Pentax-M 28mm f2.8 (MK2) disassembly

Does anyone know how to get the finishing ring off a Pentax-M 28mm f2.8 (the later version)? I have one with a bit of something nasty in which would be really easy to fix, if only I could get the finishing ring off without wrecking it in order to unscrew the front element group.

By finishing ring I mean the part around the front element which has "SMC Pentax-M..." on. On the earlier lenses this is metal and unscrews if you use a rubber band or something to get some traction on it, but it doesn't seem to want to unscrew on this one.

Hi Matt, could you put a photo up of the front of the lens to take a look at it,
Jack.

No need - there's one here

Hi Matt it's the same as one I sold recently, the front ring unscrews the same way as the old one, I used an old wooden door knob shaped to fit the angle of the ring and then I super glued some rubber on the knob, you have to push down quite hard but it should release quite easy, that's the best I can do for now, hope that helps,
regards,
Jack.

Here is mine stripped
[IMG]http://i453.photobucket.com/albums/qq253/jackitec/28strip8001.jpg[/IMG]

Go to the Pound shop. Buy a pack of double sided sticky pads (you get hundreds for a quid!). Cut one into four strips about 3mm wide and stick them around the finishing ring. Peel off the paper, then place an M42 lens cap on the pads and push down firmly. You can then easily unscrew the ring without damage.

Just put some Blu-Tak on it Matt and then turn upside down on a table and unscrew.

I'll give those a go - I'd previously tried the rubber strap from one of those jar opening levers, rolled up and used to press against the plastic ring.

I've dismantled a M28/2.8 recently and couldn't shift the filter ring either, even after trying some of the above suggestions.

I resorted to drilling two diametrically-opposed 1mm holes in the ring, unscrewing it using a caliper and then filling the holes with black epoxy afterwards.

The plastic on the M28/2.8 seems to be of inferior quality to that on my M50/1.7.

Best of luck.

Sorry, I meant finishing ring, not filter ring.

This 28mm has a bit of an odd history. Effectively it's an A series lens without the "A" position (same as the final batch of M 50mm f2s) according to Dimitrov, which explains the plastic.

I doubt I'll use it much now as I have both K and M versions of the 28mm f3.5, but it would be good to clean it out so I can store it without worrying about other lenses catching the mould. It's likely to live on my new orange ME Super to complete the '80s look.

I have tried a drip of lighter fuel around the finishing ring (which has un-jammed lens fittings in the past). No luck yet! I'll probably get hold of a doorknob of the right size and cover it in sticky foam pads.