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The Folding Knife (& Switchblade) Forum The materials, techniques and the designing of folding knives.

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  #1  
Old 03-31-2009, 12:50 AM
T. Hendrickson T. Hendrickson is offline
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Flipper stop pin

Hello,

I've been wanting to build a locking-liner flipper for some time now. I've finally worked up a nice simple design that should work well. The problem is, it uses an exterior stop pin/thumb stud, ken onion/kit carson style. I went with this because I don't have a milling machine for the precision of an interior moving stop pin.

My question is, what is the best way to attach it to the blade tang? Here are my two ideas: tap both sides of the stud and screw it together with a length of screw shaft (which is only as strong as the screw) or drill a hole the size of the stud and solder it in.

Which would you recommend? what is commonly done in such situations? Thanks in advance.

Thayer Hendrickson


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Old 03-31-2009, 09:35 AM
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Ray Rogers Ray Rogers is offline
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I'd use a hardened pin like a dowel pin (available from MSC and I think Knifekits carries them) or a piece of 416 rod that had been hardened. Then, drill and ream a precisely sized hole in the tang so that the hole is about 1 to 2 thou smaller than the hardened rod. Just press the rod into the hole with an arbor press or a vise. I believe this is the same method used to put pins into balisong tangs.

BTW, you don't need a milling machine or much precision to use an internal pin as long as you use a stationary pin. A flipper made this way is no more difficult that any other liner lock .....


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Old 03-31-2009, 10:02 AM
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Have you read this thread? there are several useful suggestions.

http://www.knifenetwork.com/forum/sh...istmas+present
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Old 03-31-2009, 08:18 PM
T. Hendrickson T. Hendrickson is offline
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Thanks fellas. Ray, would you put in the pin before or after heat treat? And where do you find reamers in number size?

also, are you talking about milling a track in the liners or blade?

Don, I read through that thread, it was helpful, thanks.


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Last edited by T. Hendrickson; 03-31-2009 at 08:21 PM.
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Old 04-01-2009, 09:35 AM
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Ray Rogers Ray Rogers is offline
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I'd put the pin in after the heat treat, otherwise it will be in the way when you try to do the final finishing on the blade. Numbered sized reamers, and even decimal sized reamers, are available from MSC.

I was talking about not milling at all. It's a different method than what you are dealing with. There would be no pin in the tang of the blade, only a pin in the handle just as you find on the majority of liner locks. Therefore, no slots need to be milled anywhere for the pin. The 'secret' is in the tang geometry:

Think of the tang on your folder. The pivot hole is centered in the tang from top to bottom. On a flipper design, the pivot hole should also be the same distance to the rear of the tang as it is from the top to the bottom of the tang (top: where you rest your thumb, bottom:the side opposite the thumb rest). When you close your blade, part of the blade comes to rest against the stop pin which is mounted in the handle. If the flipper is just forward (towards the point of the blade) then it will stick through the handle just behind the stop pin. The flipper forms a small finger guard when the blade is open when this design is used, a useful side effect.......


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Old 04-01-2009, 01:02 PM
T. Hendrickson T. Hendrickson is offline
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Ok, Ray, I think I get what you're saying; so in this configuration, would I put the stop pin much further forward in the handle and trim down part of the top of the tang to clear the pin when opening? Sorry if that didn't make any sense. I'll have to sketch something up and see it on paper.


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Old 04-01-2009, 06:07 PM
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Ray Rogers Ray Rogers is offline
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I took this picture from my liner lock tutorial and sketched a flipper onto it. If you follow this design method for the tang geometry you can see that adding a flipper is easy:



The main advantage of this method is that it doesn't require any changes from the way you usually design a liner lock (if you do it the way I do anyway) and it doesn't require any milling .......


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Last edited by Ray Rogers; 04-01-2009 at 06:11 PM.
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Old 04-01-2009, 06:19 PM
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Did you see the forward stop pin design in the thread "Late Christmas present"? It's in the first post.
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Old 04-01-2009, 10:52 PM
T. Hendrickson T. Hendrickson is offline
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Don, I checked out the forward stop pin. This is what I had in mind when I read Ray's post. Which style do you prefer yourself, what are advantages/disadvantages of each?

Ray, I've been trying to design something like that and I find it difficult to make it all fit together just right. It seems like the flipper has to be made extra long for it to work. Have you made a folder in this way, and if so, how did it work?


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Old 04-02-2009, 09:47 AM
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Quote:
Originally Posted by T. Hendrickson
Don, I checked out the forward stop pin. This is what I had in mind when I read Ray's post. Which style do you prefer yourself, what are advantages/disadvantages of each?
There are no advantages except what you see. I prefer the hidden stop pin because I like to see the smooth, straight top of the blade shank when the knife is open. With the forward stop, when you look down into the handle while the blade is open, you see the curved shank and pin.

When the hidden stop pin method is used, a person who is familiar with folders, but not of this design, wonders what in the world is keeping the blade from flipping all the way around!

The two models I made are both made to the hidden stop pin design. Of course, I have a milling machine and rotary table to make the milled track in the blade shank.

Both of the flippers I made were sold before I finished them.

Instead of experimenting, why don't you print out the design, copy it to whatever size you want, and make your first flipper to a proven design? I made my two to copies that were enlarged to 115% in order to have a 4" blade.

The design can be used only to get the mechanics right too. The blade shape, handle shape, size, etc. can be changed to look however you want as long as you make the lockup/pivot pin to the design.

This is the first time I've ever tried to persuade someone to use one of my designs that I'm giving away free.

Last edited by Don Robinson; 04-02-2009 at 09:53 AM.
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Old 04-02-2009, 10:00 AM
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I've made mock ups this way that work fine, also I've seen commercial knives made this way. In fact, I have a Darrel Ralph 'Trigger' model here at the moment and it's made that way. The Trigger has a 3.25" blade length and the flipper is only 5/16" long so I wouldn't say this design requires an extra long flipper.

It is no more difficult to get it all to fit together with a flipper than it is without one. However, a lot of the truth of that statement depends on how you go about fitting it all together. There are many ways that a liner lock folder's geometry can be designed and constructed. I follow the method shown in my tutorial which makes designing the geometry for the flipper very easy. Then, I build the knife in a specific sequence of steps which considerable simplifies the fitting together of the lock and stop pin. In short, the blade is notched for the lock, the liner is then cut to match the notch, the stop pin is placed where I want it to be and far enough forward that the blade cannot quite open, the the tang of the blade is carefully ground down until the lock will engage. After making literally hundreds of these folders and fitting the locks by hand this is by far the closest thing to a fool proof method I have found..

Still, I'm not saying this style of flipper is 'best' but it does meet your need for a flipper design that doesn't require a milling machine ......


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Old 04-02-2009, 03:45 PM
T. Hendrickson T. Hendrickson is offline
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Ha ha, ok Don, I'm going to print out your design and modify it to something more to my taste; primarily changing it to have a straighter profile when open. Thank you! I'l let you know how it works.

Also, I'm going to try designing one following Ray's tutorial exactly. I may be missing something here.


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Old 04-02-2009, 03:57 PM
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Make several copies of the design, cut out the blade and handle profiles separately using scissors, then stick a pin thru the center of the blade and handle pivots and turn the handle any way you want.

Be careful to avoid the "broken back" look. The blade should always tip downward slightly.

Last edited by Don Robinson; 04-02-2009 at 04:00 PM.
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