Patchbox latch question

[mjm46@bellsouth.net]

Attached is a photo that I saved from another entry (I'm sorry I didn't record from whom). It shows a spring latch that was used by Dickert. My question is how are these kind of springs installed into the endgrain of the rifle without splitting the wood severly. I've seen instructions for modern springs that indicate driving them into the wood. This frankly scares the tar out of me.

If I'm seeing this correctly this is a forged spring latch with the head filed to shape and the long curve is inletted??? into the end grain. There does not appear to be any mechanical attachment other than friction of the shape, and perhaps the buttplate itself. Does anyone know exactly how this is done? and would you please explain for me. It's perfectly elegant in its simplicity.

[Acer Saccharum]

Really hard maple isn't going to like being driven into. You could burn a groove, or make a really fine mortice chisel and cut the groove.

Maybe that would take a long time.

But that's far better than splitting out the side of the stock.

Tom

[Dave B]

Here is another view of this same rifle's release



Is that old leather in the gap?

Certainly the area could be burned in

[Acer Saccharum]

Certainly could be leather. This would allow a wider chisel to be used, much more do-able.

[JTR]

That looks familiar!
In the picture that Dave B posted, what he thought might be piece of leather is just the buttstock wood.  What looks like a crack on the left side I think might be the original cut where the spring was going to be mounted. I looked at that area closely, but couldn't tell if the spring had actually ever been mounted there or not. However, there was a very small crack through to the surface of the butt on that side. Maybe ol Dickert made a mistake and mounted the spring without enough wood between the spring and the surface of the stock!
At any rate, the spring is a simple one to make and easy to install. It's only about 1/4" wide so wouldn't need a lot of inletting. The way the cut looks, I don't think it was just pounded into the wood, but was inlet into the wood at least partially. The edge of the butt plate helps to hold it in place at both the curved 'spring' end and also the head end.
Even after more than 200 years the box cover still unlatches and latches easily, so I'd agree that it's a pretty good way of doing it.

Micah, if you'd like higher resolution copies of these pictures let me know, and I'll email them to you.

John  

[D. Taylor Sapergia]

I've used this method to mount the catch/spring many times.  The edge of the spring is filed thin, like a knife blade, and simply driven into the end grain.  I have never had a check or split as a result, and the installation takes less time than to describe it.  What you are seeing is the steel tipped a bit sideways and you're seeing some of the side of the spring.  I will confess, though, that I don't try for one as close to the edge as this one.

[mjm46@bellsouth.net]

Great stuff guys, that's exactly what I was looking to find out. I've been studying the new photo for a while and I think I agree with JTR that it is wood to the left of the spring. Looks to me as though the spring may have been driven in and was too dee and then moved closer to the lid about 1/16" approx. The contour of that curve cut line is a perfect match to the spring.

[rich pierce]

I did this once and used hardened and tempered spring steel (unnecessary) and made the spring too strong.  It's a bear to un-latch.  I'll err on the side of weak for the spring next time I do it and will probably just harden and temper the latch engagement part if any of it. 

For installation I just pounded it in after stabbing the outline.  But if you have weird figure or grain direction the spring could follow it and get cocked.

[Acer Saccharum]

What you are seeing is the steel tipped a bit sideways and you're seeing some of the side of the spring.

New replies have caused me to re-assess the picture.

I don't agree that I'm seeing the tipped side of the spring, or a piece of leather, Taylor.

I think I'm seeing the builder put the spring in the wrong place, and then yanked it out, and drove it in closer to the latch side.

[Jim Kibler]

I did this once and used hardened and tempered spring steel (unnecessary) and made the spring too strong.  It's a bear to un-latch.  I'll err on the side of weak for the spring next time I do it and will probably just harden and temper the latch engagement part if any of it. 

For installation I just pounded it in after stabbing the outline.  But if you have weird figure or grain direction the spring could follow it and get cocked.

Within the elastic region of a spring, hardness will not impact the spring's strength to any meaningful degree.  So if your spring was too strong, it was because it was physically too big, not because it was hardened and tempered.

[Don Stith]

This spring arrangement is typical of Lancaster rifles in the 1790's. The book Recreating the Kentcky Long Rifle depicts this method.
Acer
 If you had looked at that end of the Messerschmit rifle you had for awhile, you would have found the same set up
Don

[rich pierce]

I did this once and used hardened and tempered spring steel (unnecessary) and made the spring too strong.  It's a bear to un-latch.  I'll err on the side of weak for the spring next time I do it and will probably just harden and temper the latch engagement part if any of it. 

For installation I just pounded it in after stabbing the outline.  But if you have weird figure or grain direction the spring could follow it and get cocked.

Within the elastic region of a spring, hardness will not impact the spring's strength to any meaningful degree.  So if your spring was too strong, it was because it was physically too big, not because it was hardened and tempered.

Good to know.  Thinner is sometimes better.  I might also have had a short working arm, effectively reducing leverage.

[D. Taylor Sapergia]

OK, Acer, you're probably right.  I would never try to 'yank' out a spring installed this way - that would be asking for a crack or break out of the wood. 
I Leave my lid stud a little too long, and set the spring into the wood where I think it'll work best, considering that there is not very much mechanical advantage for the push rod on such a short spring.  The I cut the notch in the stud and fine tune it slowly until it catches and holds, and the lid is tight.  Then I can shorten and polish the stud to a happy state.
With the stud long, and coated with felt pen, I close the lid on the spring, and the spring leaves a scratch on the stud that shows me where to cut the notch.  I shoot high and gradually take off steel until the spring engages to my satisfaction.