folder makers please help asap lock geometry

jakehobackknives

jakehobackknives

Joined
Mar 5, 2012
Messages
151
Hay Guys,
I have made about 100 folders now, and now that they have been around a couple years every once in a while Ill get one back for repair or its just worn out a bit. I have been working on new designs and trying to make the existing designs better. I hope some one can give me some help on this to make my lockup design a little better.

I have had 2 flippers come back that had a little bit of vertical blade play when open. I am 100% certain it is not lock rock. so lets not get into that. it seems with the internal stop pin set up Im using causes any slight play in the pivot, translates right to the blade instead of being absorbed into the lock by camming action. so if the pivot hole is .250 and the pivot is .249 I get that .001 transferred all the way down the blade to the tip 4" later and it ends up being several thousandths.

I have Bob Ts book and know about lockup geometry for the most part. I still have much to learn.

Here is a simple drawing of how my lock is now.
lockupclosed.jpg

lockupopen.jpg

The green triangle in the open position should give you a reference as to where the camming action is taking place. it seems that I cant get the lockface of the frame below the center line of the stop pin to create enough camming action to take up and slack in the system. So basically there is not a lot of forgiveness to this setup currently.

Here is what I just drew up in hopes of moving the triangle to better account for inconsistency and have more forgiveness.
newlockupopen.jpg

newlockupclosed.jpg


I didnt have to do much but rotate the whole stop pin track a bit and adjust the blade shape to suit.
Any body have any other recommendations? besides switching to a external stop pin as I rather like the ease of making an internal compared to an external.

I have WJ waiting on new drawings.

Thanks guys! God bless
 
Your pivot needs to be a press fit on the lockbar side. .250 pin, .2485-.249 reamer.
Also for repair, do you have a carbidizer ? You can carbidize the lock face this will add a few thou to the lock bar face and eliminate the play.
 
I press fit my pivots already. That was just an example..249 on pivot side frame .2495 on other. Blade is .250

I carbidize all my locks already. I personally find it only adds maybe .0005 at the most. It's also not the lock face that is the problem as I have perfect lockup with no sliping or wiggle. It is wiggling at the stop pin and pivot.

I can make the knife work perfect with the system I already use. I would like to make it so I don't have to work so hard to get it, as there is an extremely small window for error with the triangle being so small.
 
Basically I'm trying to see if anyone else has had this issue and if my new lock setup looks like it would increase my room for error and allow for more wear before blade movement occurs
 
Let me preface by saying I have made 1 liner-locking folder to completion. I have made two to functioning level and have 11 in progress. I have however been in manufacturing my whole life. In order to have the triangle actually work the way we as knife makers want it to work, the angle originating for the pivot needs to be as large as possible, minimum being 90 degs. With the way you have it set up your pivot/pivot hole difference, will always get you a vertical rock once your pivot hole is distorted into an obround(or pivot is smashed into an elipse). Your "figure 2" is the best diagram to look at. All your lockup force is being applied to the stop pin, while little if any is being gained by the pivot. In Mr. Terzuola's diagram you can see the stop pin is working with the lock face to fight the pivot. So no matter the wear on the pivot, lock face, or stop pin, you have a firm lock up for a longer duration.
 
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I se what yall are saying. I def see how a larger triangle makes a big difference.

I have debated going back to a external stop pin but I like how much more frame space you get with an internal pin. I recently changed all my knives over to all the same components, so all of them have 4-40 screws and .187 stop pins. Over all I'm just trying for a better, beefier knife.

I'm gonna try to bring the stop pin out another .050-.080 away from the pivot to pull the triangle out some.



On a side note. Let's keep this thread going with good lockup information as its extremely hard to find on all the boards. When I first started I struggled with finding info.
 
Yeah...I'M new in the folder game no where near 100. But with my current order log I will be there shortly. I have hounded several makers for info. Every time I make one I learn something...even though I'm making the same design. Folders are finicky for sure, balance of lock bar pressure, detent depth so many ways to screw-up. I'm designing a frame lock that I hope to have out in a couple of weeks.
 
For sure man. I have another 100 or so to finish before the year is up. So I'm trying to make improvements.

Side note:
No matter how many different folder designs you make its always best to keep all the parts the same ie... Pivot size, stop pin size, bearings ect.
 
Based on your design moving the stop pin out will not leave enough room for the detent ball to track and it will fall off of the blade into the arc.

If your experiencing vertical play it is most likely the stop pin or the lock. First close the knife half way and grab the blade and pull and push it in and out. Is there any play in the pivot or noticeable movement?

Next open the knife manually and take notice of how far the lock moves over. Then flip it and compare the 2. Does it move over more when flipped? Inspect the stop pin and see if it has deformed or has wear marks. I would swap out stop pins and see if that makes a difference.

Lastly check your lock. Only the front 1/16 or so actually engages the tang of the blade. If it engages further back then you might not have the correct amount of lockup. You can put some sharpie on the tang and lock, unlock a few times to see where the lock is engaging on the tang of the blade.

Flippers take a lot of abuse and even if built like a tank something will wear out eventually.
 
Thanks for the response. I appreciate it, although these are the first things I checked and have gone over a bunch.

I believe it was nailed when Carl said it was all about the triangle. The problem isnt so much the tolerances as it is the meeting of the pivot, stop pin, and lockface.

Just so everyone knows so that I dont sound like a newbie.
I carbidize lockfaces
I dont have problems with sticky locks
I cut the lock face at 8.5 deg
I also cut the lockface of the frame at 1.5 deg with a 2.8" long lock bar
only the front .060-.080 portion of the lock bar touches the tang of the knife
my stop pin is .187" and is not smashed nor are the holes elongated
pivot is press fit on lockside .249 nonlock side is .2495
lockside stop pin is also pressfit

I think that about covers it on the normal problem things. I dont mean to sound rude, just want every one to know what I do already and the problem Im having.

Now to answer your questions:
Based on your design moving the stop pin out will not leave enough room for the detent ball to track and it will fall off of the blade into the arc. Its close, but it doesnt fall off, thanks though

If your experiencing vertical play it is most likely the stop pin or the lock. First close the knife half way and grab the blade and pull and push it in and out. Is there any play in the pivot or noticeable movement? No movement

Next open the knife manually and take notice of how far the lock moves over. Then flip it and compare the 2. Does it move over more when flipped? Inspect the stop pin and see if it has deformed or has wear marks. I would swap out stop pins and see if that makes a difference.Lock opens same with force or without, stop pin is clean and unmarked

Lastly check your lock. Only the front 1/16 or so actually engages the tang of the blade. If it engages further back then you might not have the correct amount of lockup. You can put some sharpie on the tang and lock, unlock a few times to see where the lock is engaging on the tang of the blade.Not a problem

Chuck Gedraitis Knives said:
Based on your design moving the stop pin out will not leave enough room for the detent ball to track and it will fall off of the blade into the arc.

If your experiencing vertical play it is most likely the stop pin or the lock. First close the knife half way and grab the blade and pull and push it in and out. Is there any play in the pivot or noticeable movement?

Next open the knife manually and take notice of how far the lock moves over. Then flip it and compare the 2. Does it move over more when flipped? Inspect the stop pin and see if it has deformed or has wear marks. I would swap out stop pins and see if that makes a difference.

Lastly check your lock. Only the front 1/16 or so actually engages the tang of the blade. If it engages further back then you might not have the correct amount of lockup. You can put some sharpie on the tang and lock, unlock a few times to see where the lock is engaging on the tang of the blade.

Flippers take a lot of abuse and even if built like a tank something will wear out eventually.
Click to expand...
 
The position of your stop pin is irrelevant.
Providing the blades contact on the pin is correct, it's actual location means VERY little.

What is relevant is where the lock contact is.

I don't mean the bottom .06 to .100 either, you already have that covered.

I mean the actual geometry of the location.

Providing the locking point is the same in drawing one as drawing two, you will see no difference in lockup.
None.

External stop pin, or the "perfect" equilateral triangle? No difference unless you move that contact point.

Pressure applied to the spine of the blade, or against the lock is applied in a line perpendicular to the line between pivot, and contact point.

So, as you can see from my edit of your drawing, you are pushing up on the lockbar, rather than back, or along the length of the lockbar.
There is very little strength this way, and a lot of room for play on a 2.8" long bar.

newlockupopen.jpg
attachment.php


That contact point needs to me moved as far to left and down as possible, to direct that force ALONG the lockbar.

Get your force moving in the right direction, and the pivot tolerance nice and tight, and your problems will disappear.

I love Bob to death, I've worked in his shop, ate his food, and slept in his guest bedroom.
I believe he is mistaken on the equilateral triangle thing.
Blasphemy, I know.

I was a firm believer, and took it as gospel until I really started thinking about it, made some knives, did some math, modeled it, and beat the hell out of some knives.

There are many factors, and stop pins are a big concern, but once you have some basic rules figured out, the actual location of the stop pin, in the scheme of the rotation of its location, is irrelevant.

What actually matters on stop pin location is that contact is made at the proper point on the pin, and that it is as far away from the pivot as is feasible.
Draw a line tangent to the stop pin, and through the pivots center.
That tangent point is where you need contact to happen.
And contact with an arc is better than contact with a point.
You get that automatically with an internal pin.

Once you have that part worked out, you can rotate that wherever you need it to be.

Edit: I found a drawing I posted some time ago demonstrating what I mean by moving the locks contact position.

attachment.php
 

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Thanks Brian....that makes perfect sense to me. I see your point on the equilateral triangle. It just seems like the greater the distance between stop pin and lock bar contact point....stronger.
Are you going to the Summit next weekend ? I look forward to meeting you if you are.
Jason
 
Great post Brian.

Jake, If you switched to an 1/8 in stop pin you would have more room to move the stop pin further away from the pivot. Your track would also be narrower giving you more room for the detent ball track.
 
An excellent idea for a thread jake. I've never held or handled one of your knives but I've seen plenty of pictures of them, you make some great knives but they are such tanks with a .250 blade in a flipper your points of contact probably take a beating. The fact that only a few come back for repairs is a testament to how well they are built.

I recently starting messing around with a couple flipper designs and I'm no expert by any means but the internal stop pin is the way to go. External may give you better angles on your triangle but on smaller flippers around 3 inch blade, it's a nightmare. I don't have a lot of equipment so the internal arc has to be done by hand with a file so both ways is a nightmare lol.

Hopefully we have a lot of people chime in on this thread. Being a new knife maker I'm sure I can learn a few things by following this thread.
 
Thanks Robert:) I shoot for as strong as needed without going so big its unusable.

I'll try to get some pics of my setup for cutting the stop pin track. It's actually really easy in a drill press or a mill with a carbide burr.

Internal pins are much easier for me to do than external.
Robert Carter said:
An excellent idea for a thread jake. I've never held or handled one of your knives but I've seen plenty of pictures of them, you make some great knives but they are such tanks with a .250 blade in a flipper your points of contact probably take a beating. The fact that only a few come back for repairs is a testament to how well they are built.

I recently starting messing around with a couple flipper designs and I'm no expert by any means but the internal stop pin is the way to go. External may give you better angles on your triangle but on smaller flippers around 3 inch blade, it's a nightmare. I don't have a lot of equipment so the internal arc has to be done by hand with a file so both ways is a nightmare lol.

Hopefully we have a lot of people chime in on this thread. Being a new knife maker I'm sure I can learn a few things by following this thread.
Click to expand...
 
So, as you can see from my edit of your drawing, you are pushing up on the lockbar, rather than back, or along the length of the lockbar.
There is very little strength this way, and a lot of room for play on a 2.8" long bar.
Click to expand...
Brian makes an excellent point here. Over the years, I've found it best to make the lock bar as short as possible and as close to the pivot as possible. I've made some very large folders and never had a lock bar longer than 2". Most at or below 1.5", but never made a 'frame-lock'...
 
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