Loading Slip Joint help

[Brian Avila]

I have been working on a Lanny's Clip slip joint pattern. And I have been thinking about the loading of the spring. From my understanding you have the holes in the spring and one of the ways to load it is to move the hole placement on the back in the liners up half the diameter of the hole you are using.

So the picture I have attached shows the handle and the spring.

1. The top pattern shows what I want the final handle layout to look like.
2. The second shows the spring with the hole half the diameter of the pin below the scales so you can load the spring.
3. The third picture shows what the line up would really look like if I continued to use the second from the top layout.
the spring will rotate around the spring pivot and lower the front, which loads the spring, but the holes don't line up because of the rotation around the spring pivot.

So...

4. I left the spring in the rotated state and matched the holes
5. I rotated the spring back to normal so I could see the the actual location of the holes that I need to drill in the spring.

Now this leads me to a few questions that I need some clarification on.

1. Is my thought process of what is happening when loading the spring correct?
2. If it is correct that would mean that I would need to leave the spring oversize and then when the spring is loaded, I grind the spring even with the handle?

3. If I go about it the way in #2 above, how do I account for the spring evening out when setting the open, half closed and closed positions with the blade and the spring? I would just measure from the same point on the spring, if it is oversized in the above part and then grind even?


Or maybe I am not doing this correctly..... thoughts and help.

-Brian-

 

[Wolf_HR]

I'm certainly no expert, but I always thought one was supposed to make the spring looking like in the picture 2, and drill the holes where they should be (in picture 1, aligned with holes on the handle) and then bend it a bit to give the desired amount of preload (bending when pinned like mounted in the handle).

 

[Brian Avila]

I'm certainly no expert, but I always thought one was supposed to make the spring looking like in the picture 2, and drill the holes where they should be (in picture 1, aligned with holes on the handle) and then bend it a bit to give the desired amount of preload (bending when pinned like mounted in the handle).

Nothing lines up like if I do it that way though.

 

[John L]

OK....the spring will pivot from the end hole only. I assume the larger hole is a lanyard hole? Only drill the end hole in the liners. Move the pivot end of the spring or bolster end down your 1/2 hole diameter. Clamp up spring and liner and drill the hole thru a liner for the load hole and thru for the lanyard hole. Take spring off, attach other liner and drill thru both liners and scales if attached on both new holes you just bored. The lanyard hole will move also but you do not know how much. Everything pivots off the end hole until you bore load hole and now that is the pivot point..... closer to the blade pivot. Email me if you are still having problems. Sounds like gobbledegook until you actually done.

John Lloyd

Jlloyd8313@aol.com

 

[Brian Avila]

OK....the spring will pivot from the end hole only. I assume the larger hole is a lanyard hole? Only drill the end hole in the liners. Move the pivot end of the spring or bolster end down your 1/2 hole diameter. Clamp up spring and liner and drill the hole thru a liner for the load hole and thru for the lanyard hole. Take spring off, attach other liner and drill thru both liners and scales if attached on both new holes you just bored. The lanyard hole will move also but you do not know how much. Everything pivots off the end hole until you bore load hole and now that is the pivot point..... closer to the blade pivot. Email me if you are still having problems. Sounds like gobbledegook until you actually done.

John Lloyd

Jlloyd8313@aol.com

So you are saying pivot from the back hole. And apply the load from the front hole, by moving it down?

 

[Don Hanson III]

I get confused just looking at those pictures.

It's hard to explain, but I do pretty much what John L said.

 

[Brian Avila]

I am confused a little bit. Am I moving the spring tip down a half diameter of my hole or and I moving the actual location of the front hole of the spring?

 

[Don Hanson III]

I am confused a little bit. Am I moving the spring tip down a half diameter of my hole or and I moving the actual location of the front hole of the spring?

Move the spring down, leave the hole in the spring where it is.

I've also fitted up like pic #2 & then just bend the front of the spring down (before heat treating).

 

[Brian Avila]

Move the spring down, leave the hole in the spring where it is.

I've also fitted up like pic #2 & then just bend the front of the spring down (before heat treating).

Excellent! Thank you.

The only other thing I worry about is the spring tension. I don't want a nail breaker. So... My plan is to use 1/8" pins. So 1/2 diameter of the 1/8" pin is 1/16". So the plan is to move the spring down 1/16"

Most people from what I hear use 3/32" pins. The difference between the 1/2 diameter is roughly ~ 0.015"

Should I still proceed with moving it a 1/16" down?

 

[Don Hanson III]

Excellent! Thank you.

The only other thing I worry about is the spring tension. I don't want a nail breaker. So... My plan is to use 1/8" pins. So 1/2 diameter of the 1/8" pin is 1/16". So the plan is to move the spring down 1/16"

Most people from what I hear use 3/32" pins. The difference between the 1/2 diameter is roughly ~ 0.015"

Should I still proceed with moving it a 1/16" down?

You can move it down a little less than 1/16" if ya want. You can also grind some off the bottom of the spring to make it not as strong. Or make another spring if need be. Get a prototype working like you want, then make a pattern from it.

 

[Brian Avila]

You can move it down a little less than 1/16" if ya want. You can also grind some off the bottom of the spring to make it not as strong. Or make another spring if need be. Get a prototype working like you want, then make a pattern from it.

Good points!!! Thank u

 

[Patrice Lemée]

Can't help, haven't tried one of those yet (this makes me want to ) but I just wanted to say thanks for posting a higher level question Brian. They are few and far between in shoptalk these days.

 

[stezann]

You are on the right track. You could procede as in the 4th sketch, then grind the bach flush. DOn't understimate the spring strenght, but consider that, regarding tolerances, if the holes are not very close in diameter to the pins you'll get some overall "give" in assembly, and that will eat some of the preload.
Try to get close with the positions without preload, but be prepared to adjust when everithing is heat treated (i find easier adjusting if the spring is higher in half and closed). It is wise to have the blade point a little down in open position and in closed....when the spring is under load the tip will rise a bit in both position due to spring deformation.
For the same reason you want to end the profiling of the back of the liners only with the spring under load.
When adjusting be also careful not to have the front of the spring backward respect the tang.
Then please post the results...i admire your work and i'm happy to follow your slipjoint route :thumbup::thumbup::thumbup:

Stefano

 

[kc custom]

Brian unless you already have your liners made, get your blade attitude ie- higher or lower then
put pressure on the spring pushing upward at the back- when you get the pressure you want
clamp it and drill. Its way harder to make a set of liners with the holes in them and then match the
blade and spring to the liners than it is to do it this way.
Ken.

 

[Brian Avila]

Brian unless you already have your liners made, get your blade attitude ie- higher or lower then
put pressure on the spring pushing upward at the back- when you get the pressure you want
clamp it and drill. Its way harder to make a set of liners with the holes in them and then match the
blade and spring to the liners than it is to do it this way.
Ken.

I haven't even started yet.

I went about it this way because I could actually see the lay out and the line up of the holes when I move things in the Draftsight program. This also makes sure that I have an understanding of what the movement and action is. If I didn't have a good understanding, I wouldn't be able to fix the problems I will encounter.

Having said that. I think I will go about the loading of the spring the way John Lloyd and Don are talking about. I think that makes more sense in my minds eye, I can see what is going on now, I think...

 

[Brian.Evans]

Don Robinson drills the pivot and the middle hole, then moves the back hole up half a hole width to tension the spring. Seems to work well. I'm confused as to how you guys are doing it. I'll re-read it later.

 

[Ken H>]

The method of drilling pivot and middle hole, then moving back hole 1/16" is pretty much what I do. BUT - the distance from middle hole to pivot vs middle hole to back hole makes a difference in how much preload 1/16" will put. Is there a "standard" ratio of distance between these two points?

Ken H>

 

[Don Hanson III]

I usually drill both holes in the spring, then position the spring on the liner to where I feel the best preload is. There are multiple ways to get the same results.

 

[Busto]

I usually drill both holes in the spring, then position the spring on the liner to where I feel the best preload is. There are multiple ways to get the same results.

This is the method I have used for quite some time and I built 3 spring jigs as templates each a different thickness which I can test on my liner fixture and if the load is too light/stiff I can go to either the thicker or thinner jig
based on desired pull strength.

 

[Justin King]

The method of drilling pivot and middle hole, then moving back hole 1/16" is pretty much what I do. BUT - the distance from middle hole to pivot vs middle hole to back hole makes a difference in how much preload 1/16" will put. Is there a "standard" ratio of distance between these two points?

Ken H>

I think I saw Don Robinson post somewhere that he usually places the mid pin about 40% of the way forward from the rear pin.
I built my first one with Steve Culver's tutorial, the preload drilling seemed pretty straightforward to me the way he wrote/drew it.