SlipJoint Design

colu41

colu41

Joined
Dec 24, 2014
Messages
1,598
I finally took the very time consuming & expensive plunge into "attempting" to build slipjoints. I finished my first one. And as its ok IMO, for my first, it still obviously needs a lot of work to perfect, and also I used a template I found online.

My question for you guys is, are there any tricks or steps to designing your own slipjoints without a CAD program? I've tried many times and it seems that I can never get the shape I'm looking for because it may look alright open, but not when its closed. Or it wouldn't even operate correctly, without completely changing the shape of one thing or another.
Now I've found this tutorial, which is completely amazing, for linerlocks.
http://www.rayrogers.com/ftutor1.htm

Is there something similar for slip joints?

I'll try to post pics of the slipjoint I finished later. The pic host I use isn't currently working.
 
For designing your own, I highly recommend using a program, like Google Layout. That is what I use, and it works perfectly for what I need. It allows you to rotate a design from a set point, in this case, it is the pivot. That way you can get all of your proportions right, make your tang adjustments, and see how it looks in each position. It ain't cheap, but it sure as hell is easy to use.
 
I like Draftsight for drawing 2D stuff. It's got a pretty good learning curve, unless you're already proficient in AutoCAD. I've been using AutoCAD for a LONG time so the change wasn't hard at all for me. Best of all, Draftsight is FREE!! will save as and open dwg files with no problem.
 
I use a free one called inkscape. you can do layers and set pivot points and all that good stuff.
 
i learned from Mike Vagnino ABS MS, then refined my learning with the design guide from Steve Culver mentioned earlier by Stezann
There is a guy in Texas who does some cad work for about $25 an hour, lmk if you want his contact.,

tips and tricks for w/o cad - do you have or use a layout block?

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Thanks guys. I'll look into these programs. And HSC no I didnt use a block yet, but I will probably use one on my next one. As nice as that is for fitting up the blade and tension bar, that still doesn't help with the actual design IMO.
 
one way w/o CAD is to, 1) trace out your design
2) transfer paper to cardboard backing (glue it down)
3) use a push pin or tack pin for the pivot hole and rotate it
4) make adjustments
 
I like to use cheap Lexan which cuts and files easily and you can view all the mechanics and make adjustments with an actual template prototype and the material is cheap. I also draw my designs on paper with pencil...seems to work for the last 10 years.
 
I make my "patterns" the old-fashioned way also, but I don't like using Lexan, because it melts grinding often, maybe it's just cause I"m usually too lazy to change the paper on my disc grinder, but it aggravates me. I like using thin g-10, it's still, easy to cut and grind, and even works fine for a spring, when developing a pattern, although most of the time I'm stubborn and just make a pattern out of damascus and try to finish a damn knife from go, which usually bites me in the ass.

Regardless, once you've got the pattern dialed in, make a steel pattern using 1/16 precision ground stock, like O-1, and then harden it, and temper it only enough to relieve stress and keep it from breaking if it drops. That way you have a highly wear resistant pattern than you can use for the rest of your life to scribe for cutting out parts when you need to, or even carefully file/grind to.

I used to take my blade pattern and clamp or superglue them together to cut my choil and back-square with a file on a pattern like this. A dull file would cut the annealed steel fine, but wouldn't hurt the screaming hard O-1 pattern. Eventually I got comfortable enough just knowing where I wanted to put them, but it's still nice to be able to clamp the pattern blade over for spotting the pivot pin hole. Saves fitting later.


Problem with paper or cardboard patterns is they get fucked up easily. Sometimes I'll draw a design, and cut it out, then glue it to a piece to cut out, but if it's glued to metal, the adhesive will fail as the metal heats up from hogging the profile, and if you dip it in water, the lines get distorted or disappear, the paper will also sometimes deflect from the grinding belt unless you're grinding in a certain orientation, causing you to potentially remove metal past the lines. So usually, if I'm not being lazy, I'll glue a drawing to a piece of thin g-10 or micarta, cut it on the bandsaw, then quickly profile on the disc grinding with 120 grit paper, which'll leave a fine enough finish on g10 to transfer well to a piece of steel, to make a protoype. Once I have the prototype "dialed in" I will then scribe a permanent pattern to a piece of precision ground O1 or similar, cut it out, dial it in as far as I want (not much reason to make it perfect as you'll always have to do hand fitting in the tang/spring mating) so that I can get repeatable pieces, then harden it. If you try to just use the G-10 pattern, you'll eventually change it, running a carbide scribe around it too many times.
 
Eh eh, yes, the paper template will be chewed quickly. I have not so many slipjoint under my belt yet, but every single time i ended tuning the real deal, repeating to myself to scribe that pattern on steel for the future....always ending getting drawn by the build and peening the stuff together without leaving any trace of it!!! Fortunately i'm still at the level where the last one it's always better than the previous, but a working geometry would be useful to start with, even if changing the pattern and bettering the fit & finishing
 
I'm reading How to Make Multi-Blade Folding Knives by Eugene W. Shadley and Terry Davis. One build is being designed on a light board with tracing paper. You can rotate the "pivot" and manually see what it will look like open and closed.
 
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