Slipjoint veterans, lend me your ears!

[Drew Riley]

I've been doing a lot of research and practicing on making slipjoints, and so far I've made several attempts, yielding two functional slipjoints.

Where I'm currently getting hung up the most is when it comes to setting the rise and fall, and along those same lines, the tension on the back spring.

Edit: I'm not sure why this just posted, but I'm going to continue my question below.

 

[Drew Riley]

As I was saying....

I've taken apart a handful of old slipjoints to get the feel for how they are constructed, and it seems like they all set the tension with a gradual bend inward of the spring.
Looking at some various tutorials, I see that many makers start with a straight back spring, and after drilling the center hole, "kick" it forward a 1/16" to 3/32" or so.

I've tried the latter method, and it doesn't seem to yield much tension, so I usually bend the spring forward a little more manually.
In trying to get the backspring just right, I've noticed something: My rise/fall in the closed position changes with the spring tension.

I guess my question is, how do I minimize the difference in what my RFI shows when the blade is tensioned or not tensioned, while still making sure I get a good pull tension? Hopefully my question makes sense.

To put it another way, I can get my open and half stop positions zeroed perfectly on my rise/fall indicator. However, if I zero the closed position without tension, when I put the knife together and close it, the blade is sticking out of the handle and not closing all the way. I then have to take extra material off of the kick and kind of "guess" where everything will end up.

 

[Jason Fry]

I've made 15, so I'm not the boss of this slipjoint thing either, but I can offer a few things. As far as setting the tension, I typically move the back hole down about 2/3 of a hole diameter when I drill the liner holes. As far as zeroing out everything, I typically get it close before HT, but not perfect, and don't finalize everything until after HT. You'll have to have tension on the spring for the final fitup, and as far as I've found, you do certainly have to go through some guess and check there at the end.

 

[stezann]

Jason's way to set the spring tension is smart IMHO.
One of the thing that has effect on the tension is the distance of the back hole (the one at the center of the spring)from the pivot; so taking that hole as a reference to lower the spring is better than referring to the front of the spring.
Infact if you lower the back hole, the front of the spring will go down more or less depending on the distance of the back hole from the pivot, making up for that distance.