Canon 600mm F4 lens lock knob falls out

[Sborg]

I recently bought a the subject lens second-hand and I'm missing the retaining washer.  As a result, the lock knob (the little piece of metal that butts up against the lens to hold the hood in place) frequently falls out as I'm putting the hood on or off.  Has anyone else had this problem?  I've ordered the washer but would like hear if any other users have had the problem and have any tips for inserting the washer into the lock knob.  Thanks.

[shadowsports]

Greetings,

A few pictures might be helpful.  Since you have a replacement washer on the way, what about using a small plastic or metal retention washer to hold it in place?

Possible?

[Sborg]

Two views of the knob lock.

[ebiggs1]

Its been so long since I had my 600mm lens out I have forgotten how the hood attaches but I don't remember it ever falling off. And, I carried it all over Colorado and the southwest United States for years on many photo trips there. Up and down mountains, rain and snow, in the deserts, just about everywhere.

[Sborg]

I'm guessing you still have the retaining washer in place.

[ebiggs1]

Probably so, the last time I remember using it was out in Mesa Verde carrying it all over the place. I really stopped using it when I got the Sigma 150-600mm f/5-6.3 DG OS HSM Sports Lens.

[Canonoli]

I just replaced mine. You need to get a 2mm e clip, and it slips into the knob spindle that goes into that wedge you show a photo of. You can use tweezers and a small screw driver to push it in. You can purchase a whole set of e clips of Amazon for as little as ten dollars.

[Sborg]

Thank you! 

[Sborg]

I'm not familiar with e clips but I gather that the spindle should be inserted into the lock knob (wedge in the photo) and then the e clip fitted on.  Correct?  Thanks.

[Sborg]

It worked.  I put the e clip in place with tweezers, applied a little pressure with my finger and it slipped on.  Thanks!