likely never be a collectible, and my $50 vintage K-Bar, I'll just wear the razor as I use it, and look to keep the most consistent bevel possible. Maybe my great grandson will not inherit a useable razor, but he can buy his own, I suppose. Maybe I'll buy a couple just to pass on.

But I see that no one here likes hone wear, and many here know much, much more than I about razor care and honing. So I'd welcome criticism.

Ed

You are doing everything right Ed. The reason that I discussed honing with a taped spine as I did is because people do it. If the angle is set with a taped spine and then one attempts to polish the bevel without tape then the razor will not shave well period. It is a very common mistake that I felt was important to address.

GeNn
03-04-2008, 11:10 AM
Introduction

The thumbnail test is performed by ............... Do not perform this test past the 4K stage because the edge will be damaged.



Thanks ! This is an excellent guide.
Being a newbie, I am somewhat obsessed with the thumbnail test as it is the easiest to do and consequently mess up the edge. So how do I fix it to bring it back to the shave ready condition that the razor was when I first got it back from a honemeister, when I try this test past the 4K? I have a pasted paddle strop, a small blue belgium and small yellow coticule. Also what is the recommended steps, passes and sequence with the tools that I have to refresh the razors?

GeNn

heavydutysg135
03-04-2008, 12:06 PM
Thanks ! This is an excellent guide.
Being a newbie, I am somewhat obsessed with the thumbnail test as it is the easiest to do and consequently mess up the edge. So how do I fix it to bring it back to the shave ready condition that the razor was when I first got it back from a honemeister, when I try this test past the 4K? I have a pasted paddle strop, a small blue belgium and small yellow coticule. Also what is the recommended steps, passes and sequence with the tools that I have to refresh the razors?

GeNn

I would try 50-100 passes (depending on the size of the stone) on just the yellow and see if that brings it back. If not then do another 50-100 passes and see where you are. To maintain a razor (touch-ups) I just use the belgian coticule. The number of passes will also depend on the size of your stone, but 10-20 passes should get the razor back. A razor that has been properly honed on a coticule will last quite a while though so you should not have to touch up very often. Proper stropping goes a long way.

GeNn
03-04-2008, 01:21 PM
I would try 50-100 passes (depending on the size of the stone) on just the yellow and see if that brings it back. If not then do another 50-100 passes and see where you are.

Thanks,
I'll try that tonight!

netsurfr
03-31-2008, 03:41 PM
Fantastic tutorial!!! Thanks so much for taking the time to document these techniques.

heavydutysg135
03-31-2008, 04:05 PM
This Sunday at my Southern California Straight Razor Get Together I gave a 2 hour honing clinic that was video taped. It will be posted here in full quality as soon as I can get it edited (and probably on YouTube in lesser quality) and covers all of what I consider all of the "fundamentals" of honing. The topics include stone selection, technique, sharpness tests, honing a dull eBay razor from scratch, double bevels, and advanced honing techniques for honing smiling and warped razors. My goal is to get this posted in two weeks or less, but it is going to take some help from others in editing and posting. Keep your eyes out for it in the near future as I think that you will really like it if you enjoyed my written guides.

David

heavydutysg135
05-20-2008, 02:51 PM
Here are my honing videos. Enjoy!

http://badgerandblade.com/vb/showthread.php?t=47303

leadingedge
07-31-2010, 07:54 AM
Absolutely brilliant, helps a lot, thanks!

wquiles
04-10-2013, 05:52 PM
This is an old post, but still full of good information :w00t:

Thomas Martin
04-10-2013, 09:50 PM
For me, all these tests say nothing about the shaving capabilities of my edges. I've had blades that passed a HHT with flying colours and shaved badly and vice versa. I still use them during honing but do not rely too much on them. The shave test is the only test that matters.

wquiles
04-11-2013, 06:41 AM
For me, all these tests say nothing about the shaving capabilities of my edges. I've had blades that passed a HHT with flying colours and shaved badly and vice versa. I still use them during honing but do not rely too much on them. The shave test is the only test that matters.
To be honest, that is where I am. The shave is the ultimate test, but I am using these tests as a guide as I figure out what works for me.