Secret fixings?

[dvddvd]

I have 2 pieces of wood 25mm x 160mm x 6mm and the other piece is 25mm x 160mm x 15mm.

I want to fix the 25mm x 160mm faces together, but want to be able to take them apart again.

I used to glue them.

I've looked at the button fixings but they are to big for the pieces I've got. So anybody know a simple way? I could use small screws but don't want them on view

Thanks

 

[Eshmiel]

The type of fixing you need will be determined also by what forces are trying to pull the two pieces apart. And how often you want to disassemble.

Rare earth magnet in the thicker piece on to a matching steel washer in the other piece?
Double sides sticky tape?
A small hook into a matching small slot/catch?

 

[dvddvd]

Thanks, just been looking at rare earth magnets..not sure what size to try? Do the faces have to be spot on flush for them to work? How are they for sideway pressure?

 

[dvddvd]

I've not found any hooks or slots that would be small enough

 

[dvddvd]

I suppose the forces would be more sideways then actual pulling from the front

 

[Agent_zed]

Thanks, just been looking at rare earth magnets..not sure what size to try? Do the faces have to be spot on flush for them to work? How are they for sideway pressure?

If you want to stop sideways pressure/movement you could add pins to locate each piece. could be as simple as small nails with the head knipped off.

 

[dvddvd]

Thanks I was thinking of even setting the magnet 1 mm deeper and then surface mount the 1m washer so it's got something physical to push against..

What size magnet would be suitable, you can get them in every size possible? Would a metal disc work better than a washer..where can you buy metal discs?

 

[Jacob]

Velcro? Set in to a little shallow housing on each piece

 

[JSW]

What size magnet would be suitable, you can get them in every size possible? Would a metal disc work better than a washer..where can you buy metal discs?

Use two magnets, combined with @Agent_zed's excellent 'pins to stop sideways movement' tip, should work pretty well I'd have thought

 

[dvddvd]

Thanks, only problem I could see with magnets is if the wood moves at all, twisting/ warping as the magnets would not be strong enough...I'll try some magnets. Not sure what size I should go for?

 

[JSW]

Thanks, only problem I could see with magnets is if the wood moves at all, twisting/ warping as the magnets would not be strong enough...I'll try some magnets. Not sure what size I should go for?

They're pretty strong, combined with the pins trick, should be plenty strong enough. Google 12x2-3mm neodymium magnets, cheap as chips on amazon/ebay etc. 12mm Forstner should drill them out, spot of CA in the recess, good to go.

 

[Jake]

You could attach a steel flat bar to the thin bit to reinforce it (with epoxy or MMA glue). If the steel was only partly recessed into a shallow trench in the thin bit, with a matching trench on the thicker bit to take the protruding part, the strip would also stop sideways movement. Then magnets recessed into the bottom of the trench in the thicker bit.

This way for -----------------------------------------------------------------------------------------------------> Jake's typical over (or under) engineering.

 

[dvddvd]

Thanks do they have to be spot on, and touching the washer,?

 

[dvddvd]

I do have 100s of these to do, I used to glue them and clamp them which worked fine, but I had a few failures on the switches that were embedded on the underneath of the thin piece and there was no way to change a 10p switch without destroying the full piece

 

[Jacob]

I do have 100s of these to do, I used to glue them and clamp them which worked fine, but I had a few failures on the switches that were embedded on the underneath of the thin piece and there was no way to change a 10p switch without destroying the full piece

What is the actual finished article? Photo? I bet we could redesign it completely!

 

[ChaiLatte]

They're pretty strong, combined with the pins trick...

Use the magnets as the pins: on one side of the joint (the 6mm piece) let the magnet project from the surface (that will give more choice of magnet as the 6mm thickness will be less of a limitation); on the other side of the joint, let the other magnet be recessed a little. Two magnets attracting will be stronger than a single one and a washer and the holes to be drilled will all be identical.

Three (pairs of) magnets will give proper kinematic constraint. Two will be underconstrained; four will be over constrained.

If orientation of assembly is critical, make the magnet layout non-symmetrical, so it will only go together one way. Or put them in an equilateral triangle for three choices.

Do a test run on some scrap, as the magnetic force may be strong enough that you need some means of prying the parts apart.

 

[dvddvd]

Do the magnets have to actually touch each other?

 

[profchris]

Do a test run on some scrap, as the magnetic force may be strong enough that you need some means of prying the parts apart.

Seconded! I use rare earth magnets for clamping in luthiery, and the little buggers come together with mighty force, enough to raise blood blisters if they nip a finger.

I'd suggest you buy a pack of 12mm x 2mm - I think this is where I bought mine: https://www.ebay.co.uk/itm/204451375924, cost is £7.50 for 10. Then you can experiment to see if you want more stick (I suspect not) or less.

The magnetic force varies with the square of the distance apart, but in practical terms they'll pull prety hard even if they are 10mm apart.

 

[dvddvd]

It a guitar hand excersiser. I used to make them and sell them years ago. I used to build each one by hand and took some time building them and it was not worth it.

I bought a cnc around 4 years ago and I've designed the fretboard part in Vectric 160mm x 25mm x 6mm piece of Wenge with 10 x 6mm x 6mm recessed square pockets where the switches fit with a 4mm hole drilled in the middle..now I can just stick a piece of Wenge down and 3 mins later it's cut to perfection

 

[ChaiLatte]

It it is CNC'd, you should be able to achieve very good depth control on the pockets for the magnets, so should be able to get them within a Rizla paper of touching, for maximal attraction.

Pro tip: try not to have the south pole of both sides facing outwards or crying will ensue.

You are putting a sticking plaster over the problem, not addressing the root cause.

Buy a more reliable switch that lasts for two hours longer than the guarantee runs out. Six magnets from the above link are £4.50. That buys a lot of quality switch-wise.

Why does this forum censor an alternate name for a Rizla paper? This makes talking about a bearing manufacturer whose initials are the same rather difficult (https://www.schaeffler.co.uk/en/pro..._and_plain_bearings/deep_groove_ball_bearing/).