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Hammer Width

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floydthecat View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote floydthecat Quote  Post ReplyReply Direct Link To This Post Topic: Hammer Width
    Posted: Jun 30 2019 at 5:19pm
Anyone have the spec. handy or know.

The width of a spec. carbine hammer at the base...the pin end?
I have occasional light strikes and think I have traced it to the hammer. Too lazy right now to tear-down another carbine to compare. 

This one measures .280-.283 as you move from top to bottom. It feels a little wobbly to me and I have never used shims. It’s not USGI.
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jackp1028 View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote jackp1028 Quote  Post ReplyReply Direct Link To This Post Posted: Jun 30 2019 at 7:10pm
.28 -.01 per RIA Ordnance drawing. Check hole size too. S/B .1605 Dia +.0020.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote W5USMC Quote  Post ReplyReply Direct Link To This Post Posted: Jun 30 2019 at 7:34pm
Kuhnhausen's shop manual also says .28-.01.
I just measured one of my spares and it measures .276-.278 as you move up.
I could be wrong but I don't think the width of your hammer at the base would be the cause of light strikes even if wobbly? How about the hammer spring, or gunk inside the bolt preventing full firing pin protrusion.
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blackfish View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote blackfish Quote  Post ReplyReply Direct Link To This Post Posted: Jun 30 2019 at 7:40pm
You talking about the skinny section at the bottom of the hammer below the pin where the sear rides? For an M1 hammer it's 0.28" thick



The next section up (just above the pin where hammer strut sits) is thicker, 0.387"

I'd be more suspicious of your trigger housing.
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jackp1028 View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote jackp1028 Quote  Post ReplyReply Direct Link To This Post Posted: Jun 30 2019 at 7:52pm
Also, the surface of the hammer that strikes the firing pin may develop burrs from peening against the rear of the bolt and may be dragging in the firing pin slot, especially if it's a softer commercial hammer. Does your hammer do this?

JackP
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floydthecat View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote floydthecat Quote  Post ReplyReply Direct Link To This Post Posted: Jun 30 2019 at 8:02pm
Seems like I must be ok with the width. Yep...the “skinny” part down on the pin-hole. It could very well be a pin or the hole. The problem seems to follow this hammer. I will get a good string of solid strikes and ignition, then out of the blue, a random light strike. Using all good commercial ammo with in-spec case lengths. I will tear into the bolt and check things out, but I don’t think it’s the pin or the hammer spring. I have tried three different springs.

Somewhere somehow something is either binding the pin, or the hammer is not making proper contact. I have made sure the bolt is rotating and locking. Once it locks over the cartridge rim....things have to be aligned, I would think? The hammer does have considerable “wobble”.....a little more than I would think. I’ll sleep on it and dig further into into this week. .28 spec. measurement is what I was looking for and this hammer meets that. I need to consider the pin and the hole.


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floydthecat View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote floydthecat Quote  Post ReplyReply Direct Link To This Post Posted: Jun 30 2019 at 8:05pm
Originally posted by jackp1028 jackp1028 wrote:

Also, the surface of the hammer that strikes the firing pin may develop burrs from peening against the rear of the bolt and may be dragging in the firing pin slot, especially if it's a softer commercial hammer. Does your hammer do this?

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floydthecat View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote floydthecat Quote  Post ReplyReply Direct Link To This Post Posted: Jun 30 2019 at 8:06pm
I just saw your post Jack. I’ll take a closer look at the contact areas with the bolt.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote painter777 Quote  Post ReplyReply Direct Link To This Post Posted: Jun 30 2019 at 11:32pm
Had a Plainfield come in acting up, sounding some what like yours.
The left side of the TH where the hammer strike stops had chipped enough metal away that the hammer would sometimes slip in beyond/between the top edge and bind in to the bolt slot as the bolt was returning IIRC, just like JP's picture.
When dry firing and hand cycling rounds thru. if you caught it when the hammer has wedged in, you could feel the bind on the hammer, op slide and bolt.
Hard to explain: Just take a look at the hammer strike area on your trigger housing for any excess metal missing.
We fixed his by replacing the TH.

Good Luck Floyd, keep us up to speed

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floydthecat View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote floydthecat Quote  Post ReplyReply Direct Link To This Post Posted: Jul 01 2019 at 5:27am
I have tried it in 3 different housings. An SG, a Rimer and an IJ. I don’t think it’s a housing. It is something specific about this hammer and it may just be sloppy machining. I have had it lying around for a few years and it has not been in a working gun until I decided to build-up a spare TH. I want to figure out what’s up with it out of curiosity, before I toss it. I need to do more digging-around before I toss it.


Take a look at the top of the nose. There is a ridge that is protruding inward at the top and that may be the only thing striking the pin, or dragging in the pin-channel like Jack mentioned. The nose is not polished...that ridge is preventing full contact. Could this be my culprit? The ridge is protruding toward the face of the hammer and not away as one might expect if the bolt was rolling it up.

If you can see in the shadow of the nose in the lower picture...the ridge looks very pronounced.






Edited by floydthecat - Jul 01 2019 at 7:46am
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jackp1028 View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote jackp1028 Quote  Post ReplyReply Direct Link To This Post Posted: Jul 01 2019 at 8:40am
Check the clearance between the hammer and the slot in the bolt for the firing pin tang. This is a feature of the design that is supposed to prevent out-of-battery discharges. It should be .004” min, .009” max.
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floydthecat View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote floydthecat Quote  Post ReplyReply Direct Link To This Post Posted: Jul 01 2019 at 5:22pm
Think I may chalk this up to a cast commercial hammer so far out of spec. in so many places that it’s not worth the effort. The pin-hole is significantly over-size. The face of the hammer is seriously over-size by some 12/1000th’s. Both a Wault and an Inland hammer from other carbines work fine. I’ll just grab another GI hammer. Sometimes we post things to maybe help other people and sometimes for fun, or escape from boredom. 
This is no longer fun and has become boring.

Lessons learned.....obtain and deploy good USGI spec. parts.
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