Metal Injection Molding - MIM - Why The General Dislike?

TheTinMan said:
In my non-technical opinion, there is no fundamental problem with the metal injection molding process. It is cost effective. It works when executed correctly and used for parts that aren't stressed more than MIM can handle.
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This.

I had a catastrophic failure of a Para pistol when the extractor broke. Para engineers came up with a brilliant idea for an extractor, the 4-piece "Power Extractor," then some numbnuts (bean counter, I assume) decided to make it of MIM, turning a great idea into a negative.
 
Have to weigh in on this.
Presently, I have 36 S&W revolvers with an age span of about 70 years. Newest ones are MIM ones without IL. All of these are fired regularly, some a lot, some less.
In 40+ years of shooting S&W revolvers, I have experienced exactly one catastrophic parts failure. Guess what? It was a FORGED part that broke, not a MIM one.
The bolt on my Model 60 (purchased new in the early 1970s) broke. Locked the gun up tight as a tick:
broke.jpg

Luckily, this breakdown didn't happen during some social encounter in the mountains of southern Arizona (my old stomping grounds).
The revolvers I shoot the most have had their actions smoothed and tuned.
My experience is that the MIM parts are made so smoothly that little, if any, additional polishing is ever required. Tolerances are closer, as a rule, giving a more solid feel to the weapon, especially when opening and closing the cylinder.

...my $0.03, YMMV
 
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MIM parts are fine. I've never had, nor heard firsthand, of one single issue.

I have guns with plastic (or whatever they want call it) parts. I did have a plastic part break on a new Ruger. Even then, they fixed it immediatly and for free. So I don't have an issue with those either.
 
This thread subject should be made into a sticky and locked like the ILS thread.:banghead:

Sent from my DROID RAZR MAXX using Tapatalk 2
 
Nice to see someone else in my neck of the woods, I spend a lot of time in roanoke.
As for the MIM parts I have never had any problem with my modern revolvers.
I do prefer the old ones but for mostly aesthetic reasons.
 
David Sinko said:
So why didn't S&W just rivet MIM firing pins into MIM hammers? Why the complete transition to frame mounted firing pins across the entire revolver lineup?

Dave Sinko
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I think the answer is that the hammer mounted firing pins won't pass the drop tests some states, CA to be sure, require. That seems like a good idea so that they can continue selling their guns. Don
 
Is the hammer block not supposed to prevent the revolver from firing when dropped? I have heard that it is the length of the fame mounted firing pin that caused some revolvers to fail the CA drop test. When they shortened the frame mounted firing pin to compensate for this, the result was problematic ignition in certain revolvers, such as the 625. Some shooters will correct this with aftermarket extended firing pins. This would mean that many shooters now have revolvers that are no longer compliant per S&W's original intentions.

And is the frame mounted firing pin MIM or forged?

Dave Sinko
 
" I recall my days of youth with metal parts of toys failing and seeing the crystalline composition inside and I can't shake that image when I think of MIM."


Yes, but, the toys of which you speak were of CAST construction....and probably cheap "pot metal" at that....NOT M.I.M. That is a very different process.

Yes, voids can occur with MIM, but actually that is quite rare.

I do NOT bring this up to criticize anyone. Everyone is entitled to his/ her perceptions, likes and dislikes - and no one is "wrong" for having them.

I just wanted to try to dispel any associations people may have with MIM being equivalent to "cast". It most definitely isn't - it is a far superior process.
 
Well I'm old so most people would think I hate MIM parts and I don't as long as they are the right parts and in the revolver for the right reasons. If they are there where they shouldn't be for just most cost cutting purposes then I don't want them.

Like others have said I hate the IL because it was never needed and a complete surrender by S&W to the Government.
 
MIM is currently used mostly as a cost cutting measure that should have no effect on performance. True or not, it is here to stay. Now, should I avoid any new pistol just because of MIM parts? Guess I can't because there are some nice new models I want to own. I would pesonally perfer that all pistol parts were made of forging, but that's not going to happen. Sometimes you be be able to replace the MIM parts out with forged parts. But MIM will not go away, that's for sure.
 
SweetMK said:
The firing pin should be bar stock, which would be far cheaper than MIM or forged.

Those 2 processes are for "shaped" parts like a trigger.

IMHO
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Frame mounted firing pins are Ti and are WAAAAAAY better than hammer mounted when it comes to getting trigger pull down, they can go lower.

I like well done MIM, S&W does it right. It only take 5 minutes to do a trigger job as far as polishing goes, no more cutting new sears to length etc. S&W MIM is just wicked evil hard.

From an economic standpoint it may be cheaper to produce the physical part, but the initial tooling costs are really high.
 
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The main problem with MIM is the name.

If MIM was called "Cold Forged Injected Colour Case Hardened Alloy with Big Hammers" I really think it would have been more accepted by Smith and Wesson purists.

:p

From my own experience, my MIM 686 has been sublime. I also like the dirty look to it as well.

To be quite frank, if it wasn't for the internet I would never have heard of MIM..or penguin porn for that matter.
 
As suggested above, it's mostly just a question of perception and a concern over potentially diminished quality. MIM parts can break (though sometimes only if you force them to), and the broken surface looks a little like fine-grain pot metal. Not an encouraging sight.

I have never had a problem with a MIM part and can attest that the actions on my guns that have them are among the smoothest have experienced. If I didn't know the phrase or have to look at their rather drab appearance, I would not have any negative judgment on them at all.

But despite my approval, I have to confess I would rather have precision milled carbon steel or stainless parts in the action. If it was good enough for grandpan's guns, it's good enough for me.

Don't much care for polycarbonate frames, either, but I know most of them work out just fine.
 
Most guys equate the differences of MIM vs. forged to the automoblie industry...back in the hot rod days of the 60's and early 70's the performance cars sported a forged steel crankshaft instead of the usual cast iron crank found in the stock engines. Since forged car parts are more valuble and cost more it must be that a forged gun part has to beat a MIM one {makes sense to most guys.} Both methods have their good and bad. I have seen plenty of cracked and wrung off forged steel crankshafts in my 16 year previous career as an automotive machinist so forged steel is not a cure all. Since forged parts are hot stamped metal they do have somewhat of an "alignment" of the molecules and kind of take on a grain all going the same direction. In many cases that gives the part the strength it needs to last. In example, connecting rods in engines have been forged steel for a very long time, even in stock non-performance type engines. MIM on the other hand is very fine atomized metal "powder" that is heated and pressed into shape. This has several advantages...the crystalline structure of the molecules dampen and cancel out vibration and its associated fatigue so the service life can be much longer. It is easier to MIM form much harder alloys than it is to forge and then machine so you can get a much longer wearing part. How long do you want it to wear??? Just add some tungsten carbide dust. I think alot of guys see a broken MIM part at some point and note that the appearance looks like a very clean sudden break, as if the part just let go and didn't even try to hang on; as opposed to a forging that often cracks in a small area and continues to work for a while until it finally gives in.
 
MIM parts don't have the tensile strength of machined steel parts.
 
Nothing wrong with MIM parts other than the looks. If they could just make them look as good as the forged parts with their beautiful case hardened colors.
 
David Sinko said:
So why didn't S&W just rivet MIM firing pins into MIM hammers? Why the complete transition to frame mounted firing pins across the entire revolver lineup?
Click to expand...

DonD said:
I think the answer is that the hammer mounted firing pins won't pass the drop tests some states, CA to be sure, require. That seems like a good idea so that they can continue selling their guns. Don
Click to expand...

My take on the reason frame mounted firing pins (FMFPs) were used rather than hammer-noses were that FMFPs were already used for the rimfire guns - much simpler to use the same parts across the entire line of products* (the hammer noses were different shapes between J, K, L, and N-frames).

I believe it's easier to put a firing pin into a frame than it is to put one into a hammer, and then have to make sure the tolerances are such to allow that hammer assembly to be used in a frame.

I also believe that having a FMFP also reduces the likelihood that a firing pin hole could get elongated or misshaped by repeated cycles of the action.

*The MIM K- and L-frame hammers are also the same part. I *think* the MIM N- and Z-frame (Governor) hammers are the same part (I know for sure the hand is the same between the N- and Z-frame). The K/L/N sears and stirrups were and are all the same part; the K/L/N trigger rebound slides and trigger assemblies were all the same, along with their springs, the mainsprings, etc. So having similar parts across the line helps keep costs down.
 
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Yes S+W started using MIM parts to cut the cost down...... Yea for them. They sure as hell don't pass the saving on to us. Let's face it forged parts are better. You can fool yourself into thinking there the same or better but there not. If they are the same or better why don't they use them in there more expensive P.C. guns?
 
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