Razor manufacturing methods: Is Machined > MIM > sintered > casted ?

[shawnsel]

There has been a lot of good discussions recently about razor materials (Zamak, aluminum, brass, stainless steel, etc):

• http://badgerandblade.com/vb/showthread.php/394608-How-long-do-Zamak-razors-really-last/
• http://badgerandblade.com/vb/showthread.php/412455-Pics-of-a-perishing-Zamak-razor-Or-is-it-a-myth
• http://badgerandblade.com/vb/showthread.php/416540-Zamak-hating-seems-to-be-trendy-these-days/
• http://badgerandblade.com/vb/showthread.php/406655-Modern-BRASS-DE-razors
• http://badgerandblade.com/vb/showthread.php/413356-which-razors-are-made-of-brass-stainless

But what else might also be an objective indicator of a high quality razor?

Obviously the head geometry is crucial (blade angle, blade exposure, blade gap, etc) ... but what about the "build tolerances" that a manufacturer provides towards keeping their end products consistently true to their intended head geometry?

My understanding is that "tight build tolerances" means that the manufacturer outputs razors (of a specific model) that are consistently, very precisely identical to each other? (in the context that differences too small to be discerned by the naked eye can still significantly effect the aggressiveness/smoothness/efficiency/quality of the shave)

Examples of poor build tolerances (and poor quality assurance) might then be inconsistent (or wavy) blade gap/exposure, loosely fitted jiggly parts, bubbling chrome, etc?


Why might this matter?
How can a B&B member know that the Razor X that he/she might be interested in purchasing is going to shave in an equivalent fashion to the Razor X razor that you might own and recommend?

Also, I'm thinking these differences between final product razors might not be as significant to experienced shavers whose skill might minimize the effect of subtle flaws in the razor, but those less experienced with DEs might fall into a trap of thinking that an inferior shave produced by a flawed razor is instead due to their own poor technique or sensitive skin?


So, my question for engineers and those with expertise:
What razor manufacturing methods typically create the tightest build quality towards the truest and most consistent razors?


I have heard in B&B (and read some partially supporting evidence elsewhere) that machined is generally better than metal injection molded (MIM), which is generally better than sintered, which is generally better than casted. Is this (generally) accurate? Predictably accurate ... or does it more so still depend on the diligent inspection and quality assurance by the manufacturer?

Also, where would "stamping" and "rolling" metal fit into this spectrum of manufacturing techniques?

Additionally, what affect might finishing processes have on the resulting build tolerances and head geometry?

• chrome (or other finishing metal) plating
• non-plated coating (is there a better term for this?)
• manual buffing
• anodizing
• passivation

I would assume, for instance, that manual buffing could add an element of inconsistency to the finished products?


In the big picture:
How important is the manufacturing method (and finishing) compared to the materials used? Or is it really mostly about trusting the QA of the manufacturer (and the brand)?


Thoughts?


Thanks!
Shawn

 

[jamesspo]

Great post and questions, Shawn. I've got some general ideas and opinions on this, but I'm going to have a chat with my dad, a metallurgist, to see what he says. We've had a lot of discussion about these sorts of things, but I just don't have it cleanly ready to throw into a post, until I chat with him again to get my thoughts collected. I will say this for now - most of the discussion on the Internet about metals and fabrication techniques is bologna. . This is particularly true with regard to the "cast vs forged" debate..usually about car parts, etc. Casting is always at the bottom of the barrel in those discussions, yet there is a ton of high precision work that's done with casting... jet engine turbine blades for instance (and that's not new, BTW..such things have been precision casted since WWII, at least). Like all things, the details are what typically matter, so the discussion really has to stay focused on the specific type of object one is creating, and tolerances and design criteria that are important to that application as well as the material used.

This said, I expect dad will probably initially laugh me..because quite frankly, I doubt the manufacturing method used in something like a stainless steal razor is going to matter one whit to it's performance. The tolerances are just not critical enough to matter in for shaving. But I'll see what he says.

 

[nuclearblast]

The tolerances are just not critical enough to matter in for shaving. But I'll see what he says.

Exactly.

And since I am not an expert I won't say much more.
I will just add that many people seem to forget these different processes also involve different costs. So if a Weber is sold for $70, doesn't mean you're being ripped off if you pay $185 for an ATT. People seem to forget this.

That's all.

 

[shawnsel]

The tolerances are just not critical enough to matter in for shaving. But I'll see what he says.

I'm confused by that ... it seems from our blade gap chart that a tenth of a millimeter (less than what the human eye can accurately discern) can be influential to how a razor shaves?

Shimming a razor (also just 0.10 mm I believe?) would be another example of a seemingly very subtle change making a noticeable difference?

 

[BSAGuy]

Hi Shawn, With all due respect, I think you are over-thinking this. Razors are small tools with minimal # of parts. As such, it is unlikely that any razor will experience significant "tolerance stack" or be meaningfully out of spec with others of the same model.

Also, razors operate on a very small, soft surface (human face) with significant variance in skin and underlying tissue between users. Also, beard density, hair thickness, blade choice, shave lubricant are widely differing variables.

For me, it just works to pick a razor and blade, lather up and go at it.

 

[shawnsel]

Hi Shawn, With all due respect, I think you are over-thinking this. Razors are small tools with minimal # of parts. As such, it is unlikely that any razor will experience significant "tolerance stack" or be meaningfully out of sec with others of the same model.

Yeah ... that's possible too

 

[nuclearblast]

Shimming a razor (also just 0.10 mm I believe?) would be another example of a seemingly very subtle change making a noticeable difference?

But shimming a razor doesn't only increase blade gap, it changes the cutting angle too ( in most cases at least) and I believe that is what makes the biggest difference.

 

[jamesspo]

I'm confused by that ... it seems from our blade gap chart that a tenth of a millimeter (less than what the human eye can accurately discern) can be influential to how a razor shaves?

Shimming a razor (also just 0.10 mm I believe?) would be another example of a seemingly very subtle change making a noticeable difference?

I think it's unlikely someone could really tell a difference of .1 mm, but even if they could, I see .1mm level consistency as something very easy to achieve with any metal manufacturing method, as long as basic quality control system is in place. Granted that might not always be the case...

In my discussions with my dad on different process, I don't recall seeing any differences until you started trying to control down to the the thousandths of an inch level - so around an order of magnitude smaller.

 

[sub vet]

I want the fit and centering of the blade in the cap or base, depending which model, to be repeatable and consistent razor to razor; no need futz around when I replace the blade.

I want the business surfaces; com/bar and cap, to be finely finished;

I want the plating/anodizing to be even and I want any threaded/mating parts to fit smoothly and snugly without galling.

The base material is ideally one that is not adversely affected by hard water, pretty much eliminates Zinc.

How the manufacturer gets there efficiently and economically is not my concern but I don't intend to pay $100+ dollars for a daily use shaving tool. There are a couple of manufacturers who have managed to achieve the goals I stated so it isn't impossible. I suppose as long as enough are content with Zinc "disposable" razors there isn't much incentive for the manufacturers to improve.

 

[chris.hale]

I'll be very interested to hear what James' dad says as someone in the know. My opinion is that stainless steel is stainless steel, and how it came to be razor-shaped doesn't matter. I like the thought of something being machined because the idea of it being hewn from a chunk of steel with a big machine appeals to me, however I do not believe that it makes an inherently better quality razor.

As James mentioned, some very precise parts including turbine blades and bearing assemblies are made from cast steel. I believe that it's quality control that makes the biggest difference.

 

[shawnsel]

I believe I have read in B&B that sintering for example creates shrinkage in the final product that is less predictable? I really don't know ... and I'm not even sure if it matters in the end ... but I am at least finding this interesting

 

[paintflinger]

I believe I have read in B&B that sintering for example creates shrinkage in the final product that is less predictable? I really don't know ... and I'm not even sure if it matters in the end ... but I am at least finding this interesting

While less predictable, it can be reasonably predicted, which would allow you to set a QC tolerance to weed out unsatisfactory items. I'd also wager a guess that with the larger manufacturers, they've produced enough units to fine tune their manufacturing procedures such that the final product is within spec extremely consistently.

 

[shawnsel]

Here's an example. I've read that some flawed Weber razors (which are sintered) have shipped with a "wavy blade gap" issue where the blade gets actually visibly curved (and produces a quite harsh shave). I'm sure it could have been weeded out with better QA on that day ... but would MIM or machining have been less likely to create such a defect?

As QA for razors is probably limited by the diligence and acuteness of human observation ... perhaps purchasing a razor manufactured in a certain way might decrease the likelihood of receiving a visibly (or microscopically) flawed razor?

Getting pretty theoretical I know ... but materials get discussed all the time, and these manufacturing techniques also get some sideline attention in a less direct context, so I thought a thread specifically about this might help to better understand if there are any real (potential) benefits.

Or is it really just about the razor's design, materials used, and community trust in the brand?

 

[jamesspo]

Here's an example. I've read that some flawed Weber razors (which are sintered) have shipped with a "wavy blade gap" issue where the blade gets actually visibly curved (and produces a quite harsh shave). I'm sure it could have been weeded out with better QA on that day ... but would MIM or machining have been less likely to create such a defect?

As QA for razors is probably limited by the diligence and acuteness of human observation ... perhaps purchasing a razor manufactured in a certain way might decrease the likelihood of receiving a visibly (or microscopically) flawed razor?

Getting pretty theoretical I know ... but materials get discussed all the time, and these manufacturing techniques also get some sideline attention in a less direct context, so I thought a thread specifically about this might help to better understand if there are any real (potential) benefits.

Or is it really just about the razor's design, materials used, and community trust in the brand?

I think it's worth discussing, but I also think it gets into some fairly complicated details quickly. As an example, I've had a lot of detailed discussion (years and years worth) with my dad about metallurgical failures, and how materials, engineering and manufacturing techniques play a role. It's just the kind of stuff we talk about . The problem is, that every application is different, so you have to drill down into the details. In some use cases, the material may not make any difference, in others, it's huge. Materials, engineering and manufacture are all intertwined in their effects. Now, that doesn't mean there are not trend lines you can follow. In my discussion with him, far and away the biggest cause of parts and structural failures has been design related - mainly two things: 1. Underestimating effects of fatigue 2. Misunderstanding stress concentration, and how part shape and connections between parts affects that.

Fortunately, you're talking about tolerances, and that's a lot more about materials and process, than design. Certainly some product shapes are not conducive to certain materials and processes, but since strength and durability are relative non-issues for a razor when talking about steels, product design isn't going to be very relevant. I'll chat with him about the inherent impact on tolerances from materials and process to see what he has to say.

 

[Scaramouche]

Actually, sintering is the final stage of the manufacturing process of metal injection molding, where the liquid paste of metallic powder is heated just below the melting temperature to form a solid mass. There are advantages and disadvantages to the MIM manufacturing technique, but one advantage is the ability to form small, precision parts with a minimum of finishing.

 

[KQY61]

Hi,

Well, I am an engineer and make all sorts of things, and my dad owned a machine shop. So, I started out on the production end before moving to the design end. There really are too many technical facets to go into, I think. But, that said, machining is the best method, which is cutting away what you don't want from a chunk to wind up with what you do want. That does take more time and costs more. The other methods are ways of making the shapes you want faster and at a lower cost.

Then, I have to point out that there are dozens of stainless steels out there. Not all of them are non-rusting. It depends on the amount of chromium in the alloy. There only has to be a small amount of chromium present to call it stainless. The greater the chromium, the less likely it will be to rust, and the harder it is to work.

Personally, I am not interested in a razor made from 316 alloy (which seems to be the most common) or sintered (any alloy, I don't much care for that process). I would consider a machined 303, but would prefer 304 (which is not a shiny stainless). As far as I know, no one makes a 304 alloy razor. But, I am making a copy of my Fasan Double Slant out of 304 just because I want one (and I am not getting into making more than one because this has already been more work than it is worth).

As far as tolerances go, any alloy or method can be very close. The closer, the more costly, mainly from culling out a greater number of rejects. The reject rate can be lowered by adding production steps with their associated costs. Most production tries to minimize costs, of course.

Stan

 

[Ender78]

I remember reading about a casting method that involved one use only molds where the molds are filled with what ever needs to be cast then when the stuff is hardened and cooled the molds are either broken or washed away. Would such a thing be doable with steel or brass? The reason I am asking is because someone said that steel and brass have really high melting points and can wear out a mold fast which makes the whole process expensive.

 

[JohnG10]

Personally, I'm not sure the webers actually have a manufacturing tolerance problem that sometimes results in wavy blades. In many cases, the user describing the problem was using blades that had glue/wax dots holding them onto the paper wrappers. The build up from that glue/wax may be what resulted in the issues the user observed. I use mine glue dots down and have no problems

In a couple of cases, the user mentioned that the guide bar appeared to have a slightly larger blade gap at the corners. This could be due to hand polishing/buffing. However, in those couple of cases, the users also said their top cap was perfectly straight, and the blade was not wavy.

However, since we are discussing manufacturing methods ...
I suspect the MIM/sintered/cast razors ALL get "machined" after being taken out of the mold --- to clean up any slag from the mold lines, and polish up (ie grind smoother) the surfaces. So does it matter if the WHOLE shape is formed by machining or just the final .5 mm of the thickness ? I don't think it does if you are only concerned about tolerances in the final product.

My opinion is that any powdered or liquid metal (MIM/sintered/cast) is not quite as resistant to shattering as a forged part because the hammering of the forging aligns the crystalline structure of the metal slightly. But the question is: if MIM/sintered/cast is strong enough to prevent the teeth from bending or the screw from snapping when you drop the razor on a tile floor - then what advantages does using forged metal and machining the whole shape add to a razor ?

 

[KQY61]

Hi,

Some alloys are too hard to do anything but start with a chunk and cut away what you don't want to get what you do want....

Stan

 

[shawnsel]

Part of the reason I asked this question (in addition to just genuine curiosity) is to answer:

Should I keep the manufacturing technique information that I've already collected in my, "Buyer's Guide for Currently-Manufactured DE (Safety) Razors, Ranked by User-Polled Aggressiveness" ... or is this information either irrelevant or misleading?

Thoughts?

But please also continue to answer the core questions of if/how the manufacturing technique plays into the overall quality of a razor....