Swivel Knife Making Trials And Triumphs

[shtoink]

I wasn't sure where else to put this since it was tool specific, but wasn't really anything more than a description of the process.

I thought it might be interesting to "see" things from the point of view of the the designer and possibly get some insight on the thought process. I will do my best to not get too technical, as those kinds of details just tend to bog everything down and make for a boring read. It is my hope that those of you possibly wanting to give making your own tools will glean some information from this and give it a shot and those of you who haven't given any thought as to what goes into the development of a single tool might gain some appreciation for the hard work and frustration that is generally unseen.

I started with an idea when I was browsing around to see what kinds of different knives were out there. I saw all manner of designs and quality, but the one thing that 99% of these knives had in common was that they were all made from metal. I also felt that I had the tools and know-how to give a go at making one or two of my own, but I didn't want to copy what already out there. I wanted a tool that I wanted to use. Having picked up and played with several knives and found them to be nothing close to what I wanted pushed the idea of making my own knife further to the front.

It wasn't just a spur of the moment thing and I took some time mucking about with different ideas before settling on what I wanted to try first. This was when I posted the question to the forum asking about what people like or didn't like about their knives. It didn't go anywhere near as well as I had envisioned, but it wasn't a complete loss and I pushed forward. I also wanted to incorporate some of the knowledge gained from making crochet hooks for my wife. (She had issues with the plastic ones due to the molding seam and the metal ones made her hands ache so she couldn't crochet for very long. Wood was the answer, but not just any wood, it had to be dense, hard and fine grained.)

Several attempts were made before a functional prototype even happened. After it was finished, it was glaringly obvious that I still needed to work out a few bugs and design issues before I had something that looked like anything more than an amateur hack was let loose in the garage.

My biggest issue, wrong material! I have tried out quite a few difference species of exotic hardwood and found some to work and some that just don't.

I also found that there were serious flaws in the way I had originally planned on machining and assembling these things. Each step forward seemed to put me two steps back. I was mainly using the materials that I had on hand, so it became abundantly clear that I needed to source specific sized materials of appropriate type to do things the right way after finding plenty of ways to do it wrong. I was using some 1/4" cold rolled steel rod that was laying around to make the yoke shafts, but it required machining it down to a smaller diameter and then putting a super smooth and shiny finish on it. After that, it required putting threads on one end and machining a flat spot for the set screw to bite on. This was very time consuming and brought about issues with trying to keep that shiny finish while trying to cut threads and machine the flat. Each time was met with failure to keep that finish. I ultimately decided to source some annealed drill rod of the proper diameter that already had that smooth finish.

Cutting the proper sized hole in the barrel for the bearings was another major hurdle. I was initially just starting with a drilled hole and then slowing increasing the size of the bored hole, but that was time consuming. A solution was to get an appropriately sized ream to bring it to the finished size. Once again, a solution brought about new challenges. I ended up splitting quite a few potential barrels. I also wanted to test if using a brass insert to help increase the strength might be an option, however that turned out to be a dead end, since I couldn't ream the brass tubing without destroying the test pieces

Drilling the holes and cutting threads for the set screws became a problem as I could only create ugly looking set screws. I switched to some premade ones that looked nicer, but they still need some tweaking to get the to clear the tight spaces they were going to reside. I also needed to find a way to keep the threads from just being puled out, since the one set screw is threaded into the wood barrel. The solution was a simple flat spot on the shank of the blade. It allowed a positive bite on the blade with less force involved. The same solution was used for the yoke shaft.

Another feature I wanted was the ability to keep the yoke captive. It needed to be adjustable, but not fall out when the set screw was loosened. I was keeping a larger diameter bit at the bottom of the yoke shaft, but that interfered with machining operations. My solution for that came into play with the use of a straight chunk of drill rod. I drilled and threaded a hole in the bottom end so a small screw and washer could be attached. This was another instance where the solution brought about a whole new set of problems. I was having problems getting the proper RPMs on the lathe to prevent the stuff from hardening while machining it. Very frustrating. It would be soft one second and nearly as hard as the HSS tools I'm cutting with the next. I broke a drill bit and two taps trying to get the problems worked out.

Another issue that I have been trying to work around in damaging the bearings when pressing them in. This is also a critical time for the barrel, since the added stresses can cause it to split if I haven't done everything else right. What was happening was that I was dimpling the races of the bearings as the pressure was getting applied to the inner race instead of the outer one where it would be safe. This was permanent damage and made the bearings unsuitable for smooth and free movement. This proves difficult when trying to get things to line up just right in such a confined space. I think I have worked out how it can be done, but it requires more testing.

One of the last issues that has had me irritated is drilling the access hole for the yoke adjustment set screw. I have yet to get it in the right spot with measuring it out. The solution that I am working on involves a jig that I can load the bearing carrier with the bearings attached and locate the holes placement before inserting it into the barrel so that location can be transferred to the outside of the barrel. This meant designing a tool to help build the tool.

All of this effort is for one goal, making a very high quality swivel knife from a material to help reduce hand fatigue made from a slightly unpredictable material. Each tools is unique and can easily be considered a one-off. It may have similarities to the others that get made, but everyone requires a little tweaking here and there along the way. I have invested an estimated 75 to 100 hours in this project already and I still do not feel that things are exactly the way I want them yet. It clearly isn't a simple task of taking something from the drawing board to a finished product, but I have enjoyed the challenge and I believe that I might actually be onto something. Despite all of the frustrations and failures along the way, I still feel like I am on the right track. It has also been a very huge learning experience, which is why I wanted to share it with you guys. It's not very often you get to hear about how things went wrong in the development of something that seems so simple. I keep thinking of the quote from Edison...

"I have not failed. I've just found 10,000 ways that won't work."

There is quite a bit of truth to that. We learn more from our failures than we do from our successes.

The evolution of the shape and design, as well as the optimization of the machining and assembling, of a single tool is governed by the desired outcome and the series of problems that arise and how they are overcome.

[hornm]

No matter where this ends up being placed (forum wise), keep us posted. I'm very interested in seeing what if anything you come up with.

Horn

[shtoink]

It occurred to me only after making the original post that pictures of the broken bits might be wanted. I managed to find some of the broken bits and pieces of things that failed to work the way I wanted along the way. This is certainly not a complete collection of things that broke, just the ones that I hadn't tossed out before being encouraged that pictures would go a long way for this.

Here are the pictures:

As usual, these are clickable thumbnails that will open a full size image.

This image is the full shot, but shows one of the wood barrels that split open, a couple of the taps that I broke multiple times, a busted up center drill, bits of brass all-thread that crapped out when trying to turn a pin for the set screw marking tool, and the chunks of steel that had drill bits or taps break off in them.

This is a close up of the small chunks of drill rod that devoured my drill bits and taps. There was really no way to remove the broken tool chunks, so they just got cut off.

As for the knife barrels that split, this was the only one that didn't get tossed out. I actually had a really hard time keeping that particular wood from splitting open. I think there may have been 5 or 6 that split open on me when the bearings got pressed in. I also had a couple barrels that I tried to do a brass tube insert in that failed pretty hard, too. Of the six attempts I had with that run, only two didn't get obliterated, and of those only one didn't end up all crookedly drilled and reamed.

One of the other things that I was having a great deal of problems with was lining up the hole for the yoke adjustment set screw. No matter how careful I was at taking measurements, I just couldn't seem to get it lined up on and would end up having enlarge the hole quite a bit. I finally ended up making a jig to help mark those holes. I can't show you a picture of it as it is one of those little trade secrets I'd like to keep to myself.

Despite all of the failures of tooling, materials, and ideas along the way, It's still feels like there is a good idea that will fill a niche market for those that want to have a unique, handmade tool. At least, once I get to the point of making them full swing. I don't want to rush it and have an unexpected shortcoming bite later on down the road. As it stands, I'm a hobbyist, one guy, and the whole process is a really big experiment and learning experience for me. Even though this is very small scale, I felt that getting the chance to see just how many unexpected things can crop up along the way in a products' inception to final design can give an excellent insight. Having not seen anything like this anywhere else is what made me want to share and part of the reason I did my best to keep it a bit generic on the details.

I just hope that there are those of you that might find the "behind the scenes" stuff interesting and/or helpful.

[electrathon]

If you don't stabalize the wood you will have splitting problems, either notw or two years from now. Wood swells and shrinks constantly.

I hope you get the issues worked out and make a pocketfull of money doing these.

Aaron

[shtoink]

If you don't stabalize the wood you will have splitting problems, either notw or two years from now. Wood swells and shrinks constantly.

I hope you get the issues worked out and make a pocketfull of money doing these.

Aaron

The thing is, stabilizing wood plasticizes it. This process is done in an extreme vacuum to pull out any air within the wood to be replaced with acrylic. While this does have the result of making the wood highly resistant to cracking, humidity changes, and the like, it also removes all the properties of wood that I chose it for in the first place. It makes the wood heavier, colder to the touch, and is generally unnecessary on the much denser, oily woods that I am using. The thing is, I have done my best to actually work around the slight fluctuation in dimensions from humidity in my design. This is also part of the reason that I have not immediately jumped into selling them, too, since I have some long term testing that needs to be conducted and evaluated.

[electrathon]

I realize not wanting to stabalize it, but if you don't, it is going to crack. Maybe not now, but if you don't keep it in a climate controled area it will over time. The walls are just too thin on the wood.

What size reams are you using? I have a number of spares.

Aaron

[shtoink]

Here's a couple of pictures of the 7/32" drill bit that I was using to make the very first hole in the titanium. As you can clearly see, it suffered from some pretty extreme temperatures and the debris that failed to clear only added to the sever abrasion of the tip. The leading edge along the flute is worn down to the relief that was ground into the side to reduce friction induced heat. This all happened during lower speeds, too. It was cutting reasonably well at first, but the poor heat conducting properties of titanium trapped that heat once the bit was about 1/3" into the barrel blank. Those same poor heat conducting properties are the very reason I am experimenting with it, though. It makes it feel warm in your hand instead of cold for an extended time like other metals.

I need to dig up the other one that was broken off in a bit of drill rod that's pictured above. It's a #53 in my drill index. Not that many people here are going to be digging holes into titanium, but it was a reasonable pretense for testing out the new Canon L glass we just picked up. I love macro shots, so I hope you enjoy seeing them as much as I did taking them.

[St8LineGunsmith]

you are going to ruin a lot of drill bits and cutting tools working with titanium because it is nearly as hard as the tool steel

I really dont see Ti to be very practical for making a swivel knife for cutting leather not to mention the cost of tooling to make the knife

JM.02

[shtoink]

you are going to ruin a lot of drill bits and cutting tools working with titanium because it is nearly as hard as the tool steel

I really dont see Ti to be very practical for making a swivel knife for cutting leather not to mention the cost of tooling to make the knife

JM.02

There's more to it than that, but this isn't the place to get into that area of discussion.

This was, however, my first try at doing anything with titanium, so the drill bit was a sacrifice in the quest of knowledge. It looks like I hadn't mentioned anything in this thread, but did in a another, about sourcing some carbide tooling for super cheap. Destroying one or two drill bits in an effort to learn how to work with titanium is quite a bit different than making it a regular activity and specialized tools were quickly added to a shopping list.

Practical or not, it's still an experiment to see if it could be done and was only one subsection of the overall goal in the process of taking this project from it's initial design phase to a very stable and usable product. Haven't you ever done something just to see if it could be done? That should probably exclude things that happen while alcohol is involved, though.

I think it might be necessary to point out that I am not making titanium a regular thing to be worked with and I have zero intention of making blades from titanium, either. It came up because it was presented as a challenge from a friend and fit into the goal I had put for my self, overall. This isn't a business for me, so I have the luxury of not needing to stress over many of the struggles that I have encountered along the way. It's an excellent learning experience that will allow me to take a small scale project, capable of being dealt with by one person, and scale it up to larger, more complex projects so that a better idea of how to handle 'snags' that come up during each phase of the project.

I do appreciate the input, as it does give me the opportunity to see things from a different perspective. This has actually had the result of me taking into account aspects that I would, otherwise, might never had even thought to consider.

[St8LineGunsmith]

I have been a metal fabricator for the last thirty years of my life so if I can assist you in any way I would be glad to give you some info.

the thing about working with hard metals like Ti and SS it cannot be annealed to soften it so it is essential is to keep the cutting tool as well as the work piece as cool as possible and heavily lubricated and not to have too high RPM. if you can flood the tool with a water soluble cutting oil that is designed to keep both the cutting tool and work piece lubricated and cool your degree of success will be much greater when working with these hard metals.

440 stainless would be an excellent choice of material for making blades.

check out the tangle boss swivel knife from tangle foot trading co I think it is a revolutionary design.

I really want to make a swivel knife along that design.you could probably make one with the right size tubing and a couple of end mill bits and a small lathe would be very beneficial but I don't have access to one but clever use of a drill press might sufice