Metal to metal dry lubrication... what product?

[Madsciguy]

I had thought if gluing some kind of half shell bearing into the magnet with the same radius as the screw head, but I'd never find one that's perfect. I've just looked up the tape you mention and it looks a possible "proper fix". When you say "a bit of heat" what are we talking... hair dryer heat?

The Moly slip dry lube has arrived. I sprayed both components and left to dry for an hour. When together the grey sprayed area of contact immediately gets rubbed away leaving metal on metal again. Am I missing something? It doesn't say how long to leave it to dry, maybe it needs longer? Maybe the film is invisible and I'm being led by the grey disappearing?

@terryd - found I had the same Finish Line bike lube in the garage so I'm trying that too.

A hair dryer (up close) is what I would use. You are creating a spherical kinematic joint (The Principle of Kinematic Constraint - Practical Precision). Because the countersink angle on the magnet is quite shallow, the connection won't be very stiff. I assume the forces trying to push it out of position will be quite small?

 

[davidUK]

Yes, very small. It's a self-levelling system for woodwind instrument pads. Each pad closes against the rim of a brass tone hole in the, say, saxophone. Once level it stays there in theory. In practice, squeezing a key puts the pad at a minute angle which it remains at as it lifts because of metal to metal "grabbing" friction.
If this is overcome the pad stays level. We're talking tiny air leaks but I'm a perfectionist. It has to be perfect to stand any chance of deposing 150 years of the tradition of glued in leather and felt pads.
My sealing material is neoprene.

 

[Madsciguy]

Yes, very small. It's a self-levelling system for woodwind instrument pads. Each pad closes against the rim of a brass tone hole in the, say, saxophone. Once level it stays there in theory. In practice, squeezing a key puts the pad at a minute angle which it remains at as it lifts because of metal to metal "grabbing" friction.
If this is overcome the pad stays level. We're talking tiny air leaks but I'm a perfectionist. It has to be perfect to stand any chance of deposing 150 years of the tradition of glued in leather and felt pads.
My sealing material is neoprene.

OK, I understand what you are trying to accomplish. Since the opening and closing tone hole will be essentially instantaneous, you may get some interesting tone effects. Glissandi may be difficult. Its a very interesting project, good luck!

 

[davidUK]

Of course, one solution is to buy the magnets already coated in PTFE...

Feels nice an slippery but magnetism still holds the screw in position once moved.

BUT... I then need to glue/bond the PTFE coated rear of the magnet to any of stainless steel; brass; nickel plate; silver plate.

I've emailed my contact at Loctite for their best solution to this.

The PTFE magnets are also twice the price of the plain ones.

 

[davidUK]

OK, I understand what you are trying to accomplish. Since the opening and closing tone hole will be essentially instantaneous, you may get some interesting tone effects. Glissandi may be difficult. Its a very interesting project, good luck!

If you're really bored (or interested) this is a video I made almost a year ago:




Since then I've found the ideal synthetic seal (a special neoprene foam sheet). This lubrication and leak eradicating issue may be the final hurdle.

 

[ChazzC]

Any process that would involve heat needs to be carefully reviewed as Neodymium magnets will permanently lose strength at higher temperatures: K&J Demagnetization Curves

K&J Magnetics in the U.S. stocks both N42 & N52 strength countersunk magnetics that appear to be the same as you are currently sourcing (their part number R622CS; -S or -N for the pole on the countersunk face; -N52 for the higher strength versions); R622CS-S:

Details:

R622CS-S
R622CS-S-N52


They can provide custom magnets, and have some stock high temperature magnets (but no countersunk rings). They could potentially polish the countersunk surface or apply a coating to just that face; however, there is a minimum purchase: K&J Magnetics Custom Quote


Good luck with your application!

 

[davidUK]

Thanks for the info.
I had another thought... the sole purpose of the self-levelling mechanism is to do away with the traditional method of gluing into the key cup a flexible, leather covered, felt and card disc around 4mm thick. Once glued in this has to be manipulated by heating the glue again so as to level the pad face with the rim of the tone hole which is drawn from the brass body of the sax in manufacture and then levelled. So the traditional method has variables: the glue melted into the key cup would have to be level with the inner rear surface of the key cup; heating it again when assembled could throw off this level; pulling the pad around with picks could twist it from being flat.
But... once done the slightly squidgy pad would have no tendency to move from level with the tone hole rim other than, when squeezed hard at its leading edge under finger pressure, to compress more at that edge and then spring back to its original shape when released.
Remember, the pad only has to level once, unless there is some accidental movement from a knock or other intervention. In this case, the pad would need to be re-settable but this will be rare.

So, assuming my pad material, at 1mm, is thick enough to allow for the increased compression at the edge furthest from the pivot point (around 50mm further than the nearest edge which is 20mm from the pivot - someone do the maths!) what I need to do it to let the pad self-level, then remove it and apply a locking liquid, then replace it, press the key lightly to level it again, and let it set. Then, when squeezed hard the metal to metal locking fluid would resist any further movement as with a normal glued in pad.

I'd still need to be able to unglue a pad by levering it out so it needs to be something like a removable thread locking liquid, or a rubberised glue (a little movement may be advantageous so long as it springs back again, or even a contact adhesive.

So, from allowing maximum movement I'm suggesting the opposite so as to stop the front of the pad lifting and not self-levelling completely due to the friction at the pivot caused mostly by the strong magnet. The pivot has to have enough friction to move so as to self-level but not enough to flop about when the pad is in mid air. I think that sufficient friction to achieve this is also too much for the pivot to change with tiny inputs which change its angle ever so slightly.

What "glue" will bind metal to metal lightly but also be separable? It needs to give me around 30 seconds to install and level before it starts to dry.

Thanks for your help!

 

[kwoodhands]

Thanks David. How much would powdered graphite spread around and make a mess?
Does it bond with the metal or would it disappear over time>

I was looking at white lithium grease yesterday until I found it's likely to attract dust and dirt...

DriCote is a spray on dry lubricant. I use it on sprockets and chain mechanism that raises or lowers a planer bed. Wood dust does not adhere. Any grease will attract dust.
I understand the name has changed to Bostic Dricote or something similar.
mike