Have you been using bearings with pivot pins in liner locks? Any findings would be appreciated such as do you feel they give a smoother opening, closing blade ? I have one on the go now that will be my first. I should have it completed in the next few days and will let you know what I see. Thanks Frank

Hi Frank!

I've gone completely to using bushings in all my folders. I use either bronze or 416 bushings, and have found several advantages. I did have to change some of my methods, and pay more attention to tolerances, but once I figured them all out, it made the actions smoother, the stops crisper, and now theres no more fooling around all the time with getting just the right tightness on the pivot screws.

I've used bronze bearings since I made my first folder about 8 years ago. They have the advantages that Ed stated plus one more which has been even more important to me. I surface grind my blades after heat treating. Depending on a number of factors, including sheer luck, after the grinding is finished the sides of the blade will be parallel to eah other but the centerline of the pivot hole may no longer be perpendicular to the sides of the blade. Pressing in a bearing makes it possible to correct this by creating a new hole in material soft enough to be easily reamed into alignment.

And, before you ask, I have never had anyone tell me that a bearing wore out or became sloppy even after years of use.........

Thanks for the word on the bushings. I may have to give those a try, but I am hoping I may also get a respons from someone using bearings. Frank

G'day Frank,

I use 3/16" bronze bearings and I don't know whether they operate any smoother as I've got nothing to compare it with. I use teflon washers with a 3/16" hole to accomodate the bearing which is .001=.0015" longer than the blade and washers combined. When I assemble the piece I just tighten the pivot screws until the liners have gripped the bearing and everything works fine.

Regards from Australia.
Neil C

You talking about ball bearings, Frank? I did do that once, but wasn't overly impressed with the result. There is also some hi-tech knife manufacturer whose name escapes me right now that uses needle bearings in their $1000 folders and say it's the cat's meow. My problem with ball or needle bearings is the law. In order to really see any difference between a ball bearing and a bushing the blade needs to be free to move on the ball bearing, such knives often get called gravity knives. I know that the presence of a strong detent that requires more than the flick of a wrist to overcome the blade holding force is sometimes considered enough to get such a knife off the gravity knife list but then again, sometimes it doesn't get it off the list. Courts are funny places,

Also, in a liner lock the lock will put pressure against the side of the blade (no big news there). In my opinion, this is enough to negate any advantage the ball bearing may have had in any perceived smoothness. So, in conclusion, I don't see anything wrong with using ball bearings, beyond the fact that they are more expensive and more difficult to install than a bushing. But, in actual use, I haven't seen any noticeable advantage over a well made bushing....

Frank, I've found that ball or needle bearings aren't generally available in the small sizes I use.

Also, you can't adjust the width to fit the blade thickness.

I much prefer a bronze bushing that I make to fit each knife. I make all sizes of folders, and prefer to have the bushing just wide enough to accommodate the blade thickness plus two side washers. That way, the pivot screws are simply tightened down tight and the liners squeeze the bushing. No adjustments necessary. The blade and two washers are free to rotate around the O.D. of the bushing.

That's "My Way". :)

ive used bearings a few times and i dont see where they are any better than bushings and washers...and as said they are harder to find, cant be ground to required thickness, and are more expensive

When fitting the length of a bronze bushing to accomodate the blade, washers and an extra .001 or two, what is the prefered method of adjusting the length while maintaining squareness? Do you surface grind? Grind using a fixture? Hand hone on a granite plate?

Thanks
Bill

Larry Chew, Brad Duncan, and Larry Davidson ALL offer pancake bearings on each side of the blade. I own works from both LD and LC. Absolutely zero, I mean ZERO blade play and they are smooth. I suspect it takes some engineering to pull it off.

It's a treatment that works if you care to spend the extra time and energy. I have no complaints about bushings or bearings. But it's just another way to be different.

Coop

Bill,
If you go to my tutorial on how to make a lockback folder there is a little tool I made to make the bearing the correct size.
Regards from Australia. :)

Great little jig there Neil. I may try bronze bushings on the next few folders. Now the question is, where can one acquire these bushings? I've looked through some of the knife supply houses and there is not much of a choice unless I'm missing something.

Thanks
Bill

I am pleased with the response and it sounds like this may be the only one I will do with the ball r bearing set up. Neil I do remember you writing up some information on this and I certainly will search it out. By the way I know we all would be some pleased to hear that your operation is coming up very soon or you have been through it. Thanks to all and yes where have you people being buying your bushings or material for these? Frank

G'day
I get mine from a bearing supplies business, buy by the 100s.
Regards from OZ

I hope it's ok if I expand the question a little...

I've started building liner-lock style folders and have recieved great help from you guys. I've been using Don's method of clamping a bushing between the liners to provide a presice gap for the blade and washers. I am obsessive about the pivot-hole-to-bushing fit to an almost rediculous level (but it makes me happy. he he). I'm very happy with the squareness of the pivot holes and the bushing-to-hole fit. Everything is smooth and without play. I don't see how a roller or needle bearing could make it smoother or reduce felt friction. HOWEVER, When the lock is cut and bent, and the detent ball mounted there is considerable drag on the blade action. Not enough that something feels 'wrong', but enough that it is the biggest factor. Is this just the way it is, or am I doing something wrong? If I use my nail to lift the lock away from the tang the blade will rotate free and smooth, swinging under the force of gravity. If I let the detent ball ride on the tang there is more than enough friction to keep the blade from swinging under it's own weight and more. I'm only bending my locks an amount equal to the blade width (not quite touching opposite liner) and I'm seating my detent balls to a height 1 or 2 thou less than the thickness of the washer. Also, I'm cutting my locks plenty long to avoid having a short, stiff lock.

What are your thoughts? That's just the way it is, or can I make it better? Thanks!

-Ben

When fitting the length of a bronze bushing to accomodate the blade, washers and an extra .001 or two, what is the prefered method of adjusting the length while maintaining squareness? Do you surface grind? Grind using a fixture? Hand hone on a granite plate?

Thanks
Bill

Bill, as you know, no two of my folders are the same. I use a surface grinder to grind each bushing to the precise length required for each knife.

There are pictures and an explanation of the process in "My Way". If the bushing ends are square to the O.D., you can get there with sandpaper on a flat surface. Use a little piece of scrap metal with a reamed hole in it to fit the bushing to hold the bushing square against the sand paper. Be sure the reamed hole in the scrap is square to the bottom.

I haven't seen Neil's fixture.

Hello Ben,
It sounds to me like you are doing everything right, however if your spring is wide it will be stronger than a narrow one, no matter that they are both set to travel in the same amount. If you require a given wideth, you can change the spring's strength by drilling a hole where the cut ends. I do a small hole on all of them but then will enlarge this hole in steps if necessary. I hope this helps Frank

I have a small metal lathe and turn my own bearings from rods of bronze.

Ben,

There will always be some drag and with the laws concerning gravity knives being the way they are some drag is probably not a bad thing. In addition to the things you already mentioned, the amount of tension from the spring is also affected by the thickness of the spring material and the width of the lock bar. You can widen the slot at the end of the lock cut and thin the lock bar thus reducing the pressure without having to reduce the amount of the lock face where it meets the blade. Either that, or use thinner material or make the lock bar even longer (mine run almost the length of the handle). Finally, one or two thou clearance for the detent ball may not be enough. Push the ball in a bit more and see if the drag is reduced. If it is, you know the ball was binding .........

Thanks Ray and Frank. I'll play some with those suggestions and see what I get.

-Ben

Hello Ray. Thanks on the bronze rod thing. As I said I may have to give that a try. Yes I agree that "some drag" but with the blade movement being smooth is a good thing, laws or no laws. I have now come around to where I started from, and that is to have the blade to not have side play, to be centered, to move smoothly with only enough drag to prevent it from falling open freely, and to have a positive detent position but one that is easily over come. Frank

I did complete the folder with the ball bearing with a 1/8" pin for the pivot. I also completed another done without the bearing. I can't feel a difference between the two that would tell you they were made differently or either one isn't a smooth operator. Perhaps I will try the bushing thing in the future, however I don't believe it will add anything to my folders. I believe this is one of the areas I manage to do well. Don't get me wrong, I am always on a learning curve and I don't make perfect folders but I do keep trying and that means trying different ideas. Frank

I know this discussion was pretty much over, but reading it I had a question that came to mind. Please forgive me if my take on the use of a bushing is in any way incorrect.
I was looking on a website and saw a precision pivot with pre-fitted bushing made of hardened stainless steel. The blade is meant to ride on the bushing and the bushing acts as a stopping point for the clamping action of the liners to keep from squeezing the blade to much. So the bushing does not actually rotate on the pivot barrel. In a sense, isn't the bushing just acting as a larger pivot barrel for the blade to pivot on?
If so, what is the advantage? If the bushing is just acting as a larger barrel pivot what is to be gained? I thought about the act of the bushing stopping the liners from squeezing the blade too tightly, but doesn't adjusting the length of a standard pivot barrel accomplish the same thing?
Once again my appologies if I'm getting this whole thing mixed up and turned upside down. If anyone could give me a quick word on this I would really appreciate it. Thanks!

First off, let me say that I don't use my bushings in that particular manner but there are many who do. One advantage that I can see in that method is the larger area of contact between the bearing surface and the blade. This could help prevent wear (although I've never seen a bearing of any kind wear out on a knife pivot) by increasing the surface area of contact and distributing any pressure over the larger area. In theory, that might also lead to an increase in friction but, with bronze bearings at least, it doesn't appear to do so as far as the knife's user can tell, so if it does it isn't significant In the case you mention with a stainless bearing I would anticipate a problem with potential galling if it were used with a stainless blade and the lubrication ever dried up.

Keeping the liners precisely separated seems to be the primary reason some makers use this method. The argument seems to be that this prevents any change in the perfect action of the knife, i.e., the user can't tighten the pivot down accidentally and bind up the blade. Or, the maker doesn't have to be concerned about fiddling with the pivot pressure to get the action 'just right'.......all he has to do is clamp down on the pivot screw until it is tight and he's done. No argument there providing the bearing is, in fact, the perfect length but for myself I prefer to fiddle so that I and the ultimate user of the knife have the chance to tune the action for a preferance or a circumstance that I may not have anticipated..

Yes, the fixed distance between the liners could also be accomplished with the pivot. But, using the pivot this way means making a way to prevent the pivot from passing all the way through the liner/bolster . Usually, this means a shallow pocket in the liner/bolster anddepending on your tooling this can be difficult for some people to make. Or, maybe they can make it but they aren't happy about the shallow support at the ends of their pivot that this system may result in. I've done it that way and found it inconvenient for my way of doing things but I expect some makers get good results with that method. As far as I can tell, what method you use depends more on what you get used to doing (and what you have the tooling to do) more than any built in advantage to the method itself.

So, which method is best? The one you learn to master ........

Thank you Ray.
Reading posts on this forum and asking questions has given me a wealth of information I never could have hoped for without countless hours of trial and error. I'd just like to thank you and everyone else on here for helping those of us who may not have the knowledge or experience yet and for guiding us in the right direction.
I appreciate your insight on the use of bushings. It's given me a few things to think about in how I'll construct my knives. Thanks again, I really appreciate it!

Well of course, as always, the end results are what counts. My pivots pass through the liners and the screws bottom on the pivot and of course are set with Locktight non permant type fixer. Yes this means the assembly with blade and washers must be done correctly without side play but with a minimum of drag. The idea that someone can get a screw driver or two and play with the tension , I just don't believe in. As well I use bolsters that hide the pivot screws. I took two of my folders to the Vegas show to ask opinions of from several known makers. One was done as above and one was done with a ball bearing. All said that they could not detect a difference one from the other and that they did not feel that bearings or bushings added anything, but of course, if one worked better for an individual than another then sure that would be the way to go.

I sure did miss mentioning one important thjing on how I do my pivot holes and that is they are drilled after the metal for the blade has be hardened and ground parallel. Frank

That last point is, indeed, very important Frank. I do the same thing essentially but by using a pressed in bronze bearing I am able to drill and ream the holes with regular drill bits and reams rather than the more expensive carbide drills and reams. The bearing is pressed in after the heat treating but before the surface grinding is done. After the surface grinding the original pivot hole in the bearing may be a little off center but it is easily reamed back to true. This is exactly the reason I like to use the bronze bearing and not because of any belief that it makes for a smoother action .........

Interesting thread, and now that I have dsl, I'll add another idea - the use of ceramic, ruby or sapphire ball bearings as bearing surfaces to support the sides of the blade instead of washers.
From six to eight precision balls set into slightly oversize cups cut into the liners will provide an action with no lateral play, while still light and smooth. I've used precision balls of .0625 diameter and carbide ball cutters of .063 to get the right amount of tolerance for the cavities.
I can't say that the improvement is worth the additional effort, but it is fun to try different techniques and materials.
I believe that Gerry McLure does something similar with ruby rods set into the liners, and, rather than a rolling ball, his approach is to cut and polish the rods to the same height and a smooth finish for a smooth action without any discernable lateral displacement.

That's an interesting method, kelly. I(t's worth thinking about.