[Al_The_Man]

Essentially what I am saying, were it me, I would either use the relay method in post#13 or substitute the mechanical relay for a SSR if you wish, virtually the same connections.
Two in, two out.
Al.

[jeff johnson]

Thanks Al. That looks the simplest. I like simple, just like me.

[Mzones]

When your computer starts up all I/O pins are high. The 7414 inverts the signal
and the power coming from the usb port. This keeps the spindle from inadvertently
starting when it is not suppose to. without inverting the signal spindle will turn on
when you boot up. Using usb power also keeps spindle from turning on when off.
Spindle motor can only come on when computer is on and control pin is low.
Using a SSR eliminates the need of having to provide additional power source.
Also I said that we all may do it a little differently. this works for me.

[jeff johnson]

Is this the kind of relay I need? Opto 22 120 240 Vac 25 Amp DC Control Solid State Relay SSR 3 32V DC Control | eBay

[Al_The_Man]

Is this the kind of relay I need?

That should work, all source of power to motors drives etc, should be help off until Windows/Mach is loaded, this is normally done by holding off the power to these motors via an E-Stop relay switching the main power.
Al.

[jeff johnson]

Al The Man..Would this circuit be ok as far as using receptacles to plug in the router and dust vac?

[Al_The_Man]

Yes, Ideally you would feed the 120vac from an E-stop contactor or heavy duty relay to prevent the spindle coming on at boot up as pointed out earlier.
Normally an E-stop circuit disengages all main power to steppers/servo's and motors etc.
Alternatively if the BOB had a charge pump that held off the relays off until this time, it would be an alternative.
Al.