[TheForge] Re: magnets as latches

Fri May 14 13:30:50 EDT 2004

Roger,
I have used magnets as closures a number of times, including fire doors.
The fire doors do not need to be air tight, and the magnets have never seen anywhere near the heat to affect the magnet. Plus in some cases I have actually put a little plate behind the magnet as a radiation shield.

Ray Miller
Cincinnati

> 
> From: Roger Olsen <erik at methow.com>
> Date: 2004/05/14 Fri AM 11:20:36 EDT
> To: Sponsored by ABANA <theforge at mailman.qth.net>
> Subject: [TheForge] Re: magnets as latches
> 
> Let me try asking the question this way________do any of you have actual
> experience using magnets for a closing system on firedoors?  I am not asking
> those of you who have guesses or assumptions or opinions, only those of you who
> have actually used them and what you found______did the doors latch the same
> two years from day one or did they loose a lot if not all of their magnetic
> qualities.
> 
> Thanks,
> R Olsen
> __________________________
> 
> Steve Smith wrote:
> 
> > I don't have a clue, Roger. I did find a list of Curie point
> > temperatures for different materials. Here are a few (in degrees
> > Kelvin--subtract 273 and you have Centigrade):
> > Iron 1043
> > Cobalt 1388
> > Nickle 627
> > source: http://www.nationmaster.com/encyclopedia/ferromagnetism
> >
> > etc. So your question is good, how soon do you see effects? It also
> > looks like you have a huge effect in the actual temp by what alloy
> > you're magnet is made of. I don't think this helps, just more info.
> >
> > Steve Smith
> >
> > Roger Olsen wrote:
> >
> > > So I assume the higher the heat the faster the magnetic loss but when does
> > > the affect kick in?  100 degrees________300 degrees_________500
> > > degrees________700 degress?
> > >
> > > Does anyone know the answer to this?
> > >
> > > R. Olsen
> > > _______________________
> > >
> > > Bruce Freeman wrote:
> > >
> > >
> > >>Clearly, when steel goes non-magnetic, if the steel WERE a magnet it
> > >>wouldn't be afterwards.
> > >>
> > >>However, any heating or hammering will reduce or destroy the magnetic
> > >>properties of a steel magnet.
> > >>
> > >>If using a magnet as part of a door latch:
> > >>
> > >>First, be aware that those rare earth magnets can be VERY strong.
> > >>Think pinch-points when using them in a design.
> > >>
> > >>Second, you may want to move the magnet itself away from the heat.
> > >>Imagine, for example, using a horseshoe magnet as the handle on a hot
> > >>door.  The cooler handle will be less likely to lose its magnetic
> > >>properties.  But if constructed correctly, this remote handle could be
> > >>an effective latch for the door, since the magnetic forces will follow
> > >>the path of the steel.  (Constructed incorrectly, there would be no
> > >>magnetism to latch the door, however.   Avoid a complete loop.  Think:
> > >>"horseshoe" shape.)
> > >>
> > >>Bruce
> > >>NJ
> > >>
> > >>
> > >>>>>erik at methow.com 5/13/2004 12:22:50 PM >>>
> > >>
> > >>Hey Andy,
> > >>
> > >>Ask your friend one other thing about magnets.  I wonder about heat, at
> > >>what
> > >>point does it drain a magnet of its magic affects?   I have never used
> > >>them on
> > >>fire doors but I know many have.  I have considered using them in the
> > >>past and
> > >>I am sure I will again in the future.
> > >>
> > >>If I did I would use the 'Rare Earth Magnets' sold by Lee Valley and
> > >>others as
> > >>well.  They seem to be about 10 times stronger than the radio shack
> > >>type
> > >>magnets.
> > >>
> > >>Roger Olsen
> > >>__________________________________
> > >>
> > >>Gladish Family wrote:
> > >>
> > >>
> > >>>>1. I have a number of assorted magnets used for set-ups, mock ups
> > >>
> > >>and
> > >>
> > >>>>the like...should they be stored separately, carefully aligned
> > >>>>north/south, to retain max  pull ( suck?) or is it not a problem
> > >>
> > >>just to
> > >>
> > >>>>toss them in a box with their friends?
> > >>>
> > >>>My understanding is that magnets are manufactured by applying
> > >>
> > >>overwhelming
> > >>
> > >>>magnetic fields (i.e. really really huge!) to a previously neutral
> > >>
> > >>chunk of
> > >>
> > >>>metal, and that heat or overwhelming magnetic force are the only ways
> > >>
> > >>that
> > >>
> > >>>magnets lose their pull, other than physical deterioration.
> > >>>I have a friend who sells magnets for a living- I'll ask him.
> > >>>Andy G.
> > >>>
> > >>>_______________________________________________
> > >>>Manage membership or unsubscribe at:
> > >>>http://mailman.qth.net/mailman/listinfo/theforge
> > >>>theforge mail list group photo site is
> > >>>http://www.photoaccess.com
> > >>>Login:  blacksmithblacksmith at hotmail.com
> > >>>password:  anvil
> > >>>___________
> > >>
> > >>_______________________________________________
> > >>Manage membership or unsubscribe at:
> > >>http://mailman.qth.net/mailman/listinfo/theforge
> > >>theforge mail list group photo site is
> > >>http://www.photoaccess.com
> > >>Login:  blacksmithblacksmith at hotmail.com
> > >>password:  anvil
> > >>___________
> > >>
> > >>_______________________________________________
> > >>Manage membership or unsubscribe at:
> > >>http://mailman.qth.net/mailman/listinfo/theforge
> > >>theforge mail list group photo site is
> > >>http://www.photoaccess.com
> > >>Login:  blacksmithblacksmith at hotmail.com
> > >>password:  anvil
> > >>___________
> > >
> > >
> > > _______________________________________________
> > > Manage membership or unsubscribe at:
> > > http://mailman.qth.net/mailman/listinfo/theforge
> > > theforge mail list group photo site is
> > > http://www.photoaccess.com
> > > Login:  blacksmithblacksmith at hotmail.com
> > > password:  anvil
> > > ___________
> > >
> > >
> > >
> > _______________________________________________
> > Manage membership or unsubscribe at:
> > http://mailman.qth.net/mailman/listinfo/theforge
> > theforge mail list group photo site is
> > http://www.photoaccess.com
> > Login:  blacksmithblacksmith at hotmail.com
> > password:  anvil
> > ___________
> 
> _______________________________________________
> Manage membership or unsubscribe at:
> http://mailman.qth.net/mailman/listinfo/theforge
> theforge mail list group photo site is
> http://www.photoaccess.com
> Login:  blacksmithblacksmith at hotmail.com
> password:  anvil
> ___________
> 
> 
> 