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Box Joint Pliers

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roy entwistle01/12/2021 10:10:37
1551 forum posts

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

Clive Foster01/12/2021 10:26:05
3173 forum posts
113 photos

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

Michael Gilligan01/12/2021 10:31:11
avatar
20289 forum posts
1064 photos
Posted by roy entwistle on 01/12/2021 10:10:37:

[…]

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

.

… 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.

.

Clive beat me to it

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

Speedy Builder501/12/2021 11:41:35
2653 forum posts
219 photos

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

roy entwistle01/12/2021 12:50:23
1551 forum posts

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

Roy

Michael Gilligan01/12/2021 15:03:07
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20289 forum posts
1064 photos

I doubt if these were Blacksmith-made:

.

43567141-cfd9-4e07-99ac-e7e515b4bb33.jpeg

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

MichaelG.

Tim Stevens01/12/2021 17:26:42
avatar
1622 forum posts

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

Michael Gilligan01/12/2021 17:47:37
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20289 forum posts
1064 photos

No, Tim … I wasn’t really wondering

But thanks anyway

MichaelG.

ega01/12/2021 17:53:57
2565 forum posts
203 photos

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

old mart01/12/2021 19:18:36
3900 forum posts
268 photos

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.

Ian P01/12/2021 19:47:32
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2594 forum posts
114 photos
Posted by Tim Stevens on 01/12/2021 17:26:42:

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

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

Ian P

Michael Gilligan01/12/2021 20:06:17
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20289 forum posts
1064 photos

Posted by Ian P on 01/12/2021 19:47:32:

[…]

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

.

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.

.

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

Ian P01/12/2021 20:43:37
avatar
2594 forum posts
114 photos

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

Robert B01/12/2021 21:30:48
20 forum posts
6 photos

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.

Michael Gilligan01/12/2021 23:34:16
avatar
20289 forum posts
1064 photos

That’s interesting, Robert yes

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

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

[perhaps I am just tired]

MichaelG.

ega02/12/2021 10:23:08
2565 forum posts
203 photos

Moderator:

Thank you for the end of the pier!

roy entwistle02/12/2021 11:22:21
1551 forum posts

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

Roy blush

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