For those of you who are interesed I have put together a guide to disassembling the K 28mm F3.5 lens

WARNING: This is a guide based on my NON - EXPERT approach. There might be errors in my method but it worked for me.


1. Pictured below is my work space.

1.1. Blower for removing loose dust particles (~$30 AUD from any camera shop)
1.2. Cotton tips for cleaning nooks and crannies (~$1.50 AUD from any supermarket or pharmacy)
1.3. Isopropyl Alcohol I recommend high grade 90% + (~$15 AUD from hardware store)
1.4. Standard Lens cloth
1.5. Powder free latex gloves (pictured cotton gloves leave fibres) (~$5 AUD from Supermarket)
1.6. Small tool kit (I use a mobile phone repair kit) (~$15-30 AUD from electronic store)
1.7. Soft tea towel to stop parts dropping and bouncing away (~$free from kitchens near you)
1.8. NOT PICTURED: White Synthetic grease, fine soft paint brush, tray for holding loose parts.

2. Ok Lets start by setting the lens to a default position. I go with Aperture f22 to remove tension from spring as shown latter. Focus set to infinity.
3. Now to removing the name plate. A rubber stopper from hardware store will help. My lens came with holes pre-drilled. Remove by turning anti-clock-wise.



4. Undo exposed screws to remove filter thread barrel and lift out.



5. Undo exposed screws to remove focus ring. I suggest you mark the original alignment before removing these screws just so you know the original orientation making reassembly quicker.



6. Now to remove the front lens groups. Twist top section in anti-clock-wise motion, there are a couple of small notches near the arrows if your unable to get a grip.
Pentax K 28 f3.5 disassembly-11962 | Flickr - Photo Sharing!

7. Exposing the front element is shown in the following photos and is done by twisting in directions shown in photos.





8. To get to the back of the front element undo the retaining ring as shown. the second element with come free with a gentle tap, sometimes is a bit of a pain to get out though.





9. Now you have access to all elements surfaces for the purpose of cleaning.

9.1. I personally clean the lenses by using the blower and following with the isopropyl alcohol and cotton tips. being careful not to touch any of the black paint. This should remove any oils and dust particles and sterilise any mould if there were any. I then gently polish the lens surface with a clean lens cloth.

10. Now reassemble the front group in reverse order to prevent dust getting in while you clean the rest of the lens.

11. To get access to the aperture mechanism remove the five screws indicated (yes the lens I received was missing one)



12. WARNING TAKE CARE WITH THIS STEP: You can now remove the aperture ring by sliding it to the rear of the lens, but be careful as the bearing as shown has a tendency to fall out and IT WILL VANISH! I stupidly lost mine and took over 30min of searching to find it.

12.1. If you do lose it I suggest getting a strong magnet and sweeping the area. I used a magnet that tradesmen use to recover tools from wall cavities. They are very strong!!!

13. You can now take the aperture assembly off by undoing the 3 exposed screws. (unfortunately I didn't photograph this step) and for ease of handling you can remove the aperture lever arm (ring) by unhooking the spring as shown.



14. I now cleaned everything down with Isopropyl alcohol to remove dust and old oil as well as cleaning the old grease from the aperture ring. A small paint brush does this quickly.
15. Put a very small dab of white Synthetic grease to re-lubricate the aperture ring and bearing.
16. You can now re-assemble in the reverse order for a nice clean old lens. Which if taken care of correctly will stay that way for many years to come!

Note: It appears the lens had some "loctite" or similar thread locking adhesive on the screws. This is optional when reassembling your lens. I didn't bother but if you choose to I suggest doing so sparingly.

Anyway I hope this helps you get that old lens back to tip top shape! Good luck

[Adam]

Great article! This might also make a fine addition on our homepage, but for now I think I will do a facebook share

[Chaos_Realm]

Cheers Adam,
I am slowly building my courage to tackle the K 50mm f1.2 as it has a couple flecks of dust which annoy me, but I am trying to get the "know how" first. This was just a stepping stone.

[wiseman]

Thank you for the lens disassembly instructions. It will be a great reference tool.


I did have two questions.

1. Is there any chance that the isopropyl alcohol will damage the lens coatings? Can it be used to clean any era Pentax lens?

2. Is white lithium grease OK to use in all lenses including those with plastic components? I ask this because some plastics are adversely affected by certain lubricants. Is this what lens manufacturers use or is there some special grease just for camera lenses?

[Chaos_Realm]

Thanks,
In response to your questions:

1. Is there any chance that the isopropyl alcohol will damage the lens coatings? Can it be used to clean any era Pentax lens?

This can depend on the lens coating. From what I have read, pentaxs' coating isn't susceptible to damage, yet other coatings are and I have seen no obvious signs it does either it was discussed HERE briefly or you can just do a bit of a Google it and you will get heaps of info with mixed opinions. If in doubt I would stick with commercially available lens cleaning solution.

2. Is white lithium grease OK to use in all lenses including those with plastic components? I ask this because some plastics are adversely affected by certain lubricants. Is this what lens manufacturers use or is there some special grease just for camera lenses?

I must apologize for the error in this I am used to Lithium grease which a lot of bits on the farm machinery use. What I recommend is SYNTHETIC GREASE! I used a product called Super Lube, which is a fantastic bicycle lube. it is non corrosive to plastics etc and has temp ranges from -45F to +450F so it will not 'melt' and end up on your aperture blades.

Thanks for bringing that to my attention.

[wiseman]

Is this the grease?



I repaired a zoom lens several years ago and I do not know what grease I used. I might reapply the correct grease to ward off any future problems.

Thanks again for the great article.

[Chaos_Realm]

Is this the grease?

Attachment 131131

I repaired a zoom lens several years ago and I do not know what grease I used. I might reapply the correct grease to ward off any future problems.

Thanks again for the great article.

Yep that's the stuff. I use it on my shogun push bike and it is brilliant stuff.

As for re applying grease, if you did it a few years ago I would think either a) the damage has been done and probably not worth it, or b) the grease was fine.

I personally wouldn't risk the damage/dust/scratching elements etc for re-greasing unless it was giving you trouble, Ie stiff zoom or the like.

[Lloydy]

Very good, clear and informative. Bookmarked for future reference.

[BLACKDRAGON]

This is a great reference as I know I will be doing this job in the future no doubt. Thanks for the very clear and concise explanation.

[vladimiroltean]

Hi. I have a question about this lens, because it's not clear from your presentation:
To gain access to the focus helicoids, do you need to open it only from the rear? I am only used to Takumar M42 lenses, where the access was made from the front, and the filter ring, focus ring, DOF ring and aperture ring were stacked together. In the K mounts, it seems to me that they removed the aperture ring from the bottom of the stack and made a dedicated entrance for it from the other side.
Second, is there just one ball bearing inside? Just to know how many to look for.

[Chaos_Realm]

Hi. I have a question about this lens, because it's not clear from your presentation:
To gain access to the focus helicoids, do you need to open it only from the rear? I am only used to Takumar M42 lenses, where the access was made from the front, and the filter ring, focus ring, DOF ring and aperture ring were stacked together. In the K mounts, it seems to me that they removed the aperture ring from the bottom of the stack and made a dedicated entrance for it from the other side.
Second, is there just one ball bearing inside? Just to know how many to look for.

Tough question this was a while ago. I think from memory it was both. But I didn't actually go as far as cleaning the helicoids.

As for the bearings there was only the one. I think the purpose of it was to give the aperture ring the notch feel for each step.

[Jonathan Mac]

Excellent tutorial. My K 28/3.5 is fine but I have a few other lenses that could benefit from a clean. One day I might work up the courage to do it, and this article will certainly help

[chandu612]

Nice info.

[Bcrary3]

This may or may not be relevant; however if one were to do this on say a Ricoh Rikenon-P 50mm f/2 or 1.7 would it be similar? Also, would it help with a tight/stiff focus throw?

[marquis1955]

Well done !