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Brian Dougherty

New Slip-joint Design

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I've been enjoying making slip-joints based on a design published in this book for the last few months, and have been wanting to get away from using another maker's design.  I like the look of "Coke bottle" or "Fiddle back" folders, and have taken a stab at drawing up my own version.

Sketching this was an iterative process as I "rotated" the blade in and out to check clearances.  The #3 version is where I am at right now.  It would be much easier to do this in CAD, but I do that for a living, and would rather doodle in a sketch book for relaxation. 

Mechanically, I am pretty confident in the design as I followed the design methodology described in the book and I have a good understanding of how all the dimensions interact.  However, I would like some feedback on the aesthetics.  I know a lot of people do not like the exposed corner that sticks out on many traditional slip-joints when closed, and I respect that sentiment.  I made the decision to keep that on this one.  After carrying one of my other folders around every day for the last 4 months, I have gown fond of feeling for that corner when I pull the knife from my pocket.  (Call me crazy)

I'm very fond of the look of old-school folders, and plan to make the first one of these with nickel silver bolsters and stag or jigged bone scales.

The last few knives I have made with pivot bushings to make the final assembly more predictable, and will continue doing that, although I don't show it in the sketch.

Thanks in advance!

scan.jpg

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Brian,

I love it, I would buy it......only thing I want more is to make some......

Something about #3 bothers me, looking at #2, to my eye the flare right at the end is a bit too much.

So #3 with the last half inch of #2 B)

Edited by Gerhard Gerber
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Ok, so roughed out a few parts to prototype one of these.  The spring is still oversized so I can grind it to match the scales, but I think I'm going to like it.  I'll report back when it gets further along.IMG_20190912_192124506.jpgIMG_20190912_192204168.jpg

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I like it, but the prototype raises a couple of questions regarding the two pins on the points in the middle of the handle. First, I think they are both currently too close to the edge and will create a problem for you in the final finishing, as well as a stress point in the scales prone to cracking. At least the spring pin does, not so sure about the scale pin

Looking at drawing #3, in the closed position, you have the blade stop protruding into the spring back. So the blade, as drawn, is not in the correct final position. It should be held off the spring more. The spring pin placement in the drawing has more room between it and the edge of the handle than it does on the prototype.

What size pins are you using?

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Thanks Josh.

The pins are a calculated risk, and I have the same concerns as you.  The pin along the spring side is 5/32 as is the one at the butt end that also holds the spring in place.  The other pins will only hold the scales in place, but to keep a symmetrical appearance, I used the same size pin.  We'll see how it goes with the prototype.  I knew they were close, but somehow I let them slip even closer to the edges than I intended.  I'm not sure how that happened, but here is really plenty of room to move them in a bit.

The blade stop is left long in the pattern intentionally.  The way I have been assembling these requires some hand fitting of the spring and the blade.  Once I pin the spring in place with the preload set, I grind down the stop to get the closure I am looking for.  It does make the drawing look a bit wonky because of the overlap, but I knew what I meant :)

 

Edited by Brian Dougherty

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55 minutes ago, Brian Dougherty said:

The pin along the spring side is 5/32

That's a little beefy for me. I generally do not use any pins larger than 3/32", except for the blade pivot pin, which may go up to 1/8". My scale pins are typically 1/16"

Edited by Joshua States

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Thank you for the sourcing of the book- it was on my "wish list" and I took the dive- cool design and from a noob's eye view looks nice!

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Made a bit more progress yesterday.  Heat treatment is done, and the action is tuned.  I'll probably get the bolsters soldered on and maybe epoxy the scales in place today.

IMG_20190915_092540095.jpgIMG_20190915_092626197.jpg

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The liners are mild steel about 0.050" thick.  I still need to sand off the mill scale.

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