doublegunshop.com - home Forums General Discussion DoubleGun BBS @ doublegunshop.com Help with compressing main springs

I have a Cresent-Davis 16ga that I am trying to replace one of the mainsprings on. I have followed the instructions in the NRA Firearms Assembly Rifles and Shotguns book for the Fox Model B Shotgun since the parts seem similar. I got a new spring from GunParts Inc. and it is the same length as the good one. The plunger fits in the spring and the hammer seems to fit well on the plunger. I made a tool to fit into the sear notch and it will compress the spring some but not enough to get the Cocking Lever/Hammer pin through the frame. I have tried various angles and clamp mechanisms but just can't seem to get here. Any advise greatly appreciated.

Confused in Indiana

Hi. Those mainsprings can be a real bear to compress. I've worked on a couple guns (Fox Model B, Nitro Special) and the way I've compressed the springs is by using a piece of wood with the profile of the rear of the hammer cut out of it. The piece of wood I use is maybe 3/16" thick, 2 inches wide and I cut it to about 5-6" inches in length. Anyway, I used the hammer as a template and cut that pattern out of the end of the wood. I then put the hammer in position on the spring/cup and use the wood to push down on the hammer far enough to get an alignment punch in the hole. The receiver is clamped in a padded vise during this. It helps to have a helper and cover the end of the wood you're pushing on with a rag or something cause you end up pushing down real hard.

I'm not at home so can't post a pic of the tool/wood I use. Not sure if I described it well enough. The alignment punches work well to grab the hole in the hammer. If you monkey around with it long enough you'll get it.

I'd be happy to clarify this if you have any other questions.

Vince

Using a drill press to compress the assembly is very helpful and takes the stress out of it.
You place the frame in a vise on the drill press table with the spring, plunger and hammer in position. Then compress the hammer with the leverage of the drill press handle. You need something to push on and guide the hammer down as you pull the handle down and compress the spring.
Sometimes nothing more than a screwdriver type shape tool in the sear notch of the hammer works along with some guidance from your hand.
Others need a backing like VJP describes above.

Once it's compressed far enough, slide a slightly smaller diameter punch or rod through the frame & hammer to hold it there.
A tapered end to the punch helps catch the part and slides on thru.
Then tap the pin itself through pushing that punch back out.

Lacking a drill press,,it can be done with a large C-clamp. Just pad the ends sufficiently to avoid any damage to the contact points with the frame. It's a slower process but eccentially the same thing.
Use a real C-clamp. Not one of the pistol grip squeeze type clamps. I just don't trust them for compressing springs. Too much play in the clamp assembly for me.

With either of these,,wear good eye protection and double check your set up before compressing any springs and parts.
They can do real damage if they let go.

Thanks so much for this information, I gives me some ideas to try.

Kutter's da man. His explanation is really good and the idea of using a drill press is excellent. Before you do anything make sure the spring travels freely in the receiver and lightly grease it.

I don't know that I can add much. Sometimes the Brownells spring vise helps, sometimes taped needle nose vise grips and sometimes something like the drill press and an extra set of hands. Keeping the metal blemish free during the gyrations is a challenge for me with the pressure needed. The wood tool would certainly help on that front.

Thanks so much for those that gave me ideas. I did finally get the springs to compress. It turned out a 6 inch screwdriver (ground down some)and being able to put my whole weight (which is considerable)worked. My use of a C clamp seemed to push the the hammers both down but out from where they needed to be to get the pin in. My custom tool was doing the same thing, so if your stuck try everything.

Not quite as confused in Indiana.

Hello Bob,

Just in case, for future work.
I made this "mainspring tool" to use when fiddling with some side locks. The ends are covered in leather to avoid blemishes.

Don't know if it would work with your Crescent-Davis mechanism, but...


Best regards,

JC