MIM parts. What does that mean?

[MrPhil]

MIM keeps coming up in S&W threads. Being new to S&W revolvers (actually new to hand guns), I don't know what MIM means. My guess is it refers to an injection molding process. Thread references tend to be negative. What are the problems with MIM parts? Do we not like them because we don't like change?
Please enlighten me. I've got a little metalurgical knowledge, so go ahead and "get technical"
Thanks,
Phil

 

[Steve F]

Here ya Go

http://thehighroad.org/showthread.php?s=&threadid=6763

 

[MrPhil]

Thanks, but . . .

. . . this thread did not touch on what problems (if any) have been caused by using MIM technology in S&W revolvers.
I've worked with sintered steel alloys in high pressure plastic injection molds. Combinations of properties can be engineered into those alloys that are unobtainable with previous technologies. Are these MIM parts sintered alloys or are they something else?

 

[VictorLouis]

what problems (if any) have been caused by using MIM technology in S&W revolvers.

Virtually NONE, thank goodness.

I've read one confirmed account of a trigger breaking-off where the 'C' joins the upper portion normally concealed up within the frame. I've also read one anecdotal account of the same, though I don't doubt the source. That's it.

Compare that with what, DOZENS of such reports in the 1911 community with the many and varied MIM parts???

Here's a little treatise for you:

http://www.flomet.com/MIM.asp

 

[C. H. Luke]

Some of Kimber's sales rethoric on MIM:

"Manufacturing innovation played a huge part in Kimber’s success. Metal Injection Molding (MIM) is a process Kimber pioneered in the gunmaking world. Small parts like the slide release, thumb safety and sights are made by this method. MIM parts are far superior to castings used by other manufacturers, and essentially have the strength of those machined from steel."

Below from:

http://www.guns4ever.com/kimber.htm


"Small parts like the thumb safety, slide release and sights could be made using a process Kimber pioneered in the gunmaking world-Metal Injection Molding (MIM). Far superior to casting methods used by other gunmakers, MIM parts have 98 percent of the density of parts machined from forged steel and hold vastly tighter tolerances than castings."

 

[MrPhil]

Thanks for the info and links.

 

[wintermute76]

Nothing wrong with MIM if it's done right. What I"ve heard is Kimber got cheap on their tooling and don't get many good parts per shot.

MIM is like sintered metal I guess, what I understand is its metal powder mixed with a wax or plastic resin, shot into the tool and you get a 'green' part out that is like plastic in many ways. Than it goes into a debindering/sintering furnace where the resin is baked out and flash heated to sinter the metal. Supposed to be 98% dense and negligible decrease in mechanical properties as compared to barstock.

I work at a mold shop and we've done lots of MIM tools and more than a few for S&W. Never heard any complaint about the S&W MIM stuff. Did tools for a hammer, trigger and a snubbie barrel, more recently the ejector and slide stop for the SW1911.

Supposedly Kimber is getting tired of their tooling and is going to be asking for a quote.

My .02 anyways

 

[RWK]

MIM parts are NOT inherently inferior. The fact is they can be lighter, sufficiently strong, and much less expensive than traditional metallic parts – forgings, castings, extrusions, etc. – but they must be used ONLY where they are applicable and carefully fabricated. It is interesting that many critical piece-parts used in military jets (engine disks, for example) are MIM or powered metal based. They have proven to be a reliable and sensible design alternative.

The same concept applies to firearms. MIM piece-parts can be entirely appropriate design options when used appropriately and when manufactured with high quality.

I prefer “all steel†handguns, but I'm a traditionalist. Don’t Glocks – universally believed to be one of the most durable and reliable sidearm design-families – have plastic guide-rods and who believes that plastic is as strong as MIM metallics?

 

[Ala Dan]

Greeting's All-

Some say that the new Smith & Wesson "MIM' actions
can't be made as smooth as those of case hardened
steel? Well, partner I'm here too held you that is not
true. I have a S&W 6" 686-5 that arrived from the
factory with a DA action that was a little stiff. But
with the addition of a WOLFF spring kit, this problem
was quickly solved. The weapon did not need any
other 'smithing! Problem solved, and she is as
"slick as a newborn babys butt".

Best Wishes,
Ala Dan, N.R.A. Life Member

 

[WonderNine]

Let us know if the trigger breaks in two anytime soon. Thanks.

 

[greg531mi]

I'm sorry, I would rather have machined and hardened parts. My old company, Bosch, tried MIM material, and had problems with leakage, and that's not good with fuel injectors, diesel fuel on a hot engine...mmmm.. Went back with machined parts fast. Lycoming engines had problems with their oil pump gears out of MIM, airplane engines started to quit, and they had a big recall. All for a few pennies, profit over reliablity. The trouble with MIM is that voids tend to form where the plastic was. Then cracks form where the voids are. That's not good.
I would guess it is ok for trigger guards, and other non-stressed parts, but give me a machined part any day.