How can you tell?


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Old 10-06-2011, 03:40 AM   #1
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Default How can you tell?

Over the years, I have read in all kinds of posts about the "acursed" MIM parts. How they are preceived as cheap, fragile parts prone to breakage, or at the least - not to be depended upon in a life defending battle; let alone just range shooting.

And yet recently, there is a trend of stating that they (MIM) have improved to such a point as to be just as reliable as parts made from bar stock, just less expensive for the manufacturer to produce. I know not if they are or are not, but once a preception is accepted as real than you may as well save your breath.

Whatever!

If an individual wishes to change out whatever parts he/she may have in his/her 1911 with bar stock/forged pieces - HOW CAN YOU TELL WHICH ONES ARE MIM? I have/know of more than one individual who does not bother to look, but automatically changes out ALL parts with whatever parts they can find that are "hard core."

I have called/emailed more than one manufacturer of my 1911's, asking which ones are MIM, only to get a guess/maybe/could be answer.

Yes, I have been told to look for a connecting, break away point on the part to show that it was made as part of a "tree" of the same parts, but yet also told that some companies will polish away such marks.

So...how does one check/know for/of a MIM part?



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Old 10-06-2011, 09:36 AM   #2
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The cost of machining parts increases when more action is required by the machinist.

Look at small parts (slide stop, thumb safety, grip safety, extractor, ejector, and disconnector.) Those are most likely to be MIM.

As you said, MIM is getting better. I posted a thread asking members to post pictures of MIM broken parts, but did not get too many pictures (I remember a slide from a .22 1911).



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Old 10-06-2011, 12:48 PM   #3
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Yes, I have been told to look for a connecting, break away point on the part to show that it was made as part of a "tree" of the same parts, but yet also told that some companies will polish away such marks.
That is not true. A MIM part is made in a "pill" press, from powdered metal, and individually. However, small investment cast parts are usually produced by connecting many similar parts to a central "tree". Who ever told you what they did were confusing MIM parts with investment cast parts.
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Old 10-06-2011, 01:43 PM   #4
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Quote:
Originally Posted by dahermit View Post
That is not true. A MIM part is made in a "pill" press, from powdered metal, and individually. However, small investment cast parts are usually produced by connecting many similar parts to a central "tree". Who ever told you what they did were confusing MIM parts with investment cast parts.
I think your a little confused on the process. Metal injection molded parts and investment casting are both what is termed mim. Whether the metal starts as a powder and heated in a mold or heated then poured in a mold its the same thing.

The "tree"is present in both techniques of mim. The only difference is how the heat is applied. In cheaper proccesses for mim for very small parts the heat is created by pressure. In injection its created by an external furnace.

The difference in quality is purely in the composition of the metallic powder that is used in both proccesses.

Investment casting is a preferred method when intricatedetail parts like slides and frames need to be dimensionally correct in hard to get places. Pressure molds are great for small parts that only need exterior dimensions.

Early mim didnt have enough ferrous steel to be picked up by cheap magnets. Some still doesnt depending on need. Mim is great for things like slide stops where you want the stop to wear out before the notch on the slide. Which is cheaper to replace??

Mim gets a bad wrap from things like raven 22s and cheap asian ak47s.
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Old 10-06-2011, 06:17 PM   #5
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I think your a little confused on the process. Metal injection molded parts and investment casting are both what is termed mim. Whether the metal starts as a powder and heated in a mold or heated then poured in a mold its the same thing.
No, they are a different process. They do both use a mold.

http://www.pim-international.com/aboutpim/binders
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Old 10-06-2011, 09:04 PM   #6
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So basically a mim is hot metal poured into a mold not cut from bar stock? But bar stock was hot meal poured into mold to form the bar stock and somehow it is superior? Am I missing something?

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Old 10-06-2011, 10:17 PM   #7
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So basically a mim is hot metal poured into a mold not cut from bar stock? But bar stock was hot meal poured into mold to form the bar stock and somehow it is superior? Am I missing something?
MIM is cold metal powder mixed with glue squeezed into a mold at room temp. Then the part is removed from the mold and "washed" to remove the binders. The part is then sintered (heated) to fuse the metal particles into a solid piece.

bar stock was usually forged metal that may have been cold rolled or subject to some other process somewhere along the line, it was never a molded piece part. The part is machined out of the bar stock.


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