The basic idea is simple, NEVER make adjustments with the tool running.

It is not only about what the tool can take (most of the times it can't), but also about your safety. Keep your hands far away from active cutters.

From the DF500 manual: "Never rotate the dial during a plunging operation. This can bend or break the mortising bit, and can also damage the machine."

Why would one want to change the width in the middle of cutting a mortise?

If the width was set incorrectly (too narrow), simply stop and reset the width before plunging again. Why do something against the advice given in the manual with not much perceived benefit. I always set the fence, depth and width (in that order because usually a mistake made on the last setting is easier to fix than the other two) BEFORE the machine is turned on,

Rotate the width dial when the motor is running but not plunging.

Rotate the width dial when the motor is running but not plunging.

Thanks Michael.  That's my thought also.  And what about when the machine is off?  As I see above, we have Alex for instance saying not to switch the XL DF 700 width selector at all when this on (even when not plunging in a static state).  I may have misunderstood, but that's the way I take it. 

This is where I'm asking Festool, the company, to make it clear by answering the implied discussion directly. 
 
Engineering Rule of Thumb:  Not stating to not to do something specific doesn't mean it's okay to do it or make it clear what to do to operate a feature.  I appreciate those above commenting on their experience although possibly contradictory in one case (Alex).  With another, my question has nothing to do with switching while plunging [moving the bit along the rails].  That is clearly stated in the manual of what "not" to do on Page 8 of the XL DF 700 supplement.

My two questions above specifically pertains to proper XL DF 700 operation of this dial, which I am asking Festool to clearly concur or non concur as to proper operation.   

Thanks again for the quick response as it aligns with my unconfirmed presumptions also. 
Best

From the DF500 manual: "Never rotate the dial during a plunging operation. This can bend or break the mortising bit, and can also damage the machine."

Why would one want to change the width in the middle of cutting a mortise?

If the width was set incorrectly (too narrow), simply stop and reset the width before plunging again. Why do something against the advice given in the manual with not much perceived benefit. I always set the fence, depth and width (in that order because usually a mistake made on the last setting is easier to fix than the other two) BEFORE the machine is turned on,

Chuck, we both agree. It's already clear in the XL DF 700 Supplemental User's manual not to plunge and switch the mortise dial at the same time.  But it doesn't say when it's okay to switch the dial in the manual for proper operation.  Implying it's okay to switch the mortise width dial when the XL DF 700 is off or on (on, while not plunging) is unclear per the operating instruction.  Agree, the mere thought of switching a gear that's in motion without a clutch is cringe worthy ( :  That may or may not be true when the machine is off, or on while not in the motion of a plunge.   

My two questions above ask Festool to state proper the operation of the switch.  Not merely what not to do and imply the rest.

Best
  -R23


   

Festool seems not to monitor the forum well at this point.  I suggest calling the number on the side of the machine.  The applications department always has knowledgeable people to help with these kind of questions.

Sorry Robert 23. I misread both your post and the manual. Let me try again:

From the DF500 manual: "Rotate the adjustment dial only when the motor is running."

So it's clear that for a DF500, one should turn on the machine (without plunging) and then set the width...then plunge when ready.

I need to change my setting procedures/habit. Good news (or lucky me) is that despite not following that bit of advice in the manual for years, my machine has been working fine.

No worries Chuck. I think in the end we're really all about getting to ground truth. 
On the side, thanks for the feedback/image on the DF500 above.  Perhaps Festool will reply what is true for the DF500 in print is also true for the XL DF700 (despite having no such text in their 700 manuals).

Best
   -R23

To simplify the situation so that I don't have to remember which Domino needs to be running and which Domino needs to be static  I change both of the tools widths in the static position.
For the 500, just turn the width switch slightly, if the gear alignment is in the correct position to move, it will do so easily. If there's some resistance, just blip the on/off switch and try again.
The 700 always moves easily in the static position.

The DF 500 can be adjusted when on, the DF 700 should not be adjusted when the machine is on. If you have further question regarding this, you can reach out to an application specialist @ 888-337-8600.

A few years ago, I added a blue tape & sharpie label reminder to the inside of my Domino 500 systainer that reads: "Only change width setting when running" so I wouldn't forget.Snip.

In the early days, I put the critical info. on strips of paper and taped them to the machine itself. They were removed after (I thought) I knew everything. Now, I think I need to put a reminder back there about the width dial!