Blade shapes for slipjoints

It's hard to tell without seeing them open, as well. The tang on all of those looks about the same to me, but they probably shouldn't all be the same. The closed position is fine, but the open position will need to be adjusted to keep the spline of the blade in line with the back of the handle, and keep the point below the centerline. Again, it's hard to tell while glancing at the closed pictures, so maybe you've already sorted all that out.
 
Blankblank said:
Then there's the matter of what kind of grind to put on the blades. That alone can change the look drastically.
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Definitely true, as well as the edge geometry, and swedges and jimping, and fullers and even thumb holes if you want to emulate spyderco... But for now, I am trying to simply generate an easy way to parametrially reproduce the classics. Starting with blade shapes, and moving on to frames and bolsters. It would certainly give me a good starting point, as I already know how to emulate at least a few of the different grinds.
 
Tyson A Wright said:
It's hard to tell without seeing them open, as well. The tang on all of those looks about the same to me, but they probably shouldn't all be the same. The closed position is fine, but the open position will need to be adjusted to keep the spline of the blade in line with the back of the handle, and keep the point below the centerline. Again, it's hard to tell while glancing at the closed pictures, so maybe you've already sorted all that out.
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The back of the spring is not designed in this cut. It will be predicated on what frame is put on it. The tang, walkup, and back square are identical on all of these, but I can change that as well. This is based on a knife closing to 172° and that has not been paramertized. Seemed like a safe place to start from. Also, the operational part of the spring, and the walk, are based on the tang size as well as the assumption of a 172° closing angle. They were shown in this configuration to demonstrate that when the blade shape changes, the spring profile follows. Had it been pointing in the opposite direction, you would have to simply take my word for it that it matched the profile :) There is a transform that I simply change the angle so i can see 0, 90, 172 and it moves the blade since it is a separate part from the spring. The spine of the blade and the back square are parallel to each other, and perpendicular to the walk up. So, the design is made to have the spine in line with the back of the frame, but I haven't done the frame part yet. :) Getting there though... Now time for a week's vacation to just think about it :)
 
BradleySmall said:
Definitely true, as well as the edge geometry, and swedges and jimping, and fullers and even thumb holes if you want to emulate spyderco... But for now, I am trying to simply generate an easy way to parametrially reproduce the classics. Starting with blade shapes, and moving on to frames and bolsters. It would certainly give me a good starting point, as I already know how to emulate at least a few of the different grinds.
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Are you planning to go a bit more modern on the blade steel, or keep that with the classic design, because I think something with a bit better performance than you can get on a case or gec would be great in these old designs with thin geometry.
 
Interesting, what software are you using to model this?

I don't really know too much about slipjoints (have not made one yet), so take this for what it's worth. The tang protruding from the spring looks a bit odd to me. It seems like it could get hung up on that corner. If you want to make it flush in all three positions, you would have to make the half-stop 86 degrees instead of 90. With the half stop at 90, the tang should be inset slightly from the spring, not protruding. If you are using a CAD software, you could put in parametric constraints based on the half stop and closed angles and the tang size, and get the corners of the tang and the kick positioned correctly. The kick would have one degree of freedom left and only be constrained to a line, so you would need one additional parameter for the length.
 
Blankblank said:
Are you planning to go a bit more modern on the blade steel, or keep that with the classic design, because I think something with a bit better performance than you can get on a case or gec would be great in these old designs with thin geometry.
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Right now I am working with 80crv2 but I am considering that ultimately I want to work with some air hardening things like D2. But SS is not out of the question. Also, some people have preferences for carbon steels like people doing wood carving. I am just getting started, so I am open to all sorts of things.
 
Hubert S. said:
Interesting, what software are you using to model this?

I don't really know too much about slipjoints (have not made one yet), so take this for what it's worth. The tang protruding from the spring looks a bit odd to me. It seems like it could get hung up on that corner. If you want to make it flush in all three positions, you would have to make the half-stop 86 degrees instead of 90. With the half stop at 90, the tang should be inset slightly from the spring, not protruding. If you are using a CAD software, you could put in parametric constraints based on the half stop and closed angles and the tang size, and get the corners of the tang and the kick positioned correctly. The kick would have one degree of freedom left and only be constrained to a line, so you would need one additional parameter for the length.
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This was done in FreeCAD. This is a design based on Steve Culver's design from his book. So it has a closed position of 172°. I have also worked with reproducing Don Robinson's design (since I can't find his electronic versions only the print out in the book). His design closes at more like 177° or 178°. Much less overhang. Actually more rectangular tang design, where Steve's are based on square.

However, in this run I was much more interested in getting the different blade shapes, and having the inner spring profile follow. What will be awesome is if I can figure how to integrate the different frames. So by choosing a cigar or toothpicks or swayback it could overlay and create both inner and outer spring profiles.

I have most of the frames traced out, but I haven't gotten close to parametizing them yet.

Getting there.
 
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All those degrees will go out the window when you assemble the knife.
When you assemble the knife the combination of kinds of factors come into play and you will have to eyeball it to get it flush in 3 positions and then deal with how that changes when you beat it together with a hammer
 
AVigil said:
All those degrees will go out the window when you assemble the knife.
When you assemble the knife the combination of kinds of factors come into play and you will have to eyeball it to get it flush in 3 positions and then deal with how that changes when you beat it together with a hammer
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Point taken. But if you are going to bother making a CAD model, why not put in the constraints to make it at least work correctly in the computer? I just drew this fully constrained parametric tang in FreeCAD in less than ten minutes, and I am not really all that familiar with the software or CAD in general.

sxohunZ.png
 
Did you factor it the pressure the spring is putting on the back square? Because that pin will move slightly down and no longer be where it was when no pressure is applied and where the tip sets will change as the spring is under pressure and will bend and the kick will have to be adjusted.

Sure you can do it in CAD, but what you actually have to deal with will change.
 
I would rather start from a template that at least works in theory than from a template that does not, that's all. No model is perfect. I just started using CAD a couple of weeks ago to design a hardness tester I plan on building. I figure it's probably better for me to start from a model that I know does not have any interference than from a drawing on a napkin. Whether the hardness tester will work once I start machining the parts is a whole different story, but I hope I have a better shot at it with a 3D model that I can check before ever turning on the milling machine or lathe.
 
H Hubert S.
In in the process of restoring/ fixing a Enco brand hardness tester, if you'd like I can take pics and measurements of the mechanism... No need to reinvent the wheel...
 
A template will give you actual hands on at how it all works.
It really is not a problem and millions of slipjoints have been made with them.

Have fun, for sure but once you get working on the knife you will actually adjust your template to get it to work and the CAD will have to be corrected from what you learn from the template.
 
AVigil said:
A template will give you actual hands on at how it all works.
It really is not a problem and millions of slipjoints have been made with them.

Have fun, for sure but once you get working on the knife you will actually adjust your template to get it to work and the CAD will have to be corrected from what you learn from the template.
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I'm actually not trying to design a slipjoint in CAD, that's Bradley. I only noticed an area in his CAD that I thought looked off and mentioned that it's not too difficult to constrain the geometry.

I have made a template for a slipjoint from a drawing I made in inkscape, but have not gotten around to making the actual knife. Too many projects, too little time.
 
A.McPherson said:
H Hubert S.
In in the process of restoring/ fixing a Enco brand hardness tester, if you'd like I can take pics and measurements of the mechanism... No need to reinvent the wheel...
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I appreciate it, but I am trying to do something different. I got interested in this when fitzo fitzo mentioned in another thread that knifemaker Ray Rogers had built a DIY hardness tester a long time ago. That contraption was not very practical, but it got me thinking about how to make one that works properly. I have some ideas I want to try out, it's a bit of a challenge for me now, or maybe a mild obsession. Anyway, I'll be sure to post about it once I'm a bit further along, or maybe I'll start a WIP thread to document my efforts.
 
BradleySmall said:
Right now I am working with 80crv2 but I am considering that ultimately I want to work with some air hardening things like D2. But SS is not out of the question. Also, some people have preferences for carbon steels like people doing wood carving. I am just getting started, so I am open to all sorts of things.
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Nothing wrong at all with carbon steels. I'm just a big fan of the high carbide stuff personally (not any particular reason, other than I just find them really interesting, and want to learn to get the best results I can from them) . I still own and use some carbon steel blades, and they do well.

Really air hardening, and stainless isn't too much different, provided you have the means to properly work with them. A way to get them heat treated, proper abrasives, and some patience
 
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AVigil said:
All those degrees will go out the window when you assemble the knife.
When you assemble the knife the combination of kinds of factors come into play and you will have to eyeball it to get it flush in 3 positions and then deal with how that changes when you beat it together with a hammer
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Pretty sure you are right, but still feels like a good starting point.
 
Hubert S. said:
Point taken. But if you are going to bother making a CAD model, why not put in the constraints to make it at least work correctly in the computer? I just drew this fully constrained parametric tang in FreeCAD in less than ten minutes, and I am not really all that familiar with the software or CAD in general.

sxohunZ.png
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Nice tool isn't it? :)
 
AVigil said:
Did you factor it the pressure the spring is putting on the back square? Because that pin will move slightly down and no longer be where it was when no pressure is applied and where the tip sets will change as the spring is under pressure and will bend and the kick will have to be adjusted.

Sure you can do it in CAD, but what you actually have to deal with will change.
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There are some definite parts to manage relative to spring pressure. However as long as the pressure is positive and the pivot actually matches the hole the model should match.
 
BradleySmall said:
There are some definite parts to manage relative to spring pressure. However as long as the pressure is positive and the pivot actually matches the hole the model should match.
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"Should"

Have fun using CAD, you can print out some nice templates with it.
 
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