Piece of lens fell out

[earthmanbuck]

I had my K-1000 in my backpack most of the day yesterday, and when I pulled it out today I heard a weird rattling sound. I took off the lens and the middle component on the back end of the lens had fallen out. I managed to put it back in and get it to stay by turning it—as far as I can tell, this piece does not attach by threading, but that's sort of how I treated it—and it seems like it's staying put, but I notice there is still a bit of a rattling sound, which doesn't happen with my other lenses.

I'm wondering if there's an easy way to secure this piece without taking it in for repair, or whether a little bit of rattling is no big deal. Any tips appreciated.

 

[dxqcanada]

Hmm, you have to show us what it looks like.

... and what specific lens it is.

 

[earthmanbuck]

Hmm, you have to show us what it looks like.

... and what specific lens it is.

It's an SMC Pentax-M 1:1.7 50mm.

The part that fell out is the part I've circled in red, although after continuing to turn it it seems to be even more secure....I guess it was threaded after all. It still has a bit of a rattle if I shake it gently, but that could just be the aperture ring.

 

[dxqcanada]

There appears to be a locking ring there (the one with the two notches), that I would expect to be screwed on with a spanner wrench.

 

[jcdeboever]

There appears to be a locking ring there (the one with the two notches), that I would expect to be screwed on with a spanner wrench.

There are two squares in the red groove to place the spanner tips in.

 

[earthmanbuck]

Thanks all. It seems to be in securely now, so I'm going to assume it's fine unless the pictures on this roll come back telling me otherwise.