Making a Marlin 1889 Split Trigger Spring

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Jim D
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Making a Marlin 1889 Split Trigger Spring

Post by Jim D » Wed Feb 27, 2008 7:15 pm

I've had several requests for help and a tutorial on making a split trigger spring for a Marlin 1889. I just so happened to have an 1889 that needed one so this post will document the process of making one from scratch.

The 1889 has a sear lockout bar that prevents the trigger from being pulled if the lever is not completely closed. The bar is held down by very thin spring that is part of the trigger spring. In other words, the trigger spring has a split in it, with the thin portion pushing against the lockout bar, and the wider portion pushing on the trigger. The thin portion of the split spring can break easily which causes the lockout bar to not function properly. The trigger could be pulled even without the lever being fully closed. Other safety features of the 1889 would still prevent the gun from discharging in this case however.

Here's what mine looked like:
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This is what the lockout bar looks like:
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The original spring showing the broken portion:
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Width of original:
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Thickness is .030":
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.030" flat spring stock from Brownell's:
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The next step is to cut the split with a Dremel tool with a cutoff wheel. Use the thinest cutoff wheel that they make:
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The split is your reference line for laying out the spring:
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The next step is to layout the spring. I use machinists blue layout dye. The hole is center punched:
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The outline is cut and the hole drilled with a #29 drill:
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At this point the spring is soft or annealed and can be bent by hand easily. You can't do this after it is hardened:
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Now that the spring is shaped and bent, the next step is to harden it. Heat evenly with a propane torch, moving the torch so that the entire spring is a bright orange. IT IS IMPORTANT THAT THE ENTIRE SPRING IS HEATED UNIFORMLY. It will be easy to overheat the thin part while the wider part is under heated. Once the spring is uniformly bright orange, quench it in some type of oil like 10 wt motor oil. THE PART IS NOW HARDENED AND BRITTLE! If you try to bend the spring at this point, IT WILL BREAK!!!
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The next step is to temper the spring. This will give the metal it's springy characteristic. First polish the spring so you can see the temper colors form when you heat it. Heat it VERY CAREFULLY with the torch until it turns a "fire blue" color. IT IS
CRITICAL THAT IT NOT BE HEATED BEYOND THE POINT THAT IT TURNS FIRE BLUE! Also be carefull that the thin part is not over heated. If any part of the spring is overheated, it will not spring, but merely bend when deflected. If you screw up, and you probably will because this is difficult to get right, you can simply reheat to bright orange, quench in oil, and re-temper it. When properly tempered, it should have a fire blue color, almost like a nitre blued part:
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The finished spring installed in the rifle and checked for function:
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-jim

Sure-Shot
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Re: Making a Marlin 1889 Split Trigger Spring

Post by Sure-Shot » Wed Feb 27, 2008 11:20 pm

Jim thank you, by chance do you have a background in teaching. Much appreciated.

Randy
GBOT, GBUSA

Jim D
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Re: Making a Marlin 1889 Split Trigger Spring

Post by Jim D » Thu Feb 28, 2008 12:39 am

Randy,

No background in teaching. I just try and think about how I would want someone to show me if I was learning it for the first time.

-jim

Leverdude
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Re: Making a Marlin 1889 Split Trigger Spring

Post by Leverdude » Thu Feb 28, 2008 8:28 am

Thanks Jim!

Is that the same trigger plate? Thing looks brand new.
Ken,

http://photobucket.com/albums/a186/Leverdude/?


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Wishbone
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Re: Making a Marlin 1889 Split Trigger Spring

Post by Wishbone » Thu Feb 28, 2008 9:51 am

Great post, Jim.
Outstanding.

WB
MARLIN - THE GUN FOR THE MAN WHO KNOWS

Jim D
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Re: Making a Marlin 1889 Split Trigger Spring

Post by Jim D » Thu Feb 28, 2008 10:20 am

Ken,

Since I'm going to restore it anyway, I gave the trigger plate a light bead blasting to remove the rust and crud.

-jim

Jim D
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Re: Making a Marlin 1889 Split Trigger Spring

Post by Jim D » Thu Feb 28, 2008 11:18 am

MODIFICATION:

I have modified the spring slightly since I posted the photos of it. I annealed the spring and cut the thin finger down to half it's original length, and flattened it out. I then re-heat treated it. With the thin finger for the lockout bar cut down sufficient pressure is still applied to the bar.

-jim

Leverdude
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Re: Making a Marlin 1889 Split Trigger Spring

Post by Leverdude » Sat Mar 01, 2008 7:21 pm

Thanks Jim,

Got a question. Can any spring be annealed & re tempered like this? Say a loading gate or mainspring?
Ken,

http://photobucket.com/albums/a186/Leverdude/?


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Jim D
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Re: Making a Marlin 1889 Split Trigger Spring

Post by Jim D » Sat Mar 01, 2008 10:11 pm

Ken,

Absolutely! If it is oil / water hardening spring steel, it can be annealed, bent, hardened and tempered. Over and over again! Any flat gun spring that I've ever run across can be re-hardened and re-tempered. So if you've got an old spring that has lost it's spring, anneal, re-bend and re-harden and re-temper it. I would harden in oil. And make sure you temper it properly. If it's not tempered enough it could break.

-jim

azhusker
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Re: Making a Marlin 1889 Split Trigger Spring

Post by azhusker » Thu Mar 06, 2008 7:55 pm

Jim,

What a great lesson. The pictures were invaluable and the text very clear. I thought I was pretty handy around the shop but this is impressive. I grew up in Lincoln and don't get back as often as I like. But, when the winter snow flies, Nebraska is a good place to be from. Thanks for the turtorial.
Cornhusker Dave

shotley
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Re: Making a Marlin 1889 Split Trigger Spring

Post by shotley » Thu Mar 06, 2008 9:05 pm

Jim , another great post, have needs and hope to give it a try soon. My marlin nut son is an industrial tech teacher, he intends to use your tutorial as a classroom model and challenge the students to create similar type "how to's" -
Oops, are we venturing into copy rights? Thanks again.
another Ken

Jim D
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Re: Making a Marlin 1889 Split Trigger Spring

Post by Jim D » Sat Mar 08, 2008 3:54 pm

Dave,

Great to hear from a fellow Cornhusker! Don't come and visit just yet! One inch of new snow on the ground and it was in the teens this morning. If you're in Arizona right now, you've just proven that you're smarter than I am! :)

-jim

Jim D
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Re: Making a Marlin 1889 Split Trigger Spring

Post by Jim D » Sat Mar 08, 2008 3:55 pm

Ken,

No copywrite violations here! Tell your son to have at 'er!

-jim

Gunacologist
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Re: Making a Marlin 1889 Split Trigger Spring

Post by Gunacologist » Thu Apr 03, 2008 10:25 am

I have to agree with Jim, that the sear tail should be shorter than full length. In measuring my original, the sear tail is only 1.070 from the rear of the spring itself. To function as full length is hard for contact of the safety lever unless a severe bend is made on this tail, in that the lever bends down & away as it goes forward. This lever dosen't need a lot of pressure anyway.

Leverdude
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Re: Making a Marlin 1889 Split Trigger Spring

Post by Leverdude » Thu Apr 03, 2008 7:04 pm

You sure it wasn't cut? The only unbusted one I ever saw was full length.

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