1900 Mainspring

[G.T.]

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

[RalphH]

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.

[G.T.]

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

[Ron Wood]

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

[Dwight Gruber]

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

[John Sabato]

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.

[A.Mifsin]

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

Alf.

[John Sabato]

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.

[A.Mifsin]

Thank You John
Alf

[John Sabato]

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?

[Ron Wood]

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!

[G.T.]

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

[John Sabato]

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

[Ron Wood]

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.

[John Sabato]

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.

[SIGP2101]

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

[A.Mifsin]

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

What is lead bath immersion please ?
Alf

[SIGP2101]

Originally posted by A.Mifsin
""6. Tempering by lead bath immersion,""

What is lead bath immersion please ?
Alf

Sorry, that would be a molten lead.

[RalphH]

About 620 degrees.

[jamese]

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

Jim