Possible bayonet replacement

aldo taddia · 04-15-2022, 12:25 PM

Hello everyone. I am a happy user of a Pentax-FA 100-300mm F4.7-5.8 SMC zoom that has plastic bayonet mount. Do you think it is possible to replace the plastic bayonet with a metal one (I have a new one of an FA lens, with all the contacts in their place)? If it were possible do they have the same draft? Thanks to those who can help me.

**pepperberry farm** · 04-15-2022, 12:33 PM

it is possible - several other have converted lenses with plastic mounts....

but why?

aldo taddia · 04-15-2022, 12:40 PM

Originally posted by pepperberry farm

it is possible - several other have converted lenses with plastic mounts....

but why?

I think so the aattack is safer, isn't it?

**BigMackCam** · 04-15-2022, 01:11 PM - **1 Like**

Originally posted by aldo taddia

I think so the aattack is safer, isn't it?

The concern over plastic bayonets is usually quite unfounded, IMHO. With many lenses - those with plastic bodies - the metal bayonet is simply screwed into plastic, so in the case of a serious bump or drop, the bayonet screws strip the threads in the body. In such an instance, you might even argue a plastic bayonet might put less stress on the body's mount as it's more likely to break and leave the body undamaged. The one potential benefit of a metal bayonet is that, over time, it might wear less than a plastic one if the lens is fitted to and removed from the camera very frequently. In reality, though, the plastics used are very hard-wearing. On the few lenses I own with plastic bayonets, I've not noticed any significant wear - nothing worse than rub marks.

TL;DR - a metal bayonet looks nicer, but probably doesn't offer any real benefit over a plastic bayonet for a lens that's fitted with one...

Last edited by BigMackCam; 04-15-2022 at 11:07 PM.

Not a Number · 04-15-2022, 02:11 PM

I don't know about that. On one of the defunct Yahoo Groups on manual focus lenses there were a lot of complaints about the Nikon kit lenses plastic mounts breaking not long after the end of the warranty period.

The mounts have been swapped out before. I think the dimensions are the same, don't know about number of screws and placement. You may need to provide grounding for metal mount.

**BigMackCam** · 04-15-2022, 02:23 PM

Originally posted by Not a Number

I don't know about that. On one of the defunct Yahoo Groups on manual focus lenses there were a lot of complaints about the Nikon kit lenses plastic mounts breaking not long after the end of the warranty period.

My experience is only with Pentax K-mount and Sony A-mount - and I've had no problems with either of those. Nikon may well be different, it's true...

**BigMackCam** · 04-15-2022, 02:25 PM - **1 Like**

Originally posted by Not a Number

I don't know about that. On one of the defunct Yahoo Groups on manual focus lenses there were a lot of complaints about the Nikon kit lenses plastic mounts breaking not long after the end of the warranty period.

My experience is only with Pentax K-mount and Sony A-mount - and I've had no problems with either of those. Nikon may well be different, it's true...

It's worth reading the short article below by Roger Cicala. I respect his views enough to give them pretty serious consideration - in addition to personal experience, of course - when forming my own opinions :

Assumptions, Expectations, and Plastic Mounts

Last edited by BigMackCam; 04-15-2022 at 02:37 PM.

AfterPentax Mark II · 04-15-2022, 02:41 PM

Originally posted by aldo taddia

Hello everyone. I am a happy user of a Pentax-FA 100-300mm F4.7-5.8 SMC zoom that has plastic bayonet mount. Do you think it is possible to replace the plastic bayonet with a metal one (I have a new one of an FA lens, with all the contacts in their place)? If it were possible do they have the same draft? Thanks to those who can help me.

In my experience the "plastic" mounts always feel smoother when attaching them to the camera. They leave less "trails" on the metal mount of the camera. I notice that quite some metal mounts on Pentax lenses do not "mount" that smoothly and you can see signs of wear on the metal mount. And in my experience, again, those plastic ones are made of sturdy stuff. So leave the mount alone. You might be punished for inflicting GHB (grievous bodily harm) on your lens.

**PJ1** · 04-15-2022, 04:03 PM - **2 Likes**

As a general rule, if it's not broken, don't try to fix it. I think we need to distinguish here between the bayonet and the piece at the rear of the lens that the bayonet is screwed on to. That part is almost always plastic on modern lenses and that, technically, is the "mount". Would there be any benefit in replacing a plastic bayonet with a metal bayonet if it only means unecessarily working the metal screws in the plastic mount holes? A metal bayonet will not help if a camera with lens attached is dropped because that can break the mount, the bayonet and the receiver ring on the body. Whether the bayonet is metal or plastic won't make a difference.

aldo taddia · 04-15-2022, 10:53 PM - **1 Like**

Thank you all for the helpful advice. I will leave things as they are!

**photogem** · 04-27-2022, 12:27 AM

I once had a Pentax plastic bajonett go wrong: DA-L 55-300.
But I repaired it with another plastic bajonett from a DA-L 18-55 worked alright.

I came across 2 x Sigma 28-105 UCIII with plasticmount: Those are made out of the similar plastic as the plastic socket of older Sigma AF flashes.
Those are very fragile. As the UCIII is well regarded (also for the K1) I feel here a "transplant" could be quite useful.

04-15-2022, 12:25 PM	#1
aldo taddia Senior Member Join Date: Apr 2020 Location: Ferrara Italia Posts: 139	Possible bayonet replacement Hello everyone. I am a happy user of a Pentax-FA 100-300mm F4.7-5.8 SMC zoom that has plastic bayonet mount. Do you think it is possible to replace the plastic bayonet with a metal one (I have a new one of an FA lens, with all the contacts in their place)? If it were possible do they have the same draft? Thanks to those who can help me.

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04-15-2022, 12:33 PM	#2
pepperberry farm amateur dirt farmer Join Date: Dec 2014 Location: probably out in a field somewhere... Photos: Gallery \| Albums Posts: 41,766	it is possible - several other have converted lenses with plastic mounts.... but why?

04-15-2022, 12:40 PM	#3
aldo taddia Senior Member Join Date: Apr 2020 Location: Ferrara Italia Posts: 139 Original Poster	Originally posted by pepperberry farm it is possible - several other have converted lenses with plastic mounts.... but why? I think so the aattack is safer, isn't it?

04-15-2022, 01:11 PM - 1 Like	#4
BigMackCam Digitiser of Film Join Date: Mar 2010 Location: North East of England Posts: 20,695	Originally posted by aldo taddia I think so the aattack is safer, isn't it? The concern over plastic bayonets is usually quite unfounded, IMHO. With many lenses - those with plastic bodies - the metal bayonet is simply screwed into plastic, so in the case of a serious bump or drop, the bayonet screws strip the threads in the body. In such an instance, you might even argue a plastic bayonet might put less stress on the body's mount as it's more likely to break and leave the body undamaged. The one potential benefit of a metal bayonet is that, over time, it might wear less than a plastic one if the lens is fitted to and removed from the camera very frequently. In reality, though, the plastics used are very hard-wearing. On the few lenses I own with plastic bayonets, I've not noticed any significant wear - nothing worse than rub marks. TL;DR - a metal bayonet looks nicer, but probably doesn't offer any real benefit over a plastic bayonet for a lens that's fitted with one... Last edited by BigMackCam; 04-15-2022 at 11:07 PM.

04-15-2022, 02:11 PM	#5
Not a Number Moderator Join Date: Mar 2012 Location: Venice, CA Posts: 10,526	I don't know about that. On one of the defunct Yahoo Groups on manual focus lenses there were a lot of complaints about the Nikon kit lenses plastic mounts breaking not long after the end of the warranty period. The mounts have been swapped out before. I think the dimensions are the same, don't know about number of screws and placement. You may need to provide grounding for metal mount.

04-15-2022, 02:23 PM	#6
BigMackCam Digitiser of Film Join Date: Mar 2010 Location: North East of England Posts: 20,695	Originally posted by Not a Number I don't know about that. On one of the defunct Yahoo Groups on manual focus lenses there were a lot of complaints about the Nikon kit lenses plastic mounts breaking not long after the end of the warranty period. My experience is only with Pentax K-mount and Sony A-mount - and I've had no problems with either of those. Nikon may well be different, it's true...

04-15-2022, 02:25 PM - 1 Like	#7
BigMackCam Digitiser of Film Join Date: Mar 2010 Location: North East of England Posts: 20,695	Originally posted by Not a Number I don't know about that. On one of the defunct Yahoo Groups on manual focus lenses there were a lot of complaints about the Nikon kit lenses plastic mounts breaking not long after the end of the warranty period. My experience is only with Pentax K-mount and Sony A-mount - and I've had no problems with either of those. Nikon may well be different, it's true... It's worth reading the short article below by Roger Cicala. I respect his views enough to give them pretty serious consideration - in addition to personal experience, of course - when forming my own opinions : Assumptions, Expectations, and Plastic Mounts Last edited by BigMackCam; 04-15-2022 at 02:37 PM.

04-15-2022, 02:41 PM	#8
AfterPentax Mark II Pentaxian Join Date: Mar 2021 Posts: 1,467	Originally posted by aldo taddia Hello everyone. I am a happy user of a Pentax-FA 100-300mm F4.7-5.8 SMC zoom that has plastic bayonet mount. Do you think it is possible to replace the plastic bayonet with a metal one (I have a new one of an FA lens, with all the contacts in their place)? If it were possible do they have the same draft? Thanks to those who can help me. In my experience the "plastic" mounts always feel smoother when attaching them to the camera. They leave less "trails" on the metal mount of the camera. I notice that quite some metal mounts on Pentax lenses do not "mount" that smoothly and you can see signs of wear on the metal mount. And in my experience, again, those plastic ones are made of sturdy stuff. So leave the mount alone. You might be punished for inflicting GHB (grievous bodily harm) on your lens.

04-15-2022, 04:03 PM - 2 Likes	#9
PJ1 Loyal Site Supporter Join Date: Jul 2012 Location: Toowoomba, Australia Photos: Gallery \| Albums Posts: 5,486	As a general rule, if it's not broken, don't try to fix it. I think we need to distinguish here between the bayonet and the piece at the rear of the lens that the bayonet is screwed on to. That part is almost always plastic on modern lenses and that, technically, is the "mount". Would there be any benefit in replacing a plastic bayonet with a metal bayonet if it only means unecessarily working the metal screws in the plastic mount holes? A metal bayonet will not help if a camera with lens attached is dropped because that can break the mount, the bayonet and the receiver ring on the body. Whether the bayonet is metal or plastic won't make a difference.

04-15-2022, 10:53 PM - 1 Like	#10
aldo taddia Senior Member Join Date: Apr 2020 Location: Ferrara Italia Posts: 139 Original Poster	Thank you all for the helpful advice. I will leave things as they are!

04-27-2022, 12:27 AM	#11
photogem Site Supporter Join Date: Apr 2015 Posts: 3,522	I once had a Pentax plastic bajonett go wrong: DA-L 55-300. But I repaired it with another plastic bajonett from a DA-L 18-55 worked alright. I came across 2 x Sigma 28-105 UCIII with plasticmount: Those are made out of the similar plastic as the plastic socket of older Sigma AF flashes. Those are very fragile. As the UCIII is well regarded (also for the K1) I feel here a "transplant" could be quite useful.