Timely post as my next project was going to be a folder and I need all the help I can get.

I have been wondering, it seems like there is a lot of close tolerance fitting when making folders. How necessary is it to have a surface grinder or a mill?

Can you get an equally good product using just files and a belt grinder?

Jordan

Jordan,

You can definitely build folders without a surface grinder and mill. Yes; the inside of the liners, the spring and blade tang need to be very flat. But, this can be done by hand sanding them on a sheet of sandpaper glued to a flat surface.

This thread has been very slow. I've got a bunch of information that I intend to post to it. But right now, I am working on a project that involves a tremendous amount of forge time. Trying to get it done on days when the weather is cooler. I'll get some information posted soon.

Thanks so much Steve.

Good luck with your forging! Yes, the cooler weather makes it more enjoyable.

I really enjoyed the slip-joint tutorial you posted on the folding knife topic that I started a few weeks ago. Very informative and well done.

Jordan

I've only built two folders, one a slip joint, one a liner lock. I have to say that Steve's tutorial was fundamental in the success of my slip joint project. The only part of the project I had an issue with was the machining of the relief area around the pivot. As I understand it, this acts as a washer, and also helps prevent scratches on the blade. Without a mill what is the best way to approach this? Is there another way to "mill" this area, or is better just to skip this step, or use a washer?

Thanks, Justin

The relief in the liners is to prevent scratching of the blade. You seldom see this feature on less expensive factory knives. But the knife collectors have come to expect it on custom knives.

Washers are common in folders of the tactical genre. But, the purist collector won't be happy to see them used on a sip-joint. Too, using washers brings up a whole set of other issues to deal with in the construction of the knife.

One way to accomplish making the relief areas, is to use a hand scraper to cut the liner material away. Ron Lake demonstrates this technique in the book "How To Make Folding Knives". Just use some type of sharp tool to gouge away some material around the blade pivot area. You could probably also do it with a hammer and chisel, ala engraving techniques. You only need to cut down about .003 thou. Use sandpaper to smooth out the area after cutting away some material.

An alternate way to finish the relieved area is to bead blast it. When the relief areas are cut with an end mill, the burrs created by the edges of the mill reflect light from inside the knife and look bad. I use electrician's tape on the blade pivot area and the un-relieved area of the liner to protect them from the blast media. I little light bead blasting will flatten the burrs and create a dull finish that doesn't reflect light inside the knife.

Scraping the relief areas sounds like a lot of work and it kind of is. But, it's probably less work than what you have to do to install washers.

The making of folders is such a HUGE!! body of information, it would be great to have some tips from some of the folder makers available.

I appreciate your time, Steve.

|quoted:

The making of folders is such a HUGE!! body of information, it would be great to have some tips from some of the folder makers available.

I appreciate your time, Steve.

Having tried to design and then began my first set of folders, I completely agree with this statement. Making a great knife is really hard. Making a great folder takes things to a whole different realm. Those who do are just plain impressive to me.

Jeremy

The tutorial below, began as simply some notes that I made for use in my shop. They cover the process that I developed for designing a slip-joint folder and were first written up just for my own use. After a few folks asked me how I went about designing folders, I added some text to create a tutorial from it. I've had a version of this tutorial on my web site and it has been posted to some threads on this forum. But, the version below is NEW.

I've added more information and sketches to the original tutorial. Plus, some explanations of why this process is logical and what happens if you make changes to the design plan. I'm the kind of person who not only wants to know how to do something, but I want to know why I have to do something a certain way and what are the consequences if I do not follow the plan. I hope that information is useful to all of you who suffer from this same compulsion.

I mention in the tutorial that this designing method can be used as the basis for making folders that do not have a half stop, as well as for lock-back folder designing. I may add to the tutorial later, to show how this is done.

Some explanation of what brought me to develop this designing method follows.

I built my first folders, by copying patterns that were given to me by other knifemakers. Some of them went together pretty well. Others I had a difficult time getting them to function well. I figured that it was just my inexperience with making folders that caused my struggles with them. After coming up with my process for designing knives, I realized that they were just not good patterns in the first place.

It wasn't long before I decided that I wanted to design my own folding knives. I went to a couple of seminars on folders at ABS Hammer-ins. The instructors provided some methods for designing folders, but their processes didn't work well for me. My knives sucked. I felt that I was not understanding some very basic, and probably stupidly simple concepts about the relationship between the dimensions of the parts in a folding knife. I needed to figure out a process that worked for me.

It occurred to me that for the most part, folder makers are copying knives made by factories. So, I wondered how the engineers at the knife factories design folders. BTW; Why hasn't anyone gone to a knife factory and asked the designers how they go about creating a new knife and then written an article about it? Lacking written information on how the factories go about designing knives, I bought a bunch of factory knives and took them apart to examine. I gathered both single blade knives as well as multi blade models. I looked for the dimensional relationships between the blade tang and spring as well as design features that were common to all of the knives. And yes, discovered that the concepts were stupidly simple.

I developed this process for designing folders, based on what was evident in nearly all of the factory knives. The blade tangs and back-springs had nearly the same proportional dimensions on every blade, in every knife. There were exceptions, but not many.

Let me know if you have questions about any part of the tutorial.

Slip-Joint Folder Designing.pdf

That tutorial is fantastic-thanks so much for putting it together. It gives great insight as to what it takes to make a good slip joint...

I do have a question for you. I'm not sure if the answer is dependent upon different types of folders or not. I've noticed that the corner of the blade tang can be seen when the knife is in the closed position on some knives. When trying to design a folder, I've tried to make the handle shape cover that corner. Is there a rule of thumb with folders as to when and how this is acceptable? I think I've seen more of this on slip joints, which could be a result of the "notch" in the tang for the blade-walk? Then, the transition from the spine down to the "notch" is more likely seen, showing that "corner"?

After seeing all of your drawings, this makes more sense to me. But, would you say a design where the back corner of the tang on a liner lock being visible is ok? I hope that makes some kind of sense...

Thanks again for putting so much effort into sharing this.

Jeremy

I've noticed that the corner of the blade tang can be seen when the knife is in the closed position on some knives. When trying to design a folder, I've tried to make the handle shape cover that corner. Is there a rule of thumb with folders as to when and how this is acceptable? I think I've seen more of this on slip joints, which could be a result of the "notch" in the tang for the blade-walk? Then, the transition from the spine down to the "notch" is more likely seen, showing that "corner"?

Jeremy,

That's an excellent question. There are different types of folder joints. The names of these joint types, express the amount of the blade's sharp back square that is exposed when the knife is closed. Glossaries of the terms used for folding knives can be found in many places. Great Eastern Cutlery has a very good glossary. Look under the term, "joint". I can't explain it better than they do.

GEC Knife Glossary

There is a thread on another forum, where joint types were discussed. Some good information there.

BFC Sunken Joints

The tutorial that I posted, is for a folder with a common joint. It could be used to build a folder with an extended bolster, that covers more of the back square. Extended bolsters are seen on Canoe pattern folders.

I don't know enough about sunken joint folders to explain how their construction differs. Yet.

Thank you very much, Mr. Culver. Those joints and the exposed portions of the blade tang make much more sense now. That thread was a pretty interesting read and has the hamster on the wheel in my head really tired... I've not built a slip joint, so maybe it would be easier to figure out the different design features between a common, semi-sunk and sunk joint, but it's eluding me for now. I must say, the semi-sunk or sunk joints look "smoother" on a closed knife. And the word used in that book, "elegant", I think is a good way to describe some of those sunk joint knives. But I am curious as to the statement that it is a weaker joint than the common. I guess everything has it's trade offs. Thank you again for helping explain this stuff <img src=' http://www.americanbladesmith.com/ipboard/public/style_emoticons//smile.gi f' class='bbc_emoticon' alt=':)' />.

Jeremy

But I am curious as to the statement that it is a weaker joint than the common.

Jeremy,

Let me start off by saying that I do not consider myself to be an expert on folders. The tutorial that I posted, is a result of using country boy observation and logic to come up with a work plan for use in my shop. But it works for me, in designing common joint folders. On a common joint folder, the pivot pin is significantly below the centerline of the blade. As this blade is rotated to the closed position, the majority of the blade is situated above the handle.

I've never studied sunk joint folder designs and don't have one of them in my pile of disassembled folders. I've never seen one of them apart and do not have one in hand as I write this. So, I'm using country boy logic to answer your question about the strength of the joint. Arguments to my logic are welcome.

As a sunk joint blade is situated lower within the handle in the closed position, the blade pivot must be located much closer to the centerline of the blade. The pivot located higher would leave less material for the portion of the tang above the pivot, as well as for the blade walk portion of the spring. To accommodate the spring being level with the back of the handle in both the open and closed positions, the tang would need to be nearly the same dimension below the pivot as it is above. Taken together, the reduced dimension of the tang both above and below the pivot would mean the tang of a sunk joint folder would be smaller in vertical height than on a common joint.

In looking at photos of sunk joint knives, it appears that on many of them the blade does not rotate as far to the closed position as do common joint folders. This suggests that the bottom rear portion of the tang would need to be ground away significantly to allow the spring to be flush in the closed position. So the tang is short in vertical height, plus ground to nearly a point at the rear. Some of the sunk joint folders have a dogleg in the handle near the bolster area. I assume that this is a way to minimize the amount of material that has to be ground away from the bottom of the tang.

Pick my logic apart if you know better, or think I am wrong!!

I still wish that someone would go to a folder factory and ask how the professionals design folders.

Thanks so much for explaining your thoughts on the sunk joint construction. When I was looking at some of the photos of the various knives in that thread, I was trying to pay attention to the pivot point. It made sense to me that perhaps the pivot point changed and/or the recess in the top of the blade tang was shallower and the spring was then thinner... But then my brain started losing track of changing one thing on a folder affecting 14 other things and the hamster fell off the wheel.

What you're saying makes sense about the construction necessarily taking away some of the strength attributes a common joint can give. It would be very interesting to see two knives of both construction taken apart and side by side. And yes-I think it would be great if someone had the insight from the big manufacturers on how they design their knives and write a big post with it all... <img src=' http://www.americanbladesmith.com/ipboard/public/style_emoticons//smile.gi f' class='bbc_emoticon' alt=':)' />.

Jeremy