Exakta to M42 conversion

IgorZ · 04-01-2019, 12:39 PM

I would like to convert a lens from exakta to M42 mount. I am aware that exakta register distance is shorter, so I won't get infinity focus. Also, the lens is valuable, so I don't want to shave off the mount.

I just want to glue the m39 ring over the exakta mount and wonder which glue I should use. I would like the conversion to be both secure and reversible. Is epoxy something I should use?

vonBaloney · 04-01-2019, 01:30 PM

I've done it. Plain superglue (cyanoacrylate) works fine for metal on metal (gel type might be easier to apply and set up), and can be dissolved with acetone (nail polish remover). (Keep acetone away from plastic.) Some people worry about fogging the lens with glue fumes, but it won't as long as you are careful and do it in a well-ventilated area (it dries in minutes, but you should leave it in open air for a good while to really cure). Epoxy would be more permanent I think.

IgorZ · 04-01-2019, 02:17 PM

Originally posted by vonBaloney

I've done it. Plain superglue (cyanoacrylate) works fine for metal on metal (gel type might be easier to apply and set up), and can be dissolved with acetone (nail polish remover). (Keep acetone away from plastic.) Some people worry about fogging the lens with glue fumes, but it won't as long as you are careful and do it in a well-ventilated area (it dries in minutes, but you should leave it in open air for a good while to really cure). Epoxy would be more permanent I think.

OK, thanks! So did you glue the m39 ring directly to the mount base, or did you put something in between, like tape?

**boriscleto** · 04-01-2019, 02:29 PM

ANNOUNCING: Easy cheap non-destructive Exakta-Pentax adapter

**Lowell Goudge** · 04-01-2019, 03:10 PM

Originally posted by vonBaloney

I've done it. Plain superglue (cyanoacrylate) works fine for metal on metal (gel type might be easier to apply and set up), and can be dissolved with acetone (nail polish remover). (Keep acetone away from plastic.) Some people worry about fogging the lens with glue fumes, but it won't as long as you are careful and do it in a well-ventilated area (it dries in minutes, but you should leave it in open air for a good while to really cure). Epoxy would be more permanent I think.

Be careful thenvapors can attackmlens coatings

I had this issue remounting a loose prism in a pair of binoculars

IgorZ · 04-02-2019, 11:16 AM

Originally posted by boriscleto

ANNOUNCING: Easy cheap non-destructive Exakta-Pentax adapter

thanks! I tried using Elmer's glue-all, but the lens is hefty, probably at least 500 gr, so that glue wasn't strong enough... The M39 ring came off pretty easily, which I would want to avoid.

---------- Post added 04-02-19 at 11:17 AM ----------

Originally posted by Lowell Goudge

Be careful thenvapors can attackmlens coatings

I had this issue remounting a loose prism in a pair of binoculars

thanks, I guess doing it under the kitchen fan should help?

vonBaloney · 04-02-2019, 12:42 PM

Yeah, you wouldn't want to use superglue internally unless all the glass was out and it had a long time to cure, but around the mount, I would cover up the glass with something so you don't accidentally touch it and then just yeah, keep the air flowing, let it dry overnight, it will be fine. I haven't glued rings like this a lot, but I have used superglue probably a dozen times to glue down aperture pins on the mounts of m42 lenses that didn't have a switch where I didn't want to take it apart to modify it. Never had a problem with the vapors hurting the glass.

IgorZ · 04-03-2019, 10:03 AM

Originally posted by vonBaloney

Yeah, you wouldn't want to use superglue internally unless all the glass was out and it had a long time to cure, but around the mount, I would cover up the glass with something so you don't accidentally touch it and then just yeah, keep the air flowing, let it dry overnight, it will be fine. I haven't glued rings like this a lot, but I have used superglue probably a dozen times to glue down aperture pins on the mounts of m42 lenses that didn't have a switch where I didn't want to take it apart to modify it. Never had a problem with the vapors hurting the glass.

Well, I glued the adapter last night. We'll see how it works...

By the way, I came across an Exakta to M42 adapter on Amazon. Works basically the same way - just a ring with 3 screws. It doesn't say anything about infinity focus, but I assume there won't be infinity focus with this set up... Delivery was from China and would take up to 2 months, so I went for the glue instead.

stevebrot · 04-03-2019, 12:13 PM

Originally posted by boriscleto

ANNOUNCING: Easy cheap non-destructive Exakta-Pentax adapter

You just have to love Rio Rico! His approach will work and the only notes of caution might be the intrusion of the Exakta bayonet into the mirror box and interference of the aperture stop-down extension (found on most Exakta-mount lenses) with both installation of the adapter and mounting to the camera.

The matter of the stop-down mechanism is rather complicated to explain. It is probably enough to say that the position of the extension must be accounted for when cementing the M39 thread in place and that even if properly offset, it may have a boss on the underside that will not clear the mount face on a K-mount body. Because of this, most adapter solutions are limited to manual and pre-set aperture Exakta lenses.

Steve

(...would very much like to flex my Exakta lenses to my Pentax bodies...)

stevebrot · 04-03-2019, 12:25 PM

Originally posted by IgorZ

By the way, I came across an Exakta to M42 adapter on Amazon. Works basically the same way - just a ring with 3 screws. It doesn't say anything about infinity focus, but I assume there won't be infinity focus with this set up... Delivery was from China and would take up to 2 months, so I went for the glue instead.

The grub-screw eBay adapter is sort of hokey in that it is designed for the grub screws to wedge under the Exakta mount tangs to hold the adapter in place. I would not use it with a lens having any value.

Steve

stevebrot · 04-03-2019, 12:35 PM

...Another quick note. M42 adapted Exakta/Topcon lenses will not work on M42 bodies having the aperture actuator "flipper". The lens intrudes too deeply to clear the flipper such that the flipper/mirror/shutter sequence is interrupted leaving the camera in an indeterminant state.

Steve

IgorZ · 04-04-2019, 07:44 PM

Originally posted by stevebrot

The grub-screw eBay adapter is sort of hokey in that it is designed for the grub screws to wedge under the Exakta mount tangs to hold the adapter in place. I would not use it with a lens having any value.

Steve

Thanks for the heads up. I was planning to get one...

04-01-2019, 12:39 PM	#1
IgorZ Veteran Member Join Date: Aug 2015 Location: Ottawa Posts: 1,735	Exakta to M42 conversion I would like to convert a lens from exakta to M42 mount. I am aware that exakta register distance is shorter, so I won't get infinity focus. Also, the lens is valuable, so I don't want to shave off the mount. I just want to glue the m39 ring over the exakta mount and wonder which glue I should use. I would like the conversion to be both secure and reversible. Is epoxy something I should use?

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04-01-2019, 01:30 PM	#2
vonBaloney Pentaxian Join Date: Oct 2011 Location: Albuquerque, NM Posts: 6,029	I've done it. Plain superglue (cyanoacrylate) works fine for metal on metal (gel type might be easier to apply and set up), and can be dissolved with acetone (nail polish remover). (Keep acetone away from plastic.) Some people worry about fogging the lens with glue fumes, but it won't as long as you are careful and do it in a well-ventilated area (it dries in minutes, but you should leave it in open air for a good while to really cure). Epoxy would be more permanent I think.

04-01-2019, 02:17 PM	#3
IgorZ Veteran Member Join Date: Aug 2015 Location: Ottawa Posts: 1,735 Original Poster	Originally posted by vonBaloney I've done it. Plain superglue (cyanoacrylate) works fine for metal on metal (gel type might be easier to apply and set up), and can be dissolved with acetone (nail polish remover). (Keep acetone away from plastic.) Some people worry about fogging the lens with glue fumes, but it won't as long as you are careful and do it in a well-ventilated area (it dries in minutes, but you should leave it in open air for a good while to really cure). Epoxy would be more permanent I think. OK, thanks! So did you glue the m39 ring directly to the mount base, or did you put something in between, like tape?

04-01-2019, 02:29 PM	#4
boriscleto Loyal Site Supporter Join Date: Dec 2009 Location: North Syracuse, NY Photos: Gallery Posts: 16,476	ANNOUNCING: Easy cheap non-destructive Exakta-Pentax adapter

04-01-2019, 03:10 PM	#5
Lowell Goudge Site Supporter Join Date: Jan 2007 Location: Toronto Photos: Gallery \| Albums Posts: 17,891	Originally posted by vonBaloney I've done it. Plain superglue (cyanoacrylate) works fine for metal on metal (gel type might be easier to apply and set up), and can be dissolved with acetone (nail polish remover). (Keep acetone away from plastic.) Some people worry about fogging the lens with glue fumes, but it won't as long as you are careful and do it in a well-ventilated area (it dries in minutes, but you should leave it in open air for a good while to really cure). Epoxy would be more permanent I think. Be careful thenvapors can attackmlens coatings I had this issue remounting a loose prism in a pair of binoculars

04-02-2019, 11:16 AM	#6
IgorZ Veteran Member Join Date: Aug 2015 Location: Ottawa Posts: 1,735 Original Poster	Originally posted by boriscleto ANNOUNCING: Easy cheap non-destructive Exakta-Pentax adapter thanks! I tried using Elmer's glue-all, but the lens is hefty, probably at least 500 gr, so that glue wasn't strong enough... The M39 ring came off pretty easily, which I would want to avoid. ---------- Post added 04-02-19 at 11:17 AM ---------- Originally posted by Lowell Goudge Be careful thenvapors can attackmlens coatings I had this issue remounting a loose prism in a pair of binoculars thanks, I guess doing it under the kitchen fan should help?

04-02-2019, 12:42 PM	#7
vonBaloney Pentaxian Join Date: Oct 2011 Location: Albuquerque, NM Posts: 6,029	Yeah, you wouldn't want to use superglue internally unless all the glass was out and it had a long time to cure, but around the mount, I would cover up the glass with something so you don't accidentally touch it and then just yeah, keep the air flowing, let it dry overnight, it will be fine. I haven't glued rings like this a lot, but I have used superglue probably a dozen times to glue down aperture pins on the mounts of m42 lenses that didn't have a switch where I didn't want to take it apart to modify it. Never had a problem with the vapors hurting the glass.

04-03-2019, 10:03 AM	#8
IgorZ Veteran Member Join Date: Aug 2015 Location: Ottawa Posts: 1,735 Original Poster	Originally posted by vonBaloney Yeah, you wouldn't want to use superglue internally unless all the glass was out and it had a long time to cure, but around the mount, I would cover up the glass with something so you don't accidentally touch it and then just yeah, keep the air flowing, let it dry overnight, it will be fine. I haven't glued rings like this a lot, but I have used superglue probably a dozen times to glue down aperture pins on the mounts of m42 lenses that didn't have a switch where I didn't want to take it apart to modify it. Never had a problem with the vapors hurting the glass. Well, I glued the adapter last night. We'll see how it works... By the way, I came across an Exakta to M42 adapter on Amazon. Works basically the same way - just a ring with 3 screws. It doesn't say anything about infinity focus, but I assume there won't be infinity focus with this set up... Delivery was from China and would take up to 2 months, so I went for the glue instead.

04-03-2019, 12:13 PM	#9
stevebrot Otis Memorial Pentaxian Join Date: Mar 2007 Location: Vancouver (USA) Photos: Gallery \| Albums Posts: 42,007	Originally posted by boriscleto ANNOUNCING: Easy cheap non-destructive Exakta-Pentax adapter You just have to love Rio Rico! His approach will work and the only notes of caution might be the intrusion of the Exakta bayonet into the mirror box and interference of the aperture stop-down extension (found on most Exakta-mount lenses) with both installation of the adapter and mounting to the camera. The matter of the stop-down mechanism is rather complicated to explain. It is probably enough to say that the position of the extension must be accounted for when cementing the M39 thread in place and that even if properly offset, it may have a boss on the underside that will not clear the mount face on a K-mount body. Because of this, most adapter solutions are limited to manual and pre-set aperture Exakta lenses. Steve (...would very much like to flex my Exakta lenses to my Pentax bodies...)

04-03-2019, 12:25 PM	#10
stevebrot Otis Memorial Pentaxian Join Date: Mar 2007 Location: Vancouver (USA) Photos: Gallery \| Albums Posts: 42,007	Originally posted by IgorZ By the way, I came across an Exakta to M42 adapter on Amazon. Works basically the same way - just a ring with 3 screws. It doesn't say anything about infinity focus, but I assume there won't be infinity focus with this set up... Delivery was from China and would take up to 2 months, so I went for the glue instead. The grub-screw eBay adapter is sort of hokey in that it is designed for the grub screws to wedge under the Exakta mount tangs to hold the adapter in place. I would not use it with a lens having any value. Steve

04-03-2019, 12:35 PM	#11
stevebrot Otis Memorial Pentaxian Join Date: Mar 2007 Location: Vancouver (USA) Photos: Gallery \| Albums Posts: 42,007	...Another quick note. M42 adapted Exakta/Topcon lenses will not work on M42 bodies having the aperture actuator "flipper". The lens intrudes too deeply to clear the flipper such that the flipper/mirror/shutter sequence is interrupted leaving the camera in an indeterminant state. Steve

04-04-2019, 07:44 PM	#12
IgorZ Veteran Member Join Date: Aug 2015 Location: Ottawa Posts: 1,735 Original Poster	Originally posted by stevebrot The grub-screw eBay adapter is sort of hokey in that it is designed for the grub screws to wedge under the Exakta mount tangs to hold the adapter in place. I would not use it with a lens having any value. Steve Thanks for the heads up. I was planning to get one...