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03-29-2020, 08:06 AM   #1
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Nick Rowland's Avatar

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Spotmatic II front plate screws

Hi all,

I need to get the front plate off a Spotmatic II but every one of the 5 screws is locked solid. I've tried fluids and heat but nothing frees them. I am going to have to drill the heads out to get the plate off.

My question is, what are the details of the screws as I need to buy replacements to put the plate back. I don't have any other Spotmatics to use as a reference.

Thanks
Nick

03-29-2020, 09:11 AM - 1 Like   #2
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M1.7 (1.7mm diameter) screws seems to be the most commonly used size on Asahi cameras and lenses. The Spotmatic service manual and parts list found online show the exploded diagrams but lack the actual part listings. Sometimes the diagram indicates the size of the screws but not in this case.
03-29-2020, 09:37 AM   #3
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That's my guess but wanted to be sure, it would be great to find some genuine N.O.S from somewhere. Like you, I expected the spares lists to specify but so far haven't found one that does. My guess is m1.7 or M2 countersunk brass
03-30-2020, 07:31 AM - 1 Like   #4
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They are cheese head screws. Did you use acetone to remove the screws? Acetone almost always works. The alignment of the front panel is so critical I would be worried about drilling out the screws.

03-31-2020, 12:01 AM   #5
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Ok thanks. I tried Acetone, Iso Propyl and Meths. I also held a soldering iron on each screw until it was almost red hot (took ages) and they still didn't shift. The screws are corroded judging from the heads and the self timer. The screws holding the self timer boss are rusted solid and the front plate screws had gone green but cleaned up ok to get a screwdriver in. I have a NOS front plate to fit in its place but didn't have the screws for it.

Although the front plate has bad corrosion the top and bottom of the camera are fine and all the gear wheels etc. are corrosion free.
03-31-2020, 06:33 AM   #6
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There's a penetrating oil product in the US sold as PB B'laster which is the best of this type of product that I've used. I would spray a little of this into a jar and apply with a toothpick or needle around the heads of the screws and wait maybe 48-72 hours. Perhaps a few repeated applications in between. I don't know if it is sold in the UK though.

PB B’LASTER PENETRANT – Blastercorp
04-01-2020, 04:05 AM   #7
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I don't think we can get that in the UK but I have tried WD in the same manner but that didn't work. I also tried watchmaker's oil thinned with alcohol but that didn't work either. I did both over a week putting a few spots on each day.

All five screws seem well and truly stuck :-(
04-02-2020, 08:52 AM   #8
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Regular oils and WD-40 don't have the compounds in them that penetrating oils have to cut through and loosen corrosion. WD-40 makes a specialist rust release penentrant formula. There should be equivalent products available in the UK as well.

RDGTOOLS WD-40 400ml Specialist Fast Release Penetrant: Amazon.co.uk: DIY & Tools

04-03-2020, 08:36 AM   #9
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Ok thanks, I'll try to get some before I try a more drastic approach
04-03-2020, 12:51 PM - 1 Like   #10
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Hi Nick, it may take time. I have hit this problem a few times in various endeavors and time and regular dosing nearly always works. Patience is ever a virtue. I did some servicing work on a telescope mount a few years back which had a seized bearing. It took about two weeks of constantly tinkering, heating it up, letting it cool, squirting in some penetrating oil etc before it let go.
07-07-2020, 12:28 PM   #11
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I suspect corrosion also, issue with drilling is walking and ruining the casting also. The shims are brass/copper usually tear.
Iíve found on many, vibration with penetration oil will be magic, I used a large grip jewelers blade that fits, tapping with a wooden mallet handle while seeping oil . Letting it soak overnight also helps. Iíve used a product calledĒmove it ď marvel mystery oil also can help as itís thin.


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