Ed asked a series of questions regarding switched magnets (no electrons used,
and with a history to the beginning of the 20th Cty)starting with:
> I think the basic question is: do any properties of what a magnet attaches to>
affect the strength of the bond?
Yes. Many properties.

> Magnetic bases for dial indicators are switched so you can engage or disengage
> the magnetism.  Is the hold strength of the magnet affected by the mass or 
> thickness of the iron that it will attach to?  In other words if I use a piece
> that is 2 x 3 x 1/8 will it result in less grip than say using a piece that is
2
> x 3 x3/8?


Yes. Thinner material will have less hold, but beyond a certain thickness, the
difference is minimal. What thickness depends on the particular magnet. I have
some that will hold at near maximum force on 1/8" material, and others that have
only a small percentage (maybe 25%) on on 1/8", but hold near maximum on 1/4" to
3/8". The strength of the permanent magnet determines the actual force, but the
distance between the poles and their size are the primary factors in how it
reduces with the surface you put the magnet on and what gap (magnetic) there is
between the magnet poles and the steel.


> If I try and hold two pieces of veneer between the 2 
> jaws it holds well, 2 pieces of 1/8 thick stock and it holds, but not well. 
> Does altering the thickness of the mild steel side effect anything


The force drops off rapidly as the distance between the magnet and the steel
increases. Thicker steel wont help much beyond a certain point, and you are
probably already there.

You may do better with a switchable that used a different pole configuration, or
another magnet on the other part rather than steel, if you can find  a
switchable (or modify one such that it has) with the opposite pole
configuration. A switchable with a different pole setup might do better as well.





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