Slipjoint Folder Bushing or No Bushing

T

Thom's Texas

Joined
Apr 16, 2023
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3
I have acquired some of the material needed to start making simple, single-bladed slip joints, but in my study's the question that I have is to drill the pivot hole in the blade for a bushing or not? I have seen different makers say different things about doing it. Just want to hear the whys and why-nots.

Thanks, Thom
 
Welcome Tom.

If you ask three folder makers this question you will get four answers.

But, for the main part, a bushing and pivot will be smoother and more precise than just a pivot pin.

TIP:
Having a reamer to ream the hole in the blade (and other parts) for a precise fit is a wise investment. If planning on doing folders often, a carbide reamer is well worth the extra cost.
 
I've done many of both, bushings are a little more work and require a few additional tools. Having said this I can hand you one of each style and let you open and close each and guess which is which. Make a few without before investing in precision drills and reamers/lapping tools so you will have a baseline. I still do it both ways based on Materials like Damascus and mammoth covers get bushings.
 
If everything goes perfectly it won't make any difference if bushing or no bushing. Things seldom work "perfectly" for me everytime.

My take is that when peening the pin, it's easy to get the pin a bit tight in the blade making it a bit harder to operate. With a bushing the pin can tighten up in the bushing hole and the bushing still operate smoothly in the blade. I'd be interested in other folks comments on that idea.
 
My opinion:
Why bother? The tang on a slipjoint constantly rides (rubs) on the backspring.
The backspring's job is to keep the blade from opening when in a pocket, and prevent the blade from drooping partly closed when open and between cuts. That is why a slipjoint's blade tang is always touching the backspring.
Because the backspring and tang are always in contact, using a bushing washers or bearings will not make the knife smoother or easier/faster to open.

Be better to spend the time and effort fitting bushings or bearings into polishing the contact areas of the liners, spring and tang, easing (slightly rounding) the two edges (with a half stop) of the tang that slide over the spring, so the spring is raised gradually, rather than the maximum as soon as the blade moves, or the tang radius if no half stops.
A rough tang and spring will make the blade rougher and stiffer to open, not to mention will eventually wear both to the point the spring does not move when the blade is opened or closed ... in effect becoming a friction folder that has a spring.
 
I have done it both ways.
Using a bushing dramatically reduces the anxiety and heartache of over peening the pivot.

Those who have over peened a pivot know what I mean.

One nice benefit of using a bushing is little to no break in after peening.
 
I used a bushing when I started, then stopped and didn't notice a difference and haven't gone back. I personally find the action quality/smoothness dictated by the tang shape and tang/spring interface more so than the pivot.
 
If it's your first slip joint, I'd just use a pin and call it a day. If you use reamers and precision ground pin stock, it will be about as smooth as any bushing after break in. I'm sure some makers would say that even that is overkill, but it's cheap assurance.
 
I do not use bushings currently, also I do not mill in relief for the pivot area. I use .005 bronze washers. I love the idea of a bushing though, but haven’t noticed really any difference. As for overpeening….best tip I was ever given was to squeeze the pivot pin in the milling vise to mushroom it first before final peening. Ever since I started doing that, I have very little anxiety upon the peening process. It works extremely well. I used to hate grinding blades and peening, I now only despise the grinding.
 
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I primarily use bushings and haven't built a non-bushing knife since a few of my early builds. Let me clear up a common misconception even among makers, the bushing does not mean a smoother operating knife. That is not why a bushing is used. That smooth action come primarily from the relationship between spring and tang. However when using a bushing you do want to ensure that the blade will pivot smoothly on the bushing because it will affect the action if you don't set it up right i.e. reamed and polished hole, non marred bushing running surface. Now why do we use a bushing? The answer is simple. It is a superior connection than not. Without a bushing your blade is pivoting on the pin which is peened and its connecting points are on the outside of the bolster or birdseye bushing. There is the potential that over time or if something gets fouled in the pin/blade pivot hole it can slightly rotate the pin causing it to expose at its connecting points. It ends up looking like a halo or like it hasnt been blended properly. This is assming that the maker has mastered blending a peened pin. Without using a bushing you more than likely need to shim when you peen your pivot pin. Overtightening can be an issue but honestly if your going to be proficient at building slip joint pocket knives your going to want to learn to slacken. Even when using a properly set up bushing you can overtighten so slackening a blade is a must have skill for slip joint makers imo. Ken Coates just shared a fabulous slackening jig with me so you don't have to do it the old fashioned way but that's for another topic. Back to bushings, when you use a bushing your blade is rotating on the bushing and not the pin. The bushing locks into place when you peen the knife so there is no rotational torque being applied to the pivot pin during the opening and closing of the knife. Now there is less chance that your properly blended pivot pin will be exposed due to foreign debris or negligence in maintenance. Long story short, with a bushing the pivot pin stays stationary and there is never any rotational torque being applied to it. That makes for a superior connection for the life of the knife. I don't care who you are, you'll never convince me otherwise.
 
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Signalprick said:
I primarily use bushings and haven't built a non-bushing knife since a few of my early builds. Let me clear up a common misconception even among makers, the bushing does not mean a smoother operating knife. That is not why a bushing is used. That smooth action come primarily from the relationship between spring and tang. However when using a bushing you do want to ensure that the blade will pivot smoothly on the bushing because it will affect the action if you don't set it up right i.e. reamed and polished hole, non marred bushing running surface. Now why do we use a bushing? The answer is simple. It is a superior connection than not. Without a bushing your blade is pivoting on the pin which is peened and its connecting points are on the outside of the bolster or birdseye bushing. There is the potential that over time or if something gets fouled in the pin/blade pivot hole it can slightly rotate the pin causing it to expose at its connecting points. It ends up looking like a halo or like it hasnt been blended properly. This is assming that the maker has mastered blending a peened pin. Without using a bushing you more than likely need to shim when you peen your pivot pin. Overtightening can be an issue but honestly if your going to be proficient at building slip joint pocket knives your going to want to learn to slacken. Even when using a properly set up bushing you can overtighten so slackening a blade is a must have skill for slip joint makers imo. Ken Coates just shared a fabulous slackening jig with me so you don't have to do it the old fashioned way but that's for another topic. Back to bushings, when you use a bushing your blade is rotating on the bushing and not the pin. The bushing locks into place when you peen the knife so there is no rotational torque being applied to the pivot pin during the opening and closing of the knife. Now there is less chance that your properly blended pivot pin will be exposed due to foreign debris or negligence in maintenance. Long story short, with a bushing the pivot pin stays stationary and there is never any rotational torque being applied to it. That makes for a superior connection for the life of the knife. I don't care who you are, you'll never convince me otherwise.
Click to expand...
I’ve never used a bushing. How much thicker is the bushing than your blade? Like just a few thousands I’m thinking?

Me I switched to larger diameter fancy screws. But I see you make traditionals and so screws wouldn’t be suitable for your work. This knife I made 3 years ago. It was dropped By the customer in the snow in MN and found a few months later after the snow thawed. I was able to clean it up pretty easily.
D4oGzW9.jpg
 
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bjansen said:
I do not use bushings currently, also I do not mill in relief for the pivot area. I use .005 bronze washers. I love the idea of a bushing though, but haven’t noticed really any difference. As for overpeening….best tip I was ever given was to squeeze the pivot pin in the milling vise to mushroom it first before final peening. Ever since I started doing that, I have very little anxiety upon the peening process. It works extremely well. I used to hate grinding blades and peening, I now only despise the grinding.
Click to expand...
Can you detail how to "squeeze the pivot pin in the milling vise to mushroom it?"
 
Sure - So after your final assembly (in which you have the pivot pin installed, back and middle spring pins installed) I would square up the pivot pin ends (to have equal amount of pin sticking out of both sides...say .100 proud on both sides, nice and flat). I will put a couple spring clamps on the scales to hold everything tight together. Then just put the pivot side in the milling machine vise (the vie of which has smooth, hardened jaws) and tighten it down to the pivot pin. This will mushroom the heads on each end. I typically do this about 5 times, keeping an eye on the closed blade being centered as I do that. Then you can take if over to the stiddy or peening anvil and use a 4oz hammer to finish it up.

I am not sure why it works so well, I think because the milling vise is expanding just the heads and not sending a big shock through the entire pin ( I am not certain on that though). Once the heads are mushroomed, you really dont have to be all that careful when peening with the 4oz hammer as the peening is really just swelling the head more and blending it in to the bolster.

I have a video somewhere, if you find me on instragram i'll send to you if you want to see it.
 
id like to add a great trick for peening pins.. be it for folders or other.. drill/ream the same size hole in a scrap of hard metal.
put the pin in there and peen 1side of it.. now when you need to peen the other side it becomes easy peasy ..
you can even bevel the hole a bit so the pin becomes almost a rivet..
doing this inside a piece of scrap keeps the pin held straight while peening it.. only the top or bottom can deform.. make them a little long so you can trim off
1 of the sides and still have a useable pin..(but it is straight because it was held in a reamed hole....
 
I do not use bushings on my knives, mainly because the guys i learned from didn't use them... i also squeeze the pins in my vice, peen it together and then it's just a matter of breaking the knife in. The only real difference I see is that I have to spend time breaking in a knife when you don't have a bushing...supposedly there's no break in period when bushings are used
 
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