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06-01-2018, 10:05 PM   #1
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Dumb thing I just did to my M 35/2.8

So, yes, this is a new low...

My copy is suffering from a sluggish aperture closing/opening (it is not the blades, it is 99% sure some kind of grease/residue on the mechanism). So in order to clean it I must access it from the back:

Well, the back screws are just too damn tight! They won't budge... So I researched the topic - tried a rubber band to the head, nope; tried different JIS sizes, nope... then I decided to try and heat a screw with a soldering iron... I read that you should really let the screw cool off after heating it. I did not do that; I went for it while it was hot. The result?



Yes, that screw to the right basically has the tip of my JIS 00 screw driver adhered to it! The thing just tored my JIS screwdriver and ate it!

Few things that annoy me - I know my JIS set is cheap, so I ordered a rather good one today on the web. I obviously did not get it yet, but decided that I was bored enough to give this idea a try, rather than just wait for the quality tool.

Now, can anyone suggest an option? It really irks me that I would have to send the lens somewhere to be treated - I have cleaned slow apertures on other prime lenses before, it is rather easy to do (did it recently to a 50/1.8 Zuiko "Japan", which is also notorious for this). By mid June I am sending Eric a Spotmatic and my ME Super for CLA; is this my last resort?

Some info on how bad the aperture on the lens currently is - I really cannot use it on a DSLR at f8 or above (hence, wide open or other wide apertures would work OK).

06-01-2018, 11:37 PM - 1 Like   #2
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Ouch! I wonder if whatever's causing the aperture blades to be slow is also causing the screws to be tight. I would personally send this lens off.

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06-02-2018, 01:39 AM   #3
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Drill out the heads?
Never had a piece of m glass get stuck like that.
06-02-2018, 04:26 AM - 2 Likes   #4
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You're either have to send to someone for repair or invest in screw extractors and extractor drill bits.

Moody Screw Extractor & Screw- driver, Mini, Aluminum, 6 Pc ? Micro-Tools
Left Hand Drill Bit 0.8mm (screw extractor) ? Micro-Tools

The most commonly used screw size on Pentax equipment is M1.5 (1.5mm diameter). Length depends on the application but you can measure one of the other screws. Moody Tools will sell the extractors singly - try them direct or on eBay. Search the internet for "micro screws" or Pentax forums for links to several sources of M1.5 screws.

If the lens is used it is possible a previous owner attempted a fix and stripped the screws out and glued them. If that's the case the only repair alternative is to drill off the screw heads, drill out the old screws and re-tap the threads. Usually with a larger diameter say 2mm.

Or just buy another copy of the lens.

06-02-2018, 08:12 AM - 1 Like   #5
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I have encountered similar tight screws on several Pentax-M mounts. Here's my track record:

- Lens A: 3 of 5 screws removed no problem. Soaked 2 in 'deep' penetrating oil. One of those freed up. On the last one, the star head was deformed ('ground out') by my JIS screwdriver... just a bit too much force on my part. I ended up using my smallest Dremel bit to grind out a slot for a common screwdriver -- success. I had spare screws from another sacrificial Pentax lens.

- Lens B: One screw was solid. Applied 25 watt soldering iron and managed to tease it out unharmed.

- Lens C: Similar to Lens A, except nothing worked. Drilled out the two screw heads on my drill press (sacrificing the mount), but their shanks remained with very small stubs. I'll need to get those Moody micro-extractors for the next attack.
06-02-2018, 08:49 AM   #6
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You might try knocking out the stuck bit of your screwdriver with an automatic center punch. Like a Starrett 18c type.
On some tough screws (Not on camera lenses) a couple quick hits with the center punch in the middle of the screw will
"release" it. This is my experience on industrial equipment with small fasteners, and not lenses though.
06-02-2018, 08:50 AM   #7
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Original Poster
QuoteOriginally posted by Not a Number Quote
Moody Tools will sell the extractors singly - try them direct or on eBay. Search the internet for "micro screws" or Pentax forums for links to several sources of M1.5 screws.
Thanks for this info.

---------- Post added 06-02-18 at 11:54 AM ----------

QuoteOriginally posted by c.a.m Quote
Dremel
might have to acquire one of these... thanks
06-02-2018, 09:48 AM   #8
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The broken screwdriver piece should release fairly easily I would have though.
Try aligning the broken screwdriver back to the broken part, press and turn slightly anticlockwise.
If that fails, do the iron trick again and tap the mount adjacent to the screw head to try and bounce it out.
Adding a tiny amount of super glue to the screwdriver might also work, repeating the first attempt.
Good luck anyway.

06-03-2018, 07:40 AM   #9
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Use lubricating spray?
06-03-2018, 08:38 AM   #10
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Try tapping around it while holding a powerful magnet over it ?
06-03-2018, 09:04 AM - 1 Like   #11
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QuoteOriginally posted by Not a Number Quote
Or just buy another copy of the lens.
Which will probably have sluggish blades. I have 2 copies of the M 35/2.8 and both have sluggish blades...
06-03-2018, 11:33 AM   #12
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QuoteOriginally posted by boriscleto Quote
Which will probably have sluggish blades. I have 2 copies of the M 35/2.8 and both have sluggish blades...
Yep, this is my fear.

I love my copy, it is ultra sharp! I love how close you can get to your subject too.
06-03-2018, 03:39 PM - 1 Like   #13
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Every SMC Pentax -M or -A 35/2.8 lens I have owned eventually had sticky aperture blades.

Email Eric that photo and ask if he can remove the screw. If so send him the lens for service.
FWIW that's what I would have done in the first place, and I once did this for a living...

Chris
06-03-2018, 05:33 PM   #14
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QuoteOriginally posted by ChrisPlatt Quote
FWIW that's what I would have done in the first place
Yep, I reckon now...

thanks for the advise.
06-05-2018, 08:08 AM   #15
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I reckon you just cut the aperture tab of it and turn it into a stop down green button lens
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