Replies

1. 
   forestgirl | May 14, 2002 06:19am | #1

   IMHO, a resounding yes!  I never touch (with my hand) a router bit or saw blade with the tool plugged in.  I have a small piece of wood that I use if I need to position the bit or blade slightly (checking height, exact cutting spot, etc.)  Call me paranoid, but that's my approach.

   forestgirl -- you can take the girl out of the forest, but you can't take the forest out of the girl   ;-)

2. 
   jackiechan | May 14, 2002 06:26am | #2

   Please! Magnetic switch or not, you should always unplug any machine when servicing or changing a blade.  By unplugging the machine you are eliminating that one-in-a-million chance of an accidental start-up, leaving you the ability to only count to 7 and a half on your fingers!  But seriously, it is always the best, and safest practice to unplug your machines to change blades.

   - JC

3. 
   Trees2dust | May 14, 2002 08:24pm | #3

   Frank,

   I read about a guy who was working in his garage workshop when his table saw accidentally started after a kid's errant soccer ball hit the magnetic starter.

   A magnetic switch can actually make a machine more susceptible (compared to a manual switch) to an accidental trip due to mechanical shock, and here's why: A magnetic switch uses a relay to energize the machine's motor. The relay's contacts are fairly close together, kept open by a fairly weak spring; this is by design, otherwise the transformer and on/off switches, along with the relay itself, would be prohibitively bulky and expensive. Bump it hard enough and the relay's contacts could come together, causing the saw to start. A manual switch on the other hand can be designed with a strong enough spring so that no practical amount of mechanical shock could cause it to accidentally trip.

   Aside from mechanical shock, there are all sorts of other ways that a table saw could accidentally start.

   I always unplug my Unisaw if I have to touch the blade and at the end of every work session.

   Work safely,

   Rick

4. 
   TKanzler | May 16, 2002 05:04pm | #4

   Besides seconding everything all the others have said above, here's another reason.

   I worked in a small cabinet shop after school many moons ago.  They had a 40's vintage Unisaw, with the mechanical on-off switch (with the nifty art-deco cover plate).  The owner, who should have known better, always changed blades without removing the plug (nothing in that shop was hard-wired), until one day the saw started on its own.  He only got a scratch, probably because the arbor nut was very loose when it happened, and he naturally pulled his hand out post-haste.  I don't want to think about what probably would have happened if he was at some other stage in the blade-change process.

   My guess as to why it started is that toggle switches are over-center devices, ie when you move the toggle it pushes a see-saw type set of contacts from one side of center to the other.  If for some reason (old age, perhaps?) the contact assembly fails to snap over to the off side of center, and instead remains 'on the fence', or if saw dust fouls the mechanism a bit, or if the toggle wasn't moved to the fully 'off' position (most likely all three, I'd guess) it is conceivable that the contacts could close on their own. 

   From that point forward, the rule was that everything gets unplugged for tool/blade/sanding belt changes, along with service, and repairs, with the plug placed right next to the tool/blade/belt for visual verification.  It seems a little preachy when they do it in the magazine photos (almost like their lawyers make them do it), but it is 100% reliable.  And I like my fingers just where they are.