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Karl
Tinkerer
Username: Karl
Post Number: 56
Registered: 03-2008
Rating: N/A
Votes: 0 (Vote!) | | Posted on Wednesday, February 24, 2010 - 01:53 am: | 
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I have a Vivitar 75-205mm zoom that has oil on the aperture blades so I need to get in there to clear away the mess.However,I need to remove four screws which are on the body of the lens which are fixed solid and so small that the jewelers screwdriver just does not give the required purchase.Does anyone know a way to loosen the screws without destroying them,because the lens is too good to throw away. |
Nickon51
Tinkerer
Username: Nickon51
Post Number: 122
Registered: 05-2008
Rating: N/A
Votes: 0 (Vote!) | | Posted on Wednesday, February 24, 2010 - 03:37 am: |
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Do they look like crosspoint screws? If so they will probably be JIS screws. You will need to get the correct JIS screwdrivers. They look exactly the same, but a normal cross point will tend to ride up out of the slots. Microtools stock them. |
Karl
Tinkerer
Username: Karl
Post Number: 57
Registered: 03-2008
Rating: N/A
Votes: 0 (Vote!) | | Posted on Wednesday, February 24, 2010 - 08:39 am: |
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Yes,they look like crosspoint. My scewdriver does seem to ride up when I try.The thing is I don,t understand how they can be so hard to turn,are they self tapping or glued in or what ? Seems like over engineering. |
Adrian
Tinkerer
Username: Adrian
Post Number: 292
Registered: 08-2006
Rating: N/A
Votes: 0 (Vote!) | | Posted on Wednesday, February 24, 2010 - 09:36 am: |
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JIS screws have narrower slots than Philips - they don't open out at the bottom like a Philips. It's a subtle but annyoing difference - here's the best illustration I've found (and that's not great - sorry!): http://www.instructables.com/id/When_a_Phillips_is_not_a_Phillips
So basically, your screwdriver lifts out when you apply force to it...
There's a firm called Japanese screws you might try for suppliers of JIS screwdrivers: http://www.japanesescrews.com/jis-fasteners.asp as MicroTools charge both arms and at least three and a half legs for delivery to the UK. They might not be easy to find - I had to get my set from Moody Tools in the US via a contact in Ireland, as they had no UK distibutor... |
Mikel
Tinkerer
Username: Mikel
Post Number: 207
Registered: 07-2006
Rating: N/A
Votes: 0 (Vote!) | | Posted on Wednesday, February 24, 2010 - 09:39 am: |
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Vivitar lenses were made by a variety of sub contractors. Some of them glued every screw in the lens. I'd try some acetone on them first. |
Nickon51
Tinkerer
Username: Nickon51
Post Number: 125
Registered: 05-2008
Rating: N/A
Votes: 0 (Vote!) | | Posted on Wednesday, February 24, 2010 - 02:39 pm: |
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I think you will find that they are not as tight as they seem when you get the right tool. In the centre cross of the screw head, the corner chamfers are smaller on the JIS head. Thus when a philips driver is used, the corressponding wider fillets in the centre of the cross, stop the driver from seating down properly. Most of your energy is spent stopping the driver lifting out and putting force on the centre of the screw, but not much of that force get translated into torque.
I have a set of Moody drivers, but the mid size one fractured. I will get another but of a higher quality.
Thread locker is almost always used. Acetone is good or you can try some heat fron a small soldering iron tip. |
Mikel
Tinkerer
Username: Mikel
Post Number: 208
Registered: 07-2006
Rating: N/A
Votes: 0 (Vote!) | | Posted on Wednesday, February 24, 2010 - 03:49 pm: |
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If the screws are glued in (not loctite) as some Vivitars are, you need to deal with that situation first, whether you have the right screwdriver or not.
You will either break the screwdriver, or ruin the head of the screw. I have the correct tools. After the second or third time I had to drill out a busted screw I got it figured out.
BTW until at least the early 80's the Vivitar parts department sold Ideyama crosspoint blades and Niwa handles to repair technicians. Good stuff! |
Karl
Tinkerer
Username: Karl
Post Number: 58
Registered: 03-2008
Rating: N/A
Votes: 0 (Vote!) | | Posted on Wednesday, February 24, 2010 - 07:37 pm: |
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Seems a bit of a chicken and egg situation I,m in.Destroy the lens with the wrong tools or maybe destroy lens with the right tools.As I don't have the tools I think I will try and pass it on to someone better equipped.The lens is a duplicate almost of two I have already so if nothing else I have learnt something I didn't know before which is what this forum is all about,thank you all.
"I can't fix everything!" |
Karl
Tinkerer
Username: Karl
Post Number: 60
Registered: 03-2008
Rating: N/A
Votes: 0 (Vote!) | | Posted on Thursday, February 25, 2010 - 07:39 am: |
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Please see Swap zone.
Vivitar 75-205 zoom Nikon Ai to swap. |
