MIM Parts. Are they poor quality?

[jonnybigguns]

Learning about Smith's Is the quality of Smith's poorer today then the 80's or 90's? I know the lock was introduced but what about the quality of the metals being used today? Should a guy shy away from the new ones?

 

[Baldy]

I see no valid reason not to buy the newer models. I have several and they work just as good as my older ones.

 

[Ron H.]

Learning about Smith's Is the quality of Smith's poorer today then the 80's or 90's? I know the lock was introduced but what about the quality of the metals being used today? Should a guy shy away from the new ones?

Sir, there's a thread running on the 1896-1961 board called "An Engineer's Take on S&W" that you might find interesting.

As I understand it, MIM parts are more consistent than forged, and thus require less fitting/handwork/labor, making them cheaper to produce in quantity. The reason for their adoption is pretty clear.

While I'm suspicious of the metalurgy, the MIM parts do seem to work just fine. How well they'll stand the test of time remains to be seen.

Hope this helps, and Semper Fi.

Ron H.

 

[G-Mac]

Should a guy shy away from the new ones?

I do. I like Smiths from the pre-lock, pre-MIM, era. I have no interest in any of Smiths current offerings. I like my S&W's the way God intended them to be....not some cost-cutting manufacturing engineer that's in cahoots with the bean counters.

 

[Bullseye Smith]

Nothing wrong with the new guns, if you don't know what to check for on a used S&W the new ones is the best way to go. The new MIM parts are just as good as the old ones. Nothing wrong with the lock and the action, but everyone likes different things.

 

[Aussie44]

MIM parts are cheaper to make and are nowhere near as good as the forged parts.My 2c


Ken

 

[500 Magnum Nut]

Nothing wrong with MIM. The parts are much smoother and much more to size omitting lots of hand fitting. The parts are heat treated for long life.
I don't like all the features of the new guns, but MIM is ok with me.


What is MIM?

Here is an older post that I have copied here, what is MIM?

By popular request, here's the post from Mr. Herb Belin of S&W -----------------------
"I have read with much interest the many comments in this forum pertaining to MIM, MIM Parts and the use of same in a S&W product. So far I have come away with several impressions and they are "people in general don't like/trust MIM parts" and "no one has said why" I will take a stab at this issue and see where it goes.

As background to our decision to use MIM in some areas of our Mfg Process we took a long hard look at our "Life Time Service
Policy". It was clear to us that any change in any of our products such as the use of MIM components had to show equivalent or better performance and durability to those components that were being replaced or the "Lifetime Service" would haunt us forever. The second consideration was to determine if the change was too radical a departure from S&W mainstream design.

For the performance and durability issues we decided that if MIM could be used for the fabrication of revolver hammers and triggers successfully this would truly be an "Acid Test". There is nothing more important to a revolvers feel than the all-important Single Action Sear that is established between the hammer and the trigger. Mechanically few places in a revolver work harder than at the point where the hammer and trigger bear against each other. If these surfaces wear or loose there "edge" the "feel" is lost. Initial testing was on these two critical parts. Over time we arrived at a point where our best shooters could not tell the difference between a revolver with the old style hammer and trigger and the new MIM components. Special attention was given to their endurance when used in our very light Magnum J frames such as the early prototype 340 & 360 Sc's. None of our revolvers work their components harder than these small magnum revolvers. Throughout this testing MIM held strong and finally we determined that this change judged on the basis of durability and feel was a good one.

The second area of concern to S&W was our customer's reaction to this departure from the traditional. Many heated, intense discussions resulted but in the end the decision was made to move ahead with MIM.
The issue of cost was only one of the considerations in making this decision. Equally as important was the issue of part-to-part uniformity and the result of this of course is Revolver-to-Revolver consistency. We found that revolvers that used MIM hammers and triggers required almost no Fitter intervention in those areas during final assembly and final inspection and Trigger Pull Monitor rejection rates dropped markedly on finished guns. From an internal process point of view it appeared a "Winner".

Lets shift gears for a moment and talk about the MIM process. It is unclear to me as to the reason for many of the negative feelings on the forum concerning MIM. Typically when people complain and aren't specific in the reason why, the problem is often created by a departure from the "Traditional". Perhaps that is indeed what is bothering some people when they view MIM.

The term MIM stands for Metal Injection Molding. It holds some similarities to Plastic Injection Molding and many differences as well. To start we would take a finally divided metal powder. This could be stainless or carbon steel. Today even Titanium is being used in some MIM fabrications. We would mix the metal powder and a thermoplastic binder (generally a Wax) forming slurry of sorts when heated and inject this mix into a precision mold and finally form what is known as a "Green Part". This part is roughly 30% larger than the finished part it will become at the end of the process. Interestingly enough the Green Part at this stage can be snapped in two with simple finger pressure. The Green Parts are then placed in a Sintering furnace filled with dry Hydrogen gas and the temperature is brought almost to the melting point of the metal being used. Over time the "Wax" in the Green Part is evaporated, the metal fuses and the part shrinks 30% to it's final correct dimensions. At this stage of the process the MIM part has developed 98 to 99%of the density of the older wrought materials and a metallurgy that is almost identical. Dimensionally it is finished and no machining is required. However the job is not yet done and the MIM parts are brought to our Heat Treat facility for hardening and in the case of Hammers and Triggers, Case Hardening. Depending on the particular metal alloy that was used at the start of the process we apply a heat treat process that is the same as would be used if the material were the older wrought style. Final hardness, Case thickness and core hardness are for the most part identical to parts manufactured the older way.

Lets look for a moment at how we achieve dimensional precision when comparing these 2 processes. The old parts were each machined from either bar stock or a forging. Each cut and every resulting dimension was subject to machine variations, Cutter wear, operator variations etc. If every operation was done exactly right each and every time and the cutter didn't let you down you would have produced a good part but sometimes this didn't happen resulting in a rejected gun and rework or in the worst case an unhappy customer. With MIM parts you must still machine to very high tolerances and your cutters have to be perfect and your machinist has to be highly qualified but all of this only has to come together one time. That time is when the injection mold is made. Typically a mold for this process costs S&W between 30,000 and 50,000 dollars. Once it is perfect every part it makes mirrors this perfection and you have in my view a wonderful manufacturing process.

Hopefully this description will help us all better understand the MIM process.
Please forgive the spelling errors and misplaced punctuation. I have no spell checker on this and the phone continues to ring!

Have a Great Weekend,
Herb

Additional Point.
Currently S&W is paying about $1.20/Lb for stainless steel bar stock. Raw MIM stainless steel inject able material costs $10.00/Lb."
__________________

 

[Crazy K38]

that post was very informative and I am less sceptical of mim parts for it

 

[RON in PA]

I have 5 post-2000 revolvers with MIM parts, including 4 with the dreaded lock. They are just fine in operation, accuracy and appearance.

 

[Aussie44]

Lets look for a moment at how we achieve dimensional precision when comparing these 2 processes. The old parts were each machined from either bar stock or a forging. Each cut and every resulting dimension was subject to machine variations, Cutter wear, operator variations etc. If every operation was done exactly right each and every time and the cutter didn't let you down you would have produced a good part but sometimes this didn't happen resulting in a rejected gun and rework or in the worst case an unhappy customer. QUOTE]

With todays CNC and Technology,Cutter wear and tool adjustment etc etc,are not an issue.The above comment is Crap.

Ken

 

[500 Magnum Nut]

Lets look for a moment at how we achieve dimensional precision when comparing these 2 processes. The old parts were each machined from either bar stock or a forging. Each cut and every resulting dimension was subject to machine variations, Cutter wear, operator variations etc. If every operation was done exactly right each and every time and the cutter didn't let you down you would have produced a good part but sometimes this didn't happen resulting in a rejected gun and rework or in the worst case an unhappy customer. QUOTE]

With todays CNC and Technology,Cutter wear and tool adjustment etc etc,are not an issue.The above comment is Crap.

Ken

What of this are you in disagreement with?

CNC machines still have variables and tool wear still occurs affecting the final size/part. No part is a perfect clone of itself time and time again.
This MIM process is very consistant, I feel more accurate than CNC.

I have seen MIM failures, so MIM parts are not perfect. What made with human hands is perfect?

 

[Aussie44]

What of this are you in disagreement with?QUOTE]


This
Each cut and every resulting dimension was subject to machine variations, Cutter wear, operator variations.

Which is no different with MIM parts.
I have seen CNC's here that have accuracy of 1/10 thou of an inch accuracy consistantcy.The machine checks and compensates for wear of toolong.MIM is a form of casting and like you said they fail no different than anything else made by man.My biggest beef with S&W is that they have changed the way their revolvers looked for generations.
The hammer (Hammer Nose)and trigger was and still is to me an S&W Icon.What they have done now is made a good gun look like a Taurus, Plain and Simple. And MIM (Cast)instead of forged.Even the outside has changed shape in some areas.You like MIM,No problem,Me,No thanks.If I want a cast or MIM I'll go buy a Ruger or whoever else makes one..

Ken

 

[500 Magnum Nut]

No argument here!
The problems of machine parts is cost. Here in the states we are losing factory jobs daily. In my state, 1/2 the work force were at one time factory workers such as machine operators, engineers, machinists, tool & die, programers etc. We worked at firearm factories like Colt, Winchester, Remington, Ruger, Marlin & Stag arms. S&W is on the Connecticut border. The other factories were mostly defense contractors like Pratt & Whitney, Sikorsky aircraft and Electric boat (Submarine base).
Now, most factories are closed for good. Winchester gone, Ruger gone, Remington gone, Colt 75% closed, Pratt 75% closed etc. Where they go? China, India, England, Mexico and so on.

I know something about machining. If the people don't put the parts in clean fixtures, or if a chip is under the part, when the CNC machine does it's thing you now have a defective part. Tooling or machine temperature affects part sizing, the same as tool wear causes parts to be undercut or "oversized", even if coolant is used. Sure they have carbide tooling, but carbide wears too.

To avoid some of these sizing issues they built factories in 100% air conditioned machining areas to better control sizing and final product quality. Now here comes profitability. That's why they all leave, they can make parts cheaper else where. Now we are all jobless or soon to be.
MIM is the other method...

So we have a choice of a S&W made with MIM or closed if they continued making them like the good ole days. It's a tough pill to swallow. We are all losers in the end.

 

[gizamo]

Interesting to see what Gunsmiths think...

Few questions of you gentleman...MIM and CNC changes that you may have noted.


Inside the sideplate, we used to see a pressed in boss that was precision fitted so there was minimal horizontal trigger or hammer drift. Have you noticed that now, it's very normal to see .010" drift in both.

How about the hammer, trigger, cylinder stop, and rebound slide studs. They used to be screw in and could be replaced easily. Now when they wear out, how would you fix the new style gun?

The frame lug used to be a replaceable part. It is now part of the frame. If it wears, does the frame need to be replaced?

Would you both agree that the MIM triggers now have a horrible hand spring? They can pop out and are a thrill to put back in. The older ones never popped out and made it easy to remove and replace the hand.

Remember when extractors were round instead of square? Are the goofy new extractors the cause of hang up and getting a case stuck under the star when you try to extract?

How about the general specs? Remember when cylinder endshake was less than plus/minus .002" - .003". Have either of you seen current production guns that have left the factory with as much as .010" and or a B/C gap that is just as bad?

Finally,

Would either of you say any of my questions about production changes led to an improvement in the gun?


Enquiring minds want to know....


giz

 

[Aussie44]

500, Hey I agree with you Mate,We have lost a lot of companies to Asia and other parts of the world to.But it's our fault also,We accept the stuff no matter where it's made or if quality is just OK.Also the closure of some of the factories are faults of the states or unions,The demands, taxes and wages close them up and they move out to a state that looks after them and the workers.

I agree with what your saying Giz.
Ahhh the good old days,What S&W now wants is the gun returned to the factory for any repair work.Good for them not for us.I have had MIM Smiths come thru my shop and I could not believe some of the tollerances .012 B/C Gap which was fine by the factories specs.The Hammer,Trigger and all the other studs could be drilled out and replaced.The Frame lug if you ever wore one out could be tig welded and shaped.But in the long run the owner would end up paying more for repair and refinishing.

Ken

 

[gizamo]

Ken,

Your right, the Hammer, Trigger, and other studs could be drilled in and pressed in bosses retrofitted. But it would be easier/cheaper for S&W to throw the gun frame away, and I believe that this is the design's obsolescents...as planned to accomplish getting rid of the hand fitters.


The following was written by one of the finest S&W gunsmiths I know. I take no credit here...

"I don't have a problem with MIM parts themselves. Yes they are ugly, and yes they can break...but so can F/M parts. MIM parts are held to a tighter manufacturing spec than F/M parts but as you will see in my example, that really doesn't matter. The real issue is accumulative tolerance.

Lets take the forged frame for example. S&W's spec on placement of the hammer and trigger studs is +or-.002" from dead center. The MIM hammer and trigger also have the same tolerance of +or- .002". Lets take worst case and say the studs are both mounted at the widest spec (hammer stud is .002" to the rear and the trigger stud is .002" to the front. This is an accumulative error of .004". Now lets say the hammer is on the low side of spec, .002" short and the trigger is also .002" short. This is another accumulative error of .004". Add the stud error to the hammer & trigger error and you have .008" total error (worst case). The single action sear has only .016" of surface contact. With the loose fit in the example, the sear is only 50% engaged and could easily push off. Even if it doesn't push off, it won't seat uniformly from shot to shot.

Same scenario only F/M parts. The parts specs are +or- .003" however all triggers are made with the beak sized .010" longer. The accumulative error (.006" for the parts and .004" for the frame = .010" max) is adjusted by dressing the beak to a near perfect fit, typically .001".

What would you rather have? A sear with .008" slop or one with .001" slop? I think the answer is obvious. MIM parts cannot be fitted else it will cut through the case hardening. Forged and machined parts can be fitted and are case hardened after the fitting.

Lets add side play to the formula. The older guns had a pressed in boss on the side plate. This boss was dressed down so the side play was about .001~.002" for both the hammer and trigger. Worst case with the older guns was .004" sear drift. With MIM guns, there is no adjustment in the boss or width of the parts, so it is common to see .006" side play in both hammer and trigger, or a worst case of .012" sear drift. When sear drift is added to sear contact surface, you can see where this leads; A gun with the "floppy parts" syndrome.

The point is: when you mix non-adjustable MIM parts with a forged frame, tolerances can work against you. When F/M parts are used, the error in machining is compensated by adjusting the length of the part. The net result is F/M parts are capable of much tighter specs, even though they started out looser.

Metallurgy is not the issue. A F/M part will last forever if the gun is maintained properly. They are quite hard to start with and are case hardened to make the surface even more wear resistant. The same holds true for MIM parts. So it's not a wear issue, rather a "precision fit" issue. Breakage is way less common in F/M parts though it does happen on rare occasions.

The example I used above reflects real data. Though most MIM guns won't be at the loosest or tightest end of the spectrum, some are. The MIM guns that come in the shop suffer from poor fitting parts. Some have the sear surface so tight that it binds the trigger pull. Some are so loose they will push off. Because of sear drift, some guns feel different each time you pull the trigger in SA or DA.

You can form your own conclusion. As for me, I'll take my chances on F/M every time."




giz

 

[500 Magnum Nut]

Welcome to the throw away society!

Inside the side plate, we used to see a pressed in boss that was precision fitted so there was minimal horizontal trigger or hammer drift. Have you noticed that now, it's very normal to see .010" drift in both. It's a way they avoid fitting guns, a cost saving method. If the parts are theoretically all the same, give a little slop here and there makes the guns snap together without fitting.

How about the hammer, trigger, cylinder stop, and rebound slide studs. They used to be screw in and could be replaced easily. Now when they wear out, how would you fix the new style gun? The factory would re-drill and press another in, or replace the frame. I won't even try to fix one. If I'd drill in the wrong place, your screwed. I suppose if I had to fix one, you could put another threaded rod in, or press one in. You would have to use a center cutting endmill and pre-drill the former position of the stud exactly, to make sure the drilled hole is in the correct spot.
The frame lug used to be a replaceable part. It is now part of the frame. If it wears, does the frame need to be replaced? You can remove the dog leg, then install the old style lug. S&W will replace the frame.
Would you both agree that the MIM triggers now have a horrible hand spring? Yes big time!
Remember when extractors were round instead of square? Are the goofy new extractors the cause of hang up and getting a case stuck under the star when you try to extract? Evolution, to save a buck.
How about the general specs? Remember when cylinder end shake was less than plus/minus .002". Have either of you seen current production guns that have left the factory with as much as .010" and B/C gap that is just as bad? S&W is always cutting corners to save assembly time. Sometimes, a closer B/C gap causes problems with a dragging cylinder so for the basic guns they open them up.

 

[john traveler]

As an old-time gun tinkerer/gunsmith, I too am saddened to see S&W going to MIM parts instead of using more traditional methods of parts fabrication.

But, 500MagnumNut is right. Using MIM parts is a matter of economic necessity and corporate survival. S&W (or any other producer of mass consumer goods) has no choice. It's either reduce production cost or perish.

I believe MIM was developed as a fabrication method for the automotive and aerospace industries, both heavily dependent on low-cost/high volume production of parts. It spilled over into the gun manufacturing world in the form of semi auto pistol extractors, slide stops, barrel bushings, etc to replace the traditionally milled parts. The late, great, Col Jeff Cooper wrote over 30 years ago that while quality semiauto pistols can be made cheaply, revolvers can not. I suspect he too would crap a brick over the current generation of S&W revolvers.

As for addressing the question of maintainability of a currently manufactured revolver, it should be somewhat obvious. Return to the factory. Eliminate the field (gunsmith) repairable option. That is what has happened with all other consumer goods. When was the last time you heard of a large screen LCD television or car stereo being repaired in a small electronics repair shop? It's either return for factory service or trash it as not repairable.

It's a sad but true commentary that almost all consumer goods have evolved to the use-and-discard status.

 

[gizamo]

How about the hammer, trigger, cylinder stop, and rebound slide studs. They used to be screw in and could be replaced easily. Now when they wear out, how would you fix the new style gun? The factory would re-drill and press another in, or replace the frame. I won't even try to fix one. If I'd drill in the wrong place, your screwed. I suppose if I had to fix one, you could put another threaded rod in, or press one in. You would have to use a center cutting endmill and pre-drill the former position of the stud exactly, to make sure the drilled hole is in the correct spot.

500 Magnum Nut.....

I smiled reading that one. I just did some work on a Winchester in my collection fixing a problem. Went to a friends shop as he has a digital centering setup for his end mill. The two of us had to build up a jig to hold the part precisely and then spent time centering the receiver. By the time we had it drilled and tapped it was 2 hours shop time for both of us...and this was a simple operation compared to replacing the hammer trigger studs on a S&W...


giz

 

[Aussie44]

Giz I have replaced lots of rebound slide studs because the owners broke them.I use a Co Ax indicator with an Accuracy of .0005" , after I setup the frame and have had no probs at all.

Ken