rare earth magnets questions

[Woodmonkey]

Someone recently suggested I use rare earth magnets to hold the top on the display cabinet I'm making which I liked the idea of. What size and spacing of magnets would I need - top is around 700x550mm. Want it to stay put but not be to difficult to get it off when necessary. Good place to buy them? Lots on eBay but they all look very small

 

[SlowSteve]

is the top horizontal or vertical?

It it's horizontal, than a 8mm or 10mm in each corner will be MORE than enough - you may well get away with 5mm or even smaller.

if it's vertical, the 10mm's should be more than enough unless you're using industrial thicknesses of lignum or similar. 8mm's or 5mm's are better if it's just holding doors shut.

You need something fairly extreme to hold them in place - seriously consider JBWeld or something similar and plan how you'll clean up afterwards. Those things are VERY strong. Don't let them get near anything like chisels or planes, or the next time you sharpen you'll find you are collecting filing right on the tip.


If you do go for the 8mm and especially the 10mm, be very careful when your assembling and fettling - those things can pinch hard enough to cut the skin very painfully.


Steve

 

[mouppe]

I use two 1/4" magnet to hold each of my tool cabinet doors shut. The magnets are very strong. If you can find matching cups, such as Lee Valley sells, their strength is increased.

 

[SurreyHills]

I use some on my tool cabinet as well. Got for the ones with the countersunk holes as it makes fixing them a doodle.

 

[woodchip]

I buy my magnets from here http://e-magnetsuk.com

 

[Woodmonkey]

Thanks guys. Steve, would ordinary epoxy resin not do the job?

 

[SlowSteve]

it might. or might not.

clean the magents with acetone, wear gloves so no finger print oils and use a good epoxy, not something from a diy shop.

jbweld is a lot less messy

 

[Higon]

Thanks guys. Steve, would ordinary epoxy resin not do the job?

it does, I use magnetic bars around the shop next to various machines to hold the bits I always use on that machine. Spanners for changing bits and the like. Have used epoxy and small magnets for the non metallic things like plastic dustpan and brush, 3 inch paintbrush etc. Just drilled into the plastic, dab of epoxy and seat the magnet in. No problems. I have a feeling that the magnets I'm using might only be 5mm too.

Don't think I was that fastidious either...

 

[DiscoStu]

I use heavy duty Velcro for the same thing but I use it with the Velcro cable ties. I stick some heavy duty on the machine and then I wrap the cable tie version around the tool. I Ouse it to keep Alan keys and the like with the appropriate machines. I like the magnet idea as well.

 

[Silas Gull]

The attraction between two small naked 'RE magnets is very strong. However, However when you attach them to objects of a larger weight and mass, that power is diminished.

 

[bugbear]

clean the magents with acetone, wear gloves so no finger print oils and use a good epoxy, not something from a diy shop.

I have had great difficulty getting small (3mm diameter) RE magnets to stick to tufnol using 24 hr Araldite brand epoxy.

They are used to fix a pointer to knife during sharpening.

They have repeatedly come off and needed reglueing, say every 8 months.

BugBear

 

[Mr T]

Four 10x4 should do it. I use Cermag http://www.cermag.co.uk/buy_ndfeb_neodymium_disc_magnets_online.html for the magnets in my magnetic clamp heads and for door closing https://www.youtube.com/watch?v=D8n63JswyX8.

Chris

 

[Woodmonkey]

Love the clamp head idea, that's a keeper!