An Engineer's take on S&W.

[DWalt]

You have described sintering, not MIM. Sintering is as described, where usually a mixture of powdered metals is compacted in a mold to form a shape. Depending upon the desired properties, it may or may not be heated after compaction to bind the particles together more tightly. Part designs are typically fairly simple shapes.

MIM is very similar to injection molding of plastics, but using powdered metal and a binder instead of plastic - it's forced into an intricate mold under high pressure. The mold may produce a very complex part.

 

[SweetMK]

You have described sintering, not MIM. Sintering is as described, where usually a mixture of powdered metals is compacted in a mold to form a shape. Depending upon the desired properties, it may or may not be heated after compaction to bind the particles together more tightly. Part designs are typically fairly simple shapes.

MIM is very similar to injection molding of plastics, but using powdered metal and a binder instead of plastic - it's forced into an intricate mold under high pressure. The mold may produce a very complex part.

I doubt there is a S&W MIM part that is not sintered.

 

[mbliss57]

I am an engineer.. sintering is the process of heating a material ( metal or ceramic) to the point where its not melting but the very very tiny particles are fusing together. The correct term in the engineering/ Physical chemistry world is "solid state diffusion"..the particles fuse together without ever actually melting. This can be done with heat , pressure or the combination of both. This is not new technology. It has been around in the ceramic world for a hundred years and in metals for decades. The MIM part is a solid state diffused metal part. It is not as strong as a forged part or a cast part. But it is strong enough to do duty work in many applications where it is cheap and easy to manufacture and the failure rate is very low. Hammers or triggers on a gun for instance are a work of art when made of all forged case hardened steel. But the MIM parts will "Usually" last as long as the forged parts because they are NOT stressed like a cylinder or a barrel. Are they as strong as a forged trigger? NO.
My only analogy I can come up with is the steel used in the cars from the 1950's vs the plastic used today on a car. Is it as strong as the steel bumpers of the 1950's? NO. is is adequate for the job it performs. Yes. Does it cost less? YES. Do we all demand that our cars are still made of all steel? Yes if you still look for only 1950/60 vintage cars. No if we look for newer cars.
Then with technology and science advances why do we insist our guns still be made from forged steel? Answer..Because we like them that way, they are stronger and we can afford to buy them...as older or possibly a new custom or PC guns anyway. But the new guns are made with new technology. LEOs use them daily to put their lives on the lines with them. (Now I am rambling into the polymer argument..) My point is the old revolvers of the 50/60s are like the old classic cars from a build/ strength standpoint. They don't make them like that anymore. But they sure are awesome firearms/cars. But the MIM and cast parts are here to stay. You/ we don't have to buy them but they do the necessary job.

EDIT: This link explains the MIM process in a pretty basic way. When/if you read it the reduction of porosity by heat/pressure or both without melting the materials is called sintering. The word PIM is the generic Powder injection molding. The specific MIM is Metal injection Molding.. as in the article.

http://www.pim-international.com/aboutpim/binders

 

[SweetMK]

I would bet the forged parts of the "first" versions of S&W's to use them, were not manufactured with that technology with strength in mind.

The forging technology was probably applied because it was a cost reduction from previous technology.

The forging process was a NNS advance, Near Net Shape.

Over time, many NNS processes were implemented, some successful, some less

sand casting
forging
investment casting
MIM
plastics
whatever

We could demand machined billet parts, but, we each would own far fewer guns.
AND the end result may not be as good.

Engineers just love to tinker.

 

[Oyeboteb]

I would bet the forged parts of the "first" versions of S&W's to use them, were not manufactured with that technology with strength in mind.

The forging technology was probably applied because it was a cost reduction from previous technology.

The forging process was a NNS advance, Near Net Shape.

Over time, many NNS processes were implemented, some successful, some less

sand casting
forging
investment casting
MIM
plastics
whatever

We could demand machined billet parts, but, we each would own far fewer guns.
AND the end result may not be as good.

Engineers just love to tinker.

No...

Forged Frames, Barrels, internal Parts, were Forged, because that was the most effective method of obtaining the properties/strength/toughness and shapes desired.

Some parts were also Case Hardened once 'finished' ( such as the Hammers and Triggers of the general run of early through mid 20th Century S&W Revolvers, and, the Frames of the Colt SAA Revolvers ).

I do not know about 19th Century S&W Revolver Frames, but, I suspect the Colt SAA and Percussion era Frames were Wrought Iron, and probably many Revolver Barrels were also.

The Springfield 'Trap Door' .45-70, if memory serve, had a Wrought Iron Barrel...as did most everything else Rifle wise, till the advent of Smokeless Propellants occasioned a change to various special Steels.

The methods were not elected because they were less expensive than Casting - Casting would not achieve the desired working properties.

For that matter, most any so called 'billet' is merely the perfunctory CNC Machining of Standard Stock Bar or Rod or whatever, which had been more or less Forged to begin with if via a Rolling Mill...with the difference being, that an intentional Forging of a certain shape item is done to be petty close to shape, while Machining something from Rod or Bar is indifferent to the Forging structures ( if any remain) internally.

All else being equal as for the material one starts out with, a properly made machined Forging will always be a superior item than anything indifferently milled out of 'billet'.

 

[SweetMK]

No...

All else being equal as for the material one starts out with, a properly made machined Forging will always be a superior item than anything indifferently milled out of 'billet'.

My response is a guess, as neither of us have the details at to why a manufacturing process was selected at any time in S&W history.

Your response, as is mine, are guesses, the staff that selected forging as a process at S&W are all pushing up daisies.

I agree with your details and knowledge as to why one material is better than the other, but,,,,,,,,,,,, again we are guessing as to why any material and process is selected.

I doubt the inspection techniques were available to fully understand what S&W was doing to parts when forging was starting to be used.

Heck, understanding why hydrogen embrittled steel was being studied in universities in the mid 1970's. (I was there)

Metallurgy as a science rather than an art was in it's infancy in the 1960's.

S&W made the forgings as an art, for cost savings. (My opinion)

Heck, if the guns NEEDED forged triggers and hammers, we would not see the success of MIM.

Many machinists could make a machined trigger successfully.
Many do, and are successful enough to make money.

Machining is a much lower cost technique for low volume manufacturing as compared to forging.

The opposite was true when S&W was high volume making triggers.

As usual this is JMHO, and educated guess.

 

[Gun 4 Fun]

I would have to disagree entirely with the statement that "Rugers usually outlast Smiths."

In the H.P. White Labs testing, if I recall correctly, the supposedly stronger Blackhawk failed before the S&W Model 29. Probably forgings, but I cannot say for sure. The S&W Model 29 did not fail at 80,000 psi, while the Blackhawk cylinder failed at 60,000 psi. Both are way beyond SAAMI safe levels. People think Rugers are stronger because they are thicker. See ad below.

I am not sure exactly what is meant by "outlast" or "endure better" in the post, but if you mean frames and major components damaged from long term firing, this is just plain wrong. If you mean that an S&W might need a tune up more frequently, perhaps, but I am not even sure I am prepared to concede that point.

Either way, I just disagree as do the laboratories. The one point I won't argue is that investment casting is a less costly method of manufacture.

I normally agree with your posts, but here I don't.

Brian Pearce wrote the information in the following paragraph in his excellent article in Handloader #217 "Understanding the .45 Colt". HP White labratories tested the Super Blackhawk in 44 magnum, and it took 80K CUP to destroy it. The Blackhawk in 45 Colt took over 60K CUP to destroy it. At the time the tests were conducted the 44 magnum was still listed by SAAMI at 43,500 CUP.


I have looked for it, but I have yet to find or see any data from HP White (or anywhere else) that shows the M-29 will surpass the Blackhawk in pressure tests, especially regarding the cylinder itself.

The Blackhawk will easily outlast the 29 without needing any major tune-up work. Silhouette shooters proved that time and again a long time ago, and not just with the 300 grain loads everyone worries so much about. The fact that the 29 could not stand up to constant use with full power ammo, and that shooters were starting to spend their cash on other brands was the total reason for the endurance package being introduced.

 

[Comrad]

I'm glad you broached the subject.

 

[jfp357]

As a young (very young) man I worked at S&W in Springfield,Ma. I watched the broaching operation many times. The most experienced machine operators did the work. I am NOW impressed with the process I watched, after reading this forum.

 

[Rick_A]

Then Glock came along and rendered most of this discussion moot.

Well, when Glock starts making double action revolvers that may become relevant here.

 

[BigBill]

I build a cnc lathe to machine the m1Abrams main engine rotor which is titanium. The machine they purchased from Japan couldn't handle cutting this metal. The tooling to cut the rotor was $250k in the early 80's. The federal inspector also witnessed a horse power cut we did on all the machines for the oil industry. We took a one inch wide cutter and drove it into a steel billet till we got the amperage rating and horse power from the motor running the machine. The curly q's came off the billet sounded like machine gun rounds hitting the guards. The inspector seen this and went wild about what a Bullard machine could do. These machines could hog yet hold tolerances to the millionths.

Stelite is used in making exhaust valves in engines. It can take the heat yet also take the gas we use today. We removed the materials that cushion the valves when they hit the seats like the lead. With these engines running hotter today to get the emissions better probably both valves are stellite now. My valve grinder needed special grinding wheels for stelite valves. The standard grit wheels couldn't touch this harder steel.

 

[DWalt]

I doubt there is a S&W MIM part that is not sintered.

MIM involves heating after forming from powdered metal, but the actual MIM process is substantially different from sintering.

 

[JDBoardman]

Broaching is a really cool process. We use it extensively in turbojet and turbofan engine manufacture. Each turbine, compressor and fan disk may have as many as 72 broached slots around the perimeter to hold the blades. Since the major loads on the blades are in a circumferential direction, using fasteners to hold the blades won't work, and since the blades are removable for economic overhaul of the engines, some method of positive location and retention is necessary. Hence, a Christmas tree-shaped broached slot for each blade, and a matching fir tree-shaped root on the blade. The complexity of the slots mean that broaching is the only feasible fabrication method.

The blades themselves are investment cast, so complex shapes are not too difficult to make. Again, the stress loads are axial along the blade, and are also complicated by high temperature creep, heat-accelerated corrosion, erosion, etc. Special nickel superalloys are used, since, as your friend indicates, a collection of various properties need to be considered to achieve the optimum results. In addition, specialized cooling processes are used in the casting process to achieve axially oriented solidification, or, ultimately, single-crystal solidification. These parts are not typical investment castings, and the properties desired are achieved by both alloy composition and cooling/solidification processes. (and, as an 'oh by the way... S&W Forgings make certain specialized small parts for us, so they are still in the forging business).

(edit for Mbliss57 - did Wyman shut down the 50K ton press they had in Houston? We used (2000-2001) to make Offshore Platform Risers [40' long, 36" diameter, 4" wall] from titanium mults and CFM56-3, -5 and -7 fan disks from Ti 6-4)

 

[mbliss57]

Good article explaining MIM

I posted this in an edit but many like me don't often reread old posts.
The MIN process explained. There are even Pics!!

http://www.pim-international.com/aboutpim/binders

Mike

 

[mbliss57]

Broaching is a really cool process. We use it extensively in turbojet and turbofan engine manufacture. Each turbine.....
(edit for Mbliss57 - did Wyman shut down the 50K ton press they had in Houston? We used (2000-2001) to make Offshore Platform Risers [40' long, 36" diameter, 4" wall] from titanium mults and CFM56-3, -5 and -7 fan disks from Ti 6-4)

JD.. I was not aware WG had a 50K ton forge press in Houston. I was told (by colleagues at WG) they only had the one at WG in Worcester, MA and 1 at Alcoa in Cleveland. (I have seen the one in Cleveland) I will research it. If you used it.. it must be there. The 2 up North were made under USAF contract right after the WWII when Americans found a destroyed 50K ton press in post nazi Germany. Both have been rebuilt since.
Do you still work for WG?

Edit: I was wrong about the MA location. The 50K ton press at Wyman Gordan is in N Grafton MA not Worcester. The one in Houston is a 35K ton press.
Wyman Gordon Forging Companies | Wyman Gordon Grafton Forging Operations

I wonder what the largest press S&W uses on it revolvers?

Mike

 

[Doug M.]

I'm glad you broached the subject.

*
Hahaha. I see what you did there.

 

[Abwehr]

Being an engineer myself, I have followed this thread closely and agree with most areas of firearms manufacture from the correct steel, aluminum, and various alloys. Then which is best forgings, casting, MIM, etc.

But, what about some of the latest aluminum alloy with Lithium. I know Li-Al is know the world over, but there are some "recipies" of Al-Li that is proprietory and have the ability to reach 50-60 kps. The material being lighter and stronger than other aluminum alloys. The only problem with the strength is that it is in one direction. What are the thoughts from other with Li-Al in firearms?

 

[jaymoore]

Broaching is a really cool process. We use it extensively in turbojet and turbofan engine manufacture. Each turbine, compressor and fan disk may have as many as 72 broached slots around the perimeter to hold the blades. Since the major loads on the blades are in a circumferential direction, using fasteners to hold the blades won't work, and since the blades are removable for economic overhaul of the engines, some method of positive location and retention is necessary. Hence, a Christmas tree-shaped broached slot for each blade, and a matching fir tree-shaped root on the blade. The complexity of the slots mean that broaching is the only feasible fabrication method.

Couldn't find a good christmas tree photo right quick, but these slots are likely broached as well. (Photo taken during initial set up of a spline check for re-establishing the indiron mark.)

Bringing things back a ways, we talked to some of the old Curtiss engineers and they stated that the main reason that they forged many parts was just to increase production. It was quicker to produce near net shape parts using this process than any other available at the time and still have reasonably light weight components. Nuances of refined grain structure, etc. were of secondary concern, and if other methods had been availablr, they would have used them! Very un-nostalgic fellows. No reason to assume S&W was any different. They just had no pressing reason to modernize for quite a spell.

A NOS P40 fuselage lower longeron attach forging and my tracer mill billet "in process" new production parts which are currently flying:

 

[Black_Talon]

Didn't we have these MIM pro/con discussions ad-nauseam a few years back? Does this need to be rehashed?

 

[SweetMK]

Didn't we have these MIM pro/con discussions ad-nauseam a few years back? Does this need to be rehashed?

It is either re-hash, or discuss retirement benefits!!