The tightness of the folder's pivot

D

Dmitry.M

Joined
Jun 13, 2006
Messages
1,008
As I am new to the folding knives and I would like to know the makers opinions.

Obviously ideally the blade must have absolutely no play in the pivot pin. It also must have easy walk-n-talk action. As I am making my knives with my hands and the help of the most basic machines I can not achve the accuracy of CNC made components. So i have a prblem. If I tighten the pivot pin to eliminate ANY blade play - it has no smooth action. It is tough to open.
If I relieve the pivot - the action is good, but the blade has SOME play. It is not like it wabbles all around or something, but if you try to move the blade sideways it feels like it has a joint. It feels not like a solid fixed blade.
Now.
I have few folders to compare. I have BUCK-110. Brass body(liners), steel blade, brass(bronze) pivot pins(as far as I can see). It is NEW i the box. Very easy walk-n-talk and NO play in the joint.
I have Swiss army knife. It has been in use for about 10 years. Stainless blades, looks like stainless liners, probably stainless pin. Easy action, NO play.

The second question is closed blade detention. If it is too though(wich is good for legality) - it is impossible to open with one thumb... If it is easy to open - it has almost no detention.

So... I am wondering what makers think about the this. Especially who has no surface grinders, CNC machines and do not use black magik.
I am not asking for the makers secrets, do not worry.


By the way. It is NOT about the lock. It is about the pivot only.
 
What type of folder are you making? Slip-joint, linerlock, lockback?
Are you using washers? The backspacer should be the same thickness as the blade and 2 washers. So if your blade is .125 and you have.020 of washers your backspacer needs to be .145.

I have been making folders for over 10 years and I have no CNC equipment, you don't need it.
 
I did all folder types. Slipjoint, linerlock etc.
The problem of play in the pivot pin is the same for any type.
May be I leave too small part for the blade "butt" that goes into the liners? So it has not enough support.
 
One more thing.
If I sand the blade after I ground it to the shape(bevels) it makes the joint part somewhat "rounded". Not as parallel as I would like it to be. May be I need to flat ground\sand the flat piece first to get tight fit and than grind the bevels?
 
Dmitry.M said:
As I am new to the folding knives and I would like to know the makers opinions.

Obviously ideally the blade must have absolutely no play in the pivot pin. It also must have easy walk-n-talk action. As I am making my knives with my hands and the help of the most basic machines I can not achve the accuracy of CNC made components. So i have a prblem. If I tighten the pivot pin to eliminate ANY blade play - it has no smooth action. It is tough to open.
If I relieve the pivot - the action is good, but the blade has SOME play. It is not like it wabbles all around or something, but if you try to move the blade sideways it feels like it has a joint. It feels not like a solid fixed blade.
Now.
I have few folders to compare. I have BUCK-110. Brass body(liners), steel blade, brass(bronze) pivot pins(as far as I can see). It is NEW i the box. Very easy walk-n-talk and NO play in the joint.
I have Swiss army knife. It has been in use for about 10 years. Stainless blades, looks like stainless liners, probably stainless pin. Easy action, NO play.

The second question is closed blade detention. If it is too though(wich is good for legality) - it is impossible to open with one thumb... If it is easy to open - it has almost no detention.

So... I am wondering what makers think about the this. Especially who has no surface grinders, CNC machines and do not use black magik.
I am not asking for the makers secrets, do not worry.


By the way. It is NOT about the lock. It is about the pivot only.
Click to expand...

I've made all my slip joint knives with out these tools.
And there is no blade play, but also get a smooth walk & talk.
Not an easy thing to do, you just have to make a lot of knives and keep making them to be good at it.
Take your time and keep trying.
Good luck,

Todd


.
 
Dmitry
Do you drill you holes undersize and them ream to size,also use a granite surface plate to sand the sides of your pivot area,keep things as flat as possible.
Stan
 
Thanks Stan! I did not ream the holes. Just drilled them.
The thing is - I make the pivot pins myself. Turn them from 3/8" round stock of 4140 and then heat treat them. The diameter is 1/4". And there is a bit of a broblem. I can not predict what will be the final diameter of the pin after the HT. And I have no capability to grind the pin to sertain size after HT. So every time it's a bit of a guesswork.

I use glass to put my sandpaper on. Hope it's true enough.
 
A drill always cuts oversize
You can easily determine the finished outcome for heat treated pins. Make your pivot pin .005-.010 oversize. Then heat treat it. Then turn it on centers and use carbide tooling to turn it to size. Measure it with a mic. Then drill and ream to the correct size.
 
The first thing I thought of is the spacing. The pivot area thickness, meaning the blade and washers if any should be pretty dang close to the same as the spacing in the rear for your spring holder if a lockback or a spacer or stand off in the rear for a liner or frame lock. Back spring for a slippie. If you have those off beyond tolerance levels you're action will do just what you describe. Say for example you made a liner lock and had the .125 blade with two .020 washers one on each side. .125 + .040 = .165 so you should have a rear spacing very close to this if possible. You can be off by a small margin in my experience but when I've seen knives in my shop with problems for what you describe what I've found is situations where the spacing in the rear was off by considerable amounts compared to the pivot. If you have .165 front and its .195 rear or .133 rear either way it can bind and cause problems in the pivot.

What happens often times with production knives of course is that someone buys a knife, thinks they'll change out the teflon or nylon washers with phosphorus bronze and they know nothing about the thickness. Inadvertently they stick washers too thin or too thick in the pivot and it changes the dynamics of how the entire folder works.

STR
 
You must log in or register to reply here.
Back
Top