Mim Hammers & Sears

[JeffCSR]

Right now I don't think I shoot or dry fire enough to ever wear out an MIM hammer & sear.... I'm probably a 3 to 5 thou round a year per gun max.

What's this groups feelings on these parts?

Do any of you serious shooters leave them in?

[JD45]

Your annual round count sounds like mine. I have an old Kimber with all of the stock trigger parts still in it. Using the learn-as-you-go home gunsmithing method, I did a fair trigger job, in stages, over two years. Its hammer hooks are at least .021" and breaks at 3 1/2 lbs.. The hammer has never followed the slide or had any other trouble. Currently the round count should be well past 12,000.

Since I wanted to know more about MIM hammers, and had heard that stoning one would remove the surface hardening and expose soft metal, I called Kimber. They said that it is the same hardness all the way through, and it could be stoned like any good trigger. I don't have a clue about MIM hardening other than what they told me.

[mcoliver]

Noob Q. How do you tell if the hammer or sear is MIM just eyeballing it?

[JeffCSR]

How to tell.... nipples, where the metal is injected. Like the sprue from a model airplane kit.

Several parts I have also have circular impressions in different areas.

[wide45]

How do you tell the difference between investment cast, and MIM?

[Run n Gun]

Your annual round count sounds like mine. I have an old Kimber with all of the stock trigger parts still in it. Using the learn-as-you-go home gunsmithing method, I did a fair trigger job, in stages, over two years. Its hammer hooks are at least .021" and breaks at 3 1/2 lbs.. The hammer has never followed the slide or had any other trouble. Currently the round count should be well past 12,000.

<{POST_SNAPBACK}>

I got about 20K out of my stock Kimber hammer/sear before they "went away". I replaced them with EGW and man, you should feel the trigger now!

Ed

[cking]

I read an interesting article about MIM somewhere and they claim the metal density is about 95% of a cast part. Now Cast parts have a density that varies around the 95% mark also. I believe they are all comparing that to cold rold steel density.

I also don't believe that density is the only factor, it is how the part reacts to repeated impact and stress.

Unless somebody here works at a aerospace machine shop area, or gear cutter, or tool & Die where they have access to a variety of steels I doubt we will find out.

All of the stress failures I've seen with mim and investment cast look like packed grains of sand under a 20 power scope. The hot rolled steels and forge steels don't show that grainy structure under a 20X scope.

One tool and Die guy told me that when you cut it on a lathe, the curl that comes off will tell alot about the quality of the steel.

So chime in Tool & Die guys!

[MoNsTeR]

All MIM hammers look the same. My guess is whether the package says McCormick, BUL, Nowlin, Wilson, or whatever, they're all made by the same company.

Some say the Springfield hammer is MIM too; I don't believe it.

Personally, I think MIM hammers and sears are garbage and would never use them in a match or defense gun. The cost of quality parts is so small, I see no reason to take chances.

[EricW]

MIM is easy to detect. It uses the exact same process as plastic molding and therefore has all the tell-tale defects: parting lines, ejector pin marks, gate vestiges (where the plastic is injected), and flash.

As long as people think they can buy a quality 1911 for $500, there will be MIM parts in them. The ones in my S&W tuned up OK, but getting a first-class trigger that survives an IPSC shooter is pretty unrealistic. I don't see any problem with using the MIM parts until they turn to junk, then swapping for EDM'd parts (my plan).

For anyone who isn't familiar with the MIM process, powdered metal is mixed with a binder, usually polyethelene or wax. That mixture is then put into an injection-molding machine and made into a "green" part. The green part is then placed into an oven where the binder is melted out. The part shrinks during this process. Finally, the powdered steel part is put into an oven where the grains of metal fuse together. Because of this process, MIM can never produce a durable hammer or sear. If the metal was hot enough to fuse the grains completely, you'd get a blob and not a hammer.

MIM has a place in manufacturing. Making hammers, sears, and 1911 extractors is not among them.

[TRUBL]

I believe you guys are misunderstanding the process here......a MIM part can be made out of a variety of different types of metal, just as a die cast part can be.

It is the metal used and the heat treat process used that determines the hardness and toughness.

Assuming that the injection process works (and it does).....if someone were to make, say a Trigger out of A2 mat'l....that trigger could then be machined afterwards, heat treated (hardness) and drawn back for toughness

MIM is denser than casting, and actually, it is just another form of casting....only instead of pouring the molten metal in, it is actually injected. (that's what the 'I' stands for)

If you want the strongest raw mat'l possible, I guess you'd have to settle for something like rolled plate steel or hammer forging.

Yes....there are many places that MIM parts are used with excellent results for Military, police and self defence areas.

What it comes down to is.....the MIM process is not bad.....rather the mat'l used and post processes.

Hope this clears some things up.

[JeffCSR]

I have one Springfield hammer that is MIM, it's a chromed Delta hammer. It has the same type of injection marking as Kimber hammers have, just a little lower. The other Springfield hammers I have are not MIM.

[jjanglin]

Guys:

I had some problems with Para's parts they are case hardend I took

them to the Cryogenics shop and had them done costs a few bucks Ive

also had injection molded parts done .

Major Roger Sherman M production shooter has 75,000 rounds on his

cryo treated gun.(PARA LDA)

The process is really good,conagra started doing their cutting blades here

in Omaha the process improved their cutting blade life 40%.

Some Cryo shops dont do the process right so its got a black eye or two

doing it right takes about 72 hours check it out you will be pleased.

Jim Anglin

Sailors Custom Pistols

[EricW]

But, what's heat treating and cryo got to do with the price of bananas?

You can do anything you want to a MIM part, the fact will still remain that it's MIM and will still be a melded lump of *individual* grains of metal. MIM will always be metallurgically inferior to tool steel. No amount of post-processing can change that.

Like my friend from TX used to say: "You can't make chicken salad out of chicken s***. "

[MoNsTeR]

...that trigger could then be machined afterwards...

MIM parts are never machined post-molding. It defeats the entire purpose of the process, which is to produce finished, no-fit parts. MIM'ing a blank and machining it would cost more than EDM'ing from barstock.

[TRUBL]

"NEVER"....is a very long time......yes, some parts ARE machined (I am talking grinding operations). There is a limitation to the accuracy of the process....and if you need to hold .0002", MIM will not do that.....but MIM is a lot cheaper than cutting something out of bar stock. If you look at any MIM part that is used for a hammer or a sear......you will see that the sear areas are ground......that would be a post process

MIM is a process....not a type of steel....you can make a MIM part out of tool steel...and post treating of the metal has EVERYTHING to do with it.

Post heating treating processes have everything to do with the toughness and hardness of the part.....whether or not your sears will function for 3 hits....or 300,000 hits. Cryo has significant properties of lengthing tool cutting wear and toughness of materials.

Monster....you've been in this type of discussion before on another forum, about a year ago....the things I am saying here pretty much are the same as said there....you know from that forum that MIM is a fine process for Gun parts....why try to beat a dead dog somewhere else?

Densities are 95% to 99% of rolled (or machined) plate stock......and at the tensile strengths of the metals in question (A2, O1 or even S7).....if they fail in a weapon....so will rolled plated stock......meaning there is a MAJOR design flaw in the weapon, not the use of a MIM part.

MIM is used for Cutting tools, engine parts, car suspension parts.......parts that take a lot more tension and pounding (impact) that our little springs deliver to our hammers on our pistols and rifles

Carbide......is actually.....a type of MIM part, starting out as a powdered material as well......cuts lots of hardened tool steel (that would be rolled plate...from a mill, only hardened to a 58-60 Rc)

[MoNsTeR]

From the discussions I've read, I've learned that MIM is an acceptable process for the manufacture of inexpensive, mass produced firearm parts. It is not a "fine" process, and MIM fire control parts have no place in a $2000+ race gun.

The MIM hammer in my Dan Wesson failed inside the first thousand rounds. I just had a Wilson extended slide stop snap off at the lever after less than that. That said, I have a (non-extended) MIM slide stop in my Limited gun. I could have paid 2-3 times as much for a barstock slide stop, but who cares? This one does just fine. Hammers and sears on the other hand, I'll gladly pay the premium.

[TRUBL]

Monster....we will continue to disagree for sure.....it may have no place in a $2000 race gun....but they are putting those parts in $3000 race guns.

Many AR15 manufacturers use a cast hammer in their guns.....that is only case hardened. And....cast is inferior to MIM Yes....I've seen them break (very rare), I've also seen hammers made for plate steel break as well. It was not do to Process of manufacture....in the casting case, bad casting; in the plate steel, bad design....high stress point, broke right in a corner, as predicted.

Bottom line......I can design and have made a MIM hammer/trigger that is stronger, cheaper and last longer than many of the 'high' quality hammers/triggers out there now.

One more thing, are you sure the Dan Wesson part was MIM?......not sure if that process was around at that time....or perfected. S&W uses alot of MIM parts, very hard.....very long lasting. Personally, on my 646 the parts have 5000+ rounds with no signs of wear what so ever.

I would use and/or design MIM parts for firearms anytime.....you get a cleaner, better looking part that can be designed to be as strong (or stronger) than a part that is whittled out of a piece of steel.....and be cost effective to the consumer as well.

[bountyhunter]

Noob Q. How do you tell if the hammer or sear is MIM just eyeballing it?

<{POST_SNAPBACK}>

It will have at least two "holes", one where the stuff is injected into the mold and one where the air comes out. many also have "mold lines" where the mold separates.

[bountyhunter]

How do you tell the difference between investment cast, and MIM?

<{POST_SNAPBACK}>

By looking, you probably can't. density on cast is about 65%, on MIM it's about 95%.

[MoNsTeR]

One more thing, are you sure the Dan Wesson part was MIM?......not sure if that process was around at that time

It was one of their 1911's, new around 4 years ago, with the same Kimber/CMC/BUL/Wilson/Nowlin MIM hammer that everyone uses.

Literally every small part on that DW is a McCormick, almost all MIM.

[Ross Carter]

Like my friend from TX used to say:  "You can't make chicken salad out of chicken s***. "

<{POST_SNAPBACK}>

I love that quote, I hope it's ok to use.

As my friend Geo calls them " squirted parts " I just can't use mim hammers and sears. If you want to do something interesting try to weld a mim part like a beavertail. You will see little pieces just pop out not even close to the weld, not the kind of stuff that gives me confidence. Before anyone thinks it, I am very proud of my tig but I wouldn't weld on a hammer or sear. of anyone elses anyway.

Ross

[boo radley]

The thumb safety on my Kimber Custom II broke as I was cleaning the pistol after my first IPSC match. At least it waited until I was done. :/

I believe the part is MIM - there is a faint "flash" line on the back, and the inside looks like powder....I'll attach a pic.

It's considerably irritating waiting for Kimber to send me a new part; I'd hoped to have it by now. In the meantime the gun is in pieces. <sigh>

[Jasonub]

dont wait for it just get an sv safety

[cking]

Looks to me like all of the binder didn't get cooked out and then carbonized and weaken the part. Plus theres that packed sand look.

I think MIM is ok for parts that just ride along, like rear sights, plunger tubes, grip safety, main spring housing, but that's about it.

I know somebody said you can use the same ingredients as toolsteel in MIM, but there more to toolsteel than just the mix. It how its baked, rolled, cooled and tempered. My guess is that the hot rolled, or forging gives the metal the consistent core and some machinist book I read talk about something called austites [spelling]. Hot rolled and forging lines them all up and evenly disperse them throughout the metal. Which determines how well the metal reacts to high stress and shock. Take a look at a piece of rifle target steel after it been shot at awhile. No matter how you weld it, it cracks at the weld. True we have learned alot about stress concentration points in design, stay away from sharp corners, and computer modeling has really helped. But with 1911 we don't have many options on changing the shape of a part. I you could start from scratch and come up a sear, hammer designed for MIM I bet you could get a part that would hold up. I'm just glad CNC has improved to such an extent that it allows high quality parts at reasonable cost.

[TRUBL]

I think you all would be surprised at which parts you buy are die cast, MIM or actually made from a billet or forging.

Kinda like the guy that would not buy a Japanesse car, but every appliance in his house is made over there.

Keep in mind, that in the case of like your safety nothing is 100%....there is always a reject. However, I suspect that part is die cast, not MIM.

Oh yes....the frame on a Kimber and S&W 1911's are cast (and in the same plant...imagine that, eh?)...by the way....incase you didn't know that.....so are Para's and colt's. Springfields are Forged as are Norinco's (that's a hard one to swallow). STI & SVI ofcourse are machine from bar stock. How many front ends and slides of 1911's have you seen fly off from the link hole forward because of the casting and the pounding it takes from the force of the slide slamming forward?

food for thought....ofcourse, I say this and shoot SVI

Do a search for MIM......lots of good info on the net and it will probably put your hearts at ease on the process and the strength of parts compared to others.