[mshuell]

Dear Friends,

Very often in these missives, I've read statements referring to MIM (metal injection molded) parts as the metalurgical equivalent of poison ivy. I find it quite curious.

My personal background is a foundry/engineering history. Yeah, I know the difference between mallable iron and grey iron, and the difference between 4140 steel and cheap pot metal. I understand the work hardening achieved through forging as opposed to the lack of it in a casting.

Machine shop time is very expensive. The reason MIM is used is that you get a high quality part, almost perfectly to spec, right out of the mold. The initial set up cost is fairly expensive, but once you're set up, you can produce a large number of parts quite cheaply. The amount of machine shop work required is very minimal.

Is a MIM part as strong as the same part crafted out of fine tool steel? Nope. The strength is about 97%. Geez, this means that instead of having a part thats 300% stronger than it needs to be, you have a part thats only 291% stronger than it needs to be. Who the hell cares? We're dealing with handguns here guys, not Formula One racecar engines. We don't have any parts rotating 14,000 times a minute.

There's nothing wrong with crafting a tool (handgun) out of the absolutely finest material available. There's also nothing wrong with crafting a tool out of material that's adequate for the job. One last example, Caspian cast (not forged, not tool steel) frames---did you ever see one break?

Best Wishes, Mark Shuell.

 

[Gerald McDonald]

Hello Msh. You get no argument from me. I think if done correctly it really doesnt matter too much. I do believe you can not compare the quality of Caspian or Ruger to a Charles Daly. Would I rather have a forged ,probably, would I pay twice as much , probably not.
Thanks
Gerald

 

[martyu]

I’ve read a great deal about the questions about castings versus forgings versus rolled metal parts and have a few tales to tell. Our chief engineer’s dad was the Treasurer of the A. O. Smith Corp. years ago. A. O. Smith makes truck frame (use to make millions of auto frames), silos and thousands of miles of oil drilling pipe, among many other products. Our chief engineer, Dick, told me that A. O. Smith once had a great deal of trouble with breakage of brackets in the machinery that formed the oil drilling pipe. They tried forged brackets, welded brackets and finally found the only thing to stand up without breaking was cast steel brackets. Surprised them as well as me.

Then again Elmer Keith once wrote of testing Smith & Wesson and Ruger .44Mags. to destruction. The S&W’s failed by stretching the frame, where as the Ruger cast frames broke without stretching. But the Rugers required a heck of an overload to do it. I suspect that what is important is that the designer knows the material properties well and designs appropriately.
Marty U.

<font size=-1>[ This Message was edited by: martyu on 2001-08-17 16:05 ]</font>

 

[CCV]

One last example, Caspian cast (not forged, not tool steel) frames---did you ever see one break?

I've seen one crack. Does this count?

 

[Rob Longenecker]

I have had two forged Colt series '70 frames crack. Both had over 60,000 rounds through them.

At the time several gunsmiths told me that if I didn't have them welded up I could still keep shooting them with little chance of further growwth of the crack.

Everything has a limit.

 

[Guest]

I have zero background in metallurgy or mechanical engineering, but I will categorically reject MIM parts in any 1911 firearm. I had a new Kimber 1911 from the "Custom Shop" go full auto after 200 rounds of range ammo. MIM parts (the sear in this case) fail at a much higher rate than do CNC machine steel parts. Anyone who shoots a 1911 made out of MIM parts is risking a serious injury to themselves or others.

 

[StormMaster]

I had a new Kimber 1911 from the "Custom Shop" go full auto after 200 rounds of range ammo.

Uh, yes -- and that's a bad thing? Sounds to me like you got more than you paid for. :grin: :grin: :grin:

Chuck

 

[Terry Peters]

Something folks sometimes forget in the MIM, Cast steel and Tool steel discussion is the standards or specifications used by the individual companies buying the parts.

Everyone out there is WELL aware of the LOW COST bidder concept. The helicopter I flew in the army had parts made by the low cost bidder. We still have pending crash lawsuits on that.

There is @#^% quality MIM and high quality MIM. Has there been MIM failure with low quality MIM, yes. Examine companies that produce 30,000 plus guns a year using it. Has there been MIM failures with high quality MIM. Examine companies building about 100 to 1000 guns a year using it. Have yet to hear of one but that does not make it not possible.

There is soft tool steel and high quality tool steel. We all have seen and experience this those of us who have been shooting for several years. Sears wearing out on our early 1911's. Or have to have frames/slides tightened and retighened. Why maybe, and I mean maybe the steel at that time was not of the grade that is available today.

There is cast steel and high quality cast steel (Caspian for an example)

One of the metalurgists out there can answer better than I.

By the way there was a time, I think about two year ago know when Smith & Wesson made a large amount of frames for Kimber while Kimber also used the Jericho company for the frames. So outsourcing on large quantities of parts is also a factor in the lost cost bidder concept. (there was a thread on this on the 1911 Forum)

So most if not all manufacturers and retailers go for the "bottom line." As distasteful as that may sound it is the only reason a business or any business stays in business.

You do get what you pay for front end or back end.
_________________
Be safe and keep the brass flying,
Terry Peters formerly known as PT-Partners
http://www.pt-partners.com

<font size=-1>[ This Message was edited by: Terry Peters on 2001-09-17 11:25 ]</font>

 

[Guest]

All you folks out there that know so much about "good quality MIM" and "poor quality MIM" go right out and continue shooting 1911 pistols with MIM parts if you want to, just don't come complaining when the parts fail and you shoot yourself or someone else that you didn't want to shoot.
Also ask a good quality pistolsmith like Dane Burns how many MIM parts are in the 1911 pistols he shoots.

 

[martyu]

I also know of a Kimber that went full auto because of a worn disconnector and wound up putting some rounds over the berm at the range. I would first suspect improper heat treating. Mine showed some wear. I replaced the disconnectors in my Kimbers with Colt parts from Brownell. Best to check yours when ever you clean them.

<font size=-1>[ This Message was edited by: martyu on 2001-09-20 13:58 ]</font>