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Counting Hammer Spring coils |
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sling00
Hard Corps Joined: Apr 21 2016 Location: Tennessee Status: Offline Points: 941 |
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Posted: Jan 27 2018 at 9:59am |
I’ve had discrepancies in counting coils before and thought I would ask. I was taking inventory and came across a partial package of NOS Inland hammer springs, # 377921. I counted and recounted the coils and get 25½ coils. I attempted counting coils on the spring shown in TM9-1276-1947, figure 25 and get similar count. The 1953 version shows about 26 or so, kind of hard to tell. (But then the 1947 diagram of the 22 coil spring has about 26 and the 1953 version shows about 22½.) I looked at a couple other carbines and found my CMP IBM mixmaster has a 22 coil with ground ends. Another had a 26 coil but the ends weren’t ground – aftermarket or foreign? An import marked Underwood had a blued 26½ coil with ground ends. Riesch says there are questions regarding some of the blued springs. Any idea what those might be? And then lastly I looked at my SG Austrian that has a 25½ coil with ground ends. Seems to match up with my NOS springs. It looks like in the initial production of 26½ coil springs someone counted coils by starting at the tip which leaves you 1 coil short in the real world. The later produce springs appear to have been made to include the full 26½ coils. Can't really tell by the recess in the TH but any chance they gain a coil when compressed? Just a thought. This is probably more trouble than it’s worth but what does anybody know about this? First two pics are the NOS. Last pic has: Top – NOS, Middle the blued 26½, and Bottom the 22.
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Charles
Grunt Joined: Mar 21 2016 Location: Maryland Status: Offline Points: 587 |
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The early hammer springs where 22 coils @ 2.10" long.
The later hammer springs where 26 coils@ 2.50" long. That would be from the first complete coil to the last complete coil. Hope this is of some help. Regards, Charles |
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Charles
Co B 1st Batl.115 Inf. Reg. 29th. Divi. 4.2 Heavy Mortar Co Retired Life member NRA |
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sling00
Hard Corps Joined: Apr 21 2016 Location: Tennessee Status: Offline Points: 941 |
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That's how I count spring coils but it comes up short on the aforementioned springs.
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SWANEEDMB
On Point Joined: Jul 31 2016 Location: Iowa Status: Offline Points: 119 |
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NOW you both have me wondering, I too have noticed the difference in the springs, but as the Mfg's from different companies not all (I assume) could match the tension so coil count could vary.
I have a tool to measure hardness on my cast bullets with a digital readout, do believe we can make a gizmo to check difference in tension on different springs, will give it a go and let you know.
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sling00
Hard Corps Joined: Apr 21 2016 Location: Tennessee Status: Offline Points: 941 |
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TM9-1276-1947 and [-1953] have this note which specifies the number of coils: Note. Replace early design hammer springs that had a free length of 2.125 inches, 22 coils, and wire diameter of 0.046 inch with hammer spring (A377921 [5377921]) of recent design that has a free length of 2.616 inches, 26.5 coils, and wire diameter of 0.042 inch, (fig. 25 [50]). The ~2-5/8" I'm seeing on the NOS spring is pretty much right on track. I assume the shorter lengths of the used springs is attributed to set after all these years. I didn't find a static minimal length specified but Kuhnhausen's Shop Manual describes the minimal compressed length using an 18lb test weight as 1.18".
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Charles
Grunt Joined: Mar 21 2016 Location: Maryland Status: Offline Points: 587 |
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sling00, you didn't mention how much shorter they are and I assume they are not in situ. After 60 or 70 years, some depending on use could be a little shorter. Keeping the safety on and the hammer in the cocked position to avoid any noise for long periods could take some of the strength and length out of the spring.
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Charles
Co B 1st Batl.115 Inf. Reg. 29th. Divi. 4.2 Heavy Mortar Co Retired Life member NRA |
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sling00
Hard Corps Joined: Apr 21 2016 Location: Tennessee Status: Offline Points: 941 |
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My previous statement was based on a quick observation they weren't to the 2-1/2" mark. I removed the one in my Austrian SG and measured a free length of 2-3/8".
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sling00
Hard Corps Joined: Apr 21 2016 Location: Tennessee Status: Offline Points: 941 |
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Anybody willing to dig out some NOS springs and/or look at some your carbines and counting coils?
Also, what's your thoughts on these springs having been 26-1/2 coils when made but grounding/flattening the ends used up a ~coil? I'm liking that theory. (verbatim orderly compliance..."make spring 26-1/2 coils and ends ground flat".)
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W5USMC
Moderator Group Joined: Apr 29 2017 Location: Missouri Status: Online Points: 2949 |
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Never really paid too much attention to this when filling out my data sheets, if I counted past 22 then I just checked the 26 1/2 box. I will say that when I count the coils of the type II spring pictured in Riesch's book fig 3-23 page 91, I count 25 1/2. I Plan on counting some coils later today.
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Wayne
USMC Retired NRA Life Member |
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New2brass
Moderator Group Dan Pinto, Photo Editor Joined: Nov 29 2015 Location: CT Status: Online Points: 4627 |
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having many spares and many carbines I have long noticed the 25 1/5 seems to be more of the rule with the 26 1/2 being the exception.
I have also observed springs wound in the opposite direction. Having more 25 1/2 than 26 1/2 I would think them USGI. Why the discrepancy can only be a guess. I think the specification many have been more to the free length and compression measurements. When it comes into the manuals I think it was those who wrote them in a way to explain to the user how to tell the differences. 22 coils and short vs the longer with an extra half of coil.... good enough. One thing I will note is when springs are manufactured they could vary the coil spacing. Notice how the last coil touches the previous coil and then ground flat.
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m1a1fan
Hard Corps Got Para? Joined: Jan 01 2016 Location: Virginia Status: Offline Points: 1736 |
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Have seen a few "attempts" at turning a 26 into a 22. The ends of the spring have a unique look to them though.
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sling00
Hard Corps Joined: Apr 21 2016 Location: Tennessee Status: Offline Points: 941 |
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Keep in mind the ends of the spring is to be ground flat. I was going to make an educated SWAG why and a little Googlin' confirmed my SWAG. Grinding the ends of compression springs is a secondary operation. Grinding helps springs sit more flat to reduce buckling. i.e. you don't want any forces pushing the plunger to the side. Also as in the pic, the end of the wire has it's pitch adjusted so that it rest against the previous coil which makes it a closed end. Closed and ground sit the most flat which are the most stable with regard to buckling.
That was probably more than anybody cares about. I go back to my theory the springs were made with 26-1/2 coils and then ground. I seriously doubted any QC folks counted coils on every spring during production.
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sling00
Hard Corps Joined: Apr 21 2016 Location: Tennessee Status: Offline Points: 941 |
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BTW, I'm really glad to hear this.
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sling00
Hard Corps Joined: Apr 21 2016 Location: Tennessee Status: Offline Points: 941 |
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Here's a pic of 6 random NOS springs from the package. I did my best to line them up and they seemed to all be the same length. If you look close at the far end I attempted to place the start of the coil at ~12:00. (The grease is sticky). You can see how the end, and thereby coil count, of the springs slightly differ. Two were close to making 26 coils. Most had slightly over 25-1/2 coils.
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Charles
Grunt Joined: Mar 21 2016 Location: Maryland Status: Offline Points: 587 |
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Interesting. It looks as though they were wound by 3 different manufacturers. . 3 sets of 2 each. It would be of interest to know if they were wound as one long spring and cut to length, seems most likely or wound individually.
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Charles
Co B 1st Batl.115 Inf. Reg. 29th. Divi. 4.2 Heavy Mortar Co Retired Life member NRA |
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sling00
Hard Corps Joined: Apr 21 2016 Location: Tennessee Status: Offline Points: 941 |
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Like I said these are 6 randomly picked from about 16-17 I have. As for making the springs I would think it's a long continuous spring that is cut off to a working length and then the ends are "closed" and ground to get the specified length. I think the length may be more important than a half or full coil.
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