Stronger detent

Cox Workshop

Cox Workshop

Joined
May 8, 2014
Messages
120
I've been working on a couple folding knives. Lot to learn still, but things are coming along. The knives I've completed are liner locks. The detention isn't as strong as I would like it to be. I'm using 1/16th detent balls and I'm using a #53 bit to drill the detent hole in the blade. I've relied pretty heavily on Bob Terzuola's book for placement/alignment of detent ball and hole. I feel like I'm right on with my alignment but still the detention isn't as strong as I would like. A couple violent flip of the knife will disengage the blade. The detent ball sits about .025 proud of the liner spring which I think should be plenty. I've bent the liner spring just enough that it reaches the other liner. (again per Tezuola's book) Any suggestions what I might be doing wrong? Is #53 the right size detent hole? Would a bigger detent ball help? I think I remember someone on this forum saying that with a 1/16 detent ball and proper technique they can make a flipper that has such good detention that its almost impossible to open with just one finger. For some reason I can't find that post anymore. Any help is appreciated!
 
I have been meaning to do some testing but haven't got around to it yet. I am currently doing just about exactly what you are doing except, I do not use Terzuola's technique for locating the hole in the blade; I just drill through the hole for the detent ball with the blade assembled in the liners and against the stop. What I have been meaning to try is, spotting with the #53 drill then separating the blade from the liners and using a 1/16" ball end mill to make the detent hole to depth. It just seems like a round ball will seat more securely in a spherical hole than it will in a conical hole. It is possible that it may seat too securely and require less depth for the detent hole. I'm hoping to get this checked out by the end of the month but if you beat me to it, post up your results.

Bob
 
I've tried to alleviate that by making sure I drill the hole deep enough that the ball isn't bottoming out. To test that I've placing a free detent ball in the hole to make sure it seats well. It seems to. Although I'm not entire sure how deep the detent ball should sit. Just by eyeballing it I would guess the ball is only seated about 1/3 of that way into the hole. The diameter of hole is what is preventing it from seating deeper. So you might be right. A 1/16" hole might allow it to sit deeper.
 
I use a #53 and get a strong detent. I too use the detent ball hole in the lockbar to spot my detent hole in the blade- drilling through the lock bar to mark the location. I do this with the stop pin and even the back spacer removed so that the blade is in an over-travel closed position by a few degrees, so that the detent ball is actually falling into the hole still with the blade against the stop pin. This is how Ken Onion taught me, and it makes for a strong detent, as the lock bar is actively pushing the ball against the side of the hole . Several times I've gotten them what I consider to be too active.
 
The most common reasons for that problem is the blade is not aligned with the detent ball and more commonly, your liner leaf has been cut too long.If your titanium liner is say .048 to .054 thick and your blade is say about 3 1/2" long the cut for the leaf should only be about 1 3/4" long and should be bent in a straight line near the start of the cut not a curve. For alignment of the 1/16' ball simply wait until the fit at the blade for the leaf spring is correct as is the fit of the blade between the liners, without the scales on close the blade , actually clamp it in position and then drill it. I prefer a no.55 for this and yes I drill with a carbide drill since the blade is now hard. So yes, a 53 is far too big even if you are drilling for alignment as I just said. The usually size stated to be used is a no.54 Here are a few more facts that may help you with your locks. The angle cut on the blade to take the leaf, yes, I know that it can be recommended to grind an arc, should be close to 8 degress. This lock face should be LEFT ground with a 120 grit belt and the leaf with a 400 or finer. I in fact use a 16 . The angle can be easily ground right first time and every time if you have a flat platen and a table. Place the 120 belt on your machine, clamp a 1/8" piece of flat stock 7/8" away from the belt. This will give you 8 degress or very close to it . The information I've given you avoids all the playing around trying to find what might work. The is no need to harden the end of the leaf spring. Sure I still see a problem here but only when I get sloppy with my work. By the way if you find you have drilled a bad alignment you can correct that by drilling say a 3/32 hole almost through the blade were the detent hole problem is and insert a piece of rod , give it a couple of taps to get it to expand, face it off, and then redrill .
If you cut your leaf spring a hair too short take a small cold chisel with a rounded edge and punch the scale side of the liner leaf in several places along the leaf.
These were at one time common problems for me too but these are the answers as well of course always the attention to do each step correctly.
Surprise, surprise, Mr. Terzuola gave you what worked for him .
I know washers of .010, .015, .020 will work but with .025 you just may be spreading your liners too far apart and creating an angle problem here with what I have given you.
I hope this helps eliminate some of the suggestions I have read being given by liner lock makers who may only do on their very first folders. There has been a lot of confusion created that created because they have in good will come forward but in fact are not getting the results every time as they should.
I am here a fellow member, only wishing to help out where I can, which is in truth very limited to liner locks and not even frame locks.
Frank
 
Thanks you guys for the info. Definitely gives me something to investigate. Even though I think my alignment is right on I might be off just a hair. Will try drilling it through the lock spring like you guys. Also, frank you make a really good point about how far I have my detent ball protruding, .025 may be causing or exacerbating my alignment problem. Additionally, I have probably cut my lock springs too long.

Just for a frame of reference how much of a 1/16" detent ball do you guys leave protruding from the lock spring? Would .010-.015 be more appropriate?
 
Frank Niro said:
The most common reasons for that problem is the blade is not aligned with the detent ball and more commonly, your liner leaf has been cut too long.If your titanium liner is say .048 to .054 thick and your blade is say about 3 1/2" long the cut for the leaf should only be about 1 3/4" long and should be bent in a straight line near the start of the cut not a curve. For alignment of the 1/16' ball simply wait until the fit at the blade for the leaf spring is correct as is the fit of the blade between the liners, without the scales on close the blade , actually clamp it in position and then drill it. I prefer a no.55 for this and yes I drill with a carbide drill since the blade is now hard. So yes, a 53 is far too big even if you are drilling for alignment as I just said. The usually size stated to be used is a no.54 Here are a few more facts that may help you with your locks. The angle cut on the blade to take the leaf, yes, I know that it can be recommended to grind an arc, should be close to 8 degress. This lock face should be LEFT ground with a 120 grit belt and the leaf with a 400 or finer. I in fact use a 16 . The angle can be easily ground right first time and every time if you have a flat platen and a table. Place the 120 belt on your machine, clamp a 1/8" piece of flat stock 7/8" away from the belt. This will give you 8 degress or very close to it . The information I've given you avoids all the playing around trying to find what might work. The is no need to harden the end of the leaf spring. Sure I still see a problem here but only when I get sloppy with my work. By the way if you find you have drilled a bad alignment you can correct that by drilling say a 3/32 hole almost through the blade were the detent hole problem is and insert a piece of rod , give it a couple of taps to get it to expand, face it off, and then redrill .
If you cut your leaf spring a hair too short take a small cold chisel with a rounded edge and punch the scale side of the liner leaf in several places along the leaf.
These were at one time common problems for me too but these are the answers as well of course always the attention to do each step correctly.
Surprise, surprise, Mr. Terzuola gave you what worked for him .
I know washers of .010, .015, .020 will work but with .025 you just may be spreading your liners too far apart and creating an angle problem here with what I have given you.
I hope this helps eliminate some of the suggestions I have read being given by liner lock makers who may only do on their very first folders. There has been a lot of confusion created that created because they have in good will come forward but in fact are not getting the results every time as they should.
I am here a fellow member, only wishing to help out where I can, which is in truth very limited to liner locks and not even frame locks.
Frank
Click to expand...

Thanks Frank...

You dropped some real world maker knowledge right there. I just saved that for future reference when I start folders.

You contribution is much appreciated.
 
Sorry I did miss that. I place a .010 washer over the hole and as I said use a 1/16" hole. A few taps from a hammer and it is seated. I remove say .015 material from the scale side of the liner behind the detent ball and towards the back in a taper. This will ensure the liner will move over sufficient to allow the blade to close without dragging on the ball.
Can I help further? Please ask. One of my biggest enjoyments in life is trying to help others.
Frank
 
Please, notice that this "weak detent " problem can be caused by any one or more of the above mentioned conditions.
Frank
 
Just wanted to close the loop on this thread. Followed the advise you all gave and the detent is very strong now :D. I got a carbide bit like Frank suggested (after ruining two titanium coated bits :eek:) and it cut the detent hole in the hardened blade like butter. Using the hole in the liner to line it up is so much easier and likely why it came out so much better. I'm seriously excited about the way this blade flips out now. Plus with the strong detention I feel better about keeping it in my pocket. On top of it all with your advise I think I've got a repeatable process, I should be able to nail it every time. Thanks again for all the help!
 
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