MIM vs. Machined

2

2003flht

New member
I've seen alot of bashing about MIM parts. I was wondering why people hate MIM so much. Is it a cosmetic thing? Durability? Mis-conception?

Being in the aerospace industry, and being a machinist/tool designer/engineer, I've seen technology advance through my years. I was amazed when I saw what resembled a inkjet printer produce a plastic part from a CAD model, a tank of yellow liquid goo that when a laser beam was applied, made highly detailed plastic parts. Then I was involved in SLS (selective laser sintering). I was amazed what could be done with powdered metal.

Now, we have metal injection molding... I have seen parts made this way that conventional machining could never do, or it would be so cost prohibitive. MIM is an advanced technology that keeps getting better as time goes. These MIM parts are used in aeroplanes and advanced fighter jets. Why wouldnt they work in a firearm?

I mean, if they use MIM parts in jet engines at 30,000 feet going Mach 2, what makes people think MIM parts are inferior for a firearm?



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I'm not aware of any evidence that MIM handgun parts fail at a higher rate than forged or cast analogs. Smith & Wesson switched over to MIM internals nearly two decades ago and I've seen nothing published to suggest that their guns perform any less reliably now than did previous non-MIM models. There are, however, at least a few articles out there stating that MIM parts perform more consistently, and with fewer defects, than their forged and cast analogues.

But, don't think for a minute that the lack of evidence of inferiority is going to stop those who detest any changes in handgun (and, especially, S & W revolver) manufacturing processes. A lot of the MIM-haters are part of the same group who rant on this forum and others about Smith's internal lock, its changeover in 1982 from pinned to crush-fitted barrels, its ceasing to recess the cylinders on its magnum revolvers in 1982, its decision to produce mostly stainless guns, its use of two-piece barrels on some models, its changeover from wooden to rubber grips, etc. In other words, for some, nothing beats the good old days and MIM parts are simply another sign that the world, and in particular, the Smith & Wesson revolver, are going to hell in a handbasket.:rolleyes:
 
In my opinion, people read "Metal Injection Molding", then associate 'molding' with the casting process

Through exposure to casting as only a means for ease of production, casting already had a bad rep. I make the 'cast piston in the family sedan's engine analogy' a lot. But people think MIM=casting casting=crap

Personally I don't want production methods to stagnate in eternal 'Industrial Revolution' mode but that's just me
 
I cannot improve on what Stevieboy said above, so +1.

I have two S&W revolvers, both with torqued-in barrels, firing pins separate from hammers, internal locks and MIM parts. All these manufacturing changes are anathema to someone on this website (and others). Both of my revolvers have given me flawless service through thousands of rounds. One, a 637 snubby, recently decided on its own to stop striking primers in midload (one fired with good contact, four not). I contacted S&W, who sent me a shipping label. About a month later, I got my revolving pistol back. According to the S&W rep, the firing pin bushing had failed, which they fixed by replacing the entire frame. This meant a new serial number, which brought federal law into the equation, but other than the need to have the revolver sent to my gun store and paying that fee (and getting fingerprinted and background checked yet again), none of this cost me a dime.

I believe the firing pin bushing is made of steel. The 637's frame is made of an aluminum alloy. As a retired Naval Aviator with considerable experience in aircraft maintainance, I know what can happen with such mixed marriages. And this malfunction had nothing whatever to do with torqued barrels, MIM parts and all those other horror stories.

When S&W began screwing the barrel into the frame in 1980, cracked frames on Airweight snubbies quickly cropped up, probably from overtorque. When the internal lock came out (?? also 1980 ??), there were failures to fire caused by internal lock malfunction. I believe that almost three decades is long enough for S&W to have fixed these problems. However, these glitches will be internet fodder long after I am gone.

Hey guys, both times I was involved with introducing a new aircraft into the fleet, I lost friends. Not to mention three cruises flying off carriers in the Gulf of Tonkin against North Vietnam, where I lost some more. That's big. Hateful holes in revolver frames and how hammers are fabricated, these are not big.

Cordially, Jack
 
MIM isn't a cast part

MIM stands for Metal Injection Moulded.
In a cast part the metal would be poured and then sets up by itself.
In Injection moulding the molten metal is pressed into a mold at high pressure and then it sets inside the mold under pressure until it is of the strength specified to produce the given part. The grain structure is also controlled by the amount of pressure, usually in 10's of ton's per Sq. In. The pressures cause chrystilline structure alignment of the atoms.

It is the same process as most any plastic injection moulded part.

Injection moulded metal parts are substantially stronger than cast parts and the forged parts also because of the cellular alignments

I work in the injection moulding business and understand the process.

The old parts replaced by MIM were forged and never cast, the forging made for very strong parts but brittleness could also be an issue if the process wasn't closely watched. What the purists love more than anything about the forged parts is they were also heat treated (Case hardened) and each part had a look that couldn't be duplicated. You can see the case hardening colorations on the trigger and hammer.
The MIM parts are a single steel colour and have no "personality"
 
I don't hate MIM; I just hate the way it looks and feels. Specifically, the S&W MIM trigger--it feels like a toddler toy (flat face, rounded edges) and the back of the trigger is hollowed out, a reminder of the process used to make it. The old forged triggers look and feel better to me.

On the other hand, I like the MIM hammers because I think they have less mass, and so have a shorter lock-time in single-action. And that their parts are easily swappable--I just replaced the double-action sear on my 629-5, and it was easy. Forged hammer assemblies would've required a hammer and a punch.
 
I have had two Kimber 1911 pistols. Both pistols failed with less than 3,00 rounds through them.

Parts that failed: the slide stop on one and the ejector on the other. Both these parts are MIM parts.

Go figure...
 
I can't say for sure, but parts of the Ruger LCR sure look a lot like MIM. Some gun makers began using MIM before they fully understood the process and before the MIM people understood the needs of the gun makers. The result was poor quality MIM work and some parts failed. Berating S&W for using MIM is a bit like condemning a Glock because some plastic shotgun stocks broke back in the 1950's.

I really hate to tell the "forged or nothing" gang that S&W hammers and triggers have not been hot forged for decades. They were blanked out of steel plate, then cold forged and machined to final shape.

The major advantage of MIM is not only that it is cheap or that it produces a finished part, it is that MIM makes possible the production of complex shapes that could not be produced any other way or could be produced another way only at high cost. The MIM trigger in an S&W revolver is more complex than the old one but that complexity makes it possible to eliminate three drilled holes, two small pins, and the hand work to install the pins. The MIM hammer makes it possible to eliminate two small pins, three drilled holes and more tedious assembly. And the customer cannot tell the difference.

Jim
 
Magi

I had a Colt Delta Elite that the FRAME failed on....

I had a 442 Smith that the FRAME failed...

Go figure.... No MIM part........ :confused:

My Kimber been taken a battering alot longer than either of those. Of course, my S&W 1086 has been too....


I guess some are afraid of change. Sometimes its good, other times definetly not. I still dont see why MIM is so bad. As for failure of MIM, I have still yet to see statistically fail more than cast or forged.
 
As for failure of MIM, I have still yet to see statistically fail more than cast or forged.
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I personally don't have the stats nor am I claiming fact on which is better. What I do know after separating the wheat from the chaff on my readings, it always seems MIM parts have sprouted up when failures are present far more often than forged parts. I can't help but at least raise and eyebrow.

Perfect example: How many members have you seen cranking up a thread griping about a forged part failing on them? Maybe people like to jump on a bandwagon on controversy. Who knows...
 
Jim Keenan said:
And the customer cannot tell the difference.
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And the average customer cannot tell the difference, you mean. I'd like to think that I can tell, but then my collection is dominated by S&W revolvers, some with some with all-forged parts and some with a mix of MIM and forged parts (none with all-MIM, however, as I've swapped for forged triggers on all of my recent-generation guns).
 
it always seems MIM parts have sprouted up when failures are present far more often than forged parts.
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Since I come from a tooling machine background I will take a guess. I suspect MIM parts are more dependent on the process being done correctly. You can just buy very good tool steel and machine parts, but MIM process (IMO) allows for less error. However, if done correctly the MIM can save time and money over machining parts.

Having said that my background was with forged parts and not MIM.
 
This meant a new serial number, which brought federal law into the equation, but other than the need to have the revolver sent to my gun store and paying that fee (and getting fingerprinted and background checked yet again), none of this cost me a dime.
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A bit OT, but according to Federal law (unless things have changed, i.e. new regulations/interpretations), a manufacturer can return a firearm to you regardless of whether or not the serial number has changed, if you returned the original firearm to them for repair or replacement.

If something has changed, please update me.
 
Seems ironic that a lot of folks who decry MIM praise cast guns from the likes of Ruger - a process that is not as accurately made or as strong. I guess some folks have issues with changes in the way things are made today versus years ago
 
Seems ironic that a lot of folks who decry MIM praise cast guns from the likes of Ruger - a process that is not as accurately made or as strong.
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I'm not a metallurgist and wouldn't know if investment casting is less accurate or weaker than MIM, but this article gave a new found respect for Ruger's investment casting:

http://en.wikipedia.org/wiki/Investment_casting

as per wiki:

The process is generally used for small castings, but has produced complete aircraft door frames, steel castings of up to 300 kg and aluminium castings of up to 30 kg. It is generally more expensive per unit than die casting or sand casting but with lower equipment cost. It can produce complicated shapes that would be difficult or impossible with die casting, yet like that process, it requires little surface finishing and only minor machining.
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The advantages of investment casting are:

* Excellent surface finish
* High dimensional accuracy
* Extremely intricate parts are castable
* Almost any metal can be cast
* No flash or parting lines

The main disadvantage is the overall cost. Some of the reasons for the high cost include specialized equipment, costly refractories and binders, many operations to make a mold, a lot of labor is needed and occasional minute defects.
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Couple of observations. Firstly, revolver shooters are by definition a more traditional group of shooters, relatively speaking. So we tend to be very apprehensive about changes, particularly manufacturing techniques. For most of us, it just doesn't get any better than a pre-war (that's WWII) S&W or Colt. You can talk until you're blue in the face about the new guns being "better" (a highly subjective word) but we ain't buyin' it. Better, for most of us, means lots and lots of hand-fitting and finishing. Not advanced manufacturing techniques designed solely for ease of manufacture which equates to less handwork.

Secondly, the name is probably what tanked MIM. Not the first "M", but the remaining "IM". That is, injection molding. From that point on it does not matter how good the process actually is. We, the traditional lot we are, will always associate "injection molding" with plastic. Which equals "cheap". And the fact of the matter is that they don't do it because it's better, they do it to save money. Add to that the internal locks, that is a whole 'nuther can of worms, and the other recent changes in the way S&W's are made and you end up with a group of disgruntled shooters. Because let's face it, if your passion is connected to the old guns, the new ones don't have much to offer. They cost more and in our eyes are much inferior to the older guns.

Thirdly, I must mention that you cannot do a proper trigger job, which involves changing sear engagement and reharden the affected parts afterwards. MIM parts cannot be hardened. That means in a hundred years you won't be able to weld up a broken hammer notch, recut it and reharden it. If replacements are not available, you have an expensive paper weight.

Right or wrong, that's the way I look at it.


A bit OT, but according to Federal law (unless things have changed, i.e. new regulations/interpretations), a manufacturer can return a firearm to you regardless of whether or not the serial number has changed, if you returned the original firearm to them for repair or replacement.
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gyvel is right, a replacement firearm can be sent directly to its new owner directly from the manufacturer. Some manufacturers insist on doing an FFL transfer but it is NOT mandated by law.
 
Gyvel -- S&W would not send the revolver directly to me. The support rep, who clearly knew what had been done to it and why, insisted that I must name an FFA to receive the handgun. And then I had to go through the whole bit -- fingerprint, background check, ten days -- to get it. As to any changes in law, dunno.

Cordially, Jack
 
Some manufacturers, Ruger does this too, may require it to be transferred through a dealer. State laws 'may' require it, particularly states and locales with registration, but federal law does not. For instance, my state does not require it but Ruger does it anyway, just because it's their policy. Cimarron, on the other hand, does not.
 
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