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Concerning the MIM part controversy, do these parts tend to hold and then later weep lubricant due to porosity? Or are MIM parts so dense that they wont absorb lubricant? Are there any parts in a 1911 that would cause a concern due to over or under lubrication?
 

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There is so much BS and misinformation about MIM parts out there. For one, MIM is NOT "powdered metal" pressed together. It's raw molten steel, injected into a mold under pressure and high heat. The mold for the part is dimensionally correct but slightly oversized. Once the part cools it contracts to the correct dimensions, resulting in a part with better density than cast but cheaper than forged steel parts. The problem with MIM parts breaking is not the technology, but the quality control allowing voids and porosity to form during the process. If done right MIM is an effective substitute for casting. If done poorly it's pure junk.

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D. Kamm
USGI M1911/M1911A1 Pistols Website
http://usgi1911.tripod.com

[This message has been edited by dsk (edited 11-23-2001).]
 

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DSK my friend

once the part comes out of the mold as a green part it is than baked to cook out the binders that held it together. Yes it does shrink a pre determined amount, I think a Bareta transfer bar shrinks almost 1/2"
if the parts lay funny when they cook em
they distort. the 98% # thrown around is the density of the finished part.

With vacume, centrifuge, and some other advanced casting, I do not think porocity is a major problem
geo ><>
 

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Thanks, I knew there was part shrinkage somewhere in the manufacturing process but I wasn't sure where.


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D. Kamm
USGI M1911/M1911A1 Pistols Website
http://usgi1911.tripod.com
 

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I got weary of the BS and tall tales about this as well, and spent the afternoon researching MIM. There is a lot of info out there. There are two websites that I found http://www.injectamax.com and http://www.amt-mat.com that explain this process quite clearly, and de-mystifed this whole thing for me. So far, I've learned...

MIM is a means to an end. The end being more accurate and less expensive castings.It's a different and better mousetrap. You still end up with a piece of metal at the end, which is the same or better as investment casting or forging. Ya get a hunk of quality metal of whatever shape or characteristics you desire without post machining or trial and error fitting.

After reading up on this, I must say that I am impressed with the whole process. My impression that you get toy car type metal was completely wrong. Some relatively exotic mixtures of alloys can be obtained with this method. And the densities, voids, impurities and hardness can be better controlled with this method. It kind of makes the lost wax method look like cave man technology.

I would imagine the reluctance to these parts would be because it's new technology. I recall that there was a time in the mid 80's when some people would moan because all automobiles became fuel-injected. Now you can buy a new set of fuel injectors and replace them in your driveway quicker than you can rebuild a Holley carb. And electronic fuel injectors are much smoother and meet tighter emission requirements.

I would imagine that in a while, this MIM thing will be no big deal. Until I hear solid proof of some sort of chronic failures due to this like something approaching the lines of the KB! Glock or Taurus frame controversy will I become concerned about a MIM part in a firearm. Are there any current controversies concerning a chronic problem with a MIM part from any manufacturer? I personally don't care much for a polymer framed pistol, even though they have been proven to be quite reliable, so I sure as heck should'nt be concerned about a METAL part in a METAL firearm.

Enough ranting for now....
 

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Originally posted by Paveway:
I got weary of the BS and tall tales about this as well, and spent the afternoon researching MIM. There is a lot of info out there. There are two websites that I found http://www.injectamax.com and http://www.amt-mat.com that explain this process quite clearly, and de-mystifed this whole thing for me. So far, I've learned...
Bravo Paveway! I have been trying to fight this BS everytime it comes up. I have seen no statistical evidence of increased failure based on current usage of MIM parts, or castings, or alloys, or polymers.

I have started to call this crap that people spew "Forged Chunk of Metal Syndrome". Basically everything that is done now-a-days is because new technology has allowed advances in metalurgy and manufacturing processes. Its damn expensive to be forging little parts out of chunks of metal, especially when you can get a comperable product that meets your quality needs at a much cheaper overall cost.

Yeah, you can still get a completely forged steel parts 1911. But it will cost you $1500-$2000.

Plus, my argument has been all along, if MIM or Cast, or alloys, or polymers are inherently more prone to failure in the ways that they are used in guns, then the companies that use them are opening themselves up to *LAWSUITS*. There would be wrongful death, injury, and product liability litigation all over the place. That is just not happening here.
 

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While I have no problem with the concept of MIM (I ain't smart/educated enough) or "properly" manufactured MIM parts, my experience has been that, for whatever reason, I can't get nearly as nice trigger job tuning MIM parts. My techniques are evolving over time (28 years) with the wealth of knowledge from Kuhnhausen, George Smith, Jack Weigand, etc., and the newer tools available. I've used the Tom Wilson jigs for years. I now also use the Ron Power jig in conjunction with the Wilson jig to do different parts of the process. All this to say that my personal opinion
is that they may be perfectly fine for the average shooter who doesn't want the ne plus ultra trigger job, but not for a really nice job. Too many mould lines. Can't polish for beans! I get nice 1-3/4 to 4 # pulls with Wilson, C&S, Brown, original S70 Colt, but I won't try less than 5# with MIM just because it doesn't have that "feel."
George still hasn't explained the "goo" running out of the MIM parts that he mentioned on another post. George?
 

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I too tire of the 'Great MIM Controversy'! I have two Kimber SS 5" guns that have consumed more rounds than I like to think about loading. They came with pulls between 4 and 4.5 lbs, and that ain't never changed. Nothing, and I repeat NOTHING has ever broken or changed/worn. When I see it, I'll believe it.

I do have a Colt GM that has never had a good trigger, and some of the best in the business have tried, at my considerable expense. I carry and use it, but the trigger will always suck. I also would not posess, carry, or use any 1911 with a 1.5 lb trigger; at least not for any sort of social work. I carry one of the Kimbers every day, and 4.5 is plenty light when things get tense.

As far as porosity, I've seen none of that. My Kimbers have to be lubed as often as any weapon, and when the parts are dry, they're dry. Anybody who carries for a living won't carry a 'POS'.
 

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.... I also would not posess, carry, or use any 1911 with a 1.5 lb trigger; at least not for any sort of social work...
Who said anything about social work?
My personal carry guns are set up at anywhere from 4 to 6 pounds depending on the feel of the individual trigger job. Done right, 6 # feels like much less.
I have done much lighter competition only trigger jobs for myself and very experienced shooters, but only for competition. Anyway, you're right. If MIM serves your needs & you're happy with it, that is just fine. No argument from me.
 

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What most people do not realize is that investment castings are in most cases more porous then a MIM part. Investment casting is taking molton metal and pouring it into a mold. The only difference between investment casting and sand casting is that more complex shapes can be accomplished with an wax or styrofoam part that is then sprayed with a ceramic coating and the molton metal vaporizes the styrofoam. There is no pressurization of the metal like in MIM and that is why you actually are able to get a more dense part with MIM. No yes there is shrinkage with MIM, but there is also shrinkage with investment castings of around 1%. I wish people would get off of the "MIM is crap" bandwagon.

Mark
 
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