I have a zinc lock box that looks like this:

enter image description here

where there's a top and a bottom part. Notice that there're two interesting features (circled in red):

enter image description here

After cutting it up slightly: enter image description here enter image description here

The section view (of the right feature) looks like the following:

enter image description here

And the part circled in blue previously looks like:

enter image description here

Are those features results of some staking operation? If so, is it common for staking to produce such clean, squarish dents (red arrow) even on the lower part? My guess is that these might be designed for holding the two parts together.


I've now cut another piece off to hopefully aid better understanding:

enter image description here

enter image description here

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 features in the lower component that "bite" into the upper 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?

  • $\begingroup$ This looks like a casting. Possibly the dents were originally "risers" or "feeders" (see en.wikipedia.org/wiki/Riser_(casting) which ensure that the mould remains completely filled as the molten metal cools and contracts. The excess material is cut off from the finished part. If they will be invisible when the part is being used, there is no particular reason to cut them off "neatly". $\endgroup$ – alephzero Aug 5 '16 at 23:11
  • $\begingroup$ @alephzero I've cut another piece off now. It looks like there's a feature in the lower part that might be designed to "bite" into upper part. Please see update. $\endgroup$ – John M. Aug 6 '16 at 5:08

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