Tight fitting Pentax-M 50mm f 1.7?

photoptimist · 11-27-2017, 05:34 PM

Originally posted by ZombieArmy

I thought it was common sense to stop using a lens that requires 6x the force to mount onto the camera. The thread is for causes and possible solutions, not to tell me to call it all a loss "because it doesn't cost much".

We are trying to offer causes and solutions which may include the solution of not using that lens.

Note: if the lens is scuffing the front of the mount, it's also potentially damaging the back-side of the camera's bayonet tabs.

EarlVonTapia · 11-27-2017, 05:35 PM

Originally posted by ZombieArmy

The thread is for causes and possible solutions, not to tell me to call it all a loss "because it doesn't cost much".

The most likely causes were identified. pschlute provided a solution (toss it and get another one), and he even provided a reason (they ARE cheap and plentiful). Therefore pschlute was on point.

stevebrot · 11-27-2017, 05:42 PM

By any chance do you have the auction number or a link to the auction page?

Steve

**17dew** · 11-27-2017, 05:43 PM

Originally posted by ZombieArmy

That's the thing. When compared to my other M lens it looks no different at all. .

All the screws on the lens mount are tight and recessed as they should be?

ZombieArmy · 11-27-2017, 06:26 PM

Originally posted by 17dew

All the screws on the lens mount are tight and recessed as they should be?

Yeah the screws look like they're the same as my 200 m. No play in the mount either

**c.perkins** · 11-27-2017, 07:13 PM

Look at all three locking lugs and see if one is bent.
Good luck to you.

**GUB** · 11-27-2017, 10:41 PM

Can you find a dead old film body that you can unscrew the mount off? That way you can get a good look at what is catching. Great little mystery - let us know what you find out.

leekil · 11-28-2017, 12:38 AM

If you have another lens which has other types of issues, you could possibly remove the lens mount from that and put it on the 50 1.7.

sqrrl · 11-28-2017, 03:13 AM - **1 Like**

Get a vernier gauge with a lock on it - they are cheap and super useful - even some calipers with a lock - then compare them by feel, check the diameter and the depth of the mount, you will find a difference between this and a good mount. Get the measurement, lock it, and then move it to get a feel of where the fault is.

If it is in the measurement across the shaft of the mount then toss the lens, it's been crushed from the side - else if it is in the depth of the mount then look at how much is is and see whether you could reduce or shift the offending bit of metal.

0.2 of a mm will be enough to bind up a mount totally, and with brass fittings that could be caused by dropping it on it's mount end. Also look at the screws, if they are marred at all then it's probably been taken apart and put back together wrong.

It could be a range of things and still be visually ok, Measuring it precisely will tell you where the problem is, and give a hint as to how to fix it.

No matter what is wrong, you will probably not have an optically optimal lens, keep that in mind.

If you force it so it works, you risk screwing up your mount so that your mount is bad with every other lens you own.

ZombieArmy · 11-28-2017, 10:26 AM

Originally posted by dcshooter

I'd check to make sure all of the screws are fully tightened down, then if one of the tangs on the bayonet is bent upward.

If you don't want to shell out for a whole new lens, the mounts on Pentax M and K lenses are all completely interchangeable, so if you can find someone willing to sell you the part or a donor lens cheaply, it's easy enough to switch out.

Here are some pictures of the lens:

https://puu.sh/yvibY/2c12708f7b.jpg
https://puu.sh/yvidH/0ffe8ce456.jpg
https://puu.sh/yvifs/6ece41fd3f.jpg

The only thing I can see is a slight crack in the black plastic next to the metal mount. The screws seem to be in tight. If you'd want any other pics let me know.

The seller of the lens also fully refunded me and told me to keep the lens. So fixing it will be a bit of an experience for me to understand these lenses better.

If there's no obvious problem I'll probably look for a new lens mount.

Not a Number · 11-28-2017, 10:43 AM

Nothing obvious from the photos you posted. Get a nice set of JIS drivers and remove the bayonet and try mounting it on the camera. Maybe can see where it is binding that way.

leekil · 11-28-2017, 10:52 AM

A photo of the bayonet from the side might reveal any bent bayonet flanges, but I think that might be a difficult photo to take. The Vernier gauge suggestion would probably be a more useful diagnostic, though not everyone has one of those available.

Not a Number · 11-28-2017, 02:30 PM

Originally posted by leekil

A photo of the bayonet from the side might reveal any bent bayonet flanges, but I think that might be a difficult photo to take. The Vernier gauge suggestion would probably be a more useful diagnostic, though not everyone has one of those available.

A wooden kitchen matchstick would do the trick. They are about the right thickness for the space on tabs. Using the good lens as a guide find one that is slightly thicker and force it in to compress it (soft wood) or shave it down to fit. Or if it is slightly thinner wrap some sticky cello tape around it.

stevebrot · 11-28-2017, 03:15 PM

Originally posted by ZombieArmy

The only thing I can see is a slight crack in the black plastic next to the metal mount.

The lens has been dropped or at least banged badly and something is fishy with a couple of the screw heads; they don't look quite like the others. The plating is also worn off a section of the flange adjacent to one of the strange looking heads.

Glad you got a refund though. With any luck you can resolve the mount issue with other damage limited to the plastic collar.

Steve

jddwoods · 11-28-2017, 05:28 PM

Originally posted by stevebrot

The lens has been dropped or at least banged badly and something is fishy with a couple of the screw heads; they don't look quite like the others. The plating is also worn off a section of the flange adjacent to one of the strange looking heads.

Glad you got a refund though. With any luck you can resolve the mount issue with other damage limited to the plastic collar.

Steve

I agree, the third picture looks like the screws on the left side are partially stripped and the mount is scuffed. It is a good thing you (OP) got your money back. I bought a used ME super a year ago at a charity flea market. The camera was beyond repair but it had the same M 50mm f1.7. Mine mounts as easily and smoothly as any other lens on my K-5 and K-3 bodies. I am sure yours has some hidden damage likely from being dropped.

Similar Threads
Thread	Thread Starter	Forum	Replies	Last Post
Fungus and fitting Pentax M and Pentax-A lenses on Pentax MZ S body?	RustyT	Film SLRs and Compact Film Cameras	5	02-16-2018 05:43 AM
Tight fitting M42 adapter - suggestions?	6BQ5	Pentax DSLR Discussion	5	05-26-2017 07:20 PM
Pentax 70-200 not fitting on tripod	kellys	Troubleshooting and Beginner Help	8	01-28-2017 11:44 AM
Fitting a SMC Takumar 50mm to a K-r	jamesd256	Troubleshooting and Beginner Help	6	02-01-2012 09:46 PM
Help with fitting 6x7 lens to K fitting	Mick C	Pentax Medium Format	5	02-04-2011 02:37 PM

11-27-2017, 05:34 PM	#16
photoptimist Pentaxian Join Date: Jul 2016 Photos: Albums Posts: 5,121	Originally posted by ZombieArmy I thought it was common sense to stop using a lens that requires 6x the force to mount onto the camera. The thread is for causes and possible solutions, not to tell me to call it all a loss "because it doesn't cost much". We are trying to offer causes and solutions which may include the solution of not using that lens. Note: if the lens is scuffing the front of the mount, it's also potentially damaging the back-side of the camera's bayonet tabs.

11-27-2017, 05:35 PM	#17
EarlVonTapia Veteran Member Join Date: Oct 2012 Location: Vancouver Photos: Gallery Posts: 1,207	Originally posted by ZombieArmy The thread is for causes and possible solutions, not to tell me to call it all a loss "because it doesn't cost much". The most likely causes were identified. pschlute provided a solution (toss it and get another one), and he even provided a reason (they ARE cheap and plentiful). Therefore pschlute was on point.

11-27-2017, 05:42 PM	#18
stevebrot Otis Memorial Pentaxian Join Date: Mar 2007 Location: Vancouver (USA) Photos: Gallery \| Albums Posts: 42,007	By any chance do you have the auction number or a link to the auction page? Steve

11-27-2017, 05:43 PM	#19
17dew Loyal Site Supporter Join Date: Mar 2008 Location: Ohio Photos: Gallery Posts: 1,822	Originally posted by ZombieArmy That's the thing. When compared to my other M lens it looks no different at all. . All the screws on the lens mount are tight and recessed as they should be?

11-27-2017, 06:26 PM	#20
ZombieArmy Pentaxian Join Date: Jun 2014 Location: Florida Posts: 3,210 Original Poster	Originally posted by 17dew All the screws on the lens mount are tight and recessed as they should be? Yeah the screws look like they're the same as my 200 m. No play in the mount either

11-27-2017, 07:13 PM	#21
c.perkins Loyal Site Supporter Join Date: Jun 2017 Location: New Lisbon, WI. Photos: Gallery \| Albums Posts: 515	Look at all three locking lugs and see if one is bent. Good luck to you.

11-27-2017, 10:41 PM	#22
GUB Loyal Site Supporter Join Date: Aug 2012 Location: Wanganui Photos: Gallery \| Albums Posts: 5,757	Can you find a dead old film body that you can unscrew the mount off? That way you can get a good look at what is catching. Great little mystery - let us know what you find out.

11-28-2017, 12:38 AM	#23
leekil Pentaxian Join Date: May 2016 Photos: Albums Posts: 2,003	If you have another lens which has other types of issues, you could possibly remove the lens mount from that and put it on the 50 1.7.

11-28-2017, 03:13 AM - 1 Like	#24
sqrrl Veteran Member Join Date: Mar 2017 Location: Otago, New Zealand Posts: 422	Get a vernier gauge with a lock on it - they are cheap and super useful - even some calipers with a lock - then compare them by feel, check the diameter and the depth of the mount, you will find a difference between this and a good mount. Get the measurement, lock it, and then move it to get a feel of where the fault is. If it is in the measurement across the shaft of the mount then toss the lens, it's been crushed from the side - else if it is in the depth of the mount then look at how much is is and see whether you could reduce or shift the offending bit of metal. 0.2 of a mm will be enough to bind up a mount totally, and with brass fittings that could be caused by dropping it on it's mount end. Also look at the screws, if they are marred at all then it's probably been taken apart and put back together wrong. It could be a range of things and still be visually ok, Measuring it precisely will tell you where the problem is, and give a hint as to how to fix it. No matter what is wrong, you will probably not have an optically optimal lens, keep that in mind. If you force it so it works, you risk screwing up your mount so that your mount is bad with every other lens you own.

11-28-2017, 10:26 AM	#25
ZombieArmy Pentaxian Join Date: Jun 2014 Location: Florida Posts: 3,210 Original Poster	Originally posted by dcshooter I'd check to make sure all of the screws are fully tightened down, then if one of the tangs on the bayonet is bent upward. If you don't want to shell out for a whole new lens, the mounts on Pentax M and K lenses are all completely interchangeable, so if you can find someone willing to sell you the part or a donor lens cheaply, it's easy enough to switch out. Here are some pictures of the lens: https://puu.sh/yvibY/2c12708f7b.jpg https://puu.sh/yvidH/0ffe8ce456.jpg https://puu.sh/yvifs/6ece41fd3f.jpg The only thing I can see is a slight crack in the black plastic next to the metal mount. The screws seem to be in tight. If you'd want any other pics let me know. The seller of the lens also fully refunded me and told me to keep the lens. So fixing it will be a bit of an experience for me to understand these lenses better. If there's no obvious problem I'll probably look for a new lens mount.

Thread Tools	Search this Thread
	Search this Thread: Advanced Search

11-28-2017, 10:43 AM	#26
Not a Number Moderator Join Date: Mar 2012 Location: Venice, CA Posts: 10,526	Nothing obvious from the photos you posted. Get a nice set of JIS drivers and remove the bayonet and try mounting it on the camera. Maybe can see where it is binding that way.

11-28-2017, 10:52 AM	#27
leekil Pentaxian Join Date: May 2016 Photos: Albums Posts: 2,003	A photo of the bayonet from the side might reveal any bent bayonet flanges, but I think that might be a difficult photo to take. The Vernier gauge suggestion would probably be a more useful diagnostic, though not everyone has one of those available.

11-28-2017, 02:30 PM	#28
Not a Number Moderator Join Date: Mar 2012 Location: Venice, CA Posts: 10,526	Originally posted by leekil A photo of the bayonet from the side might reveal any bent bayonet flanges, but I think that might be a difficult photo to take. The Vernier gauge suggestion would probably be a more useful diagnostic, though not everyone has one of those available. A wooden kitchen matchstick would do the trick. They are about the right thickness for the space on tabs. Using the good lens as a guide find one that is slightly thicker and force it in to compress it (soft wood) or shave it down to fit. Or if it is slightly thinner wrap some sticky cello tape around it.

11-28-2017, 03:15 PM	#29
stevebrot Otis Memorial Pentaxian Join Date: Mar 2007 Location: Vancouver (USA) Photos: Gallery \| Albums Posts: 42,007	Originally posted by ZombieArmy The only thing I can see is a slight crack in the black plastic next to the metal mount. The lens has been dropped or at least banged badly and something is fishy with a couple of the screw heads; they don't look quite like the others. The plating is also worn off a section of the flange adjacent to one of the strange looking heads. Glad you got a refund though. With any luck you can resolve the mount issue with other damage limited to the plastic collar. Steve

11-28-2017, 05:28 PM	#30
jddwoods Pentaxian Join Date: Nov 2012 Location: Newark, Delaware Posts: 1,035	Originally posted by stevebrot The lens has been dropped or at least banged badly and something is fishy with a couple of the screw heads; they don't look quite like the others. The plating is also worn off a section of the flange adjacent to one of the strange looking heads. Glad you got a refund though. With any luck you can resolve the mount issue with other damage limited to the plastic collar. Steve I agree, the third picture looks like the screws on the left side are partially stripped and the mount is scuffed. It is a good thing you (OP) got your money back. I bought a used ME super a year ago at a charity flea market. The camera was beyond repair but it had the same M 50mm f1.7. Mine mounts as easily and smoothly as any other lens on my K-5 and K-3 bodies. I am sure yours has some hidden damage likely from being dropped.