Forgive me if this is in the wrong section - I’m not quite sure where it fits!
I’ve picked up an old Ibanez mandolin which is in excellent nick except for a couple of screws that have oxidised and will not budge. I would like to try and refurbish it as a surprise for my son, who loves vintage instruments. I have found a variety of appropriate methods for removing the oxidisation where it’s visible (without damaging the lacquered wood on the mandolin), so so far so good. But - and it’s a big but - I do not know what product will give me the most chance of lubricating the threads of the screws so they can be turned with minimum effort in order to mimimise the chance of damaging the rest of the instrument. Would any of you (especially those who dabble in cars perhaps?) have any ideas as to the best product obtainable here or over one of the borders? I would of course protect the other parts of the instrument and am very aware there’s a reason that it was cheap!
First thing, take something sharp and pointy (like a sewing needle) and clean out any gunk in the head of the screw so that your screwdriver makes the most contact possible ( and be sure use the correct size screwdriver, width and thickness).
Try slightly tightening the screw before loosening, it may free the screw.
If that doesnt work, you could hold the tip of a soldering iron to the screw head for a few seconds, then try again.
Any chance to have a photo to see what we are talking about? It matters a lot what the screws are in contact with, what state they are in…
The typical response to unscrewing rusted threads is WD40, but whether that will damage any finishes around is a very difficult question without a view of the situation
Thank you both! I have taken 3 photos to show what I’m talking about as my explanations would definitely leave a lot to be desired!
I’ve heard that WD40 would be bad for the wood; I know I shall have to be as careful as I possibly can whatever I do in the hope that I can achieve my objective.
Well the first two photos show copper based oxidation (the green stuff), not sure if WD40 would be good for that. I hope someone else has a better suggestion. I’m confident though this should be very easily treatable.
The last photo I don’t see anything wrong with, looks like a very nice instrument
Thank you - as you can probably tell, you know more from a photo than I do so all help gratefully received. It really is lovely and if I can just refurbish the parts that need it I’m hoping to give my son a lovely surprise.
It is a lovely thing, but please take off the remaining strings–hope they haven’t been tight all this time! As for the screws, machine oil is your friend. It’s one step thicker than kerosene and is used to lubricate things like sewing machines. Keep it off the wood, but soak a cloth in it (or apply with a Q-tip) and bind it around the screw, with the instrument elevated so that the oil doesn’t drip on the wood. Then try the other techniques people have suggested. Good luck!
I think it fair to say that the strings are not tight but I shall remove them completely now and make my way to the local sewing machine shop over the weekend. Thank you all for your really helpful advice!
For the copper based pieces (brass probably) people use mildly acidic solutions (such as vinegar, lemon juice etc), but these also
attack and dull the laquer. You can make a paste with baking soda or other components, use masking tape on the laquer and apply very, very carefully
Some suggestions here
But I would try to unscrew them and treat them off the instrument though
Landi sells penetrating oil in spray cans which I find to be very useful.
They squirt through narrow plastic tubes so be careful to just keep it close to the screw.
I would actually not try to undo the bottom screw - seems to be screwed into the wood and undoing it risks to damage the wood, you might not be able to tighten it back properly. I’m not even sure the top screw needs loosening up - does it have any function? I would just try to clean the oxidation on the brass part, first mechanically (soft cloth, with some oil/soap) then with some light acidic solution, and with masking tape and care not to touch the lacquered parts.
For this bit
I would try to check if there are hidden screws in the holes holding the upper saddle and undo those. Otherwise the brass part may be cleaned in place with similar techniques
I own 4 mandos, one of them a 1918 Gibson that I refurbished, refretted, etc. myself.
Do not take the strings off- the instrument is designed to have string tension at all times, except when changing strings (approx 180 lbs linear string tension, creating approx 50 lbs of pressure pushing down on the bridge and soundboard) If anything, you should tighten the strings until they get changed.
The oxidation on the bridge thumbscrews should be easy enough to deal with- the bridge is only held against the soundboard/top by string pressure and can be easily removed. The top piece of the bridge will just lift away. The thumbwheels can be soaked in vinegar to remove the oxidation, or if they wont budge, the whole bridge can be suspended upside down with the corroded parts hanging in vinegar ( using a jar lid, for example).
A new bridge/saddle is not expensive, but is not so easy to install and would get expensive at any Swiss luthier.
The oxidized mount for the finger rest should come off without extreme measures, just take your time and be careful. It could also be soaked in vinegar.
What kind of condition are the frets in?
It looks to me like it was a much loved/much played instrument- if i had to guess id say the oxidation in the pictures is due to a lifetime of sweaty gigging.
The frets are pretty perfect at the top and become more oxidised as you get towards the bridge - seems consistent with, as you say, a much loved instrument. I have to admit I have much more knowledge of classical instruments (cellos/violins) and therefore haven’t come across metal issues but am learning fast.
One of the most important things I’m learning from all this helpful input is definitely to take it slow and try to make as few errors as possible.
If it were my instrument, I‘d try to find a luthier who might give me a bit of advice here. Some professionals are only too happy to help an interested amateur.
