MIM Parts Question.

G

Garycw

New member
Maybe a dumb question but what are MIM parts ? Molded? Cast metal? And why don't you want them??
Just bought a Sig 1911 and wondering if there's alot of those and if I should even be concerned about them?
 
Who doesn't want them? If you have your heart set on non MIM parts, start waking, You can't fly { even a F-35 }, drive a car, travel on a train, use a snowmobile, ATV, motorcycle or even watch a NASCAR race. As has been discussed, the use of MIM parts is universal and a non issue.:)
 
The way MIM works is in a nutshell as follows (correct me if I'm wrong)-

A mixture of roughly 60% powdered metal and 40% wax/plastic are mixed togethr and shot into a mold, removed, put through some hardening processes to include cooking the hell out of it to achieve a solid density of 96%-99% (according to Wikipedia). http://en.m.wikipedia.org/wiki/Metal_injection_molding

What I take from that is MIM can be almost as strong as forged or machined but not quite. I have no problem with a manufacturer using MIM for a part that isn't under significant stress to get their product to me for a better price. I don't think the hammer on a 1911 qualifies as a part not under significant stress. Correct me if I'm wrong.
 
I have built engines that have had MIM parts, specifically rods. Someone can correct me if I am wrong but a MIM rod at 7k RPM running 25 PSI boost from a turbo is under more pressure than any gun part I know. Having said that, just like any other manufacturing process I am sure there is a right way and a wrong way to do it and everything in between. So In my humble opinion there is nothing wrong with the MIM process itself.
 
mim

I believe the powdered rods for engines you are talking about use a diffrent process. Powered metal is forged in a die under insane pressure, enough to basically make it a solid part. The result is a part that has the density of a forged rod but none of the internal stress points you can get by beating a solid block into shape. Be it as it may I still think that most of the mim parts in a gun have the needed strength. The strength required in a high performance connecting rod makes the stress inside a firearm look like kittens playing tug of war
 
I kept hearing about guns with minimum or very few MIM parts being more desirable. Also many people with plans of replacing MIN parts as much as possible. It sounds like if its a part that's not under extreme , Very extreme conditions they're fine. I don't believe I'd want a barrel or firing pin made from it.
 
I believe the powdered rods for engines you are talking about use a diffrent process. Powered metal is forged in a die under insane pressure, enough to basically make it a solid part.
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I am sure you are correct, which makes sense as manufactures will develop a part to handle the stresses required and not be too much overkill. Mainly the point I was trying to make is that it is not the MIM process itself but individual manufactures specifications. Also as far as I know a MIM parts hardness is uniform throughout, which is a plus to me.
 
Thats good point. The process they use is good enough for the application. To make them stronger then needed would negate the cost savings.
I think mim parts are a lot like kevlar radial tires and polymer guns. People are used to something being the standard for strength because it is a proven accepted material like forged or machined from billet steel. It takes time for people to get comfortable with a new material or process.
 
It takes time for people to get comfortable with a new material or process.
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Very good point. And I just want to add I don't think there is anything wrong with case hardening, in fact I have a soft spot for the classics and the look of case hardening has a definite elegance to it. But, things change, and not always for the worse no matter how much we hate change.
 
The way MIM works is in a nutshell as follows (correct me if I'm wrong)-

A mixture of roughly 60% powdered metal and 40% wax/plastic are mixed togethr and shot into a mold, removed, put through some hardening processes to include cooking the hell out of it to achieve a solid density of 96%-99% (according to Wikipedia). http://en.m.wikipedia.org/wiki/Metal_injection_molding

What I take from that is MIM can be almost as strong as forged or machined but not quite. I have no problem with a manufacturer using MIM for a part that isn't under significant stress to get their product to me for a better price. I don't think the hammer on a 1911 qualifies as a part not under significant stress. Correct me if I'm wrong.
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Compared to other things, the hammer on a 1911 doesn't see significant stress. The connecting rods of a new Ford 5.0L engine are powdered metal (same process everyone is referring to as MIM). They see more stress than I ever plan on putting my 1911 through. FWIW, Ford has been using the process since the early 1990's, so it isn't exactly new...

I'm wondering what you are referring to when you say machined? I'm guessing billet.. which is better than forged, which is better than powdered metal. The MIM process was developed to save time and make a product that is still adequate for probably 90 percent of the applications that used to take a forged piece. There is nothing wrong with overkill, but it always comes with a price.
 
Oddly enough, many of the folks who go into ecstasy over the old "forged" hammer and trigger of the pre-MIM S&Ws might not realize that for decades those parts have not been forged; they have been blanked out of steel plate.

Jim
 
Originally posted by saleen322:

It stands for Metal injection molding. The advantage is you can more cheaply make intricate parts that requires little machining.
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Actually the investment in the machinery and the cost of materials to make MIM parts makes them much more expensive than similar forged or stamped parts. But....because every part, even the smallest most intricate are exactly the same, with precise tolerances, they fit, every time, and do not need to be hand fit. The monies saved in production are not the cost of the parts, but the cost of assembly. So whenever you hear someone talk about "cheap MIM parts" it's an indication they generally are only repeating what they have heard on the interweb. This process also means that those parts can be easily changed without hand fitting and the gunsmithing that used to be standard procedure. This is why most folks despise MIM, not because they are inferior, but because it was the demise of handfit parts. Reliability, function and accuracy have never been shown to have changed in the least for the worse since their introduction. MIM parts are no more prone to breakage than their forged/stamped counterparts. This is the reason major manufacturers like S&W, Ruger and Colt use them.
 
If you wish to avoid MIM in your pistol buy a Dan Wesson, Les Baer, Ed Brown, or
You can get aftermarket Lone Wolf cast steel extractors to replace the MIM one in ~2008 and newer Glocks, and a Lightning Strike steel striker to replace the alleged MIM striker in recent Glocks.
You are not totally stuck with MIM in a pistol, but avoiding or replacing will cost.
 
The monies saved in production are not the cost of the parts, but the cost of assembly. So whenever you hear someone talk about "cheap MIM parts" it's an indication they generally are only repeating what they have heard on the interweb.
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Chip McCormick used to sell a selection of high-end 1911 hammers, made from exotic alloys and EDM machined. They were beautiful, and cost $50-$75 each, fifteen years ago. He later replaced his entire line with a single MIM hammer that cost $15. I'd call a $15 hammer "cheap", compared to a $50 hammer. We are talking parts, so there's no assembly. I suspect CMC made more money selling $15 hammers than they did selling $50 hammers, so everyone should be happy?
 
Both sides have their points and the weak link in the whole subject is the makers/subcontractors and their combination of QC and pushing the envelope too far in the name of cheap.

When done well, MIM parts are marvelous.

They *can* break and supposedly more frequently than forged/machined. I've seen enough forged, machined, cast, stamped and filed-to-shape metal parts break that I'm not even close to suspecting that MIM fails more frequently than any other variety of gun part.

I'm okay with them being use on generally lump-shaped parts but not long skinny rod-type things that take anything other than longitudinal stresses. So nail-type firing pins, okay, hammers okay, slide stops are pushing it in most shapes, and L-type firing pins and M1 Garand extractors I think I'd rather have either forged or cast and "bumped" but I don't think anyone makes them that way. Those last two are the best examples I have personally seen of conventional machined stuff breaking, so it's really probably more of an inherently troublesome design.

AR extractors are another I have no problem being MIM.

BUT, and this is a HUGE issue for me, the makers/subcontractors and gun assemblers absolutely MUST properly inspect, gage, and preferably finish-machine the parts! When a mid-priced (high priced for me and my circle) Kimber 1911 won't drop the magazine when the release is pushed all the way in because the shape is WRONG on the side opposite the magazine's notch, that's just plain shoddy and stupid.

Imagine looking down into the magwell from the top of the pistol at slide-lock. There's a nice curve at the front of the mag well to match the front curve of the magazine itself. Push the mag release in from left to right and the curve hidden under the thumb-button is not wide enough, to metal intrudes into the magwell. That was not really what I expected from an $1,100+ "carry" pistol.

Can't remember what other MIM parts on it had problems, but none of them were from breakage.
 
Chip McCormick used to sell a selection of high-end 1911 hammers, made from exotic alloys and EDM machined. They were beautiful, and cost $50-$75 each, fifteen years ago. He later replaced his entire line with a single MIM hammer that cost $15. I'd call a $15 hammer "cheap", compared to a $50 hammer. We are talking parts, so there's no assembly. I suspect CMC made more money selling $15 hammers than they did selling $50 hammers, so everyone should be happy?
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By "assembly" he means finish work/machining.. I.E. Man Hours. The less machine work, the less man hours go into it, the cheaper it is. An added bonus from less machine work is less wear and tear on tool heads, CNC tool heads are absolutely not cheap.

If you were a manufacturing company making a part... say it takes a CNC machine 10 minutes to machine a forging into your finished part. You are paying an operator an hour's wages to make six parts, essentially.. now lets say a new raw product comes in, that maybe costs slightly more as raw material but the CNC machine can finish it in 2 minutes.. so now you pay the same operator an hour's wages to make 30 parts instead of 6..

The economy's downside of it is that if your manufacturing goal is to make about a hundred of these an hour, you can now do so with about three or four employees rather than seventeen, so overall your profit goes up, your quality doesn't really suffer, but you employ fewer people. To some this makes you a bad guy. Realistically though, it is how life works when you use technology.. eventually it makes more sense to use more technology and less people. If a modern F-150 was made the same way as a Model T, there would be a lot more jobs.. but nobody would have cars because nobody could possibly afford them.


And yes to the above statement.. a poorly manufactured part is still going to be poor, regardless of what process it starts with.


I
believe the powdered rods for engines you are talking about use a diffrent process. Powered metal is forged in a die under insane pressure, enough to basically make it a solid part. The result is a part that has the density of a forged rod but none of the internal stress points you can get by beating a solid block into shape. Be it as it may I still think that most of the mim parts in a gun have the needed strength. The strength required in a high performance connecting rod makes the stress inside a firearm look like kittens playing tug of war
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What I gathered of the MIM process is nearly the same, the main difference being how the powdered metal gets into the die, but it is a similar process with similar results.
 
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Actually the investment in the machinery and the cost of materials to make MIM parts makes them much more expensive than similar forged or stamped parts.
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Yes, but also, manufacturers don't have to invest in the MIM equipment. Just buy the parts from somebody that has. This from my rarlier posted link.
Taurus manufactures MIM part for more than 100 other companies, many of them other gun companies!
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