First liner lock

L

LANNISTER92111

Joined
Nov 5, 2014
Messages
17
Hi all,

I'm working on the design for my first liner lock, and I thought I'd post sketches, and ask a few questions.

The Specs (so far)
5/32" blade thickness
The whole blade is just under 4", with about 3-3/16" long edge.
Folded length of about 4-3/8"
Not sure what I'm going to use for scales.
Leaning towards A2 for the blade - largely for availability and it is relatively simple to harden. I don't think I want to work with anything exotic or expensive yet.
5/32" dia stop pin
3/16" dia pivot

1. Titanium seems very popular for the liner; is there a special grade that everyone likes to get the proper springyness? What thickness? (I was looking at 1/8" thk)

2. Is the slit area of the lock long enough (about 2" long as sketched).

3. What size screw do people like for assembly? I see several sizes on the knife supply web sites; I had picked out some 1-72 torx head screws.

4. How much of the liner should you leave exposed when fully assembled?

5. Any other design tips welcome; particularly when it comes to the locking mechanism.

6. Planning to use 5/32" thk material for the blade with a .015 bronze washer on either side... then use a 3/16" thk spacer in the back to get me within just a few thousandths of matching the thicknesses. Seem like a good plan?


Thanks in advance for any tips.
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I've only finished my first liner lock this past August and I'm in the middle of making my next three, so my experience is limited, take it with a grain of salt.

1. Titanium seems very popular for the liner; is there a special grade that everyone likes to get the proper springyness? What thickness? (I was looking at 1/8" thk)
The grade used for liners is 6Al4V (6% Aluminum, 4% Vanadium) Grade 5. 1/8" is pretty massive, you'd pretty much have a frame lock by then. I used 0.050" on mine, but it was a 3", 1/8" thick blade, so you might be better served with something along the lines of 0.063" thick.

2. Is the slit area of the lock long enough (about 2" long as sketched).
I would maybe extend it another quarter inch or so if possible. Also, as others have pointed out, you don't need the second lock bar cut, it's just going to add a lot more work. Your lock bar also looks really tall, but I'm not too familiar with how different geometries end up working.

3. What size screw do people like for assembly? I see several sizes on the knife supply web sites; I had picked out some 1-72 torx head screws.
1-72 will work just fine. For a big and beefy folder though, you might consider 2-56 or even 4-40, but 1-72 shouldn't be a problem. I used 0-80 flat heads in my spacer bar, and 2-56 for the pivot (1/8") and scales.

4. How much of the liner should you leave exposed when fully assembled?
I don't actually understand what you're asking with this question. How much of a thumb cutout perhaps? That's a preference thing, just as long as it's relatively easy to open with your thumb.

5. Any other design tips welcome; particularly when it comes to the locking mechanism.
As mentioned, your lock will likely hit/scrape your washer, you need to clear out more room for it.

6. Planning to use 5/32" thk material for the blade with a .015 bronze washer on either side... then use a 3/16" thk spacer in the back to get me within just a few thousandths of matching the thicknesses. Seem like a good plan?
3/16 = .1875
5/32 + 2*0.015 = 1.8625
0.005" of slop is pretty massive, I'd suggest lapping your spacer to get it to maybe just a thousandth of an inch oversize, not 5.

Hopefully the more experienced folder makers of ShopTalk will chime in.
 
Good tips here, Thank you. Sounds like the first thing I need to do is drop some washers into the model, I really should have done that already - doh!

NeilJBorja,
That was exactly the lead I needed on the titanium, thanks!

I was talking about the thumb cut. I hem and haw over how much I'd like it to stick up above the scales. I'll probably just leave it large, and shave it down until it feels right. Same for the locking bar, although I everyone's point about not needing the second cut.

0.1875 - .15625 = .0012" … less than 2 thousandths seems reasonable (but I've never built one). That assumes everything is at perfect size.
 
LANNISTER92111 said:
That assumes everything is at perfect size.
Click to expand...

In my experience, even precision ground stock is not accurate enough. You need to plan on adjusting thickness on everything. Additionally, it is a "best practice" to fit as much blade length as possible. I feel you are missing out with your spacer taking up the space at the butt of the knife. There is also no need for the short cut of the lockbar to extend past the centerline of the pivot. Lockup will take place at the distal edge.

Bob
 
Go to "Hiden stop pin set up ---" in above thread and follow Bob's link. I suggest you go to page 1 for more help. Frank
 
I would go a little higher up with the stop pin. Closer to the top edge. The long cut for your lock should be closer to the centerline of your stop pin
I use 2-56 screws for my folders. Buy extra taps in case you brake one. You could reposition the end of your spacer to allow for your blade to be a little longer. Good luck. Have fun!
 
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