Broken Hammer

[Rogan]

Apparently all the recent talk of broken parts was meant to be as I broke my C&S firing pin and my factory hammer (which I dremeled) two days apart. Here's a photo of the damage (assuming I've figured out how to post it).

Edited December 9, 2007 by Rogan

[HighVelocity]

Ouch. That's a show stopper for sure.

What do you gain by taking so much metal off of the hammer? I'm not trying to be facetious, I really don't know.

Gary J.

[Rogan]

Well, my understanding of the fall of the hammer, after a great deal of research here, is that a hammer with less mass travels faster for a given main spring weight, thus giving the frame mounted firing pin enough energy to ignite the primers.

Now I know things get way more complicated than that, but in a nut shell, the lightened hammer allows for less spring weight, which means a lighter trigger pull. By dremeling the hammer, I took off 200 grains of wieght and dropped 1 3/4 lbs off the trigger pull weight. I was at 5 lbs with federal primers, 100% ignition.

[Carmoney]

Rogan's exactly correct. I've never seen one break like that--I usually leave a little more "meat" in the spot where that hammer broke, but not a whole lot more--I think it's a fluke.

[Round_Gun_Shooter]

Looks like 2 problems:

1. Extended firing pin not going flush with the rear of the frame caused

2. Over cut hammer to fail at a point where torque was was exerted from (see #1)

Because of this, both parts failed. I have never considered the extended pins drop on and have always fit and checked those I have used. Maybe that is why I have never had one fail.

[warpspeed]

If that is out of a 625, I think I have a factory one kicking around if you want it. PM me if interested.

[scooterj]

Cut that tail off your next one. The extra weight, located where it is, was a contributing factor in the failure. Less weight=Lighter trgger:)

[steiny]

Two words for you.....Randy Lee......

He can fix all your woes.......

Edited December 10, 2007 by steiny

[bountyhunter]

Ouch. That's a show stopper for sure.

What do you gain by taking so much metal off of the hammer? I'm not trying to be facetious, I really don't know.

Gary J.

Reducing the hammer mass increases striking energy so you can go to a lighter mainspring setting and get a lighter DSA pull.

[Rogan]

RGS,

When I installed the C&S fp, I made sure it went all the way flush. In fact, the lower portion of the hammer face was making contact with the frame, I had a wear mark where they made contact. The fp broke off where it necks down.

I left the "tail" on the hammer because I was concerned about debris falling into the action. Might not be a real issue, but that was my thought at the time of dremeling. I can see where the extra weight would have added additional torque to cause the break. At least it was during a practice session .

Steiny,

Already have message sent to him.

Thanks for all the input guys.

[Tom E]

Sounds like the normal C&S firing pin breakage. Too bad you didn't save the forged hammer and cut down an MIM hammer instead. I just make a straight cut down the back side of the hammer. No "dip" like yours and Carmoney's. Stuff falling in hasn't been an issue. They run 238 grns, MIM, no stirrup or sear.

[T3P_Guy]

Quick question, is there a limit as to how much metal you want to take off when doing this? Like is it possible to get it too light to where it starts requiring more mainspring pressure to get reliable ignition?

[Round_Gun_Shooter]

RGS,

When I installed the C&S fp, I made sure it went all the way flush. In fact, the lower portion of the hammer face was making contact with the frame, I had a wear mark where they made contact. The fp broke off where it necks down.

I left the "tail" on the hammer because I was concerned about debris falling into the action. Might not be a real issue, but that was my thought at the time of dremeling. I can see where the extra weight would have added additional torque to cause the break. At least it was during a practice session .

Steiny,

Already have message sent to him.

Thanks for all the input guys.

Thanks for clarifying. Did you ever get pierced primers from pin over travel? Did you use the stock FP spring or did you modify it? As for the hammer, it is a little too radical for me. I have used heavily cut hammers since starting in PPC long ago but never took that much off. If you don't get a hammer, let me know. I have a MIM I took out of Mooney's gun somewhere. Maybe the Post Office won't loose it like it lost the one I sent Ralph

Edited December 11, 2007 by Round_Gun_Shooter

[10mmdave]

Rogan, sorry about your hammer, after all that work and to have it snap really s-cks.

I like your version with the tail to keep the lines of the original.

Good luck on the next version, maybe the MIM version this time ??

A side issue here though, to go with the broken C&S firing pin issue ?

The folks that have had a pin break (or 3), were these pins being used in lightened

hammer revos

I ask because I don't run the modified hammers and haven't broken any C&S pins.

(Not trying to dredge this whole subject up again,

just wondering why some work and some don't)

[Tom E]

The folks that have had a pin break (or 3), were these pins being used in lightened

hammer revos

I ask because I don't run the modified hammers and haven't broken any C&S pins.

(Not trying to dredge this whole subject up again,

just wondering why some work and some don't)

Two stock hammers, one light weight. 2 "out of the bag" pins, and one where I ground the convex hammer contact surface flat, which also effectively shortened it some. One lived long enough for the convex (domed) end to put a dent in the MIM hammer. Not good, hence the flat one. Then the .495" S&W pins showed up and I could stop taking a spare pin to the range with me.

That aside it seems you can't make the hammer (in a center fire) too light, unless they break. Rimfires (617's) may be different. We've got titanium cylinders, a titanium hammer would be nice.

Edited December 11, 2007 by Tom E

[imashooter2]

A side issue here though, to go with the broken C&S firing pin issue ?

The folks that have had a pin break (or 3), were these pins being used in lightened

hammer revos

I ask because I don't run the modified hammers and haven't broken any C&S pins.

(Not trying to dredge this whole subject up again,

just wondering why some work and some don't)

Unmodified MIM hammer, lightened main and rebound springs (7 pound DA pull), stock firing pin spring. My C&S pin should have lived forever under those gentle conditions, but it lasted less than 2,000 shots.

[ocx]

Just goes to show that anything can break. What are the odds?

[bountyhunter]

Just goes to show that anything can break. What are the odds?

If that's a factory MIM hammer, the odds are the vibration from the Dremeling found a minute internal grain defect which allowed the part to fracture later.

I'm not a MIM hater, but it can have internal defects from grain variance or air voids in the mold.

[Tom E]

the odds are the vibration from the Dremeling found a minute internal grain defect which allowed the part to fracture later.

The Dremeling Vibrations combined with the Martian Death Rays are probably causing the firing pin breakage. I need to try some of Carmoney's scotch.

Edited December 11, 2007 by Tom E

[RePete]

Just goes to show that anything can break. What are the odds?

Or is that "goes to show that you can break anything"?

[professor]

From looking at the matching faces of where the hammer cracked, it appears that your Dremel action reduced the amount of metal there to a U-shaped cross-section. The solid metal of the hammer is machined for a pocket to hold the sear. As a function of forming that pocket, there is also a notch cut across the "face" of the hammer. In your first picture of the two pieces, as seen from the side, this notch is at the right hand end of the crack.

I don't think your Dremel action started the crack, but the degree of metal removed at the back of the hammer reduced the cross-section of the hammer to such a degree that there wasn't enough metal left to handle the stresses of firing the gun.

That face notch concentrated the stresses at the point where the crack started.

Consider the simple analogy of a solid bar that has a notch cut about half-way through one face, so the cross-section of the bar at the point of the notch is only 1/3 of the normal cross-section of the bar. Now, holding the bar so that the notch is facing in the direction you are swinging it, repeatedly slam the end of the bar against a solid brick wall. [wear gloves ]. The bar isn't going to bend evenly because you've created a localized weakness with that notch. Each swing will cause a crack to start there and spread through the remaining cross-section. Eventually, the bar is going to fracture at the notch. While the crack is gradually spreading, the mating surfaces of the crack will probably be smooth, as the metal gradually tears apart. However, the final hit will likely fracture a goodly chunk of the remaining metal, and leave a rough surface.

In a stock hammer, there's so much metal backing up that notch that the stresses of the hammer hitting the firing pin, and the shock against the hammer pivot pin from firing the gun are dissipated through a tremendous cross-sectional area. The weakest part of a stock hammer is probably at the base of the striking surface, where the metal is still so thick that you would not experience a hammer snapping there, ever. However, every little bit you Dremeled away reduced the cross-section in the vicinity of the sear pocket. At some point, the metal there became less than that at any other point of the hammer. Further reductions made it thinner. Obviously, you ended up with so little metal that it fractured there.

Next time, leave enough metal behind the sear pocket so the metal cross-section there is about the same as the width of the hammer. That should leave enough metal.

[LPatterson]

A side issue here though, to go with the broken C&S firing pin issue ?

The folks that have had a pin break (or 3), were these pins being used in lightened

hammer revos

I ask because I don't run the modified hammers and haven't broken any C&S pins.

Mine broke with less than 500 rounds with a new 625-8 & a JM hammer spring. The replacement Smith firing pins from Brownells are longer than the original.

[slflr]

Reducing the hammer mass increases striking energy so you can go to a lighter mainspring setting and get a lighter DSA pull.

Reducing the hammer's mass is not the object of the dremeleur. Reducing the hammers moment of inertia is. Removing the material at the far radius of the hammer, ie the "spur" is more effective than removing material closer to the hammer stud. Additionally, polishing your dremel work to a hi luster will remove potential stress risers.

[scottyinAZ]

Hello Rogan!! what gun is that hammer off??? 627 or 625?? i will have my 625 next week and would like to try to get together sometime soon. hope to pick your brain a little, i want to do the 625 work myself. Let me know how long till Randy responds, i would like to get another hammer from him and a FP for the 625 but i called him over a month ago on my 627 with no reply yet. I am not sure what it was you were doing when this broke, you had a word for it, ummm.. p r a c t i c e ? ? what is that?? i thought sunday WAS practice. anyways if you get some time to talk, i will PM you my phone number. i would like to get my 625 going ASAP, i know the guy i have to beat next year at the classic and he is kinda fast, and practices too i see. Hope you get it back running soon.

Thanks in advance

Scott Shepherd

[Revopop]

Ummm, did anybody look at the year in the date of the previous posts?