1900 Mainspring
 

Here are some views of the flat laminated spring found in the early 1900 and 1902 Lugers.
The mainspring consists of two laminations that are riveted together. The longer leaf includes the hook that engages the S-shaped transfer link connected to the toggle.
http://forum.lugerforum.com/lfupload/multiview1.jpg

The laminated mainspring is difficult to find, so occasionally you will encounter a gunsmith replacement that was made to restore a Luger to operational condition without regard to "cosmetics". The following example came from a 1900 Luger that made its way from Old Mexico across the border into Texas. It is hand forged and has the same aesthetics as homemade soap, but it works! The ingenuity and resorcefulness of craftsmen is always a source of wonder.
http://forum.lugerforum.com/lfupload/forged.jpg

As noted by Levallois, the shape of the mainspring varies and what may function in one Luger may not be "tuned" to another. The next photo shows the different curvatures from left to right of the individual leaves, two original examples, and the hand forged example.
http://forum.lugerforum.com/lfupload/side.jpg

The actual dimensions of the components of the mainspring can only be estimated from a photo. The true dimensions would have to be determined by having the parts in hand. In addition to the dimensions, the tensile strength of the springs would have to be measured. The following illlustration shows the relative dimensions of the components, but I would guess that it falls far short of that necessary to make a reproduction.
http://forum.lugerforum.com/lfupload/length.jpg

Thanks Ron for a great photo essay on the early mainspring. From your photos it seems that the size of the "foot" on the longer spring also varies... does this foot play a role in keeping the lower end of the spring in place during operation? I imagine it does, and if I am correct, approximately what length would you consider optimum?

On my screen, it appears that the photo is approximately 1.5 to 1.6 times larger than life. Measuring the original spring's "pull" would seem to be a challenge...

Once last question. Appoximately what thickness of spring steel are we dealing with here? are both leaves the same material or is one thicker than the other?

John, You make an exc point: a couple of the springs shown in profile in one of Ron's photos, appear to be missing the "foot", which is essential to holding the spring into the frame. Without this bend at the bottom, the spring will lift and not allow the toggle to come back all the way. TH

Tom, does that mean it is possible that the spring already contained in 1900 discussed in the other AE thread might have a "foot" issue as a source of the problem?

All the springs shown have a foot on the longer leaf, albeit it is a bit smaller on the disassembled mainspring. Both leaves are the same thickness on a 7.65mm spring. For the 1902 9mm spring, the long leaf is approximately 50% thicker than the 7.65mm spring but the short leaf is the same thickness for both calibers.

I will measure the thickness of the spring steel and get back to you.

Thanks Ron... Did you get my PM on this issue?

Now a question regarding the spring tension. I would imagine that the "pull" that this spring should have would be roughly equivilent to the same pull created by a coil spring Luger when compressed to the same length that it takes when the toggle is in the rearmost position.

In order to get a quote on fabrication of these springs, I guess we would need to simulate the compression using a fishing scale or trigger pull scale... this would be easiest using the coil spring setup from a .30 caliber luger... which I don't own.

Anyone out there equipped with an appropriate scale and a .30 caliber Luger who could determine this pull weight strength? I have found a company who will create a small quantity of prototype springs... to get a quote, they need dimensions, and specs. I believe that the photos taken by Ron Wood, (along with the width and thickness dimensions) combined with the estimate "pull" requirements may be enough for them to quote the manufacture of these springs...

Any help would be appreciated... I am sure that in the near future, there will be a demand for these springs as the pistols that use them age.

John,
I will measure my 1900's & 1906's when I get the chance, leaving for a gunshow in a few minutes---- Maybe someone will do it before I can. Both of my Lugers with the flat mainspring have considerable less resistance to pulling the toggle back than any of my Lugers with a coil mainspring.

Thanks Hugh... I had a suspicion that the resistance would be less with this type of spring. Are both of your lugers that use this type .30 caliber? or is either 9mm?

I received your PM and I am mulling over a reply. There are a bunch of factors involved and I want to think about it a bit. In addition to "pull weight" there may also be some pre-loading that needs to be considered. The pre-loading may already be covered by pull weight and length of the spring but it is going to take someone with a lot more mechanical engineering skills than I have to figure this out. Also as noted, there is significant variance in curvature of the springs even in the small sample I have posted. What is the correct configuration and which ones have already taken a "set" and may or may not be a candidate for a prototyping standard? There may be a requirement for a larger population sampling and I admit that I am loath to start taking the springs out of my collection pieces to increase the sample.
Perhaps these aren't significant factors and the spring company can address them with ease. But it never hurts to have most of the answers figured out up front.

Thanks Ron... appreciate the update while you are mulling over the issues.

I have been wondering what kind of breakage is normally experienced with these springs?

I would imagine that the most common breakage might be the "hooks"... but if anyone has had one of these types of springs actually fail, I would sure like to know the manner in which it failed...

Got soft? (what a terrible way to go! :D)
Snapped? (in what location?)
Separated at the rivet?

Since one of Ron's springs is actually a replacement made in Mexico out of 1 piece, instead of sandwiched leaves... I wonder how the original spring failed?

..finally does anyone know what kind of steel hacksaw blades are made of? I know a few old gunsmith's (unfortunately now deceased) who used to make rifle magazine follower springs out of them when an original couldn't be found. They look like they might be a good candidate for replacement stock to create new Luger springs.

Spring steel
 

Hi to Ron, John and all... John, on the type of steel and the weight of the "pull" needed, you will find your options are thankfully limited... The original springs were made from a basic high carbon steel, probably comparable to 1075 spring steel, perhaps a bit higher in carbon, as they obviously had a high failure rate, which could be attributed to either brittle steel, or improper tempering.. To support this statement, now days, you have to have very special climate controlled conditions, and ovens, to properly heat treat and temper 1095 spring steel..... 1050 to 1075 small parts, you can temper and draw successfully with a torch... Your reproduction springs are going to fall into these ranges of steel, both from a production cost factor and a design requirement parameter... In essence, if you use the correct material, and build it to the exact spec's, and temper / draw (pigeon blue) it using todays modern methods,your springs tension will be automatically correct... I'm thinking 1075 annealed spring steel, and you'll have a better spring then they ever dreamed of making!! Best to all, til....lat'r....GT :cheers:

GT... 1075 Flat Steel is what Brownell's stocks ... I just need to know what width the springs are so I can get the right size to experiment with. I think trying to make a spring from just the photos and measurements in this thread would be an interesting experiment.

Thanks for your input...

spring steel
 

Hi John, I see where Brownells has 1095 annealled, you might have to use this and get it professionally tempered.... The problem is getting 1075, or any other "annealed" spring steel! It is dead soft and easy to form and cut, it also has a grain you need to pay attention to, it runs linear with the sheet or coil... Then, when you have the final part shape, you have it heat treated, and then drawn back to the correct strength for the intended spring... The small quantity spring steel most often offered is unfortunatly, already tempered!! Soooo, to get what you need, you usually have to buy a minimum quantity coil of so many pounds and it cost several hundred dollars to start with... Making the springs is the easy part...finding the "annealed" spring steel in the exact thickness needed, is the hard part!!.... Has to be annealed to work with... and no, you can't anneal and retemper... too much work to get correct, if possible at all... I will certainly assist you if i can John... best to you, til....lat'r....GT

BTW John, you can compare compression by clamping one end of the flat spring to a flat surface and pressing down on the apex of the bend to a preset stop, with the whole works on a scale... do the same with your test samples, when you get then made, and the pounds of force needed should be close and comparable.....

John,
I have owned 2 broken springs (one was in a gun and the other I picked up as parts, I didn't break them!). The hooks were both good. They were snapped about 1/3-1/2 way down from the hook. One had the main spring (with the hook) broken and one the auxillary spring. I salvaged the good main and good aux spring and riveted them together...worked great.

I bought the disassembled spring in the photo that had been fastened together with a lousy makeshift rivet. The rivet had not been properly peened so the whole assembly was floppy. I will get around to putting a new rivet in it someday.;)

Once upon a time I needed an odd shaped flat spring for an old revolver. I didn't know diddly about steel types, but I found some steel shim stock at a machine shop that was the right thickness. It was in the white and cut relatively easliy so it must have been annealed. After cutting and bending it to shape and polishing it, I heated it to peacock blue and tried it. Got lucky the first time! This was an internal spring that worked the cylinder pawl so it did not have to be terribly exact in its performance. Just thought I would mention where I got the steel as a possible source.

Thanks Ron... how about leaf thickness and width?

Hang on, it will be forthcoming.

Greetings, Gentlemen,

I purchase 1075 annealed from Brownells in 12" lengths of different widths and thicknesses. If I need larger sizes I buy from McMaster-Carr.
I make many different springs for my antique revolver restorations, and
the 1075 from both sources work very well.

RalphH thanks so much for your input. Your advice is very helpful. Can we inquire about your procedures for shaping and tempering your springs made from this material?

great source
 

Hi RalphH and John, great source for the strips of 1075 annealed spring steel in McMasters-Carr, John, you should be able to get pretty close with their offerings... RalphH, Thanks for your info.. best to you, and good luck to all....til...lat'r...GT

Greetings,

1075 is very soft and malleable in its annealed state. Cutting, filing, grinding and bending to shape is quite easy. It should be the same shape and dimensions as the original spring. Polish the surfaces that would be on the outside of the flex. You don't want any minute scratches or defects that might contribute to a fracture later. I use 1200 wet-or-dry paper.

I use an electric furnace to heat treat. Mine was made by "Ney". It has a maximum temperature of 2000 degrees, and can be brought to temperature very slowly or quite fast. The temperature gauge is marked in 25 degree increments, and is extremely accurate. I bought it about 30 years ago from Brownells for $300.00.

I place the soft spring in the cold furnace in a small steel pan.
I bring the heat up to 1500 degrees slowly, remove the spring and quench in quenching oil. I turn off the furnace and let cool to 575- 600 degrees with the door slightly ajar. I quickly place the spring back in the oven and shut the door. It cools very slowly with the door shut. I return the following day and remove the spring. If I want it shiny, I polish with 1200 wet-or-dry and buff with Jewelers rouge. Spring is done.

P.S. Brownells still sells the Neycraft 240V furnace, only now it's $750.00.

kiln
 

Hi RalphH, thanks again for the info.... does your furnace have a thermometer or do you have to use a seperate pyrometer?? Also, what do you do about scale and such on the quench?? Do you have to polish before drawing?? Best to you, til...lat'r...GT

Greetings,

The Neycraft furnace has a built in thermometer.

The spring is coated with Keepbryte before it is put in furnace. The compound keeps it free from any scaling. I use it on all my heat treated die parts. Parts stay just as clean and bright as before heat treating. Made by Kasenit.

Polishing before drawing is not neccessary unless you want the spring to have a beautiful even blue color.

Sorry I forgot to mention Keepbryte in the process. One of those steps that I do without thinking about it.

great info.
 

Thanks RalphH, great info. it's much appreciated.... Best to you, til...lat'r....GT

John,

Here are the dimensions as near as I can measure them:

Leaf Thickness - 1.0mm

Leaf Width - 11.4mm, +/- 0.1mm

Overall length measured tip to tip:
Long Leaf - 93mm
Short Leaf - 88mm

Hook radius fits around a 7/64" drill shank

Depth of "notch" at top of long leaf - 7mm
Depth of "notch" at top of short Leaf - 4mm
Width of notches - 4.7mm

Length of "foot" (inside measurement) - 2.75mm

http://forum.lugerforum.com/lfupload...size_copy1.jpg

John,

Fyi the "hooks" at the top of the spring must not be too long. I put a repro spring in a 1900 shooter, and the toggle kept jamming back. I finally figured out that at full recoil the hook-ends were jamming into the bottom of the breechblock, actually gouging it, and keeping it from returning forward. Judicious application of a file shortened them to the point where they no longer contacted the breechblock and everything was fine from then on.

--Dwight

S=Flat Sprint Specifications
 

Ron, Thanks for all your effort. That's as complete a set a specs as anyone could have asked for, short of hammering out the spring flat and measuring the actual length. That should be enough for a prototype.

...and Dwight, thanks for that bit of advice. I would have thought that slightly longer hooks would have been an improvement. I will endeavor to keep them exactly the same length as the original.

...and I can't leave out Jamese... who has kindly offered to send me his old broken spring to use for shape and whatever else it can be used for...

let''s get this show on the road... I will report back when I have obtained the necessary raw materials.

Any particular reason why the original flat springs were made with two pieces instead of one?
:D
Alf.

From an engineering viewpoint, I believe that two sandwiched thin springs probably provide more "oomph" that a single spring of the larger dimensions... and probably also altered the response to a a more favorable force curve for the Luger's operation... sort of like a compound bow effect.

Thank You John :cheers:
Alf

Ron,

11.4 millimeters works out to 0.448818898 inches

I believe that this necessary 1075 steel is available in a 0.50" width... in your opinion, would that be too large? Do you think there would be room to operate at that width? or should I plan on shaving .005 " off of the stock material?

John,

At the bottom of the spring it is absolutely no problem. But the top of the spring is a pretty precise fit inside the frame opening, so that extra .005" might be a tight fit. The thickness of sheet of paper is only about .005'" so the extra width may or may not bind, but since you will be working with such a short piece of stock a couple of passes with a draw file would remove that .005 in a heartbeat. A small amount of work considering what effort will go into the whole assembly!

stacking thou's....
 

Rick has it pegged.... .050" is a bit different then .005" unless your going really, really, really fast! Best to all, til...lat'r...GT:D

Thanks guys that was my goof.... a typo should have been 0.050 not 0.005 DUH!

Ah yes, .05" is a bit more stock to remove but still not to hard to do with a file. Good catch...I didn't even bother to do the math.

Hey Rick, since we are not engineering for NASA, the level of precision might be less than they expect... :) If the old master gunsmith that I apprenticed under 38 years ago thought that I would would take the time to set up a milling attachment to hone .050 inches off the side of a new spring instead of putting the flat steel in the vise and filing it down the appropriate amount he would probably turn over in his grave... and think that he wasted his time with me. Before he would trust me to work on a customer's gun with tools I had to pass his "test"...

Take a sawn off piece of steel bar that was larger than an inch in cross section and from it, create a 1.0" cube that didn't vary in dimensions more than .005" and that is no typo... Using only the vise and files.

I wish I could remember what happened to that cube... I used to keep it on my desk to remind me about doing precise work. Now only the memory has to suffice. Thanks for your input, Rick... it always opens my eyes.

I don't have a milling attachment yet... but will eventually... in the mean time making only .050 inches protrude above the flat vise jaws and laying waste to it with a file will have to do. Now, if I was going into immediate production on these springs... I would tell a different story... but first I have to make ONE and be satisfied that the investment will be worth it.

For all of you who would like to venture into this, and do not have oven here is a really short course of what needs to be done.


1. Anneal old spring by heating to 1500F,
2. Cool slowly in wood ash,
3. Reheat to red - reshape,
4. Reheat to critical, (that is 1500F again. This Is non magnetic state),
5. Quench in warm oil (150F mixture of 5W30 and transmission oil), now is hardened.
6. Tempering by lead bath immersion,
7. Let it cool aside.



Thanks

SIGP2101

""6. Tempering by lead bath immersion,""

What is lead bath immersion please ?:confused:
Alf

Sorry, that would be a molten lead.

About 620 degrees.

John,
you should have gotten the spring by now.......or maybe with the long weekend it was delayed a bit.

Jim