Need suggestions to change the stop pin on my folding knife

[Alan0354]

I bought a knife that looks to be very robust. It uses ball bearing pivot which I want to change to bronze washers. Nice thing about this knife is they do not thin out the pivot area either on the blade or the liner. So it's easier to change to bronze washer to make it tougher and also thin out the knife a little. Below is the picture of the internal of the knife.

Notice the stop pin is not a simple dowel type. Instead it's like shown in (C) below.

Pin.jpg (50.03 KiB) Viewed 947 times

Because the stop pin is like that, changing to bronze washer will make the thickness at the pivot point like 0.03" thinner than the area at the stop pin. The blade can be wobble. I have to somehow make the stop pin narrower to make it solid.


Ideally, is to make the stop pin a little shorter shown in RED in (C) above. But it's not easy. Next is to open up the liner a little shown in (D) above. But that's not easy to get a clean SQUARE edge to give the best support on the stop pin.


​What I did is shown in (E) above. I just find a drill bit that is the same diameter as the stop pin and drill down just a little. THIS WORKS. BUT you can see there is a little on the stop pin that is UNSUPPORTED as shown in RED and GREEN in (E) as the tip of the drill bit is NOT SQUARE.


So the next thing I can think of is to change to a straight dowel pin of 3mm or 1/8" diameter. This is have to drill through the liner plates. If this is the best way, what drill size should I use for 3mm and what for 1/8" diameter to get a tight but movable fit?




If you have other suggestions, I am all ears.


Thanks

[Alan0354]

Anyone?

[edge213]

This is only my opinion.
Seems like a lot of trouble for no practical gain.

[Alan0354]

This is only my opinion.
Seems like a lot of trouble for no practical gain.

I am just playing around and learning more about folding knives.

This is one of the cheap knife that I consider to have very good engineering thoughts in it. The original ball bearing is very cheap plastic one. Bronze washer will make the pivot point stronger.

I already drill the hole down a little as shown in (E) in the second picture in post #1. It works well. My only complain is the tip of the drill bit is not flat, so the shape of the mouth of the hole is a "V" shape. The stop pin is not supported in that area. If I can drill the mouth of the hole with flat bottom, that will work already.

So the second best is to drill the hole out and fit a slightly and fit a straight dowel pin.

[philco]

Seems like a valiant effort to solve a problem that does not exist.

[orvet]

My only complain is the tip of the drill bit is not flat, so the shape of the mouth of the hole is a "V" shape. The stop pin is not supported in that area. If I can drill the mouth of the hole with flat bottom, that will work already.

A flat bottom straight fluted carbide drill will drill a nice clean hole that has 90° shoulders. They won't be tapered. You can probably get one for under $20. In order to achieve that nice square shouldered hole, you will need to drill press or a milling machine, and a good vise to clamp it down so the work can't move. It is critical that the work cannot move when you are drilling the hole. Any movement in the work can exert sideways pressure on the carbide drill and they can shatter. Be sure you're wearing safety goggles or face shield.

[ea42]

Alan another option along with Glenn's suggestion is a square end end mill. They come in a lot of sizes so there's a good chance there'll be one in the size you need. You can use it in a drill press since you'll only be using downward force but set the drill to slow speed. You also need to clamp the piece down and have the table lined up perfectly with the hole. End mills won't guide themselves into a hole like drill bits do, they'll just cut straight down regardless of where the hole is.

Eric

[Bill DeShivs]

Why don't you just chuck the stop in in a drill and file the offending material away?

[Alan0354]

Alan another option along with Glenn's suggestion is a square end end mill. They come in a lot of sizes so there's a good chance there'll be one in the size you need. You can use it in a drill press since you'll only be using downward force but set the drill to slow speed. You also need to clamp the piece down and have the table lined up perfectly with the hole. End mills won't guide themselves into a hole like drill bits do, they'll just cut straight down regardless of where the hole is.

Eric

Thanks

I decide to try both ways. This is a cheap knife with very robust design, I bought 5 of them ( yes, I have some OCD!!! ). I can afford to ruin one or two.

I just bought 3mm X 6mm 304 steel dowel, then I bought a set of flat headed milling bits that has 3mm bit. They all arrive tomorrow.

my bet is on drilling the hole bigger and fit the 3mm X 6mm dowel. But I am going to experiment the flat head bit on some metal to get the feel how to do it.

My question is if I have a hole that is 0.1" diameter, if I use a 0.116" diameter flat head drill bit, will it follow the hole? Or I have to be very careful to match the hole? It is important to be dead center if the bit is the same size as the dowel.

Thanks

[Fisher Cat]

Endmills have cutting edges on their sides as well as their ends, so you will need to be perfectly aligned with, and perpendicular to the hole. The part must be held rigidly during the process as well. You should be able to use your gage pin in the chuck to get alignment, then switch to the endmill to cut. A milling machine of some sort is really the best way to get all this done correctly. Good luck! - John

[Alan0354]

Thanks for all the suggestions. I received both the flat head milling bits and the 3mm X6mm dowel.

I started the easier way sacrificing one knife to drill the hole bigger. It's quite an effort to drill. To prevent walking, I step increased the drill size to step up to 0.116" in 2 steps to make it easier to drill through each step. IT WORKED.

The dowel fitted very snug, I actually manage to use 2 bronze washer with one at 0.01" and one 0.02". The original ball bearings were 0.03" thick each side. I literally took out 0.03" to make the linings much closer to the blade.

It is smooth in opening, no side way movement of the blade. Everything is tight just like when the knife first came with bearings. It is a success.

I never get to using the flat drilling bit. I am going to return the set. I checked, it's not going to just easily fit into a slightly smaller hole and drill dead center. So it's a lot harder to align given I don't have a milling machine, just a drill press.

Anyway, I am very happy, I have 4 of this knife only $12.99 each. The metal of the liner is very hard, I really had a hard time drilling even through there's already a hole of 0.1". I have to keep putting oil to cool it down and drill one second and let it rest of a few second. I can feel the hardness when I try bending the liner lock out more to give it more secured lock, together with the hardness to drill, I conclude the steel of the liner is very good.

The blades come very sharp on all 4, no accident on this. Sharper than my Cold Steel and many of the Steel Will knives. It's the sharpest out of the box out of over 2 dozen of knives of different brands.

I am going to take my time doing the others. But this experiment is a success.

The design of the knife is very robust for it's size(3") and weight, not a good looking knife and is cheap. Even it has ball bearings pivot, they don't need to thin out the blade or the liner to fit the bearings, so there's no weak point at the pivot. The spine side of the blade is of full thickness to about 3/4" of the way that make it strong and harder to break.

Also you can see the distance from pivot point to the edge of the liner lock distance is 0.47", which is longer distance than a lot of knives particular only 3" blade. This make the liner lock more secure.

Also another thing I like this knife is the flipper tap is very long, it serve as good protection of the hand when thrusting into a hard object.

I guess this is the end of this thread.

Thanks