Slip joint pivot problems

J

Joseph H.

Joined
Oct 20, 2018
Messages
77
Hi!
I'm having a problem with my selfmade slip joint. I like to make slip joints in my spare time and been using my second (or third..) knife for about a year withou any problems. It was holding up very nicely. This is the one.

MhNzDDU.jpg


A couple of days ago it suddenly was hard to open and close. I thought there was some dirt in between de tang and the spring but that didnt seem to be the case. Afther opening and closing a couple of times, it was smooth again.
Then i noticed the pivot had turned about 45 degrees. And the spring had rised a small amount. It rised in al three positions. It was flat at first but not anymore... mabye the picture shows.

6sJxz4j.jpg


I cant feel any play at all in the blade in any direction and it functions nicely and crisp.

I think i know what happend... allthou its strange theres no bladeplay and it functions crisp. But i would really like to hear what you think. I like to learn and be able to make a knife that lasts.

So my questions are:
- what do you think happend?
- how can i prevent this from happening?
- general advise is always welcome... :D

Some relevant specs:
The blade and spring are O2 and about 0.08 inch thick (2mm). The pivot is 304 ss about 0.12 inch (3 mm). Handles are g10 0.16 inch (4 mm).
Thanks for your time and effort in advance.

Joseph.
 
Pivot was probably over peened and had a slight bend/bow in it.
As it wore and dirt got in it, it seized up a bit and was hard to open.
In "working" it to free it up you rotated the pivot.
Now the bend/bow is facing the spring and it is slightly lifted.

If it is working fine otherwise, I would let it go. If it gets snug again or bothers you, drill out the pivot and either replace it ( with less peening) or replace it with a pivot barrel and screws.
 
Yep, sounds like you bent your pivot and over time it rotated where the pin was convex upward.

That is why it is high in three positions.

Nice slippy btw
 
Thank you Stacy and Adam for your replies!

I would never have guesed this! It sound logic and it explains why it still functions and has no bladeplay.

I am going to drill the pivot out and replace it. (304 or 410?) I made some more slipjoints the last year so i might have to learn this for when i made the same mistakes on the others.. :p

My initial thoughts on the defect:
I thought it was the 304. I read on the forum that is perceptable to galling. So i figured some dirt got in the pivot and somehow caused this.

Is it possible that 304 can start to do that? Because i can change the pivotmaterial to 410. I read this was the most used.
 
Have you ever drilled a pivot before? It may cause you less heartache to keep it the way it is, if you have never drilled a pivot before.
 
Randy3000 said:
Have you ever drilled a pivot before? It may cause you less heartache to keep it the way it is, if you have never drilled a pivot before.
Click to expand...
Thanks for the advise. Never drilled a pivot out, till today!!!

That was an interresting exercise! :eek: But the pivot is out and de handle is undammaged.
 
Are you reaming your pivot holes to size and using precision round stock for the pivots? It's not absolutely necessary, but it may help. Definitely watch for over-peening.
This is part of the reason a lot of slipjoint makers use bronze pivot bushings, though it's certainly a bit more work.

I really like that pattern by the way.
 
Stacy E. Apelt - Bladesmith Stacy E. Apelt - Bladesmith
AVigil AVigil
And others...

Look what I found afther drilling out the pivot.

A6TFWrW

304 galling https://imgur.com/a/A6TFWrW

The pivot shows a decent amount of wear. But doesnt looks bend by eye. Doesnot mean it isnt.

My theorie. The galling occured before I grinded down the exces material of the spring. The extra force made it wear in the first couple of openings/closings. ( ps. I do this totally different now...)

Grinded it flush and it stayed this way for almost a year.

Does this sound plausable? Is there any connection with the 304?
 
Drew Riley said:
Are you reaming your pivot holes to size and using precision round stock for the pivots? It's not absolutely necessary, but it may help. Definitely watch for over-peening.
This is part of the reason a lot of slipjoint makers use bronze pivot bushings, though it's certainly a bit more work.

I really like that pattern by the way.
Click to expand...

Thank you sir!
I dont use reamers. I dont use precision round stock. I would if i knew where to buy them metric. I havent found a supplier for this in Europe.

I was thinking about switching to inches. But to import everything from de US is a bit silly for a hobbist I think...
 
There's always gonna some unavoidable wear on slip joint pivots. How long they last depends on a number of variables, from spring tension, tang and spring geometry, materials used, and roundness/smoothness of the holes and pins. A little bit of oil on the mating surfaces helps, though it can also attract dirt and debris which doesn't help. Apart from going to a bronze pivot bushing, starting off straight, round and polished should give you a serviceable pivot for years. A reamed hole and precision round stock certainly doesn't hurt. As for where to get them, I don't know enough about European suppliers to give you any suggestions, but I'm sure it's got to be available.
Any industrial supply should have precision dowel pins at the very least, or maybe check whatever your local equivalent of Amazon.com is?

At any rate, whatever pinstock you're using is probably pretty close to round enough, just buy the closest chucking reamer to drill the pivot holes, and maybe run a little polishing compound over the pin stock before you peen it into the knife.
 
Probably has more to do with galling than the wear. Wear should make the spring sink in, like you see in old knives. Yours is poking out.

I don't use stainless pins, so can't say anymore.
 
Drew Riley said:
There's always gonna some unavoidable wear on slip joint pivots. How long they last depends on a number of variables, from spring tension, tang and spring geometry, materials used, and roundness/smoothness of the holes and pins. A little bit of oil on the mating surfaces helps, though it can also attract dirt and debris which doesn't help. Apart from going to a bronze pivot bushing, starting off straight, round and polished should give you a serviceable pivot for years. A reamed hole and precision round stock certainly doesn't hurt. As for where to get them, I don't know enough about European suppliers to give you any suggestions, but I'm sure it's got to be available.
Any industrial supply should have precision dowel pins at the very least, or maybe check whatever your local equivalent of Amazon.com is?

At any rate, whatever pinstock you're using is probably pretty close to round enough, just buy the closest chucking reamer to drill the pivot holes, and maybe run a little polishing compound over the pin stock before you peen it into the knife.
Click to expand...
Thanks, i think my pivots need an upgrade. I googled the translation for chucking reamers and that gave me a local supplier! Seems it makes a lot of difference which words you search for... now find some precision round stock. Wat type do you use if I may ask?
 
Randy3000 said:
Probably has more to do with galling than the wear. Wear should make the spring sink in, like you see in old knives. Yours is poking out.

I don't use stainless pins, so can't say anymore.
Click to expand...
I think I mixed those two up. The blade and spring had no visible wear, the pin defenitely galled.

Is youre not using stainless, what type do you use if you dont mind me asking?
 
Joseph H. said:
Thanks, i think my pivots need an upgrade. I googled the translation for chucking reamers and that gave me a local supplier! Seems it makes a lot of difference which words you search for... now find some precision round stock. Wat type do you use if I may ask?
Click to expand...
I’m pretty sure the last stainless pin stock I bought was 416. I don’t remember where I bought it now.
 
Look at pivot barrels with threaded center holes. You put then through the blade like a pin, but use screws to hold it in place from the outside, This allows minor tension adjustments, the use of thin bronze washers, and use of hardened pivot barrels. The parts are available from most all knife supply companies and many industrial suppliers. Tapered reamers are available from all industrial tool suppliers.

Look at these pivots and parts here to get some ideas:
knifekits.com ( they ship to Europe, IIRC)
https://www.knifekits.com/vcom/knife-making-parts-pivots-c-60_83.html

Making precise holes in the blade and liners will assure clean operation. A tapered reamer in the proper size for the pivot you use is a very wise investment. Most folks use one between .0005" and .001" oversize.
 
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Pivot holes on slipjoints do not have/need to be precision reamed.
As a matter of fact, they should be considerably oversized.
 
Stacy E. Apelt - Bladesmith said:
Look at pivot barrels with threaded center holes. You put then through the blade like a pin, but use screws to hold it in place from the outside, This allows minor tension adjustments, the use of thin bronze washers, and use of hardened pivot barrels. The parts are available from most all knife supply companies and many industrial suppliers. Tapered reamers are available from all industrial tool suppliers.

Look at these pivots and parts here to get some ideas:
knifekits.com ( they ship to Europe, IIRC)
https://www.knifekits.com/vcom/knife-making-parts-pivots-c-60_83.html

Making precise holes in the blade and liners will assure clean operation. A tapered reamer in the proper size for the pivot you use is a very wise investment. Most folks use one between .0005" and .001" oversize.
Click to expand...

Oh man... maybe i have to go in inches some day and import the nice and shine, precision round and hardend stuff .:D (i'm just jealous i cang find it local...) Many thanks for the help and advise you are all giving me!! Upgrading my pivots is something that is going to make my knives a lot better. So thats something that I'm going to do. Which way... I'm not sure yet. But making the holes straighter and rounder with a reamer is probably going to help al lot for sure. Better steel (400 series) and rounder pivotsteel and carefull peening will help. Using the nice hardware in inches will help also.

I'll figure it out and make it work!
Many thanks to all of you! Cant say too often how much i appreciate it.
 
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