Metal key box assembly

Hi

I have a small, cheap metal (zinc) key box looking like this:

which I *think* is made up of two parts.

However, I can't find any bolt or welding joint. Here are some other pics with coincident faces highlighted:

There seem to be complex undercuts inside, so I think these are two separate parts:

Does anyone know how the two parts might be joined? I'm guessing it wouldn't be epoxy since it's meant to be a secure key box. I got it new for just £10, so I'd guess there's no fancy work involved.

Any thought would be appreciated.

Edited By John Munroe on 30/07/2016 11:58:37

At that price, if you really can't figure it out after an hour or so, buy another one and take it apart with a sledge hammer. That way you will know for sure.

It may slide together and be locked by a simple staking operation, hidden away under the gunge - possibly those 2 horizontal features either side of the green oval in the last photo. 

Edited By Muzzer on 30/07/2016 12:01:53

@Muzzer Unfortunately they're out of stock and this is probably the last one.

There actually seems to be a groove inside, but I can't imagine how any feature in there could be used to lock the parts together.

Lower down inside the enclosure, there seems to be a stud of some sort:

However, nothing protrudes out the other side (top of the box).

Edited By John Munroe on 30/07/2016 12:23:56

Don't know exactly how yours is done, but on similar ones for electronics and valve motor housings I worked on at a big American controls firm they were staked together , the stakes ground off flush, then painted or powdercoated.

The parts were die cast zinc aluminum alloy. The stake operation was just cast in pins on one part passing through holes on the other. After putting the parts together a press was used to deform the ends of the pins like a rivet. Usually the upper part of the holes on the holed part had a countersink to receive the staked "rivet" head of the pressed post. The heads and upper surface of the assy was ground or sanded off after pressing and it was hard to tell where the joins were. After paint or powdercoat they were invisible. The pins could be made quite heavy for a very strong joint, almost as strong as the rest of the box. Both parts were of the same metal so there was no opening up or working of the joint due to thermal expansion.

Yours could be made that way. JD

My son has one & from memory ( I have not seen it for a while so a bit of brain fade has to be allowed for) the lid pivots on a rod down the side which is part of the staple & locks on the opposite side when the staple is depressed into place. The staple is released by a combination lock.

However, yours seems to have a flat rod down the side so perhaps it is different. I certainly did not hinge from top or bottom & was retained by the staple extending into the key storage area when locked

Edited By Sam Longley 1 on 30/07/2016 14:54:55

@Jeff Could the depressions (circled in red) be results of some stake operations?

Also, those two round marks (circled in blue), are they ejector marks or some kind of intended design? Ejector marks shouldn't be so visible - right?

@Sam The round rod is actually a shackle. The flat rod is like a lever and is spring-loaded. It clicks onto the shackle to lock it.

Apologies. I typed staple instead of Shackle -- Brain fade -

Maybe the items circled in blue are pins cast on the end cap, with radial grooves or slots on them. The grooves or slots would be made to receive displaced metal from the rectangular stake impressions circled in red. The red impressions could be stake features. They look a little far away from the blue circled pins though- the further away the stake is, the harder it is to displace enough metal to get a secure connection. If it is done this way, the joint would work much like a shaft with a groove and an E ring clipped to it.

A second thought - maybe the red circled areas started out as cored holes, and additional metal or some kind of resin was poured down them around the mentioned grooves in the pins cast on the second part to secure them.

Any plans to buy a second one and cut/break it to see for sure how it was done? JD

OK, I've cut off a bit of it now:

Here's a section view of the top part:

It's quite clear that the features circled in red also exist in the top part. Are these stake impressions? Could stake create such a clean, squarish finish even the second layer?

Thanks

Edited By John Munroe on 04/08/2016 19:27:49

Hi John,

I'm sorry but I can't tell anything to offer further comment on from the newest photos. I haven't got a sense of where things fit relative to each other in the new photos. JD

Sorry about that. Let me try clearing it up a bit.

The bit I'm holding in the 3rd pic actually fits in here:

So it's the right hand part of the top component. My guess is that the rectangular dents are what holds the top component down.

Hopefully I've explained the component a bit better this time.

"He that breaks a thing to find out what it is has left the path of wisdom" - Gandalf

Neil

I agree (refer to the second post!) - the 2 parts slide together and are staked.

Murray

@Muzzer,

Yeah, appreciate that! The lower component is actually 2mm thick, but the top component gets a perfect rectangular cut:

Does staking through a piece zinc that thick still produce a nice rectangular cut though?

Thanks

Surely that's the cavity that the upper part is "staked into". It is deformed into this cavity and thus won't slide apart. If I'm seeing it correctly.

@Muzzer, I've now cut another piece off to hopefully get a better understanding:

The features highlighted by red arrows don't seem to be regular shapes. The corners of the deformations in the upper component seem to have very small radii, but the "staked out" parts in the lower component look quite rough. Could this mean that the dents in the upper part were part of the cast and not deformations created by staking into the lower part?

Looks to me like the top cap goes on/in then the sides are staked into the recesses in top to hold it all together.

Pete

@Pete Right. In that case, how does the staking machine position itself with such high precision so that it hits almost precisely above the recesses? Is there meant to be a separate die for staking in place?