How do ya make a lock back dual action scale release folder?

Bruce Bump

Bruce Bump

Joined
Dec 2, 1999
Messages
9,910
Been trying to work this one out in my head. I want to use a coil spring because I dont think there is enough room for a leaf spring because of the lock back bar but cant figure out how to hold the coil in loaded position while the blade swings using the thumb bob. Any fresh ideas are welcome.
 
Bruce Bump said:
Been trying to work this one out in my head. I want to use a coil spring because I dont think there is enough room for a leaf spring because of the lock back bar but cant figure out how to hold the coil in loaded position while the blade swings using the thumb bob. Any fresh ideas are welcome.
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You use a coil spring, and you cut a locking notch in both the top and bottom of the blade. the knife locks both open and closed.

Knifemaker Chris Crawford has an excelent dvd on how to make one. The scale release auto is his stock and trade.
 
Bruce Bump said:
how to hold the coil in loaded position while the blade swings using the thumb bob. Any fresh ideas are welcome.
Click to expand...

You don't want to fight the tension of the coil (that would want to snap it open via auto) when you're opening manually correct ?

Bruce, I'm not sure I fully understand your predicament but I'll give it a shot. Maybe a rotating insert that the coil sits in that is inserted into a cavity in one of the frames or liners One that could be activated (or not) by a pin (kind of like a safety on a trigger guard) Am I understanding you correctly ??

I'm sure you are light years ahead of me when it comes to making mechanisms but, nonetheless, I will think more about it while I'm in the shop today ;)

I can't wait to see what you come up with :cool: ;)
 
Bruce would this spring set up be a option with a lock notch in the tang instead of a place for a button ? It looks as if you could put the spring completely down in the bolster out of the way.



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You guys are going to save me on this one I can tell already. Basically what I want is a scale release auto with a lock back but as a bonus it will be a dual action.

The coil spring style is cool (Knifekits Darrel Ralph) but has its limitations as a dual action. I want to keep the lock back because of its traditional design, yep its going on another pistol.

This by far my biggest challange yet and you guys need to bail me out. I just opened my big mouth and said I could do it and my customer said OK I will buy that.
 
Leaf spring dual action would be much easier than coil.

I've been trying to wrap my mind around dual action coil fired for a while now......
 
Bruce,

I think the way to do this is to use a one way ball bearing clutch. Basically a large pivot hole in the blade inside of that you have you pivot gearing that has a for or more lobed cam the lobes need to have clearance enough in the low areas to hold roller or ball bearings. the coil spring assembly goes inside this cam. the clearances will have to be pretty tight so that when the spring is used the clutch locks to the blade as it should, but loose enough to let the blade swing aaround it. this type of clutch is used in the bendix of starter motors. It would be worth while to find one and tear it apart to get the idea of what I am talking about. email me and I will try and draw something up and send to you.

Bill
 
Bruce, maybe you can do a step by step pictorial on this one, so that we can all start copying your work and making the big bucks! ;o)
 
burke531 said:
Bruce,

I think the way to do this is to use a one way ball bearing clutch. Basically a large pivot hole in the blade inside of that you have you pivot gearing that has a for or more lobed cam the lobes need to have clearance enough in the low areas to hold roller or ball bearings. the coil spring assembly goes inside this cam. the clearances will have to be pretty tight so that when the spring is used the clutch locks to the blade as it should, but loose enough to let the blade swing aaround it. this type of clutch is used in the bendix of starter motors. It would be worth while to find one and tear it apart to get the idea of what I am talking about. email me and I will try and draw something up and send to you.

Bill
Click to expand...


I might be able to find a drawing of a drawn cup needle roller bearing clutch assembly. My company doesn't make the ball bearing version, but we do make needle roller versions. The smallest bearing we make in a clutch assembly is .125" bore x .281" outside diameter x .250" width.

You can see a brief description of this bearing here.

http://www.timken.com/industries/torrington/products/needle/drawncuproller.asp

I hope that this is helpful.
 
I suppose I'm not the only one to put some thought into this.
Leaf spring is the way to go and does not take up much room. Butch Valloton just squeezed one into a small sebenza for me recently. I doubt the lockback issue would be harder to figure in to it....

The coil fired would depend on a more complicated system, and I had the same thinking about the bendix, and like burke said, it would be tight. It is intriguing and I'm sure there is a solution, but just how complicated that solution is, is another question.
 
burke531 said:
Bruce,

I think the way to do this is to use a one way ball bearing clutch. Basically a large pivot hole in the blade inside of that you have you pivot gearing that has a for or more lobed cam the lobes need to have clearance enough in the low areas to hold roller or ball bearings. the coil spring assembly goes inside this cam. the clearances will have to be pretty tight so that when the spring is used the clutch locks to the blade as it should, but loose enough to let the blade swing aaround it. this type of clutch is used in the bendix of starter motors. It would be worth while to find one and tear it apart to get the idea of what I am talking about. email me and I will try and draw something up and send to you.

Bill
Click to expand...

That may be what Im looking for. Im very familiar with this kind of bearing because almost all jap motorcycles use them for their starting motor clutches. Is there one available that small or do I have to make one?
 
Bruce look at the post above by Ickies and follow the link. It looks like there may be something that you can use there. The advantage with making your own would be getting exactly what you want and need.

Bill
 
Bruce, that makes my head hurt. A leaf spring would be way easier and you should have plenty of room. I have made over 300 autos but not one with a coil spring.

If you pull this off with a coil, it would be something for sure!
 
Don Hanson III said:
Bruce, that makes my head hurt. A leaf spring would be way easier and you should have plenty of room. I have made over 300 autos but not one with a coil spring.

If you pull this off with a coil, it would be something for sure!
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The whole problem is that Im determined to make it a lock back instead of a liner lock. The leaf spring and the back lock bar would take up the same space. I dont think there is room for both there. The coil spring will solve that problem but causes another with the double action. Let me ask this: does anybody make double action autos with a coil spring?

I have it figured out how to make a coil fired lock back but cant figure out how to hold the coil in the "loaded position" so it will be a double action. I think if the coil tab that goes through the blade is extra long I can hollow out the bolster for a stop/catch mechanism that is activated with the scales. Its tricky but possible.
 
heatride said:
Bruce would this spring set up be a option with a lock notch in the tang instead of a place for a button ? It looks as if you could put the spring completely down in the bolster out of the way.



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I have these springs and the cutters for the pockets. My spring will need an extra long tip that goes through the blade tang and protrudes into a cut-out in the bolster. I need to invent a mechanism to hold that spring tip for dual action. The blade tang will have a half moon slot in it for the spring tip so the blade can be opened manually when the spring tip is locked. Know what Im saying?
 
Bruce Bump said:
The whole problem is that Im determined to make it a lock back instead of a liner lock. The leaf spring and the back lock bar would take up the same space. I dont think there is room for both there. The coil spring will solve that problem but causes another with the double action. Let me ask this: does anybody make double action autos with a coil spring?

I have it figured out how to make a coil fired lock back but cant figure out how to hold the coil in the "loaded position" so it will be a double action. I think if the coil tab that goes through the blade is extra long I can hollow out the bolster for a stop/catch mechanism that is activated with the scales. Its tricky but possible.
Click to expand...

Bruce, I've seen many lock back autos with leaf springs. Kious, Osborn, Dake, Stagerwalt, just to name a few. Plenty of room in there :)
 
Bruce Bump said:
I have these springs and the cutters for the pockets. My spring will need an extra long tip that goes through the blade tang and protrudes into a cut-out in the bolster. I need to invent a mechanism to hold that spring tip for dual action. The blade tang will have a half moon slot in it for the spring tip so the blade can be opened manually when the spring tip is locked. Know what Im saying?
Click to expand...
Will you have enough room for this?
My issue when contemplating the double action coil fired is overall thickness.
It would be relatively easy to make in a 1" thick knife.
Where it gets tough is when you start getting down to a useable thickness.
Those coil springs are thick, even if you make one with only 2 coils, they are still pretty thick....
 
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