Don Young wrote:

"Dave B" wrote in message
news
One our customers recently had an operator that left the chuck key in
the chuck and started the spindle.

They asked us to provide a solution and here is what it looks like.
We have installed 20 of them in the last few weeks.

Will not allow the spindle to start without the key in place and if
removed of course the spindle stops.

http://s32.photobucket.com/albums/d1...chuck_safe.jpg


Dave B
That's a very neat arrangement. I saw an idea years ago to hang the key on a
lever type microswitch connected to open the power leads if the key was not
present. Your idea would be more foolproof.

Don Young

Never underestimate fools. I see irritated users just dropping a big
drill bit or boring bar in there to eliminate the hassles.

Try something better to detect when the chuck key is in the vicinity of
the chuck, not when it's in a specific holder. if the chucks aren't
changed often, I can see an arc of hall effect sensors positioned around
the chuck to detect a magnet epoxied on the chuck key. Detect when the
chuck key is in the chuck to disable, as long as it's not in the chuck
let 'er rip. Why would one care if the operator puts the chuck key on
the tool cart, in their back pocket, etc.

Even simpler would be a curved piece of plexiglass as a flip down shield
over the chuck, with a switch to detect when it's down. Flip the shield
up and do your thing with the chuck key, when you take the key out flip
the shield back. If the key is in the chuck, the shield can't come down
and the lathe can't start. Flipping the shield down as you take the
chuck key out takes less time and effort than inserting the chuck key
into a little tube much further away.