Flattened Detent ball for flipper

A

Andre V

Joined
Oct 6, 2005
Messages
268
Hi Guys,

I have been making flippers and I am looking to increase the “holding strength” of the detent to make the flipping action better. My method till now is by just bending the lock a bit stronger, but i am finding this to be unsatisfactory with either the blade action being a bit stiff, and if i bend it too strong the blade goes slightly off center. After a bit of research I see that a some guys are flattening the top of the detent a little, which seems to increase the holding ability of the detent making it better for flippers.

Any advise on flattening the ball? (must i set as normal and then just grind the top flat, open hole size a bit in blade, etc…)
Any other suggestions to get a better flipping action.

(My method at the moment : I am using 1/16balls and setting the detent by drilling right through the liner into the blade in the closed position using 1,4mm (#54) Drill. I use feeler gauge to check the depth between liner and blade and then press ball into place with that measurement)

Thanks
 
I have tried on one folder but it has not worked well.
I am not getting much holding at all. (less than what i had with the rounded ball)
 
I have barely started on making a flipper. One of the things that is very important is the positioning of the flipper stud itself. I just couldn't believe that flattening the detent would do anything but cause trouble.
Frank
 
I would really like to see some genius put together a masterclass on flippers. There are so many variables that play into creating a great flipping action. I'm having moderate success with mine but, they are not near the level of what some are able to achieve. My wife bought one of Bruce Bingenheimer's "3/4 BingaLor" and that thing is a rocket. No doubt, every detail has to come together to make it all work. I believe my biggest issue right now is too much strength in the lockbars causing excessive friction.

Bob
 
Might be what the Detent is made of...
Check Alpha Knife supply or better yet give them a call. Always willing to help out the knifemaker with advice
 
I see this as you do Bob, with lots of things that must be done correctly in order to get a good action. Better than that will require some very close attention but right now I can't help. I've got work ahead of me that I must do so the flipper will have to wait. I wasn't going to give it a try since I thought it was illegal in Canada, but I was told not so.
Hope you find ALL of the answers and will perhaps pass along a few helpful points .
Frank
 
I was at ECCKS this past weekend and asked this same general question of some of the greats. The funny part was that they all had differing answers.

I passed by one vendor and saw a Cucchiara mid-tech which I always wanted. Flipped amazing so I overpaid just so I could get it home and take it apart. The ball was flat and it sat all the way in the hole when closed.

What I have found is that the material is essentially irrelevant for the detent strength. To a point so is the strength of the spring once it is appropriate. The cost of bending it in further has too many adverse effects. What really does matter is how deep the ball is in the hole. Looking at mine closed from the side with a light behind it I realized the detent ball of the proto I've been carrying was sticking out of the hole too far. Simple fix was to drill out the hole in the blade a little bigger. I think I went with a #53. Huge improvement.

Flattening does work and I'm going to try it. The simple principle I believe is that the edge of the flattened ball is either holding or it's not - no middle ground, and if sunk deep it will hold longer. I'll try and get some pictures of the Cucchiara tomorrow but it's really all about experimenting.
 
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Great thread, something I've been struggling with for a couple years on and off (mostly off, since kitchen cutlery is my main interest).
If you think about the force vectors, what would matter would be the angle of the side of the detent ball, relative to the angle of the side of the hole, when it's as deep as the design will allow it to go in the drilled hole.
If you took a good design that had plenty of resistance to opening and countersunk the hole, for instance, that shoulder would allow the ball to slip out of the hole much more easily. If a ball was sunk into the spring leaf so deeply that only a small arc was available to go in the hole, same effect, right?
If a ball was set so that it was just the smallest squeak over halfway into the leaf spring, and went all the way into a sharp-shouldered hole that precisely fit it, that would give you the most resistance to opening.
I bet there's more to it, though.... :)
 
Thank you guys for the response and ideas

As this may be of interest to current & future readers; I will also note that on another forum, where i asked the same question, Tom Mayo suggested the following

"Flattening the ball is more about a smooth ride across the tang and less movement of the lock than tighter detent grip.
Relieve the back of the detent hole, make sure the hole is plenty deep, make sure you have enough tension on the lock bar.
But the most important part is where the hole is in relation to the ball, thats what creates the tension."

I think I need to play around with the detent hole on the blade and see what happens. Will report any findings
 
So a flattened ball is an interesting solution. I can understand why it could work; it's a tradeoff of increased contact patch for decreased pressure by spreading out the load of the spring on a larger surface area. In order for the flat to give a benefit, it would need to ride dead flat against the tang. Ideally, the edges of the flat would need to be delicately rounded though, it's possible the tang could do that for you if you open and close the knife several dozen times.

Going back to my understanding of why the flattened ball works, it seems to me that using the largest ball possible, sunk as deep as practical into the tang, and accompanied with the lightest spring detent pressure that will still function correctly is going to be as effective and easier to set up.

Great discussion guys!

Bob
 
I'm looking forward to playing with this- making sure that the flat has a soft rather than crisp transition on the edges so it doesn't grab, and as you said, parallel with the blade.
 
Well since I've just started on this I'm very pleased to be wrong on saying to flatten the ball would be incorrect
As well Varga's information appears to be very useful.
Frank
 
Who am I to argue against Tom Mayo and I could be way wrong (maybe someone with an engineering or physics background can chime in) but on the Cucchiara I mentioned earlier the closing of the knife doesn't seem to be any smoother than mine or any other knife for that matter. Wouldn't flattening the detent, if anything, make the pressure/tension/friction of the blade opening and closing increase? More surface area equates to more friction, no? I think there comes a point where more surface area would be advantageous over less and actually reduce friction, i.e. thin tires over mud would sink right in whereas wide tires would help in displacement and roll over the top. I don't think those same principles comes in to play here, however, due to the hard surfaces we're talking about, ~60+Rc each.

My thinking is that the flat ball bearing would make the opening less smooth and not more. Potenially the difference could be so minute for our purposes as to make no difference. I'm still leaning more toward the advantage a flat ball may have is in closed/holding vs opened/released. The angled face makes a very distinct demarcation whereas round is obviously less distinct.

Almost a seperate isssue, I also think that the distance off center between the hole and the ball is nearly irrelevant so long as 1) that distance is more than zero so you can maintain tension and 2) You are able to get the ball deep enough to "bite".

Last thing to ponder is how natural wear on the ball effects the strength of the lock when it flattens over time and usage.

I think I may just have to destoy some knives tonight. Someone who knows what they're talking about please help!
 
A great attitude and that is to search it out until you have the answer for what will work for you and of course the most probable thing that will work for any that are made. You certainly are drawing me into this, which I really love in searching out to find answers. Please don't destroy any of your good knifes but power to you to find the answers to have the flippers work better.
Frank
 
Not much time nor tooling to work on it tonight. Wanted to open up my detent hole a little bigger but found nothing carbide in the right size so I just took pictures and thunk 'bout it some more.

To be clear, these are from the Cucchiara Dorado mid -tech and not my knife.

Detent ball is 1/16" and sits up .0125".



Detent hole is ~.080" across with flat walls and a rounded bottom. I found the size of the hole interesting in that conventional wisdom says that the hole is smaller than the ball.


 
I didnt have time to read through all the posts but I will give you a couple things that I do that several of my buddy makers have come up with through the years. You want the ball to fall almost all the way in the hole but not completely, you dont want the lock bar to hit the blade when the knife is closed. You want the ball seated depth in the lock bar just past half so you still have close to a 90deg angle on the ball when its in the detent hole.This is what store the energy to pop the blade open. Flattening the ball helps with smoothness but not really to help it flip better, you have to get like five things right here. You want a thinner lock bar relief and more bend angle or bend load on the lock bar. A lock bar relief cut that is too thick will work against you after the ball is overcome with flipper tab pressure. Design design design, if the flipper tab is too far back and you dont have any flipper tab leverage will kill your flipper action right away. You can overcome some of this with a good detent ball tune but not all of it. If you started with a design that mimicked a Ken Onion design with Speedsafe the flipper tab will be too far back on almost all these designs, ask me how I know, lol. Ken helped me alot when I got started and his knives were what I owned at the time I started building flippers so who did I emulate in my design, it didnt work. What I do now with my detent balls was learned exclusively through Lee Williams, Tim Galyean, and a couple others with I think Gerry McGinnis taking this to the next level as he came in the mix. He came in and fine tuned this after we were building knives and now his are just about second to none when it comes to stored energy in your detent ball to open your flipper and do it smoothly. I personally never wanted a huge detent to overcome but more and more customers want it this way. Better make sure your flipper tab is very ergo and has NO SHARP edges if you make yours like this. Customers like to play with these and dont like sore or cut trigger fingers, lol. You can tell by my spelling and grammer I am not the best to describe this but I hope it helps. Thanks
Matt

I forgot to tell you we back cut the detent hole so the detent ball can fit very far into it without touching the other side which will cause a sloppy detent closed position. Im sure I will have more as it comes to mind, lol.
 
I meant to quote the post above by Vargas showing the flat detent ball in my knife. The ball needs to be flattened at the right angle too so your not just riding on the edge of it...


There are two things at work here and none of it is proven and some works in some knives and others it does not. Flattening the ball would seem to spread out the lock bar pressure. Some knives this is true and others it is not, it just depends on so many things you cant say it for all knives. Also flattening the ball gives a better or closer to 90 deg angle to release the stored energy from your detent fitment. Also true in some knives and not needed in others. In my knives I just do them all this way, it does nothing but good in some and maybe nothing in others but never any negative effect in my knives. I still to this day after making a couple thousand knives in over 12 years of making, try to get my consistency better and better by trying new things and tune tune tune... Makers like Gerry get this down in a few years and I am still learning things every day.
 
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