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I was just browsing "Ready to make my first 1911 purchase" and I did not want to hi-jack the thread, but the question came to me, 'how would I know an MIM part if I saw it?'.

According to some metal engineering information, MIM is a way to allow for a quality part. According to the gun/shooting forums, MIM parts are the snap, crackle and pop of pistol parts.

I have three .45 ACP's; Colt Government, Springfield Loaded and a Kimber UC II. I assume that MIM are potentially used in all manner of pistol, but the question is 'how do I know if a part is MIM' by looking, or otherwise?'.

AndyC wrote:Snap it in 2 and see if it looks crystallized

Seriously, I don't know how to tell just from its looks.

You stole my line!

Not being much of an interweb kind of guy and finding myself a bit slow on the latest acronyms, what is MIM? My guess is made in Mexico. Secondly, to push the original post a bit further down the pike, are these MIM parts a serious issue and should these parts be replaced before the weapon malfunctions when you need it most?

Some things to look for:

Parting lines and ejector marks
Stolen from another forum, so I'll quote it:

A parting line is a line that runs all the way around the part (where the mold closes). Ejector marks are (usually) little circles, all on the same ide of the part. They are left there by little punches used to force the part out of the tool. They may be disguised as counterbores around holes, at least that's how I always tried to hide them.

MIM parts also generally do not have tool marks on them, are dull, and actually sometimes look 'too' perfect.... but not all of these are always true.
Sometimes you can also see crystallization if you look closely.

Parting lines and ejector marks are normally cleaned up on high-end parts though.. so you may not be able to find them.

It's an art, being able to look at something and determine if it's MIM. I'm pretty good at it, but I'm not perfect.

03Lightningrocks wrote:Not being much of an interweb kind of guy and finding myself a bit slow on the latest acronyms, what is MIM? My guess is made in Mexico. Secondly, to push the original post a bit further down the pike, are these MIM parts a serious issue and should these parts be replaced before the weapon malfunctions when you need it most?

Metal Injection Molding.

Eg, parts made in a mold, and not cut from bar stock.

dicion wrote:

03Lightningrocks wrote:Not being much of an interweb kind of guy and finding myself a bit slow on the latest acronyms, what is MIM? My guess is made in Mexico. Secondly, to push the original post a bit further down the pike, are these MIM parts a serious issue and should these parts be replaced before the weapon malfunctions when you need it most?

Metal Injection Molding.

Eg, parts made in a mold, and not cut from bar stock.

Wow...glad I asked. I was way off. Thanks.

dicion wrote:

03Lightningrocks wrote:Not being much of an interweb kind of guy and finding myself a bit slow on the latest acronyms, what is MIM? My guess is made in Mexico. Secondly, to push the original post a bit further down the pike, are these MIM parts a serious issue and should these parts be replaced before the weapon malfunctions when you need it most?

Metal Injection Molding.

Eg, parts made in a mold, and not cut from bar stock.

I thought that MIM was more of a sintering type process, where the metal is put into a mold in powdered form and then heated until it fuses. Molding liquid metal is casting, and casting is not necessarily bad. I once bought a set of cast 1mm overbore pistons from Yoshimura for my race bike, and they performed just fine, spinning at 11,500 rpm for hundreds of miles. It's hard to imagine a tougher environment than that.

The Annoyed Man wrote:

dicion wrote:

03Lightningrocks wrote:Not being much of an interweb kind of guy and finding myself a bit slow on the latest acronyms, what is MIM? My guess is made in Mexico. Secondly, to push the original post a bit further down the pike, are these MIM parts a serious issue and should these parts be replaced before the weapon malfunctions when you need it most?

Metal Injection Molding.

Eg, parts made in a mold, and not cut from bar stock.

I thought that MIM was more of a sintering type process, where the metal is put into a mold in powdered form and then heated until it fuses. Molding liquid metal is casting, and casting is not necessarily bad. I once bought a set of cast 1mm overbore pistons from Yoshimura for my race bike, and they performed just fine, spinning at 11,500 rpm for hundreds of miles. It's hard to imagine a tougher environment than that.

According to Wikipedia:

The process involves combining fine metal powders with plastic binders which allow the metal to be injected into a mold using equipment similar to standard plastic injection molding machines. After the part is molded and before the binders are removed, the part is referred to as a 'green part'. The next step is to remove the binders with solvents and thermal processes. The resultant metal part is sintered at temperatures great enough to bind the particles but not melt the metal.

It's not exactly powdered, but its not a liquid either. it's mixed with plastic 'binders' that make it inject-able. Then it's injected into the mold, the binders are removed, and then it is sintered.

So you are correct that it is not melted together, but it is still injected into a mold sort of like a liquid. It's actually all quite fascinating to me how this stuff is made!

Ok, pistols use MIM parts, but think about this. ALL Tungsten-carbide parts are sintered parts with binders in them. So are ceramics. Proper sintering allows ample time for atomic diffusion to decrease the voids in the material to a point where they are no longer an issue. This is why the part always gets smaller after sintering.

I would much rathar have a quality MIM part which was properly sintered after formation and made with wuality raw materials than a part made of cheap mild steel billet which was hot forged and then not properly tempered.l

As for being able to tell a MIM part from a part made of bar stock, it all depends on the type and temper of the bar stock part and they type of fracture.

Just like with aluminum parts, one manufacturers "high strength" aluminum might be a 5052-H32 with a yield strength of 28ksi where anothers could be 6061-T6 with a yield of 40ksi. Everything is relative.

IAAME (I am a Materials/Mechanical Engineer)

7075-T7 wrote:Ok, pistols use MIM parts, but think about this. ALL Tungsten-carbide parts are sintered parts with binders in them. So are ceramics. Proper sintering allows ample time for atomic diffusion to decrease the voids in the material to a point where they are no longer an issue. This is why the part always gets smaller after sintering.

I would much rathar have a quality MIM part which was properly sintered after formation and made with wuality raw materials than a part made of cheap mild steel billet which was hot forged and then not properly tempered.l

As for being able to tell a MIM part from a part made of bar stock, it all depends on the type and temper of the bar stock part and they type of fracture.

Just like with aluminum parts, one manufacturers "high strength" aluminum might be a 5052-H32 with a yield strength of 28ksi where anothers could be 6061-T6 with a yield of 40ksi. Everything is relative.

IAAME (I am a Materials/Mechanical Engineer)

good answer.........

7075-T7 wrote: ALL Tungsten-carbide parts are sintered parts with binders in them.

Except for binderless Tungeten Carbide. Great stuff, except for the higher cost.

Thanks for all the info. I have never heard the word 'sintered', nor had any idea of the process. Now, I'm a MIM genius!

7075-T7 wrote:Ok, pistols use MIM parts, but think about this. ALL Tungsten-carbide parts are sintered parts with binders in them. So are ceramics. Proper sintering allows ample time for atomic diffusion to decrease the voids in the material to a point where they are no longer an issue. This is why the part always gets smaller after sintering.

I would much rathar have a quality MIM part which was properly sintered after formation and made with wuality raw materials than a part made of cheap mild steel billet which was hot forged and then not properly tempered.l

As for being able to tell a MIM part from a part made of bar stock, it all depends on the type and temper of the bar stock part and they type of fracture.

Just like with aluminum parts, one manufacturers "high strength" aluminum might be a 5052-H32 with a yield strength of 28ksi where anothers could be 6061-T6 with a yield of 40ksi. Everything is relative.

IAAME (I am a Materials/Mechanical Engineer)

Gosh...this should have been posted right up front. It all makes sense now.