Lets Talk Bushings

T. Hendrickson said:
Thanks for that info, Nathan; do you believe the liner/bolster pivot holes should also be reamed?
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At first I was going to say yes. But I don't know. It might depend on your construction. If it is not a moving part, the quality of the hole would be less important. Though I wouldn't want play there.

I was commenting on how to get a decent hole in an area where a drilled hole is obviously not ideal. But other areas on a folder - I don't know enough about it to give a recommendation.
 
Any precision hole should be reamed (imo).

If using bushings..,say .250 O.D bushings you'd be wise to get yourself an over/under reamer aswell. so if bushing is .250, get a .249 and .251 reamer.this will solve many problems :)

i find almost all PB bushings are always off spec.where SS bushings are a little more consistant.
 
Every pin, pivot or screw hole used to assemble a folder should be drilled and reamed. They all need to be square for the assembly of the folder or you risk the parts skewing during assembly. I take it a step further. For the pivot hole in the blade, I finish the hole with a barrel lap and Clover 600Grit polishing compound.



Now for the bushing laps. They never made it on to my web site as I brought them to a show and they sold like hotcakes. I had a few left and never posted them. I only have a few of the 1/8" left and one of the 3/16" (which may be sold). I have to get working on another batch.

Bill
 
Hey Bill,do you any anyone else have any photo's of them?? i'd like a look at it,even though ones on the way :)

It seems most guys use the 1/8" I.D bushings. i've always used 3/16" I'D with 1/4" O.D bushings. maybe because of the type of knife your building??

Either way,glad i scored the last lapper that holds 1/4" O.D bushings :)
 
Here is a quick photo of the Lappers. I need to get some more done.

They were made thick enough to handle both pivots and bushings.

ppal.jpg
 
Cool!!

How exactly to you adjust the depth of the lapper?? say i'm using blade steel thats .185 finished thickness and i want bushing at .187 thick.how do i adjust accordingly?? does the insert pin have a screw?
 
balibalistic said:
Bill,that is freaking ingenious :thumbup:
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I only wish I was the genius that came up with the idea. Makers have been using these for quite a while now. I heard about these a while back and made one for myself. I just thought I'd make some extras to see if anyone else could use them.

The credit for this idea goes to someone else. I know that Tony Bose uses something similar as well as Neil Charity. I'm sure there are many other makers too.
 
Well..,it was ingenious of you to make'em for us :D

i have made myself several different lappers and never put 2 and 2 together to create one of these.so kudo's to you :thumbup:
 
I'm still trying to understand the concepts.
I'm assuming the spacer bar holds the knife apart at the distance of the blade + the washers. the pivot point is this same distance of the blade + washers.
You want the blade in a folder to rotate smoothly between the liners, correct? A washer provides a smooth contact surface to rotate on? A bushing allows the pivot to be screwed down tight, but held up sufficiently enough that the blade moves with friction but freely, correct?
Why do some aparently not use a bushing and others use them? R.B Johnson's drawings show no bushing. Bob Terzuola shows no bushing.
And to further confuse me, Bob Terzuola says in his book on p. 98:
"punch the anti-rotation "D" into the pivot hole using a slightly domed punch...My pivots look like a "D" because there is a flat milled into one side to prevent the pivot from rotating when the blade is opened and closed...A crosss pin in the pivot which fits into a small slot in the handle may also be used."?

1. when is a bushing needed?
2. When is it not needed?
3. why does Terzuola indicate that the pivot is to be prevented from rotating?

And as a separate question:
4. Does the STOP PIN need to be any more than a press fit solid rod, rather than Bob's steped pin? (On P. 57 his stop pin is steped down from 5/32" to 9/64" so that aparently provides some aditional spacer use along with the spacer bar) (?).


The knife I'm working on is a 2 7/8" blade with, (I thought), a 1/8" pivot and no bushing, and a 1/8" solid rod pivot point, and a spacer bar of blade + washers thickness.
So far I've made the plastic model; I'm working on grinding aluminum blades for practice, and next I start on the real deal....So nothing lost yet. Thanks for your help.
 
These bushings tend to be used on slipjoints more than liner locks...I think....at least I have only seen them used for slipjoints. For example, I think Tony Bose uses them...but his son, Reese, does not.
 
EdgeCraft said:
I'm still trying to understand the concepts.
I'm assuming the spacer bar holds the knife apart at the distance of the blade + the washers. the pivot point is this same distance of the blade + washers.
You want the blade in a folder to rotate smoothly between the liners, correct? A washer provides a smooth contact surface to rotate on? A bushing allows the pivot to be screwed down tight, but held up sufficiently enough that the blade moves with friction but freely, correct?
Why do some aparently not use a bushing and others use them? R.B Johnson's drawings show no bushing. Bob Terzuola shows no bushing.
And to further confuse me, Bob Terzuola says in his book on p. 98:
"punch the anti-rotation "D" into the pivot hole using a slightly domed punch...My pivots look like a "D" because there is a flat milled into one side to prevent the pivot from rotating when the blade is opened and closed...A crosss pin in the pivot which fits into a small slot in the handle may also be used."?

1. when is a bushing needed?
2. When is it not needed?
3. why does Terzuola indicate that the pivot is to be prevented from rotating?

And as a separate question:
4. Does the STOP PIN need to be any more than a press fit solid rod, rather than Bob's steped pin? (On P. 57 his stop pin is steped down from 5/32" to 9/64" so that aparently provides some aditional spacer use along with the spacer bar) (?).


The knife I'm working on is a 2 7/8" blade with, (I thought), a 1/8" pivot and no bushing, and a 1/8" solid rod pivot point, and a spacer bar of blade + washers thickness.
So far I've made the plastic model; I'm working on grinding aluminum blades for practice, and next I start on the real deal....So nothing lost yet. Thanks for your help.
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I havent done many, but peening the pivot pin would be much less a stressful/fragile process if you didnt need to worry about binding the blade, using shims, etc. With a bushing thats a few thoundths thicker than the blade, no matter how much you peen that pin, the blade will still swing freely.

From what I gather from comments here, I think bushings on liner locks are slightly different, but a similar concept.

Heres a pic series of how a sebenza uses bushings:
3-parts.jpg

5-oil-blade.jpg

6-pivot-washer.jpg
 
Its already been said in this thread i believe??

In a slipjoint,a bushing lets you peen parts together without pinching blade.same theory goes for the knives i make.balisongs..

As long as bushing is properly tuned/adjusted it only needs to be a couple though thicker then blade,this way your liners/handles can be tightened directly to bushing,eliminating the "pinch" that could be caused by squeezing handles.not only does it eliminate pinch,it also eliminates blade coming into contact with liners/handles. i always use washers with bushings,this gives you between .010 - .020 on each side of blade.with bushing properly tunes you cant see a gap between washer/blade.

thats why I use them.

slippie makers can pipe in on their uses.but i cant see it differing to much?
 
and my question on a "D" shaped pivot on a liner lock folder, should that be bumped to a new post?
 
@balibalistic: The use of bushings in slipjoints is basically the same -- however, most slipjoint makers don't use washers (some do, but I personally don't like washers in slippies). What is often done instead is to mill both liners down about 0.006" +/- 0.001" around the pivot hole, leaving untouched the area around the hole - say for about a 3/8" radius or so - essentially creating extremely precise integral washers in the liners (and reducing blade to liner contact of course). The liner milling also stops just short of where the spring will be at the back of the liners. When you are using pinned construction, it always pays to minimize moving parts. And it's just a hell of a lot more elegant solution in my opinion.
 
I recieved my lapper a half hour ago.i've got a couple knives just about finished which will use bushings,so ofcourse i had to give it a try :)

let me tell you guys: how i ever lived without this tool,is beyond me :confused: it literally took me 2 minutes to get two bushing mic'd in with in .001 of my blade.the knife functions absolutly beautiful!! would have taken me an hour + to get these results and about 15 bushings cut to short :)

The lapper is reamed to .251 which is great as i never get an exact .250 bushing,so my bushings fit perfect.if you use bushings,get one of these!! Bill,when you make more i'll take another 1/4" one. just incase.

Thanks for a great tool,Bill! you DA MAN!!!!!!
 
balibalistic said:
I recieved my lapper a half hour ago.i've got a couple knives just about finished which will use bushings,so ofcourse i had to give it a try :)

let me tell you guys: how i ever lived without this tool,is beyond me :confused: it literally took me 2 minutes to get two bushing mic'd in with in .001 of my blade.the knife functions absolutly beautiful!! would have taken me an hour + to get these results and about 15 bushings cut to short :)

The lapper is reamed to .251 which is great as i never get an exact .250 bushing,so my bushings fit perfect.if you use bushings,get one of these!! Bill,when you make more i'll take another 1/4" one. just incase.

Thanks for a great tool,Bill! you DA MAN!!!!!!
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Thank you. I am glad it's working out for you. I have to get the next batch in the works as they are all gone except for a few 1/8". I'll post back here on the forums once they are done.

Bill
 
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