SMC Pentax-M Stiff, Very STIFF Aperture Ring

rcolman · 09-11-2018, 05:25 PM

I have a very nice copy of this lens, but the aperture ring is quite stiff and very hard to adjust.

So, I took off the back mounting plate, and, SHAZAMM ! the aperature ring is OK.
Then, I place the mounting ring back on, and it is too tight again.

Once I got the mounting plate, and little shim off, there is no obvious way to adjust or dissasemble from there.

Any guidance, appreciated.

- Troll Rick

**jlstrawman** · 09-11-2018, 06:52 PM

Which SMC Pentax M?

Not a Number · 09-11-2018, 07:01 PM

Obviously something isn't put together right or out of kilter. Check with the lens disassembly database to see if the lens is question is covered. It could lead to clues on how to put it together correctly or where the problem lies.

Pentax Lens Disassembly Database - PentaxForums.com

**Just1MoreDave** · 09-11-2018, 09:48 PM

Usually for the M series, when the mount is off, you can then pull the aperture ring off. But don't do that yet. There is a ball bearing trapped between the ring and the lens body. Usually for the M series, it's where the orange diamond focusing mark is. A spring in the lens body is pushing it against teeth in the aperture ring's inner surface. You can slide the aperture ring off inside a bag so the ball bearing doesn't shoot off into space. They are tough to find after that.

Once you get the ring off, clean up the old dried grease and possibly grit on the ring and lens body. Also the recess for the ball bearing. You don't need to add very much grease back to the ring to get it to work. If you want a lens for video, don't reinstall the bearing, so you can change apertures without a click. Reassemble and it should be fine for another few decades.

rcolman · 09-11-2018, 10:59 PM

Originally posted by jlstrawman

Which SMC Pentax M?

SORRY, SMC Pentax-M 50mm f/1.4

footyphotobeats · 11-26-2018, 08:19 AM

I'm having the same problem with my lens - was there a fix for this? Or do you know what the source of the problem was?

pschlute · 11-26-2018, 01:21 PM

Originally posted by footyphotobeats

I'm having the same problem with my lens - was there a fix for this? Or do you know what the source of the problem was?

Same advice as the original poster got. look up a video for instructions and take the thing apart

stevebrot · 11-26-2018, 01:32 PM

Originally posted by pschlute

Same advice as the original poster got. look up a video for instructions and take the thing apart

...or pay someone to do it for you.

Lens disassembly requires a few special tools, not the least of which is a set of JIS cross-point screwdrivers. The screws on the lens are not Philips-head and use of a Philips screwdriver carries a significant risk of stripping the screw head. The set at the link below are of excellent quality (lifetime warranty) at a decent price too.

JIS Driver Set - iFixit

(...no relation to ifixit or Moody Tools...)

Steve

09-11-2018, 05:25 PM	#1
rcolman Senior Member Join Date: Jul 2016 Photos: Albums Posts: 118	SMC Pentax-M Stiff, Very STIFF Aperture Ring I have a very nice copy of this lens, but the aperture ring is quite stiff and very hard to adjust. So, I took off the back mounting plate, and, SHAZAMM ! the aperature ring is OK. Then, I place the mounting ring back on, and it is too tight again. Once I got the mounting plate, and little shim off, there is no obvious way to adjust or dissasemble from there. Any guidance, appreciated. - Troll Rick

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09-11-2018, 06:52 PM	#2
jlstrawman Site Supporter Join Date: Feb 2010 Location: Midwest US Photos: Gallery Posts: 1,058	Which SMC Pentax M?

09-11-2018, 07:01 PM	#3
Not a Number Moderator Join Date: Mar 2012 Location: Venice, CA Posts: 10,526	Obviously something isn't put together right or out of kilter. Check with the lens disassembly database to see if the lens is question is covered. It could lead to clues on how to put it together correctly or where the problem lies. Pentax Lens Disassembly Database - PentaxForums.com

09-11-2018, 09:48 PM	#4
Just1MoreDave Site Supporter Join Date: Feb 2007 Location: Aurora, CO Photos: Gallery \| Albums Posts: 6,340	Usually for the M series, when the mount is off, you can then pull the aperture ring off. But don't do that yet. There is a ball bearing trapped between the ring and the lens body. Usually for the M series, it's where the orange diamond focusing mark is. A spring in the lens body is pushing it against teeth in the aperture ring's inner surface. You can slide the aperture ring off inside a bag so the ball bearing doesn't shoot off into space. They are tough to find after that. Once you get the ring off, clean up the old dried grease and possibly grit on the ring and lens body. Also the recess for the ball bearing. You don't need to add very much grease back to the ring to get it to work. If you want a lens for video, don't reinstall the bearing, so you can change apertures without a click. Reassemble and it should be fine for another few decades.

09-11-2018, 10:59 PM	#5
rcolman Senior Member Join Date: Jul 2016 Photos: Albums Posts: 118 Original Poster	Originally posted by jlstrawman Which SMC Pentax M? SORRY, SMC Pentax-M 50mm f/1.4

11-26-2018, 08:19 AM	#6
footyphotobeats New Member Join Date: Nov 2018 Posts: 1	I'm having the same problem with my lens - was there a fix for this? Or do you know what the source of the problem was?

11-26-2018, 01:21 PM	#7
pschlute Moderator Loyal Site Supporter Join Date: Mar 2007 Location: Surrey, UK Photos: Gallery Posts: 8,198	Originally posted by footyphotobeats I'm having the same problem with my lens - was there a fix for this? Or do you know what the source of the problem was? Same advice as the original poster got. look up a video for instructions and take the thing apart

11-26-2018, 01:32 PM	#8
stevebrot Otis Memorial Pentaxian Join Date: Mar 2007 Location: Vancouver (USA) Photos: Gallery \| Albums Posts: 42,007	Originally posted by pschlute Same advice as the original poster got. look up a video for instructions and take the thing apart ...or pay someone to do it for you. Lens disassembly requires a few special tools, not the least of which is a set of JIS cross-point screwdrivers. The screws on the lens are not Philips-head and use of a Philips screwdriver carries a significant risk of stripping the screw head. The set at the link below are of excellent quality (lifetime warranty) at a decent price too. JIS Driver Set - iFixit (...no relation to ifixit or Moody Tools...) Steve