Box Joint Pliers

Good morning folks. I have several pairs of CK box joint pliers. I am just wondering how they are made. There doesn't appear to be enough metal to expand the hole in one leg, then insert the other leg and then close the hole up particularly with end cutters

Roy

Roy

Blacksmith technique is

start by forging the hole the "correct" shape

then heat it to red hot

stretch it with a shaped chisel type tool

push the other jaw through

reheat to red

forge the stretched eye back to shape

make hole for pin

Video of the blacksmith method here

**LINK**

https://www.youtube.com/watch?v=vPoFdNgQn4s

Industrial techniques will be basically the same but adapted to series production. I suspect the apparent lack of metal to expand the hole in you CK pliers is due to grinding down to size after the pliers have been made.

The bit I really don't get is how they manage a precise fit in the hole with just enough clearance for operation but not so much that the jaw wobbles sideways.

Clive

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… But of course there must be [because that’s how they are made]
I’m sure that the likes of C.K. and Lindstrom have more mechanised production … but this is worth a look: **LINK**

https://youtu.be/vPoFdNgQn4s

MichaelG.

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Clive beat me to it

Edited By Michael Gilligan on 01/12/2021 10:32:02

Another thing, why don't the two halves weld themselves together at white heat ? Mystery.

Thanks for your input gentlemen. They manage to get the joints nice and tight.

Roy

I doubt if these were Blacksmith-made:

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… It would be interesting to see how they do it !

MichaelG.

The object of the box joint (just in case you were wondering) is to have a joint which can withstand twisting in both directions. Very useful for manipulating body parts and bending wires etc. With a conventional joint you can only twist one way without risking the joint pulling apart (and so, the blades not meeting properly).

Very popular with making jewellers, as well as the Surgeons who like the whole tool to be a) polished) and b) stainless.

Cheers, Tim

No, Tim … I wasn’t really wondering

But thanks anyway

MichaelG.

For the benefit of posterity could the thread title please be amended?

The halves will not weld together because firstly the steel is only heated a dull red, and secondly because the joint is only closed enough to fit.

I imagine that surgeons instruments would need to be dismantled for sterilisation so unlikely to box jointed (in the blacksmith forged) manner.

Ian P

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Although the ones I photographed were purchased ‘non-sterile’ … I feel pretty sure that they are a surgical design: and as such, they would be sterilised in an autoclave.

MichaelG.

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Edit: __ That pair don’t have the locking mechanism; so technically they are not ‘Artery Forceps’ … but this should confirm my supposition:

https://www.healthandcare.co.uk/artery-or-haemostatic-forceps/kelly-artery-forceps-with-box-joint-140mm-straight.html

Edited By Michael Gilligan on 01/12/2021 20:15:46

I have a vague recollection that (about 8 or 10) years ago that a patient under surgery suffered because some jointed instrument had crevices that did not fully sterilise. One of my relatives sold medical equipment to theatres and I said I was sure I could design something that dismantled for cleaning but he assured me that I needn't trouble my little self as the products in use had separatable components.

I have a pair of forceps like Michaels and I would say that because the length of the slot is long in relation to the thickness of the part that has to pass through the slot, they could be manufactured by the blacksmithing method without even needing to apply heat,

Ian P

Surgeons tools may now be destroyed as a prevention of BSE infections getting through. This happened to metal implements used for dressing a wound in an A&E visit. I don't know how though as the nurse didn't.

That’s interesting, Robert

‘though it appears to conflict with this: **LINK**

https://www.nice.org.uk/guidance/IPG666/InformationForPublic

[perhaps I am just tired]

MichaelG.

Moderator:

Thank you for the end of the pier!

Apologies for the Pier instead of Plier. Put it down to old age.

Roy