Addressing a Bent Filter Thread (Pentax 105mm 2.4 SMC)

jchabalk · 04-14-2021, 06:11 PM

On my particular lens it's a small but distinct mark, it must have hit a small solid piece, i'm thinking like a wrought iron fence spike or something similar. It got it pretty much straight on too.

With the small amount that the metal is deformed it got *just* enough of a hit to change the pitch of those threads. total bummer.

I'm going to try to work something out with the seller as otherwise the lens is great. It looks great through the viewfinder but i'm going to run a roll of film through it in the next couple of days before making a final decision.

**ProfessorBuzz** · 04-15-2021, 05:31 AM

I have the Neewer gizmo. It's adequate, not impressive. I picked up a few old 6x7 Taks that were in rough shape. The Neewer expanded out the lens but unfortunately pushed the opposite side out of round into an oval shape. Took some effort to sort it out.
In the end, I sacrificed a step ring to this lens to make it usable. The price is right, use with caution.

jchabalk · 04-15-2021, 01:09 PM

I spent some time last night examining this lens some more and found evidence of other damage. Using a powerful flashlight to look around at it showed me that there was another big dent in the filter ring 180 degrees opposite the first mark. It's basically invisible in regular light but the reflection changes with the flashlight showing the bend.

then looking in towards the threaded section carefully you could see what looks like either the finish being damaged by the bend, or the marks from one of those filter thread repair tools.

So i'm going to walk away from this lens, i contacted the seller with what i found, he's apologetic and is going to accept the return.

I wouldn't have noticed this, and probably wouldn't care so much if the filter ring worked properly - although finding this larger damaged area would have caused me to rethink it a bit.

**Eric Auer** · 04-15-2021, 01:23 PM

Originally posted by jchabalk

I spent some time last night examining this lens some more and found evidence of other damage. Using a powerful flashlight to look around at it showed me that there was another big dent in the filter ring 180 degrees opposite the first mark. It's basically invisible in regular light but the reflection changes with the flashlight showing the bend.

then looking in towards the threaded section carefully you could see what looks like either the finish being damaged by the bend, or the marks from one of those filter thread repair tools.

So i'm going to walk away from this lens, i contacted the seller with what i found, he's apologetic and is going to accept the return.

I wouldn't have noticed this, and probably wouldn't care so much if the filter ring worked properly - although finding this larger damaged area would have caused me to rethink it a bit.

Wonder if the "repair" tool caused that fracture or if it was from the impact that caused the dent...or a bit of both?

Either way, don't think I'll get any of those "tools" anytime soon.

jchabalk · 04-15-2021, 04:11 PM

It seems like it's from the impact. but at the same time it's weird that the 2 dents are almost exactly 180 degrees apart from one another.

With this other bend i found there enough force to deform a full inch + of that heavy aluminum (i assume that's what it is) and to mar the finish due to the amount of flex.

It's a shame, the lens overall still appears to be in great shape, that one event pretty much buggered it though.

jchabalk · 04-30-2021, 02:18 PM

I've got this whole thing sorted out and figured i'd close this thread out.

The seller took back the lens (and refunded shipping both ways), i was a bit nervous about this but they did the right thing given the situation, so i'm satisfied. I took a bet on another lens from a different seller, it actually arrived just a couple of days before my return was processed so for a few days there i technically owned 2 of them.

This new one has no such hidden issues - at least that i've been able to find. This morning i had a chance to run a roll of film past it and i can definitely see the appeal. I think the first one i had had been knocked out of whack with that barrel hit. I had put a roll through it but the images lacked the sharpness that i'm seeing out of this copy. I posted a couple of images in the Post Your Photos thread

**RICHARD L.** · 04-30-2021, 02:40 PM - **1 Like**

This P67 105 mm f/2.4 lens is "crazy-sharp", particularly on a 645Z.

jchabalk · 04-30-2021, 05:14 PM

The images i shot today are razer sharp. When i saw them fresh out of the rinse i was really glad i'd returned the other lens (as i'd considered keeping it)

johnha · 04-30-2021, 10:59 PM - **1 Like**

I acquired a 6x7 45mm with an oval filter thread (no other apparent damage). I had a huge struggle removing the filter which is when I realised the problem. I haven't been able to fit another filter, but will try a step up ring for more leverage.

I also worried about how it could become deformed, but there was no other damage to indicating any fall. I now suspect a filter repair tool may be the cause.

In my case I got a discount having found the lens to be Ok in all other respects with no obvious IQ issues.

**Eric Auer** · 05-01-2021, 04:59 AM

Originally posted by johnha

I acquired a 6x7 45mm with an oval filter thread (no other apparent damage). I had a huge struggle removing the filter which is when I realised the problem. I haven't been able to fit another filter, but will try a step up ring for more leverage.

I also worried about how it could become deformed, but there was no other damage to indicating any fall. I now suspect a filter repair tool may be the cause.

In my case I got a discount having found the lens to be Ok in all other respects with no obvious IQ issues.

Are you sure it's oval? Did you measure it?

You can trace the front of the lens to a piece of paper and measure that. Sometimes filters are just stuck on hard, for various reasons.

johnha · 05-01-2021, 06:59 AM

Originally posted by Eric Auer

Are you sure it's oval? Did you measure it?

You can trace the front of the lens to a piece of paper and measure that. Sometimes filters are just stuck on hard, for various reasons.

I haven't measured it, perhaps I should, but a new (presumably round) filter won't go on. I haven't really tried to force it but a step up ring as mentioned above might help.

**kaseki** · 05-01-2021, 07:59 AM

I think that the issue with this thread repair tool is that for any significant damage, the lens body has to be restrained against the tool. Conceptually to achieve this the user must first take two hunks of e.g., aluminum that have flat faces that mate together. Drill and tap so that the pieces can be locked together with bolts outside the diameter of the lens. Then bore this assembly out to the diameter of the lens body at the filter thread* such that the two pieces can be clamped against the lens with some masking tape on the lens. Now the thread repair tool has something to react against and the lens should remain cylindrical at the thread. I doubt that this will be cost effective at nominal wage rates unless one is starting a business of thread repair.

*Some lens bodies won't have much smooth cylindrical space at this point and may require a more complex boring pattern to provide enough support. The thread tool doesn't look like it provides much overhang allowance.

**Eric Auer** · 05-01-2021, 10:13 AM

Instead of being a spreader design the tool should just be a clamp with various diameter inserts that can restore a radius.

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04-14-2021, 06:11 PM	#16
jchabalk Junior Member Join Date: Apr 2021 Posts: 29 Original Poster	On my particular lens it's a small but distinct mark, it must have hit a small solid piece, i'm thinking like a wrought iron fence spike or something similar. It got it pretty much straight on too. With the small amount that the metal is deformed it got just enough of a hit to change the pitch of those threads. total bummer. I'm going to try to work something out with the seller as otherwise the lens is great. It looks great through the viewfinder but i'm going to run a roll of film through it in the next couple of days before making a final decision.

04-15-2021, 05:31 AM	#17
ProfessorBuzz Loyal Site Supporter Join Date: Feb 2018 Posts: 1,903	I have the Neewer gizmo. It's adequate, not impressive. I picked up a few old 6x7 Taks that were in rough shape. The Neewer expanded out the lens but unfortunately pushed the opposite side out of round into an oval shape. Took some effort to sort it out. In the end, I sacrificed a step ring to this lens to make it usable. The price is right, use with caution.

04-15-2021, 01:23 PM	#19
Eric Auer Site Supporter Join Date: Jul 2012 Photos: Gallery Posts: 1,211	Originally posted by jchabalk I spent some time last night examining this lens some more and found evidence of other damage. Using a powerful flashlight to look around at it showed me that there was another big dent in the filter ring 180 degrees opposite the first mark. It's basically invisible in regular light but the reflection changes with the flashlight showing the bend. then looking in towards the threaded section carefully you could see what looks like either the finish being damaged by the bend, or the marks from one of those filter thread repair tools. So i'm going to walk away from this lens, i contacted the seller with what i found, he's apologetic and is going to accept the return. I wouldn't have noticed this, and probably wouldn't care so much if the filter ring worked properly - although finding this larger damaged area would have caused me to rethink it a bit. Wonder if the "repair" tool caused that fracture or if it was from the impact that caused the dent...or a bit of both? Either way, don't think I'll get any of those "tools" anytime soon.

04-15-2021, 04:11 PM	#20
jchabalk Junior Member Join Date: Apr 2021 Posts: 29 Original Poster	It seems like it's from the impact. but at the same time it's weird that the 2 dents are almost exactly 180 degrees apart from one another. With this other bend i found there enough force to deform a full inch + of that heavy aluminum (i assume that's what it is) and to mar the finish due to the amount of flex. It's a shame, the lens overall still appears to be in great shape, that one event pretty much buggered it though.

04-30-2021, 02:18 PM	#21
jchabalk Junior Member Join Date: Apr 2021 Posts: 29 Original Poster	I've got this whole thing sorted out and figured i'd close this thread out. The seller took back the lens (and refunded shipping both ways), i was a bit nervous about this but they did the right thing given the situation, so i'm satisfied. I took a bet on another lens from a different seller, it actually arrived just a couple of days before my return was processed so for a few days there i technically owned 2 of them. This new one has no such hidden issues - at least that i've been able to find. This morning i had a chance to run a roll of film past it and i can definitely see the appeal. I think the first one i had had been knocked out of whack with that barrel hit. I had put a roll through it but the images lacked the sharpness that i'm seeing out of this copy. I posted a couple of images in the Post Your Photos thread

04-30-2021, 02:40 PM - 1 Like	#22
RICHARD L. Loyal Site Supporter Join Date: Oct 2018 Location: Quebec City, Quebec Posts: 6,582	This P67 105 mm f/2.4 lens is "crazy-sharp", particularly on a 645Z.

04-30-2021, 05:14 PM	#23
jchabalk Junior Member Join Date: Apr 2021 Posts: 29 Original Poster	The images i shot today are razer sharp. When i saw them fresh out of the rinse i was really glad i'd returned the other lens (as i'd considered keeping it)

04-30-2021, 10:59 PM - 1 Like	#24
johnha Veteran Member Join Date: Apr 2012 Location: Lancashire, UK Photos: Albums Posts: 1,155	I acquired a 6x7 45mm with an oval filter thread (no other apparent damage). I had a huge struggle removing the filter which is when I realised the problem. I haven't been able to fit another filter, but will try a step up ring for more leverage. I also worried about how it could become deformed, but there was no other damage to indicating any fall. I now suspect a filter repair tool may be the cause. In my case I got a discount having found the lens to be Ok in all other respects with no obvious IQ issues.

05-01-2021, 04:59 AM	#25
Eric Auer Site Supporter Join Date: Jul 2012 Photos: Gallery Posts: 1,211	Originally posted by johnha I acquired a 6x7 45mm with an oval filter thread (no other apparent damage). I had a huge struggle removing the filter which is when I realised the problem. I haven't been able to fit another filter, but will try a step up ring for more leverage. I also worried about how it could become deformed, but there was no other damage to indicating any fall. I now suspect a filter repair tool may be the cause. In my case I got a discount having found the lens to be Ok in all other respects with no obvious IQ issues. Are you sure it's oval? Did you measure it? You can trace the front of the lens to a piece of paper and measure that. Sometimes filters are just stuck on hard, for various reasons.

05-01-2021, 06:59 AM	#26
johnha Veteran Member Join Date: Apr 2012 Location: Lancashire, UK Photos: Albums Posts: 1,155	Originally posted by Eric Auer Are you sure it's oval? Did you measure it? You can trace the front of the lens to a piece of paper and measure that. Sometimes filters are just stuck on hard, for various reasons. I haven't measured it, perhaps I should, but a new (presumably round) filter won't go on. I haven't really tried to force it but a step up ring as mentioned above might help.

05-01-2021, 07:59 AM	#27
kaseki Loyal Site Supporter Join Date: Dec 2017 Photos: Gallery \| Albums Posts: 1,138	I think that the issue with this thread repair tool is that for any significant damage, the lens body has to be restrained against the tool. Conceptually to achieve this the user must first take two hunks of e.g., aluminum that have flat faces that mate together. Drill and tap so that the pieces can be locked together with bolts outside the diameter of the lens. Then bore this assembly out to the diameter of the lens body at the filter thread* such that the two pieces can be clamped against the lens with some masking tape on the lens. Now the thread repair tool has something to react against and the lens should remain cylindrical at the thread. I doubt that this will be cost effective at nominal wage rates unless one is starting a business of thread repair. *Some lens bodies won't have much smooth cylindrical space at this point and may require a more complex boring pattern to provide enough support. The thread tool doesn't look like it provides much overhang allowance.

05-01-2021, 10:13 AM	#28
Eric Auer Site Supporter Join Date: Jul 2012 Photos: Gallery Posts: 1,211	Instead of being a spreader design the tool should just be a clamp with various diameter inserts that can restore a radius.