MIM parts ?

The extractor and ejector are both MIM. You can look at the parts and see the sprue spot. On the ejector it is on the side and on the extractor on the inside back edge by the slot. The Mag catches are also.

Brian
 
Nick19; thank you very much for the most excellent elucidation, nay, treatise on this subject. I think that I understand this better now.

I was confusing this with the superalloys produced by the particle metallurgy process (see the Crucible Particle Metallurgy website: http://www.crucibleservice.com/crumain2.htm
if you are interested.)

In particle metallurgy, as you probably know, the molten steel is sprayed and freeze dried (in a non technical description), then the particles are brought very rapidly to HIP (Hot Isostatic Pressure), where they undergo diffusion-bonding at FORGING temperatures (as opposed to sintering, which is at melting temps.). The rapid cooling after diffusion-bonding freezes the alloying elements in a uniform mixture. This has several advantages; this from the CPM site:

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>1. CPM grades are 100% dense - there is no residual porosity.

2. CPM grades are 100% steel - no binders are added.

3. CPM grades are bonded by diffusion-bonding at forging temperature, not sintered at melting temperatures - there is no inherent brittleness due to melting.

4. CPM grades are completely alloyed in the molten state for uniformity - there is no mixing or blending of elemental powders.[/quote]

This offers several advantages, and is widely used in the high end custom knife industry. For example, you can only get about 2% Vanadium in tool steel such as M2, using traditional ingot steel making (if you add more Va, it just is lost on the surface, like fat in frozen chicken soup). CPM offers alloys with up to 15% Vanadium! Other alloying elements, including carbon, can be produced at high levels as well. The two elements I mentioned are very important in knives, as a hard knife will be in the low 60's on the Rockwell C hardness scale. Vanadium carbides, compounds formed of Vanadium and carbon have a Rc of 70-80!!

Obviously, MIM is a completely different process with a completely different aim.

Thanks for the info. Walt
 
We've had a good number of responses over the last fourtyeight hours. However, we still haven't heard about a first hand MIM part failure.

Anyone? Anyone?
 
Well, I'm not inclined to "follow instructions" or take orders from someone who is without some authority over me, so I'll just post something in response to the 18.5# spring post. I use a 20# spring on my 70 Series Gold Cup, for firing .400 Cor-Bon. No signs of damage, wear, or failed parts. I really do have a stainless bushing.
 
This has been one of the most informative threads I have ever read. I've learned a lot and enjoyed it immensely. Many thanks.
 
Now, now, no name calling.

I have never had a MIM part fail, but I have had some parts that just didn't "mate up". The out of tolerance parts have nothing to do with the process. Like many Kimber owners, I am having the MIM parts replaced because of their bad reputation. Perhaps a waste of money, but it makes me feel better (like insurance) so what the heck.

Brian:

Just curious, have you ever received a pistol for repair because of failed MIM parts?
 
Ankeny,

Yes I have. I have seen broken front sights, broken hammers, broken slide stops and slide stops and hammers that were warped or not fully finished (chunks missing). Most of these parts when examined in the areas that fractured showed porosity or over heat treating. And yes this process can lead to tolerance problems and out of spec parts. If the part not cooled properly it can be warped or brittle or if not fully sintered can be porous.

Brian
 
Thanks for the response Brian.

Is there any one particular brand that you have dealt with that has had a problem with MIM parts, or do you just find them to be inferior across the board? Do you see a large number of these out of spec parts, at least more than any other kind?
 
Gun Plumber; there are two Walters on this thread. I presume that your 'pompous ass' remark is directed toward the other one.

I have, after all, declared myself to be a Medical Doctor on this forum, and by definition, I am a pompous ass, therefore labeling me that would be redundant. ;)

Walt
 
224,

They were all Kimber parts. I have seen a few broken stainless Colt slide stops too, and those were due to them being brittle. But as far as the MIM parts go, it's been Kimber. Thing is that Kimber has had two sources of MIM parts. Originally, they got them from Chip McCormick who was supposedly getting them from a MIM factory in Spain. Later, Kimber went to making them in house and now McCormick is supposedly selling those as he can't get them from Spain due to the quantity he alone would order.

The biggest problems I have seen are out of spec slide stops and front sight breakage. Also some guns have had their triggers go creepy or to half cock because the edges and hardness wear through on the sear.

Brian
 
Thanks Brian, that's very informative.

In your opinion are these problems related to the proccess itself or to a lack of quality control?

Do you think that MIM parts are satisfactory when done well, or are they best avoided altogether?
 
Those of us who are perceived by the less-fortunate of the proletariat as "pompous asses" might just be folks who don't march in lockstep to unsolicited dogma.

I'm really just an ordinary, conservative guy who likes to shoot, and who doesn't take himself too seriously. I thought that my input regarding the recoil spring/bushing relationship was pretty straightforward.

Walt: My best friend is an M.D. I don't consider him to be a pompous ass. He's a very well-trained plumber of the fairer sex.
 
Let's try and lay off the name calling guys, and please stay on topic.

It's not about following instructions, it's about being mature.
 
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