Cleaning up back springs

B

BradleySmall

Joined
Mar 6, 2022
Messages
317
So I am buying sets of springs with their liners and blades. When I go to assemble, I must modify the spring in a couple different ways.

1. As I am receiving them, the springs are hardened but not "reshaped" to reduce to the final tension.
2. Resting on a blade with the blade pin and the middle pin in place, I assume I want the spring to be somewhat even with the scales/liners.

If I put the blade in and the center pin and scribe the spring along the liner, is it reasonable to simply grind that off (right off the bat)?
Once that is done, seeing where the kick makes contact in 2 positions, can I safely assume that I need to thin beyond (towards center pin) to reduce tension as necessary?
I am assuming, that the spring should appear the same in all 3 positions of the blade, Open, Closed, and 90°, yes?
Is there one position that is more critical for setting the spring depth to the scales? At which point do I consider modifying the blade? Knee-jerk says that if it is happy at open but proud at 90° I need to grind the bottom of the tang. And if it is proud closed then both ends of the kick need modification. But, I fear getting into the "leveling a 4 legged chair" situation :) I was also considering figuring out which position was the lowest, and simply trying to match the other two to that.
 
Busto said:
Instead of guessing what you need is a "Ruple" rise/fall indicator. I've been using one for 12 years, you can visually see where adjustments are needed.

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That's a great idea. However, that raises the question about how thick the spring needs to be then. In this description, he is keeping his spring as-is and modifying the blade/tang to adjust the spring down to the liner back. This makes more sense than thinning down the spring so much, but it is also very tight, and will definitely need to be thinned somewhere.
 
AVigil said:
There is a lot to learn for slip joints and you should by this book https://smile.amazon.com/gp/product/1545388326/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1

This will give you the answers to most of your question on how a knife is made, why and how to set spring tension.
It is a good start on a long journey
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Okay, so I bought the book. I just read the book. It is about 20 pages. Maybe I will try to reproduce the work in the book. I am not sure I got any more out of it than I did watching Loz Harrop and Makers Movement videos on YT. Thanks for the recommendation. My library has begun.
 
Wait until you go to make one from scratch. You will be glad you have it. The information on dimensions on making the back square ratio is worth the price alone when you go to design your own.
Makers movement learned from Luke Swenson. Luke has a video on Chris Crawfords website and it will knock off years of the learning curve as well as the Craig Brewer and Bill Rupple videos.
 
AVigil said:
Wait until you go to make one from scratch. You will be glad you have it. The information on dimensions on making the back square ratio is worth the price alone when you go to design your own.
Makers movement learned from Luke Swenson. Luke has a video on Chris Crawfords website and it will knock off years of the learning curve as well as the Craig Brewer and Bill Rupple videos.
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I ordered up some metals from Jantz when It gets here, I will look into doing one from scratch.

As for books, most of the rest of them I see have reviews that bemoan the fact that the author is working out of full on machine shops or what have you, or the other books are so focused on black smithing that they are a waste for me. So this was probably a good starter book. Not sure what changes when I decide to do liner or back locks. But first things first.
 
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