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Guard Span vs Gap | Is This A Missing Piece In Our Discussions?

Chan Eil Whiskers

Fumbling about.
Guard Span vs Gap Discussion.full sized..png


This ⬆ information ⬆ strikes me as very important.

I've long thought guard span to be a missing ingredient in discussions about gap, but this is the best explanation I've come across to explain anything about the mysteries of guard span. I'm interested in your thoughts about what's being discussed in the material.

It's long been clear to me that a number of factors play into how a razor shaves. We evaluate the shaves by how efficient the razor is, how mild or rough it feels, how much work is required to give us a good shave, whether the razor allows us to do the necessary work without damaging our skin, how mild or rough the razor feels as we use it, whether the razor is prone to biting, how smooth and comfortable our skin is after the shave, etc.

Surely blade rigidity, blade exposure, gap, and other factors are important determinants of a razor's performance. I believe there are others not much (or ever) discussed , some of which are, in how they impact the shave, very unclear to me. The material I found today, pondered, and posted here makes my understanding of the role of guard span less sketchy.

...the guard span is in fact far more influential on razor safety (than the gap). The guard span forms the effective gap into which your skin can deform in front of (or into!) the blade.
This material ⬆ explicitly states ⬆ that guard span is more important that gap.

The material was found on the Maggard website. Just in case you're interested in the context which I'm not. I'd prefer to discuss guard span.

Happy shaves,

Jim
 
That quote is imo spot on. Apparently blade gap is much easier to measure but certainly guard span a more meaningful measurement and I think it would be great if razor manufacturers all listed guard span and blade exposure.
 
What does guard span mean in the above context? The smaller span=milder razor mentioned in the last paragraph makes no sense.
 

Cal

Contributor
What does guard span mean in the above context? The smaller span=milder razor mentioned in the last paragraph makes no sense.
You are correct sir it doesn't.
More context:
1623276505882.png

Not so confusing when you realize it's referring to the Henson Razor. HERE's their Technical Data Page which includes the above and plenty more (these boys have done their homework).
 

Chan Eil Whiskers

Fumbling about.
What does guard span mean in the above context? The smaller span=milder razor mentioned in the last paragraph makes no sense.
You are correct sir it doesn't.

How so?


same gap, different guard span.png


Grant @ShavingByTheNumbers explained to me his drawing above. Here is Grant's explanation.

This post contains my attempt to explain my understanding of what's going on with guard span (and should be relevant to this discussion). There are a few follow up posts.

This illustration of course is always relevant...


Grant's Safety_Razor_Parameters_around_Blade_Cutting_Edge.jpg


Perhaps I'm not understanding what you guys see as incorrect here? Missing the obvious is one of my special gifts sometimes.

Happy shaves,

Jim
 

Chan Eil Whiskers

Fumbling about.
More context:
View attachment 1279332

Not so confusing when you realize it's referring to the Henson Razor. HERE's their Technical Data Page which includes the above and plenty more (these boys have done their homework).
Thanks, Cal. I was unaware of that technical data page. You're right, they've done their homework.

I'm not terribly interested in just the one brand of razor though. I am interested in how this applies across the board. It's not a new interest for me of course as you know, but the material in my OP brought me back to something I'd understood less well than I do now: It's not all about gap and blade exposure and blade rigidity.

Happy shaves,

Jim
 
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Chan Eil Whiskers

Fumbling about.
I have been using on my vacation only the Timeless Ti 95 OC. I am not able to take very good photos of it showing the gap and guard span, but just looking at it it looks to have a very small guard span for its gap.

1623281596253.pngThis photo, if you imagine the handle tightened, might illustrate the matter to a degree.

I've long though the curled upwards combs were very cool. What do they do to the guard span?

My backup for my vacation is the Timeless Bronze 38 baseplate (which I've not used on vacation). It too, has less guard span for its gap as compared to some razors I can visualize or find photos of.

Timeless did their homework in my opinion.

Happy shaves,

Jim
 
How so?


View attachment 1279328


Grant @ShavingByTheNumbers explained to me his drawing above. Here is Grant's explanation.

This post contains my attempt to explain my understanding of what's going on with guard span (and should be relevant to this discussion). There are a few follow up posts.

This illustration of course is always relevant...


View attachment 1279339


Perhaps I'm not understanding what you guys see as incorrect here? Missing the obvious is one of my special gifts sometimes.

Happy shaves,

Jim
I'm thinking of guard span as it's used to alter exposure (as in the examples I mentioned) rather than an all else held constant consideration.

Sent from my Pixel 4a using Tapatalk
 
Sometimes I'm so stupid I don't know what you're talking about, but that doesn't mean you don't.
Short guard span as I thought of it . Probably the two most aggressive razors I own. Span on the Caged Head is pretty much non-existent. If the cage and guard span were larger exposure would be less and the razor milder not more aggressive. Ditto with the iKon if you pulled the guard farther out.



Sent from my Pixel 4a using Tapatalk
 
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View attachment 1279150


This ⬆ information ⬆ strikes me as very important.

I've long thought guard span to be a missing ingredient in discussions about gap, but this is the best explanation I've come across to explain anything about the mysteries of guard span. I'm interested in your thoughts about what's being discussed in the material.

It's long been clear to me that a number of factors play into how a razor shaves. We evaluate the shaves by how efficient the razor is, how mild or rough it feels, how much work is required to give us a good shave, whether the razor allows us to do the necessary work without damaging our skin, how mild or rough the razor feels as we use it, whether the razor is prone to biting, how smooth and comfortable our skin is after the shave, etc.

Surely blade rigidity, blade exposure, gap, and other factors are important determinants of a razor's performance. I believe there are others not much (or ever) discussed , some of which are, in how they impact the shave, very unclear to me. The material I found today, pondered, and posted here makes my understanding of the role of guard span less sketchy.



This material ⬆ explicitly states ⬆ that guard span is more important that gap.

The material was found on the Maggard website. Just in case you're interested in the context which I'm not. I'd prefer to discuss guard span.

Happy shaves,

Jim
Great minds think alike. I've been thinking about guard span myself recently and for the same reason. I've been looking at that technical section on the Henson website for the past week and they've absolutely been doing their homework as @Cal mentioned.

Guard span is one of those measurements that would be great to have on a razor. For that matter, having a blade exposure measurement would be terrific because it's the single greatest determinant of a razor's aggressiveness/efficiency. Gap is the least important, but it's the easiest to measure, so that's the one that's commonly used.

Interestingly, both exposure and guard span can be measured using a good photo of the profile of a razor provided there is something in it for scale. @Rosseforp has recently been taking the best profile photos that I've seen to date. He's been using a Pluggable 2.0 USB microscope, which are pretty inexpensive ($40).

The picture below is one of Rosseforp's and I've overlaid measurements on it. For scale, I'm using the blade thickness which is known to be .1mm. A steel metric ruler in the photo on the same plane as the razor profile would be ideal, but the blade thickness worked pretty well. I calibrated it by measuring the gap, which is stated as .98mm, and came up with .94mm using my PowerPoint measuring technique. That's pretty close.

Ideally a open source tool like ImageJ would be used for measurements since it was developed by the US National Institute of Health to taking measurements of microscope photos, but PowerPoint works in a pinch. ImageJ also has focus-stacking capabilities, which allows you to take multiple photos with different focus points, and join them together using software so you have a single image in perfect focus at all depths of the photo (@Esox came up with that idea). At any rate, here are the measurements I took using Rosseforp's photo of a Karve SB-D plate. Guard span is ~1.49mm.

 
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The above measurement of exposure is wrong. You ‘ve actually measured the length of blade beyond the
shaving plane.
But blade exposure is the distance between blade’s edge and shaving plane ,perpendicularly,and not following the blade’s angle.

0.4 mm is rather huge exposure for plate D .Muhle R41 has about 0.28 - 0.3 exposure while Merkur Futur @6 has about the same if not a bit more.

Karve plate G has a 0.25 mm blade
exposure ,while the D plate has 0.13 mm ,stated by the manufacturer:


Furthermore,
The blade gap distance has to
be parallel to the fully tightened handle of the razor.
From the pic one can tell that the
blade gap measurement is not
kept parallel to the handle,thus
it is missing the 0.04 mm from
being 0.98 mm .
 
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The above measurement of exposure is wrong. You ‘ve actually measured the length of blade beyond the
shaving plane.
But blade exposure is the distance between blade’s edge and shaving plane ,perpendicularly,and not following the blade’s angle.

0.4 mm is rather huge exposure for plate D .Muhle R41 has about 0.28 - 0.3 exposure while Merkur Futur @6 has about the same if not a bit more.

Karve plate G has a 0.25 mm blade
exposure ,while the D plate has 0.13 mm ,stated by the manufacturer:


Furthermore,
The blade gap distance has to
be parallel to the fully tightened handle of the razor.
From the pic one can tell that the
blade gap measurement is not
kept parallel to the handle,thus
it is missing the 0.04 mm from
being 0.98 mm .
Yup, it is wrong. The corrected blade exposure measurement I get is .157mm, which is bigger than the .13mm stated by the manufacturer, but I'm pretty happy at how close it came. The gap is off by a few hundredths of mm too, which I'm pretty happy with. It looks like a surprisingly accurate way to get measurements with $40 worth of equipment. Once you have the picture, it's about 5 minutes worth of work to get measurements. I think ImageJ will probably do a better job than my proof-of-concept attempt with Powerpoint, especially if "focus stacking" can make the reference lines a bit crisper.

It's great to have Karve to check the measurements against. It's one of the only razor companies that publishes that data. Now I'm curious to check the blade exposure on the RR Game Changers and Lupos.

 
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Chan Eil Whiskers

Fumbling about.
Good photos are crucial and very hard to take. I have failed many many times to achieve the accuracy this sort of project requires. I'm glad you gentlemen are on it and figuring it out.

Same with the rest of the measurement stuff.

I have enough problems getting my head around the concepts at a macro level. Yes, I realize it's all just scale changes.


1623326073821.png


I'm glad to see more and more of us becoming seriously interested in the design parameters arena.

The idea of beta testing a snazzy new $600 razor grows less and less appealing to me.

Happy shaves,

Jim
 
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Christ. At least I get it now, thanks for the explanation. In my book span is the width of the baseplate.
The span used above will work with the Henson, but will now every producer invent a new metric, most suitable for their razor?
Why not go the bullet proof way with blade exposure, this can be measured even with your thumb.
 
Christ. At least I get it now, thanks for the explanation. In my book span is the width of the baseplate.
The span used above will work with the Henson, but will now every producer invent a new metric, most suitable for their razor?
Why not go the bullet proof way with blade exposure, this can be measured even with your thumb.
Exposure can be measured with your thumb to see if it's positive vs negative, but it's a trickier proposition when the razor is $250 and it's not returnable! I'd love to see a table of razors that lists the exposure, gap, and guard span etc.

The closest we have to that are subjective accounts of how "aggressive" a razor is, and those accounts vary quite a bit. Even on a razor like the Fatip Grande, some people describe it as smooth and efficient, and some describe it as a monster. Knowing that the gap is 0.14mm, and that the exposure is 0.14mm is a lot more informative (to me). If I also know that an R41 has a gap of .3mm and a blade exposure 0.25mm, it helps me compare those two razors.

I'm a bit of a geek though. Not everybody will be interested that stuff, and that's fine too. Razor parameter interest mileage may vary... 😃
 
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