Missed parameter of DE safety razor?

[dawid]

As mentioned in the Understanding DE safety razor parameters thread, for testing purposes I designed a DE safety razor.
While creating a sketch of it, I noticed that there might be a parameter which was not mentioned before, at least not on the Safety Razor Parameters: Illustrated and Defined page.

Preliminarily I called it "Guard to shave plane distance".
Overview picture:

Zoomed in:

Without defining this parameter, the sketch is not fully constrained, so it shall be set either by defining guard plane angle with respect to the neutral shave plane (4.3 deg in the picture), or by guard to shave plane distance (0.1 mm in the picture).
The way I create this distance is following:
- create a neutral shave plane (in my design it's a straight-line tangent to the guard and tangent to the cap)
- create a perpendicular line from the neutral shave plane to the guard at the height where the guard shifts to the surface where the blade gap is measured (in my case this surface is horizontal, but it's not always the case in various razors).

I hope I explained it clear enough how it's being created.

The picture above shows the geometry with this distance being set to 0.1 mm. Have a look what happens if I change it to 0.5 mm, without changing any other parameters of the razor:

To understand it more, I reversed engineered the infamous Muhle R41 which is known for its aggressiveness.
I found that this distance in case of R41 is 0.42 mm:

However, in case of R41 it get's even worse if we check how the geometry looks in the cross-section of the open comb, as the distance increases up to 1 mm:

Considering the fact that R41's open comb is very wide, perhaps it's not an overkill to assume that the skin can get that deep into the OC.

I believe this parameter could influence the aggressiveness of razors and the sensation of the blade, as it may allow skin to be more readily caught beneath the blade. These are my current speculations, as I have not yet examined the effects of this parameter.
Could it be that the "guard to shave plane distance" plays a crucial role in the feel of a razor?

Your input ang thoughts are very much needed here.

 

[Iridian]

Hey, I think you discovered on your own what is named exposure.
And here is also where I lost you: How is "guard to shave plane distance" actually different from exposure???

Blade exposure represents the position of the razor blade cutting edge in relation to the shave plane.
Basically, if it is sticking out, it is positive, if not it is neutral or even negative.

OCs indeed allow more skin to get "closer" to the blade, effectively increasing exposure even more.

 

[Goblin]

I think this is an interesting observation.

Basically, this particular measurement seems to influence both the gap and exposure.

It's almost like we need two measurements for "gap". There's the actual gap, then the "effective gap" which is a factor of this guard to shave plane measurement.

Although maybe you already have another name for this. I need to look at the other thread!

Edit: Okay, it looks like what I am talking about is effectively the guard span, so by increasing guard to shave plane, you increase guard span. It's quite a complicated interplay of variables, but the impact on the shave would be significant!

 

[Hercule]

You seem to ignore the similar gap plane above the blade between the blade and the cap?

 

[tiberius]

Safety Razor Parameters: Illustrated and Defined

...

www.badgerandblade.com

You may want to refer to that picture ...

 

[Quaznoid]

It’s just shavin’ man !

 

[dawid]

Hey, I think you discovered on your own what is named exposure.
And here is also where I lost you: How is "guard to shave plane distance" actually different from exposure???

Blade exposure represents the position of the razor blade cutting edge in relation to the shave plane.
Basically, if it is sticking out, it is positive, if not it is neutral or even negative.

OCs indeed allow more skin to get "closer" to the blade, effectively increasing exposure even more.

Have a look at the first two pictures in the original post. You can see that blade exposure stays the same (0.00 mm) in relation to the shave plane, even though the distance I am describing changes.

I think this is an interesting observation.

Basically, this particular measurement seems to influence both the gap and exposure.

(...)

Edit: Okay, it looks like what I am talking about is effectively the guard span, so by increasing guard to shave plane, you increase guard span. It's quite a complicated interplay of variables, but the impact on the shave would be significant!

Yes, the effective gap you marked corresponds to the guard span, indeed.
I am changing the guard to shave plane distance without changing the blade gap (0.65 mm), nor the guard and cap span (both 2 mm). These parameters are disconnected from each other. That's exactly why I think this might be yet another parameter of razors.

However, you gave me a thought. Perhaps defining it as an effective blade gap makes sense:

You seem to ignore the similar gap plane above the blade between the blade and the cap?

Yes, because I think that the blade reveal, free-end distance, and blade rigidity describes it all in the zone above the blade.

Safety Razor Parameters: Illustrated and Defined

...

www.badgerandblade.com

You may want to refer to that picture ...

I actually did, my design and parameters are based on the information provided there.

 

[tiberius]

I actually did, my design and parameters are based on the information provided there.

Aaarrrghhhh sorry I saw your first post have already linking to that article. I was reading the reply by @Goblin mentioning guard span as effective gap, and he's discovered that article too. There are already too many nomenclatures that risk misunderstanding if not following an established convention.

 

[Goblin]

However, you gave me a thought. Perhaps defining it as an effective blade gap makes sense...

I had always assumed that gap measurements refer to the effective gap, rather than the gap as you have measured it here. Now I wonder if that isn't the case, otherwise some designs would have huge stated gaps. As you have shown, the R41 would be an example of this, where people claim the gap is very low because of the distance from the underside of the blade to the plate, but the way that plate curves away means the effective gap is huge, thus explaining the character of the razor.

I would expect that in milder razors actual gap and effective gap will be probably quite similar, but for designs with higher exposure, there could be a significant difference depending on the shape of the baseplate. As you have shown, this also means that you could increase the efficiency of an otherwise mild design by "under cutting" the plate to increase that guard to shave plane distance.

Basically, yes. It seems like this is an important measurement.

 

[dawid]

I had always assumed that gap measurements refer to the effective gap, rather than the gap as you have measured it here.

I think it's difficult to say and I am sure different manufacturers define the blade gap differently.

As you have shown, the R41 would be an example of this, where people claim the gap is very low because of the distance from the underside of the blade to the plate, but the way that plate curves away means the effective gap is huge, thus explaining the character of the razor.

Yes!

I would expect that in milder razors actual gap and effective gap will be probably quite similar, but for designs with higher exposure, there could be a significant difference depending on the shape of the baseplate. As you have shown, this also means that you could increase the efficiency of an otherwise mild design by "under cutting" the plate to increase that guard to shave plane distance.

And the plan is to test it.

 

[DesertIguana]

It’s just shavin’ man !

Well some people are OCD, they educate rest of us.

 

[Teutonblade]

As mentioned in the Understanding DE safety razor parameters thread, for testing purposes I designed a DE safety razor.
While creating a sketch of it, I noticed that there might be a parameter which was not mentioned before, at least not on the Safety Razor Parameters: Illustrated and Defined page.

Preliminarily I called it "Guard to shave plane distance".
Overview picture:

View attachment 1865331

Zoomed in:

View attachment 1865332

Without defining this parameter, the sketch is not fully constrained, so it shall be set either by defining guard plane angle with respect to the neutral shave plane (4.3 deg in the picture), or by guard to shave plane distance (0.1 mm in the picture).
The way I create this distance is following:
- create a neutral shave plane (in my design it's a straight-line tangent to the guard and tangent to the cap)
- create a perpendicular line from the neutral shave plane to the guard at the height where the guard shifts to the surface where the blade gap is measured (in my case this surface is horizontal, but it's not always the case in various razors).

I hope I explained it clear enough how it's being created.

The picture above shows the geometry with this distance being set to 0.1 mm. Have a look what happens if I change it to 0.5 mm, without changing any other parameters of the razor:

View attachment 1865333

To understand it more, I reversed engineered the infamous Muhle R41 which is known for its aggressiveness.
I found that this distance in case of R41 is 0.42 mm:

View attachment 1865335

However, in case of R41 it get's even worse if we check how the geometry looks in the cross-section of the open comb, as the distance increases up to 1 mm:

View attachment 1865336

Considering the fact that R41's open comb is very wide, perhaps it's not an overkill to assume that the skin can get that deep into the OC.

I believe this parameter could influence the aggressiveness of razors and the sensation of the blade, as it may allow skin to be more readily caught beneath the blade. These are my current speculations, as I have not yet examined the effects of this parameter.
Could it be that the "guard to shave plane distance" plays a crucial role in the feel of a razor?

Your input ang thoughts are very much needed here.

Congratulations Dawid! This is a brilliant analysis. It would be cool to see a chart showing the stated and effective gap of some of the most popular razors.

 

[dawid]

Congratulations Dawid! This is a brilliant analysis. It would be cool to see a chart showing the stated and effective gap of some of the most popular razors.

It would require rather detailed reverse engineering of razors, what is not as simple as it seems and takes time. I noticed that even small deviations in geometry have a significant impact on parameters (BTW machined razors are superior in terms of tolerances compared to cast ones, since cast ones have parameters all over the place).

To properly reproduce R41 it took me a few hours of work and it's still not perfect...

 

[Goblin]

To properly reproduce R41 it took me a few hours of work and it's still not perfect...

Wait...are you saying you now have the models to 3D print an R41 head?!

Respect!

 

[Brutus]

To understand it more, I reversed engineered the infamous Muhle R41 which is known for its aggressiveness.
I found that this distance in case of R41 is 0.42 mm:

View attachment 1865335

However, in case of R41 it get's even worse if we check how the geometry looks in the cross-section of the open comb, as the distance increases up to 1 mm:

View attachment 1865336

Considering the fact that R41's open comb is very wide, perhaps it's not an overkill to assume that the skin can get that deep into the OC.

I too do believe that for all practical purposes we are talking blade exposure here.
As far as the bottom drawing is concerned, I also believe that the geometry between the teeth is of secondary importance as the distance between the teeth is small enough that the protruding teeth define the blade exposure and not the small gap between.

That is, if someone shaves with the universally recommended light touch.
If someone digs in like driving an excavator, that is another matter.


Just think “If it looks like blade exposure, defines the shave like blade exposure, and feels like blade exposure, then it probably is blade exposure.”
(Akin to “If it looks like a duck, swims like a duck, and quacks like a duck, then it probably is a duck.”)


B.

 

[dawid]

Wait...are you saying you now have the models to 3D print an R41 head?!

I actually do:

I too do believe that for all practical purposes we are talking blade exposure here.
As far as the bottom drawing is concerned, I also believe that the geometry between the teeth is of secondary importance as the distance between the teeth is small enough that the protruding teeth define the blade exposure and not the small gap between.

(...)

Just think “If it looks like blade exposure, defines the shave like blade exposure, and feels like blade exposure, then it probably is blade exposure.”
(Akin to “If it looks like a duck, swims like a duck, and quacks like a duck, then it probably is a duck.”)


B.

In my opinion the exposure is a different thing here. Remeber that the exposure can stay the same, while the parameter we discuss can be changed significantly (picture #2 and #3 in the original post), so the parameter should not be linked to exposure then.
I will test it soon and will see how it influances shaving experiance, if it does at all.

 

[Goblin]

I actually do:

View attachment 1866640

That's both ridiculous and fantastic at the same time!

I do hope that we will get to see the fruit of all your labours in a series of designs that are commercially available in some form. I think you are putting in the work to justify it!

 

[dawid]

I do hope that we will get to see the fruit of all your labours in a series of designs that are commercially available in some form.

Never thought about it this way, thanks Goblin.

 

[Stikeyoda]

As mentioned in the Understanding DE safety razor parameters thread, for testing purposes I designed a DE safety razor.
While creating a sketch of it, I noticed that there might be a parameter which was not mentioned before, at least not on the Safety Razor Parameters: Illustrated and Defined page.

Preliminarily I called it "Guard to shave plane distance".
Overview picture:

View attachment 1865331

Zoomed in:

View attachment 1865332

Without defining this parameter, the sketch is not fully constrained, so it shall be set either by defining guard plane angle with respect to the neutral shave plane (4.3 deg in the picture), or by guard to shave plane distance (0.1 mm in the picture).
The way I create this distance is following:
- create a neutral shave plane (in my design it's a straight-line tangent to the guard and tangent to the cap)
- create a perpendicular line from the neutral shave plane to the guard at the height where the guard shifts to the surface where the blade gap is measured (in my case this surface is horizontal, but it's not always the case in various razors).

I hope I explained it clear enough how it's being created.

The picture above shows the geometry with this distance being set to 0.1 mm. Have a look what happens if I change it to 0.5 mm, without changing any other parameters of the razor:

View attachment 1865333

To understand it more, I reversed engineered the infamous Muhle R41 which is known for its aggressiveness.
I found that this distance in case of R41 is 0.42 mm:

View attachment 1865335

However, in case of R41 it get's even worse if we check how the geometry looks in the cross-section of the open comb, as the distance increases up to 1 mm:

View attachment 1865336

Considering the fact that R41's open comb is very wide, perhaps it's not an overkill to assume that the skin can get that deep into the OC.

I believe this parameter could influence the aggressiveness of razors and the sensation of the blade, as it may allow skin to be more readily caught beneath the blade. These are my current speculations, as I have not yet examined the effects of this parameter.
Could it be that the "guard to shave plane distance" plays a crucial role in the feel of a razor?

Your input ang thoughts are very much needed here.

I think you are on to something. I've been designing a shared shave diary and inventory system to support research on our hobby. Working through what parameters to record on razors it kept bothering me that 2 different razors with identical gaps and exposures shaved differently with the same blade. Some of it seemed material related. TiBird shaves differently than a BrassBird. Some of that is weight and implicit pressure. Some of it is how the blade is secured (flex and chatter). But there still seemed to be something missing. I think you've hit on it, an effective gap versus the recorded gap. It is also likely the source of a lot of YMMV as slight pressure difference could make a big outcome difference in both efficiency and irritation.

 

[dawid]

(...)
TiBird shaves differently than a BrassBird.

What I noticed while printing razors and then playing with the design is that manufacturing tolerances matter. This applies not only to razors but blades too. Blades width varies from 21.95 mm to 22.05 (give or take, for varied brands).

Blackbird is designed with a nominal blade exposure of 0.101 mm.
Let's assume it was designed for a 21.95 mm blade, but then a shaver uses a blade which is 22.05 mm. It would mean that the blade exposure increases to 0.106 mm only because of the wider blade (I'm exaggerating though, as it's not directly proportional due to bent blade). Adding razor's manufacturing tolerances to it could increase this value even further.

Is it a lot and does it even matter? I don't know, these are really small values, I am not sure if they can be felt at all.
On the other hand, so it happens that Feather blades are on the wider side, measuring around 22.05 mm, while most other brands are around 21.95 mm. Perhaps that's one of reasons why Feather is considered aggressive.

Tolerance is there and maybe it matters. Perhaps that's why a TiBird shaves differently than a BrassBird, but also what is not considered and applies to every razor and brand, a TiBird may shave differently than a TiBird.