Slip joint tips

R

Randy3000

Joined
Jun 3, 2017
Messages
811
I've made several slip joint folders, and could use a little advice. I typically make them about 3-4" long using 1095 steel 1/16" thick. The basic design i found that works for me is

1) two pins through scales and spring, one at the far end from the pivot and the other in the middle area of the handle.
2) one pin through both scales, but not the spring, close to the pivot. This pin serves as a blade stop and, with proper clamping force while epoxy dries, minimizes side-to-side play in the blade without much friction.
3) a hidden pivot pin that goes through the liner and a little into the bolster. This pin is the only one to get no epoxy, else it will gum up the action.

The distance from the middle pin to the pivot is about 1.5" to 2" usually, with a spring width of about 3/32" or a little more.

The main issue I'm having is getting the spring filed flush with the handle, without being too weak. Ideally, I'd like to get the spring to about 1/8" and be flush with the handle, and then take material off the inside of the spring until it has the force i want to open and close the blade. This isn't really feasible though since i have such a hard time getting it all together without the pins whallering out the holes a little from the force and getting loose after several dry fittings.

I feel like i can never get it right doing things the way i am now. Need some tips.
 
Are you using a "Rise/Fall" indicator(Rupple Gauge) to pre-set the Tang dimensions, Full Open, Half Stop, Closed. This device will help you set a flush spring in all 3 positions by adjusting the tang without removing spring tension for a crisp "Walk&Talk".
 
I've only made about a dozen slipjoints but I took a class
have you read the Steve Culver pdf download on design and building?

are you using a setup block? see my pics here on my IG, swipe left to see the three pics

https://www.instagram.com/p/BSoyK_glMwh/

A setup block also allows you to see the rise/fall without the dial gage setup.

I'm not sure I understand the #2 pin, seems like you are using this in lieu of the kick point
pics would help

Perhaps you could consider making a standard basic pattern and firming up the three positions, then translating that to your pin design

Harbeer
 
I don't have any pics currently, although I'm starting a build this weekend and will add them then.

I always start with the handle material (wood usually) and build the knife around that. I have tried fitting the spring and blade before making the handle, and usually get some error when transferring to the scales, so i quit doing that.

Basically i cut, flat sand, and shape the wood scales. Then i design and cut the liners and spring. I drill two holes in the spring. Clamp the spring to a liner and drill the liner. Then i epoxy wood and bolster to the liners. Then i drill the wood and bolster. At this point i have a completed handle, an unfitted spring, and no blade.

Then i design the blade and fit to the spring using one of the completed handle sides to pin everything in place. I think this is how the pins mess up the holes if the spring is too strong during fitting. It would help to have both sides of the handle holding the pins when i try to load the spring, but I can't do so because the hidden pivot pin isn't long enough with the blade and spring not in the same plane.

This needs pictures. I'll add them soon as i can.

As far as pin #2 in lieu of kick point, yes, that's what I'm doing. I prefer it to be impossible for the edge to ever contact the spring, even if you squeeze the blade while closed.
 
Looking back on it, i think i know where i messed up when i tried designing and fitting the spring and blade before working on the handle. I think i may have marked the holes on the liner and then drilled them without using the spring as a guide, so when i pinned it all together the spring didn't go on straight. I did some dumb stuff when i first started making these. I bet if i use the spring as a guide when drilling the liner I'll have much better luck.
 
I also make slip joints and highly recommend the advice you've been given here. While not necessary, a rise/fall indicator makes getting the spring flush really simple. Also, having a working template or pattern is essential for me. I draw all my slip joints on a free program called inkscape, and I can pivot the blade around and make sure all my dimensions/geometry are accurate before I even cut the first piece of steel. I take my drawing and transfer that to some harder material, either wood if it's a one-off, or metal for something I want to make more of. I treat that template like a real knife and get the rise-fall dialed in. After that, i'll clamp it to my "real" steel and scribe around it, bandsaw it out leaving a tiny bit extra for adjusting around the tang. I then drill my holes that I've already spotted with my template, clamp them to my liners (usually stainless) and drill the center hole. Put a pin in it and position my blade and clamp it to the liner against the spring. This was always a hairy operation for me until I got the smallest size kant-twist clamp, 3/4". Now it's no problem. drill the blade, stamp my mark, cut my nail pull, heat treat. Come back to the liners, set my preload and drill the back hole, solder the bolsters...blah blah blah...lots of grinding, finish work etc...I'm not sure how all that I've said applies to using a stop pin, but if nothing else try to get a working template somehow.
 
Interesting that you start with the Finished Handle and work your way back to building the spring and blade last. I can't say that I have heard of another maker doing it this way. Correct me if I am wrong but seems counter intuitive. If you super glue the liners together clamp the spring to the liners you can drill the spring pivot holes at the same time in perfect alignment. If your spring is heat treated and properly bent you can also drill the rear stop tension pin hole at the same time. However this will only apply so long as you have the correct geometry on the blade tang.
 
Turns out i did have some pictures

Here you see me trying to fit the blade and spring. If it takes a lot of force to load the spring it will mess up the pin holes. You can also see what i mean by "spring and blade not in same plane" which makes it hard to get the other half handle to grab the pivot pin.
EjFlFHL.jpg


I made this one for a friend, he wanted straight oak, no bolsters. It came out pretty decent, but didn't have the stiffness i would of liked. He loved it though.
7cs1vG8.jpg


I'm going to do it the way suggested in this thread, and the way everyone else does it. I think i understand how i can incrementally fit everything.
 
I got this guy going. I solved my problem of transferring to the handle by drilling the liners and using them plus the board when i do the fitting. So now i have a whole lot more material holding the pins straight, and don't have to worry about widening pin holes. I got this sucker fairly stiff, not a nail breaker, but it is pretty stiff.

InvTwrV.jpg
 
Why don't you just use a regular pivot?
There is way too much excess steel on your spring.
 
What advantage does a "regular pivot" have over a hidden pin? In this particular knife, i can afford a little extra thickness. I'm making it to a specific width for some antler i have. There is nithing worse than a broken spring, so i always make it as thick as possible.
 
A regular through pivot can be peened so that the handle is more secure and the backspring can't slip off the blade during hard use.
You have other pins exposed, so I see no need to hide the pivot for aesthetics.

Your spring will only be as strong as it's weakest point, and all that extra around the pins accomplishes nothing.
 
Ok, I'll try doing the pivot pin like you said. I am worried about peening it too tight. My spring is about .005 thicker than the blade. I guess i can stick a scrap piece of steel inside the handle to help from peening it too tight?
 
use .002 stainless shim and some stainless lube,
cut out the shim to make it look like a pull tab, with a slot for the pin.
pull the the shim out and it gives you .002 clearance
of course if you peen the pivot too hard then then shim might be stuck
you have to find the right balance

NsuO4vh.jpg



D4dlMtD.jpg
 
I appreciate all the tips i can get. I did grind some more off the spring. I made and heat treated the blade. Tempered the spring at 450 and the blade at 375. It has a very solid action to it, best I've done so far.

Turns out the antler isn't going to work on this piece. I tried to follow one design i saw online and it isn't going how i visioned. I have a ton of shaping still to do on the handles, don't feel comfortable doing much more until i get the bolsters on and the rest of the holes drilled. The wife is asleep so i have to stop here.

wfvQNAU.jpg


The wood is oak that i split off a log, dried, and sanded flat. Going to use 1/32" brass stacked with 1/16" nickel sheet for the bolsters, nickel on outside. I'll use a nickel rod for the pivot, and peen it. Should i counter bore it slightly?
 
A slight chamfer on the pivot hole will fill when you peen the pivot. Clean the chamfer and he pivot pin and it should blend with no shadow when you sand flush and polish. Peen easy with nickel rod or it will swell in the blade pivot hole and possibly lock up the movement.
 
Looks like you're having big fun, so keep it up!
For myself, I began by choosing a pattern and set of instructions from someone with a lot of success, and doing a few exactly like he did so I began to understand all the little relationships that have to be right in a slippie. Then branch out and experiment.
When I see an especially tasty design, I'll make one as close as possible to that, and keep it for my own use, then come up with my own version if I want to make some for sale.
This type of knife is hard enough to get right when you're following a precise step by step....
 
I definitely enjoy the challenge! It's a lot to fit in a small package. There are a lot of design elements that don't seem important until you neglect them.
 
Re temper your spring at 675 to get it correct. You can use heat treat foil doubled as the spacer when you do the pivot. Make sure blade is at half stop when you do the pivot to help from collapsing the sides.
A friend told me when you get the first one to work right save it as a pattern for future knives.
 
I got it together for the first time. It is a nail breaker right now, it got stiffer with the handles put on. I still have some to file off the kick point and that'll weaken it a bit, about 1/64". I have a LOT to file on this thing. About 3/16" around the bolster on the spine, and about 1/4" to round that weird looking corner at the end of the handle. It'll come out close to what i was going for. I know it looks weird now.

nuTIqmk.jpg

kermiKL.jpg
 
You must log in or register to reply here.
Back
Top