Hidden stop pin setup and help cutting

nosaj750

nosaj750

Larevo Knives
Joined
Aug 28, 2010
Messages
207
I'm in the process of trying to perfect a knife design I'm working on and when cutting the slot in the blade for the hidden stop pin should it be a complete 180 degrees? I ask because the last one I cut was too long. Luckily I didn't cut all the way thru the steel and left a bit to fit by hand and file down as needed otherwise it would have been a total loss. Should it be cut with only 170 deg? Can't seem to get my head around where the mistake is for some reason. Any suggestions or recommendations are very welcome. cutting with a 1/8 end mill on mini cnc mill. As you can see in the pics my mill doesn't cut circles exactly round, still trying to work that bug out but, it's getting closer. pics are the first blade I did and cut. the second is the new one I'm getting ready to cut but want to make sure it's right this time. at least try to make sure it's right...
thanks for the help.

stop pin slot1.jpg

new blade1.jpg
 
I don't see the liner lock making process getting any better than this WIP done by Lorien !
You can go back to page one and do the flipper with the bearings or do a liner lock without the flipper and or bearings. Anyone wanting to start a liner lock should be directed here. I missed this when it first was posted. How? Frank
 
There is no set arc that will work for every knife. It all depends where you want the blade to stop in the open and closed positions. Drill out the hole in the closed and then again in the opened positions and connect the two.

Mark
 
Varga Knives said:
There is no set arc that will work for every knife. It all depends where you want the blade to stop in the open and closed positions. Drill out the hole in the closed and then again in the opened positions and connect the two.

Mark
Click to expand...

Do you drill the hole all the way through the frame and taper the pin to fit the hole tightly? Or, are the pins completely hidden? I take it they aren't completly hidden if your drilling both holes? I've made 2 knives now with completely hidden stop pins but it's very difficult to place the pin the correct spot and get the open and closed positions set just right. I think I got lucky both times actually... It's near impossible I'm beginning to think unless I'm missing something and there is another way to complete this process correctly. This last one i did today the arc is to long. I cut it at 170 deg and the closed position doesn't hit the pin. It may come a bit closer after grinding the blade or reprofiling the blade to fit in the frame and not hit the back spacer. I have some room to adjust but, I think this last one is gong to end up a practice piece or, keep it for another build to try and fit properly later. I like your suggestion of drilling the hole in the open position and one in the closed position, then connecting the 2 holes. I can see how this would help drastically. Thank you for the advise.
 
You said you cut the arc with a CNC? What dept cut? What cutting speed? I've fooled around with blades a bit on the desktop CNC I've got, but cutting steel with an 1/8" endmill just goes so slow with my CNC. I do engrave name/logo with CNC, and that's usually about .003" to .005" deep.

I'm running LinuxCNC

Ken H>
 
Ken H> said:
You said you cut the arc with a CNC? What dept cut? What cutting speed? I've fooled around with blades a bit on the desktop CNC I've got, but cutting steel with an 1/8" endmill just goes so slow with my CNC. I do engrave name/logo with CNC, and that's usually about .003" to .005" deep.

I'm running LinuxCNC

Ken H>
Click to expand...

I bought a HF mill from a guy who converted it to cnc I found on craigslist a couple of months ago. windows based running Mach3 and just use one of the wizards installed for cutting an arc. I cut it real slow and .001 steps with a total depth of about .150 depending on the blade thickness I'm using. It does take forever to run the job but it turns out pretty good for the most part. More accurate and a hell of a lot easier than doing it by hand with a file and drill. I use a .1250 carbide 4 flute end mill that seems to work the best. But, I've also used the 2 flute end mills from Lowes or Homedepot that are really for wood working when in a pinch. They will last about one job and then they are shot. Slow and shallow cuts and it works fine. I couldn't tell you the actual feed rate but it's just about as slow as I can tune the motors. I figured I would rather run it slow and not screw something up rather than pushing it to save time. My main problem is figuring out how long to cut the slot. This last one i cut was 170deg and it still came out too long. Tomorrow I'm going to cut out another blade and only cut the arc to about 150 deg and see how it turns out. I've got enough ti and D2 for about 3 more knives so hopefully by then I'll have a system in place that's repeatable for cutting the stop pin slot.
 
Sorry, I was thinking internal and not hidden.

You could try drilling through the blade and into the bottom scale with the top scale off. Do this opened and closed using a depth stop. Assemble the knife with a try pin of the right diameter. This pin would only go into the blade and one scale. Don't use any washers. Now the trick is to disassemble the knife while keeping the positional relationship of the blade and the undrilled scale the same. Maybe a drop of CA glue between the undrilled scale and the blade while you assemble. A heat gun can get them apart later.

Once they're seperated and in the right position. Remove the try pin and drill again through the same hole in the blade and into the scale using a depth stop. Do the same for the other position, open or closed. Then connect the arc.

I know you have a mill but it might be easier to connect the arc with drill holes. You can make a template of a hard flat material with a hole drilled into it of the same diameter as your pivot. Put a pivot through the hole and and into the blade also. Insert the chucked drill bit into one of the stop pin holes and clamp down the jig. Now the pivot is a pivot and you can drill holes in between the blade holes in a constant arc. Chuck an endmill and connect the webbing between the holes.

I hope that made sense. I hadn't had coffee yet.

Mark
 
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If I were doing it on a hidden pin framelock (which I haven't done), I would make three scales. One would be for setups and templates so, it could have the pin hole go through. I suspect you could cut the pin slot in the blade faster using Bing's technique than you can using CNC. I use a rotary table and it makes very quick work of it.

Bob
 
nosaj750 - You've got a nice CNC mill. It doesn't take that long to make 150 cuts with a CNC, just press the "GO" button and sit back to drink coffee. A rotary table works pretty good also with larger mills. I've been thinking about a rotary table for my Grizzly, but am now using a homebrew bracket for milling the relief arc in liners for slipjoint folders.

Ken H>
 
If I may offer a bit of help here. This is just the way I do things. I keep things as simple for me as possible.

I make a working template before ever starting to drill holes in my liners and blade steel. The key here for me is that before I cut any liner / frame or blade steel I want to get all the geometry figured out before hand. Including to open / closed positions. Then I can transfer those to my liners / frame / blade.

If you are wanting to do blind holes in a frame lock. I would lay my template on one side of the frame. Drill my dowel holes first. Insert dowels. Then you could drill the stop pin hole to what ever depth you need to keep it concealed. Then repeat to the other side frame.

If I were doing it on a hidden pin framelock (which I haven't done), I would make three scales. One would be for setups and templates so, it could have the pin hole go through. I suspect you could cut the pin slot in the blade faster using Bing's technique than you can using CNC. I use a rotary table and it makes very quick work of it.

Bob
Click to expand...

It takes me less than five minutes to cut the arc. I would imagine with a rotary table it would be less than that.

Rotary table is on my Christmas wish list. :D

Hope this helps

Bing
 
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Thank you everyone for the suggestions, some great stuff that will definitely help. I will post some pics of the next blade I cut to let you see how it turned out using this info. I think it may just work out now and be able to duplicate the process easily.
 
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