MIM vs forged

[steelslaver]

This isn't about which is better. Both have there points and MIM has kept cost down

But, I recently learned that MIM parts are also considerable harder than forged ones

In the past I picked up a 38-44 outdoorsman with a funky hammer spur. My plan was to replace it with one of the spare 1917 hammers I had. Imagine my surprise when I found out the hammer stud on the outdoorsman was larger than a 1917. Verified the size of the hole in the outdoors trigger and was able to upsize the hole in 1917 to that size with a regular numerical reamer of the correct size. went right through

A forum member wanted to replace his blue MIM trigger with a flash chromed MIM one and found the flash chromed one would not go on the stud. He asked me if I would make the hole in it match the one in the blued one. No problem I said. When I checked them with pin gauges the blue one's hole was .125 and the flash chromed .106 . No problem I had a couple .125 (1/8') reamers. So I took the hand off the trigger and discovered that the springs are not pinned in like on earlier models. So there is a hand spring free ranging in my shop now. Learned something. Anyway My reamer would not cut on the MIM part. Too hard. But luckily it being 1/8" I had several 1/8" 4 flute carbide end mills and one of those made short work of enlarging the hole.

The next question I have is whats with the different sized hammer and trigger studs. I got it with J frames. But you would think all N frames would run the same stud sizes and I thought all K, L and N frame triggers were the same.

 

[ProCarryNAustin]

I never worry about MIM in my firearms or commercial aircraft (engines) or the transmission in my truck (transmission).
If done properly it works great.
Improperly done, it is the same problem as improperly done forgings.

 

[Brownie0486]

A remarkable precision gap exists between MIM parts and forged components. MIM achieves ±0.01 mm tolerance, while forging reaches ±0.5 mm. Metal Injection Molding (MIM) technology has transformed parts manufacturing and delivers 95-100% density. Traditional powder metal only reaches 75-80%. Forging stands out in producing larger components up to 30,000 kilograms. MIM excels with complex, smaller parts under 250 grams. Smith & Wesson demonstrates this fundamental change by converting 54 components in their firearms to MIM production

https://jhmim.com/mim-parts-vs-forged/

 

[BB57]

A remarkable precision gap exists between MIM parts and forged components. MIM achieves ±0.01 mm tolerance, while forging reaches ±0.5 mm. Metal Injection Molding (MIM) technology has transformed parts manufacturing and delivers 95-100% density. Traditional powder metal only reaches 75-80%. Forging stands out in producing larger components up to 30,000 kilograms. MIM excels with complex, smaller parts under 250 grams. Smith & Wesson demonstrates this fundamental change by converting 54 components in their firearms to MIM production

https://jhmim.com/mim-parts-vs-forged/

Sinter forged parts used in firearms, like the receivers in the post 1963 to 1982 Winchester Model 94 carbines and rifles, generally achieve about 95 percent density. In the case of the Model 94, they made up for that slight loss in density by using a stronger alloy with higher chromium content (which is what causes the rebluing issues with traditional bluing salts). In the case of the Model 94 there was no loss of strength and arguably again in total strength. There is no doubt at all that the steel alloy itself was more consistent than forging and could be made to very close to final dimensions, greatly reducing the milling required.

MIM parts are similar in terms of being able to be made to very close to final dimensions. Density will range from 95 percent to 995 percent, depending on the application and the process selected to achieve the desired density.

Ruger used MIM fire control parts in its Service Six, Security Six, Speed Six series revolvers and chose to make the parts slightly larger than required to ensure longevity. Fire control parts are face hardened to produce a long wearing surface, but hard also equals brittle which is why it is only face hardened. However, over time and repeated impacts, that harder crystalline structure at the surface migrates deeper and starts to embrittle the softer, tougher steel at the parts core. Ruger designed those revolvers for a steady diet of full power .357 Mag loads to offset the flaws in the Model 19 and similar .357 Mag K frames, and also designed those fire control parts for the long haul.

By the time the Security Six, etc were designed, the effects of migrating crystalline structure was well understood and well documented in Walther PP series fire control part failures due to decades of decocking in high round count pistols.

Ironically the same problem occurred in Beretta M9 pistols, mostly those used in training or security units where they were subject to frequent function checks with repeated slide drops and decocks that produced embrittlement and parts breakage in what were otherwise low round count pistols.

S&W got on board when most of the negative reaction to MIM subsided and it became mainstream, as it significantly reduces production costs without compromising strength or quality.

 

[steelslaver]

My personal belief is that MIM parts are superior to forged in everything but appearance. I love the older guns and noting looks as great as nice color case hardening. Forgings also fail and often the cause is a inclusion in the parent billet. ALL forgings start out as casting billets. The hammers and triggers are color case hardened. They don't start out as high carbon steel but are forged then machined to tolerance then subject to a 1500f soak in carbon rich material then quenched. This causes carbon to migrate into the surface layer of steel and harden. That surface isn't deep and fairly easy to remove. Case in point a regular reamer can remove it from the softer material or reworking the sear surfaces can expose soft quick wearing steel. Not so with MIM, It is uniform hardness through out

 

[SnidelyWhiplash]

Here's a three part discussion on MIM technology...

Part 1
Part 2
Part 3

 

[oO_Rogue_Oo]

I'm no expert but my personal experience has been that MIM is fine for light polishing but if you are re-profiling a part it needs to be avoided. Kind of like an M&M; hard shell, gooey in the middle. Every MIM part I have ever tried to re-profile has ended in failure.

 

[BB57]

I'm no expert but my personal experience has been that MIM is fine for light polishing but if you are re-profiling a part it needs to be avoided. Kind of like an M&M; hard shell, gooey in the middle. Every MIM part I have ever tried to re-profile has ended in failure.

That’s not a MIM issue it’s a face hardening issue.

Consider the old school Hi Power. Those parts are forged and face hardened. If you take too much metal off in the course of a trigger job, and remove the outer face hardened metal, you’ll get a superb trigger, but one that won’t last more than a few hundred rounds before that softer, tougher steel you exposed wears away.

Consequently, any time you remove much metal from a face hardened part it must be rehardened.

At the same time that tougher, softer steel underneath is what gives the part its strength. Hard steel is brittle steel' and you need both in a part that requires both strength and a long wearing surface.

It’s no different than nitride hardened cam shaft lobes or cylinder bores.

 

[steelslaver]

How hard and how deeply hardened can be controlled either on MIM or forged. I would think that triggers could be harder though out than a hammer because the trigger is not subject to nearly the impacts a hammer is.

Interesting article on case hardening and other methods of surface hardening, iron and steel
https://en.wikipedia.org/wiki/Case-hardening

 

[Nightowl]

I have no trouble with MIM, but I have trouble with all the loose parts! That hand torsion spring is a real bear to install and will take flight never to be found. The trigger rebound shaft is easier to find but falls out just about every time I handle the trigger. UGH!! Plus they sound tinny!

 

[wproct]

I have no problem with MIM parts what so ever. My only problem is when they alter the profile for no real reason.

 

[TAROMAN]

In over 50 years shooting many dozens of gun types, the only broken parts failures were forged. Once on a USGI 1911 and the other on a Model 60 S&W.

 

[Lt.Donn]

I never worry about MIM in my firearms or commercial aircraft (engines) or the transmission in my truck (transmission).
If done properly it works great.
Improperly done, it is the same problem as improperly done forgings.

Amen...I'm too busy to get wrapped around the axle on such things

 

[b737lvr]

Just a friendly reminder that prior to MIM parts the hammers and triggers on Smith revolvers were stamped soft steel with a case hardened skin.

 

[Thaddeus Beauregard]

This isn't about which is better. Both have there points and MIM has kept cost down

But, I recently learned that MIM parts are also considerable harder than forged ones

In the past I picked up a 38-44 outdoorsman with a funky hammer spur. My plan was to replace it with one of the spare 1917 hammers I had. Imagine my surprise when I found out the hammer stud on the outdoorsman was larger than a 1917. Verified the size of the hole in the outdoors trigger and was able to upsize the hole in 1917 to that size with a regular numerical reamer of the correct size. went right through

A forum member wanted to replace his blue MIM trigger with a flash chromed MIM one and found the flash chromed one would not go on the stud. He asked me if I would make the hole in it match the one in the blued one. No problem I said. When I checked them with pin gauges the blue one's hole was .125 and the flash chromed .106 . No problem I had a couple .125 (1/8') reamers. So I took the hand off the trigger and discovered that the springs are not pinned in like on earlier models. So there is a hand spring free ranging in my shop now. Learned something. Anyway My reamer would not cut on the MIM part. Too hard. But luckily it being 1/8" I had several 1/8" 4 flute carbide end mills and one of those made short work of enlarging the hole.

The next question I have is whats with the different sized hammer and trigger studs. I got it with J frames. But you would think all N frames would run the same stud sizes and I thought all K, L and N frame triggers were the same.

As for forged, S&W stopped forging the hammers and triggers across models in the 1950s and switched to 1018 mild steel that was stamped out, broached and swaged to shape, then case hardened. 1018 is very soft and was selected to make it easy to swage the spur pad. So, the pre-MIM hammers and triggers made from at least 1960 to 1994 were not forged at all and were soft in the center below the case hardened layer.

The current MIM hammers and triggers are through-hardened, not soft in the center.

Most triggers across K/L/N/X frames have the 0.106" stud holes, but the new Combat Magnums (M69, new M66) and some competition style N frames have the larger stud diameter and 0.125" trigger holes for who knows what reason.

 

[steelslaver]

Stamping is forging no matter what type of steel

 

[rpv-ak]

I have no trouble with MIM, but I have trouble with all the loose parts! That hand torsion spring is a real bear to install and will take flight never to be found. The trigger rebound shaft is easier to find but falls out just about every time I handle the trigger. UGH!! Plus they sound tinny!

Any part that self-launches itself, I remove while the firearm is completely covered in hay plastic or a gallon ziplock bag.

 

[b737lvr]

Stamping is forging no matter what type of steel

And driving your car off a cliff is flying

 

[steelslaver]

Ya, I mad an assumption that the hand torsion spring was fixed in the trigger on MIM triggers like the older ones are. Assume bites again

 

[steelslaver]

And driving your car off a cliff is flying

Hardly a close analogy, not even close in fact.

IF you need to heat the steel up red hot to form it it is forged. If you can just smack it into a die it is stamped. Lots of mild steel is forged to form parts.

The Key is the heat part. I assure you that those 1018 hammers really hot when they get staped out. Ig they were not they would be work hardened.

 

[adrianolsen]

MIM sucks. As a LE gunsmith, we saw all sorts of breaking. Trigger and hammer hooks, sear. If you bought a CHP 4006TSW, beware

 

[Thaddeus Beauregard]

Stamping is forging no matter what type of steel

No it isn’t. Forging involves heating the material cherry red and hammer forming it under extremely high tonnage impact. Stamping is cold forming a relatively thin part and cutting it out of a piece of sheet or plate material like a cookie cutter. Forging reorients the grain structure of the steel and strengthens it, stamping does not. Stamping just cuts and cold forms thin plate or sheet material and doesn’t improve its mechanical properties. Low carbon mild steels like 1018 don’t work harden to any significant degree; they are too soft and malleable.

Read starting 3rd paragraph under section “MIM Improvements” here, quoting former S&W engineer Norm Spencer:

https://revolverguy.com/all-about-mim-part-three/#:~:text=Take the new MIM hammers,with the stronger MIM part.

 

[Autonomous]

I did a trigger job on a ~2015 build Springfield Armory 1911 with MIM ignition components that came out very well. Will it stand up to 10,000s of uses? I don't know how deep the hardening on the hammer and sear are. Even if it only stays crisp for 5,000 rounds rounds that is a fair amount of shooting without the kneejerk MIM replacement some 1911 owners suffer from.

 

[steelslaver]

Never thought of or knew they used punch pressing on hammers and triggers but it would certainly work with a good punch and dies and a hefty press. Post work machining also. I did know that the hardening was only skin deep because and done by color case hardenin

 

[Brownie0486]

I did a trigger job on a ~2015 build Springfield Armory 1911 with MIM ignition components that came out very well. Will it stand up to 10,000s of uses? I don't know how deep the hardening on the hammer and sear are. Even if it only stays crisp for 5,000 rounds rounds that is a fair amount of shooting without the kneejerk MIM replacement some 1911 owners suffer from.

My 1982 SA 1911 didn't have mim parts and I shot that gun over 300K rds in 5 years in matches and practice. Rebuilt the guts at 130K or thereabouts. If I only get 10K out of their new product 1911's, that's a fail and a problem if it only lasts through 5K rds.

I guess mim isn't up to the same standards as cast/forged parts are regarding longevity.

 

[Autonomous]

Your car has MIM components, it is common in aerospace and aircraft. Lots of healthcare products use it.
Some is hardened all the way through. Quality MIM is better than you want to think.

 

[Brownie0486]

Your car has MIM components, it is common in aerospace and aircraft. Lots of healthcare products use it.
Some is hardened all the way through. Quality MIM is better than you want to think.

When I bought this AO parked 1911, I had my armorer replace the guts with high dollar parts. In working over the gun, he looked for any MIM parts and found NOT one part was MIM. I'll stick with cast/forged when possible. Why? Because I have had two 1982 SA 1911's that ran over 100K rounds [ and they also didn't have MIM parts as MIM wasn't even on the table as a possibility back in those days ]

 

[SnidelyWhiplash]

Your car has MIM components, it is common in aerospace and aircraft. Lots of healthcare products use it.
Some is hardened all the way through. Quality MIM is better than you want to think.

Pratt & Whitney has a proprietary process that hardens MIM parts completely through. P&W is the vendor that supplies Colt’s MIM parts.

 

[Brownie0486]

Pratt & Whitney has a proprietary process that hardens MIM parts completely through. P&W is the vendor that supplies Colt’s MIM parts.

But are they hardened completely through on Colts is the question.

 

[Autonomous]

Do they need to be?
Are all hardened parts through hardened?