Rare earth magnets

[John Keane]

I have built a cabinet with two 43" doors. When closed they are almost flush with the inside frame. My thought was to put an earth magnet at the bottom of each door as a closing/holding device. After purchasing the magnets and the washers I realized that I did not have a methodology for keeping the magnet in place. My thought was to drill a 1/2" hole (forstner),slightly countersink and insert a metal screw and the magnet will attach to the screw. Then screw the washer to the door and the closure is complete. I intend to test this theory tomorrow to see if it works (i.e holds two pieces of wood together without extracting the magnet).

Any opinions or suggestions I can receive between now and test time will be appreciated.

[Justin King]

I think that your idea will work, but it may be a little bit "weak" on holding power. I think that it will work though.

I'll be the one to ask.... Why not use countersunk magnets on each side? I usually countersink them from the back side.

**EDIT** Upon rereading, I think you may be asking how to adhere the magnet to the piece? If so, I like to hot glue the magnet on a dowel, insert into hole that you drilled with forstner bit, and flush cut the remaining dowel.

Justin

[Cliff Rohrabacher]

drill a 1/2" hole (forstner), slightly countersink and insert a metal screw and the magnet will attach to the screw. Then screw the washer to the door and the closure is complete.

That'll most likely work so long as the opposite attraction on the other side of the magnet a isn't more robust - which is not a thing you can guarantee except by ensuring that the screw you are retaining the magnet with will be larger and present more dead flat surface area than whatever chunk of steel you are using to keep the door closed. If it's a magnet on the other side forget it the screw will loose.

I'd use any brand Epoxy in the Forstner hole and be done with it.

[John Grossi]

John, As I am sure you are aware, rare earth magnets are very strong. I would do it the way you describe and then fill the countersunk area with a colored epoxy. The screw will hold the magnet in place, while the epoxy, once sanded will hardly be noticable.

[John Keane]

Great ideas, thank you. This site is priceless. R/John.

[Alan Schaffter]

I use two 1/4" by 1/4" rare earth rod magnets. For flush inset doors I drill a 1/4" hole in the top edge of the door and one in the bottom edge of the top faceframe. I glue the magnets in place with a little super glue. It works great. For full overlay doors you'll need to holes in the back of the door and front of the faceframe. You can do it either way with 1/2 overlay doors

[glenn bradley]

The place you got the magnets may sell these:

http://www.rockler.com/product.cfm?page=10713&filter=magnets

The magnet stays in the cup by virtue of it's attraction. The demo unit I saw worked fine; no escaping magnet.

[John Keane]

Glenn, I was at Rockler today and got 2/3 rds. I got the magnet and the washer. Sales clerk must have thought I knew what I was doing. I didn't.
Guess I need to go back or order online. Thanks for the tip. R/John.

[Curt Harms]

That'll most likely work so long as the opposite attraction on the other side of the magnet a isn't more robust - which is not a thing you can guarantee except by ensuring that the screw you are retaining the magnet with will be larger and present more dead flat surface area than whatever chunk of steel you are using to keep the door closed. If it's a magnet on the other side forget it the screw will loose.

I'd use any brand Epoxy in the Forstner hole and be done with it.

Drill holes with a forstner bit for the flat bottom and epoxy the magnet in. One word of caution--all magnets have polarity and even if used in woodworking applications like poles still repel. Make sure when using one magnet in the frame and one in the door that they attract each other, not repel each other. Know how I found that out??:o.

Curt

[scott spencer]

Even small rare earth magnets are really strong...stronger than most magnets used to hold doors closed. I have no way of knowing for sure, but my gut reaction was that you'll have too much power from the magnet. They always blow me away when a play around with them. If you decide to pursue them, there are cups available to hold them in place.

Good luck and please let us know how you make out.

[Andrew Williams]

IIRC, the cups are not just holders but also direct the flux lines to make the magnets more powerful in the opposite direction. It might soften the field a bit not to use a cup.

[Doug Shepard]

I've experimented a couple of times trying to make hidden catches and each time I ended up using something else. If you cover them with a plug and sand flush, the wood will have a HUGE impact on the holding power. I think it's doable but you'd need a lot bigger magnet than you might expect. About the thinnest plug layer over the mags I was comfortable with was around 3/32" and the attaction between the two mating mags was extremely weak. Using the mag cups or not using them didn't seem to make much difference through the wood. All my experiments to date have been trying to do it with both mags covered by a plug. I still think maybe it's doable, but with bigger (stronger) mags. Next time I try it, I'm going to look into the longer cylindrical type for going into board edges, and much bigger diameter discs for board surfaces. I haven't tried yet only covering one side with a plug and either a bare mag, center-screw mag, or metal plate on the opposite side. Let us know how this turns out.

Edit:
Forgot to mention - these guys have a pretty complete selection of stuff.
http://www.kjmagnetics.com/categories.asp?PARTNER=Google&gclid=CMH5tK3W14sCFQstWAodXHlvaw

[John Keane]

The magnets and washers that I used from Rockler's were 1/2" x 1/8". I scratched the 'back' side of the two magnets, drilled the 1/2" hole 1/8" deep, expoxied the holes and inserted the magnets. So far so good. Today I attached the washers. Not a strong connection.

I think that perhaps the magnets should have stood a little proud rather than flush. The distance between the magnets and the mating washer may just be a hair much and thusly not a strong connection. Good exercise though for future endeavors. Thanks for all of the contributions.

[Jim Knishka]

A note on how strong rare earth magnets are - I bought an old Powermatic planer with no dust hood. Fabricated one out of sheet metal air duct fittings, left a flange, and tied it down with two of the 100lb capacity magnets from the hardware store - $14. Didn't have to drill holes and tap in the cast iron, comes off instantly, and steady as a rock.

[jeremy levine]

As usual a ton of useful info
http://www.leevalley.com/hardware/page.aspx?c=1&p=40077&cat=3,42363

[Phil Clark]

I'm with Scott - these magnets are very strong. I only use them when I want the holding power. I use ball catches, which are attractive, if I just want the door to stay in the closed position.