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The Folding Knife (& Switchblade) Forum The materials, techniques and the designing of folding knives.

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  #1  
Old 12-07-2008, 10:33 PM
T. Hendrickson T. Hendrickson is offline
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Which pivot pin?

Which style of pivot pin do you guys use? I'm trying to decide whether I should use step-type pivots, barrel pivots, or...?

Also, how big, in this case for a 3.5" tactical.


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  #2  
Old 12-08-2008, 07:42 AM
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Ed Caffrey Ed Caffrey is offline
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I personally use barrel pivots.... 1/8" in size. I also use bushings.


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Old 12-08-2008, 09:45 AM
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I'm with Ed. Straight pins, 1/8 or 3/16" depending on the size of the knife, bushings and washers. I get my pivot pins and Torx screws from Halpern Titanium.

I've never used any other type, so I can't help you there.
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Old 12-08-2008, 12:02 PM
T. Hendrickson T. Hendrickson is offline
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Ok, thank you sirs.

Can I get the bushings from Halpern also? The bushing as I understand it, is like a washer that goes between blade and the pin. Right? What is its function?


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Old 12-08-2008, 02:03 PM
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No, a bushing is a straight, plain bearing usually made of brass or bronze, that fits inside the pivot hole in the blade. It's purpose is to provide a dissimilar wearing surface. The blade rides and turns on the outside of the bushing on my folders. Some other makers have the bushing I.D. turning on the pivot pin.

Some makers use hardened steel bushings.

I don't know if Halpern sells bushings. Knifekits does.

I always make my own to suit each knife.

And thanks for saying thanks. Right, Ed?
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Old 12-08-2008, 11:19 PM
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I get my bushing from two sources.... MSC, where I purchase bronze bushings that have an ID of .125 (1/8") and an OD of .252. Bronze bushings are "easy" because you can "spin fit" them, meaning you can lock then onto a pivot and using a cordless drill, spin them into the pivot hole on a blade so they match perfectly, and have zero slop.

The second source is Alpha Knife Supply. (Chuck Bybee) who sells 416 bushings with .125 ID and .250 OD.

The bushing is left about .0005 to .001 thicker than the blade, used along with bronze washers it allows me to fully tighten down the pivot screws, clamping the bushing between the liners and forces the blade to pivot on the OD of the bushing.


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Old 12-09-2008, 01:29 AM
T. Hendrickson T. Hendrickson is offline
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Thanks Ed, that makes sense as to why a bushing is a good idea. So do the washers also go on the OD of the bushing then?


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Old 12-09-2008, 08:02 AM
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No, the washers are .125 ID, and 3/8" OD. They become sort of "clamp plates" when everything is assembled. They hold the bushing and the tiny space between the washers and the exterior of the blade is a place for grease/lube to be.

I purchase my washers from Small Parts.com On that site they only cost about $12 per 100, rather than .50-.75 cents a pair if you buy them from knife supply outfits.


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Old 12-09-2008, 09:04 AM
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There are 101 ways to do anything. My method differs a little from Ed's.

I make my bronze bushing about .001" longer than the thickness of the blade and both washers. The blade rides on the outside of the bushing and the washers slip over the bushing. That way the liners clamp tight against the ends of the bushing and the washers are free to turn.

A typical setup would be: 100" thick blade, two .015" thick washers. .100+.030+.001 clearance =.131 width of bushing.

I make my own bushings and washers.
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Old 12-09-2008, 11:05 AM
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Don's right....for everyone doing this stuff, theres another way to accomplish it. None are right or wrong....its all about what works for the individual. Some people look at me funny when I ask them about the methods they use for various knifemaking operations.....but I'm just like everyone else....wanna learn all I can, and if someone else is doing it better/easier, I'd be a fool not to do it their way!


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Old 12-09-2008, 03:38 PM
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I would say if your just starting out trying to make a folder, its harder to make one with a bushing. A lot more work.

Dave
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Old 12-09-2008, 04:19 PM
T. Hendrickson T. Hendrickson is offline
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I have made some folders, but I think I'll make a few more yet before I attempt one with a bushing. I'm not quite the precision machinist you folks are!

I can imagine it makes the knife action much smoother however.

I think I'm going to go with a 1/4" barrel pivot from Tracey Mickley for this one.

Many Thanks


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  #13  
Old 12-25-2008, 09:35 PM
Bob Cannon Bob Cannon is offline
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Bronze bushings are "easy" because you can "spin fit" them, meaning you can lock then onto a pivot and using a cordless drill, spin them into the pivot hole on a blade so they match perfectly, and have zero slop.


Ed, could you explain how you spin fit your bushings into the pivot hole? I sure would appreciate it...Thanks...
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  #14  
Old 12-26-2008, 09:35 AM
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David Broadwell David Broadwell is offline
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Thayer,

All these guys make nice folders. Like Don said, there are different ways to make a blade swing. Here's mine based upon about 17 years of making folders. Since you mentioned a tactical knife, I'm assuming that you are using a side (liner) lock. Personally, I don't care for bushings on my folders, and haven't used them since I made lock backs with 14k gold master pins. On less expensive knives I generally use commercial pivots in 3/16" diameter. Heads are usually 9/32 or 5/16 in diameter. On more complex and expensive folders I make my own pivots. The pic shows one I made with a 3/16 pivot diameter and a 1/2" head diameter (with matching screw). I've also started using Alpha Knife Supply's (Chuck Bybee) new 3/16" pivots with the 6-64 threads pictured here: http://www.alphaknifesupply.com/hardware.htm All of these pivots have an oversized area next to the head for a press fit into the bolster or liner to keep it from spinning. All the blades are rotating on the stainless steel pivots (some 303, others 416). I haven't had any gall up or get sloppy. I did have some with brass bushings, however, get a bit loose.

The idea of "spin fitting" bronze bushings just doesn't blow my hair back. I believe that if you can easily fit a bushing to the blade just by spinning it in a drill press, then it's not really going to last the life of the knife. Yes, it will feel great at first, but if it's that easy to fit initially, it's going to be that easy to get sloppy after some use.

If you are going to use a bushing I'd recommend using turned and ground O-1 drill rod. Drill and ream the inside diameter to whatever you need. Don't heat treat it. I believe it will be less likely to wear out than brass or bronze. O-1 is tougher than brass, and because your blade isn't spinning at 4000 RPM like a car's engine that uses bronze main bearings it will be fine.

I can feel .001" side play. It does little good to have any thrust washers if they aren't touching the blade. By the way, I use .015" nylon washers. Nylon is tough, and they allow the blade to rotate smoothly even if it is tight.

After heat treating the blade, I use a barrel lap and 400 grit Clover compound to size the pivot holes.

To answer your question about size. I believe that a 3 1/2" blade will work just fine with either a 3/16" or 1/4" pivot. The knife in my pic has a 3 3/8" blade. If you're pushing the length to 4" or more I'd use the bigger diameter.

Hope this helps.

David


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Last edited by David Broadwell; 02-18-2009 at 08:05 AM.
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  #15  
Old 12-26-2008, 09:58 PM
Bob Cannon Bob Cannon is offline
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Ok guys, I'm learning quite a bit.

David, what is a barrel lap and how do you do it? Thanks.
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