View Full Version : Pivot Pin sizes


doctor_mech
04-03-2003, 10:52 PM
Can anyone help? I started making a folder (I have the blade cut out) and I wanted it to be the strongest thing around. So without thinking, I made a 1/2" hole for the pivot pin to ride in. Unfortunately, I can't find any commercial pins that size. Does anyone know of a place where I can get some premade pivots in that diameter? Or should I scrap the blades because that size of a pin is ridiculous? I thought the larger the pivot, the stronger the knife?

Thanks,

Ed.

Geno
04-04-2003, 02:46 AM
Ed, Just off the top of my head,I would suggest you look into purchasing some bearings to fill that hole, and give a smaller diameter pivot pin at the same time.
MSC has tiny bearings mounted in casings that size, or you could just make a bronse bushing for the blade to spin on. It reduces friction in the pivot, holds the liners at a certain gap, and again gives you a smaller pivot hole to work with.
I think a 1/2" pin running through the handle might be a bit much, so this way you can step it down and still save the blade.
(and tell people you meant to do that);)

Ray Rogers
04-04-2003, 08:52 AM
I agree with Geno, that's probably the best approach. On the other hand, you didn't tell us anything about the size of this monster folder you're making. I make a model of heavy folder that uses 3/16ths blade stock and the finished knife weighs 3/4 of a pound. For that folder I use a half inch hardened pivot that I make myself. All you need to make a pivot is a piece of drill rod in the desired diameter - drill a hole through the center and thread it ....

doctor_mech
04-05-2003, 08:13 PM
Thanks for the reply guys!


First let me say that I am by no means a qualified knife maker. I'm about as fresh as fresh can get. I just decided to start dabbling in making knives because I really like the challenge and I think they are the nicest form of expression there can be. Plus I'm an avid reader of blade and I am just awestruck at the pieces of art people can make in a garage! So excuse the ignorance. Now, a bearing? Like a roller with a cage etc, and press fit it into the hole? Wouldn't that cause lateral travel? I kinda like the idea of a bushing, but I thought that a large pivot will make it stronger. As for the dimensions, well, the blade is: 3.8144 " to the centreline of the pivot pin. It is made from 3/16" stock. I have 4 of them (I wanted to surprise my hunting gang with them). I can get a piece of O1 drill rod and fit it into the hole, but its very snug and doesn't rotate freely. The blade is D2. The lock mechanism I originally wanted it to be a lockback, but since, I really like the axis lock concept, I redisgned it to have a modified axis lock. Hope it works! The liner material I have for it is 304 stainless. I haven't scavenged anything else for it yet, but this is the concept. I thought it wouldn't be too difficult, but from what I read, these little critters got the same precision in them as aircraft engines (take my word on that! :D ). Anyway, I got a lot to learn and very little to do it with.

Thanks again,

Ed.

doctor_mech
04-05-2003, 08:23 PM
If I go with the hardened pivot. How tight does it have to be? It seems to me that if the pivot is too loose to provide free travel, then the blade will be sloppy (and travel laterally). If I make it too tight then it won't pivot (so it'll just be a pin). Is there a clearance spec that you guys work to, or just trial and error.

Thanks,

Ed.

doctor_mech
04-05-2003, 10:01 PM
Ray,

Just checked out your website. Love your folders! Tell me, is the liner lock a good lock mechanism? Or is the axis lock better?

Ed.

Ray Rogers
04-06-2003, 10:33 AM
Ed,

From what I've read about the Axis Lock I have no doubt that it is a good lock. What impresses me is that you've never made a folder and you want to jump right in and make an Axis Lock. Most of us would work our way up to something like that but I gather you have some engineering background.

The liner lock is the most popular lock around for folders. Properly made, it is as strong and secure as you could want. It also has the advantage of being relatively simple to build. No small parts to make, yano. Still, simple as it is in design it does take some practice to make one that fits up properly.

On the subject of your pivot, that's just another problem of getting parts to mate. You're going to have a lot of that if you build that Axis Lock.:D With the big pivots like yours, I buff the pivot on a Scotchbtite belt until I can acheive some movement of the blade. Then, I put some lapping compound on the pivot and work the blade on it until it gets smooth.

As for lateral movement, there shouldn't be any even in the blade hole is much bigger than the pivot. Lateral movement is controlled by washers that go on either side of the blade. If the blade thickness and the washer thickness match the thickness of the back spacer and the pivot is the right length, there won't be any lateral movement...

doctor_mech
04-06-2003, 10:08 PM
Hi Ray, and thanks. Yup. you can say I have some experience in engineering. Matter of fact, I'd give it all up to be able to make some of the things that I see in Blade and on the Net from you guys. Actually, reflecting on the complexity, I think an axis lock is more forgiving than any other design. Seems to me that the liner lock is very difficult to make and you need specialized equipment. As well as the lock back. I tried to work out the kinematics on the computer without actually doing it and was satisfied that I could do it with the limited equipment I have (a very cheap belt grinder from Sears (2X42) and some files and buffer). When I was in a different life, I had access to some NC machine tools where on weekends I would cut up some stock laying around, and dream of the nice things I could make. But time and money did not permit. Now, I have 2 mouths (soon to be three) to feed and I am limited on what I can afford.

As for jumping right in and making a folder, well, let's just say that it's in my personality. As with all engineer's perspective, it's simple on paper. Now let me put my money where my mouth is and DO IT! Sometimes you have to do that to convince yourself that you can produce useful designs. Its not a turbofan engine, but the tolerances are close. Anyway, I agree with Jerry Hossom, knife makers are the nicest people in the world. I like the fact that y'all share your experience. Unfortunately, though, I am limited on what I can use.

I WILL succed. It's just a matter of time. Soon it will be warm enough to work outside and I can get started.

BTW, I have a really cool D2 skinner I have buffed and cut out that only needs a HT. What a pain that was to buff. I got that stupid orange peel from the coarse grain structure and couldn't do anything with it. I finally got a really nice polish on it by taking a popsicle stick with 1200, 2400, and 4000 grit metallographic polishing paper. (The 4000 I used backed by a piece of inner tube and swirled it). Took a while, but in the end the blade looked like a mirror. Hopefully I can send all away together and get them all HT'ed at the same time.

Thanks, and take care from up north.

Ed.

Ray Rogers
04-07-2003, 09:10 AM
Ed,

You be sure and post some pictures of that axis lock when you get it done.

Mirror polish on a D2 blade, huh? That does take a lot of work. The really interesting part will be to find out how much trouble you have getting the mirror finish back AFTER the blade is heat treated. A lot will depend on how successful you are at preventing scale formation and pitting. I'd like to hear about that adventure after you get the blade back and do the final finishing....

striper28
04-07-2003, 09:43 AM
I thoought that the Axis lock was patented and only licensed to McHenry and Williams?

hammerdownnow
04-07-2003, 09:45 AM
Ray, speaking of pics. I would like to see some pics of your big folders. I have a few large Navaja fighters from the 1700's. I have heard they made them up to 3 feet long because the king then did not allow the peasants to carry swords. I don't want to make anything that big,but a 16" folding fighter sounds reasonable. I have some sketches in the Spanish fighting style. Now that i have new equiptment, I am going to start one soon. Thanks for the tips, Roc

Ray Rogers
04-07-2003, 01:31 PM
Roc,

Here is a rather crude picture of a Mata-Porco folder I made. It measeured about 14" overall. It's the only Spanish themed folder I have made so far, but I have plans for a Sorocabana and a Peixeira:

http://www.rayrogers.com/mataporc.jpg

The Mata-Porco is not pictured on my website as I do not make these knives regularly. If you would like the see the heavy folder I mentioned earlier, go here: www.rayrogers.com/chupie.htm

Striper28:

I'm sure you are right about the patent on the Axis Lock. However, it is my understanding that a patent does not prohibit an individual from building a patented device as long as it is for their own use and not for manufacture or sale. I'm not a lawyer, so take that for what it may be worth ....

doctor_mech
04-07-2003, 09:31 PM
Thanks Ray, I will. Hopefully by the end of the summer I'll have something done on it. As for the scale, I understand, but what happens if you heat treat in Hydrogen? It has 7 times the heat capacity of air, and I know some industrial heat treaters use it as a medium. The tool steel comes out yellow. I really hope it won't be too difficult to get the polish back.

As for the patent on the axis lock, I suppose if you are SELLING the knife, then you have to pay royalties or licensing, but if you make it for your personal use, then I can't see why there would be any infringement.

Take care all!

Ed.

P.S. Ray, I'll keep you posted. YOu only have so much metal removal with files... Very nice piece by the way. You really should post that!

Ray Rogers
04-08-2003, 08:32 AM
What would be the result of heat treating in a hydrogen atmosphere, you ask? I'm not sure, but I think the effect would be much the same as in downtown Bagdad right now. :D

Maybe some outfits do use hydrogen but I've never heard of that being done. However, using argon is common. Paul Bos uses argon and so do I. Blades treated this way have some color change and very little scale, sometimes some tiny pits. Generally, finishing a blade beyond 400 or 600 grit before heat treating may be counter-productive....

doctor_mech
04-08-2003, 09:40 PM
Ray, you're correct, they heat in argon, but cool with H2. AS I said before, H2 has many times the heat capacity of air, and therefore it cools at a quicker rate.

Take care,

ed.