How to socket 28-pin DIPs?

Question

Recently I switched from the leaf-spring type of DIP sockets to the more expensive machined MIL sockets. The leaf-spring type were failing (by the spring parts pulling out of the socket) after a few insertions, or maybe just over time), but the MIL types don't seem to hold the part securely. Notice how this one relaxes into a cockeyed position after having been pressed firmly into the socket:

Are the MIL sockets supposed to be used with some kind of a hold-down? Did I get an atypically bad batch of leaf-spring types, and is there a brand or supplier whose sockets can be counted on?

Update: Isn't the point of socketting to permit removal for replacement or, more frequently, for reprogramming (and if not, then why socket instead soldering the chip directly)? ZIF is a tool for the lab or assembly house, not a part to go on a product. It's bulky, heavy and expensive. Is there no kind of socket that's any better than having to unsolder a part?

Answer 1

If you want to put DIP packages into milled sockets you have to be conscious of the side forces from the package leadframe.
Milled sockets such as you are using are NOT designed to have large side forces on the socket and your DIP package leadframe is bent out at an angle as shown below (typically 5-15 degrees):

For milled sockets your DIP package should ideally be able to stand with the package lead pins in the center of the sockets without having to put side pressure on the DIP package pins. For hand insertion there are a bunch of creative leadforming jigs (from simple to complex) that will ensure the leads are normal to the body and at the right width:

I usually just hand bend on a flat hard surface. You just have to be careful to bend the leads right at the shoulder and not just bend the lower leg.

some open frame slide contact IC sockets can actually withstand considerable side force without popping out, but they have a high shoulder to surround the leadframe pins:

...and not designed for continuous re-insertion.