MIM parts??

[CandRFan]

I've noticed in a lot of the 1911 threads that guys are mentioning how they're replacing MIM parts in their 1911s. How do you know what parts are MIM and what aren't?

On the one hand I'm not thinking that I'm shooting near the volume of .45ACP that would break any of these parts. I know that MIM parts are a way to lower manufacturing costs that help keep the prices of "entry level" 1911's low.

But to be honest, I don't see many threads here on INGO about people having their 1911s breaking parts.

On the other hand though...I wouldn't mind learning how to do some basic gunsmithing skills. And tinkering with guns is a good time. Would replacing the MIM parts in my RIA .45 compact be a good starter project? What parts are MIM in a RIA .45? What would be a good project to start off with (best bang for the buck AND something that a n00b could handle?)

 

[Bluedragon]

I have never seen any 1911's with "MIM" parts breaking, and I think it is a little bit exaggerated. But to check with what parts are "MIM", and what aren't. I would say to check this forum out. I remember seeing a list of what are "MIM" in the Springfield Armory section.

The M1911 Pistols Organization Forums Site

 

[CandRFan]

I have never seen any 1911's with "MIM" parts breaking, and I think it is a little bit exaggerated. But to check with what parts are "MIM", and what aren't. I would say to check this forum out. I remember seeing a list of what are "MIM" in the Springfield Armory section.

The M1911 Pistols Organization Forums Site

Thanks!

 

[Bluedragon]

No problem, and good luck with your project!

 

[t413]

I think the whole MIM debate came from 1911 purist, kid of like SIG purist that don't like Rails on their guns.
Basically grown men having a hissy fit.

 

[Wabatuckian]

MIM, if done correctly, is about 98% the strength of forged.

The problem is that many companies do not do this correctly.

For example, the thumb safety that comes on RIA Tacticals will break easily - I know because I broke two of them.

On the other hand, I had no problem with STI's ambi thumb safety. Then again, compared to STI, Kimber's ambi thumb safety is quite light and feels soft.

Not much margin for error in the machined stuff.

You can tell an MIM part because it will have a line down it where it's been separated from the mold. I'll try to post pics if you're interested.

Josh

 

[Claddagh]

I'm old enough to remember when a lot of the old timers sneered at Rugers because they used investment castings for receivers and other major parts, which they considered to be just a cheap manufacturing substitute for traditional forgings. They swore that we'd see them constantly breaking and that they couldn't possibly hold up under any kind of regular use.

We all know how that actually turned out.

I've not had what I'd consider to be enough trigger time with firearms containing MIM parts to have accumulated enough data to try and either confirm or refute the (predominantly) anecdotal fooraw that's out and about. All I can say is that I haven't personally had one fail in service nor been present when it happened to someone else.

Just my $0.02, but if it makes you feel better to replace an MIM part that hasn't caused any trouble because you heard it might break, go ahead. IIWY, I'd hold onto them though. Any sort of part can break, and having spares handy, if and when, ain't a bad idea.

 

[OD*]

You can tell MIM by checking to see if there is a square, triangle, rectangle, circle etc., on the part. Like so;

MIM - Barstock


A line down the center does not mean the part is MIM, it normally means the part was cast, but that isn't necessarily true 100% of the time either, even rough forgings have a flange line.

and castings
http://img.photobucket.com/albums/v323/sv1cec/reviews/ColtTour2/smallimages/Coltframeforging.jpg

 

[rockhopper46038]

It's not 100% (because part geometry plays a role) but most MIM parts will have one or more ejector pin marks on them where the part is pushed out of the die. An MIM part may appear a bit less "crisp" at its edges than a machined part because sharp corners in the MIM die interfere with the proper flow of molten metal and can result in stress concentrations that are very undesirable (and most likely the source of the failure in the MIM parts that we're talking about). A well designed MIM part will probably never fail, in fact in some cases it will be a stronger part than one hogged out of an billet*; but having said that, I too prefer the look of a milled/turned part over a mass produced MIM part (and an MIM die would only really be economical for a part that you planned on mass producing, a class A die doesn't start much south of a million bucks)
*material homogeneity, stress relief, chill skin, bunch of other boring reasons

 

[NealWright]

I see people argue the same thing on S&W's. Typically, nobody has ever seen one fail ... they just like "old" parts.

In some ways MIM can produce a better part (not saying it has). Depending on the design, many time MIM parts can be formed into finished shapes that can't be machined. Plus, don't think MIM is just a cheap replacement. The presses to produce these parts cost many times more than the CNC machines they often replace. It's only beneficial in high volume.

Again, I never can put a figure on MIM disrespect ... but I don't automatically fear a MIM, just because. Many times it can be a better part.

Thanks, Neal

 

[OD*]

I have seen a few MIM parts break, very few really, but more than forged.

 

[CandRFan]

MIM, if done correctly, is about 98% the strength of forged.

The problem is that many companies do not do this correctly.

For example, the thumb safety that comes on RIA Tacticals will break easily - I know because I broke two of them.

On the other hand, I had no problem with STI's ambi thumb safety. Then again, compared to STI, Kimber's ambi thumb safety is quite light and feels soft.

Not much margin for error in the machined stuff.

You can tell an MIM part because it will have a line down it where it's been separated from the mold. I'll try to post pics if you're interested.

Josh

Sure, post pics!

Thanks everyone so much for taking the time to post pics, give tips, and the discussion. I appreciate the education.

I guess I wasn't really worried about my RIA breaking on me or anything...but I think I'm going to change my reasoning for wanting to swap parts and such from thinking that the MIM parts were inferior to "just because I want to!"