I have a few guitars that need glue softened for neck removal. Some use the silicone heating pads used often on oil pans but looking online they range from 6/12/24/110/220v and 50-350w, few even say 1200w.

Not sure how to use that to determine heat, and in most cases, heat not mentioned in specs and from China (ie. Aliexpress) so fat chance getting a response that makes sense. Some reviews have mentioned temperatures though.

Is there a cheap part off Aliexpress or something I could put between the plug and the pad that will allow me to turn the power up/down? Like the motor speed controller board but for this? Or is there a way to calculate what the amount of heat would be? I assume not given the variables involved (ie. size, overall length of heating coil).

Heat pad example

 

Something like this work for the 24v version?

 

A regular light dimmer will do that. One with a rotary knob would be the easier to adjust precisely. Re/store recyclers should have some for cheap, or they're fairly common at thrift stores. It would need to be wired inline with an extension cord or something, or mount it in a two-gang surface-mount electrical box along with a receptacle if you want it less sketchy. These also work as motor speed controllers, so if you already have one with a sufficient amperage rating, try it.

https://forum.allaboutcircuits.com/...sing-dimmer-switch-as-a-motor-control.138385/

 

Oh, that would be easy and cheap... so just buy the 110v one, preferably with the cord/plug and just add a dimmer in the middle.

Yup... that's exactly the type of easy/cheap I was looking for.

Speaking of motor control, my next easy/cheap would be a light switch based mod for a drill press to add reverse, though from what little I know (not researched it much yet) it depends if the motor has "something" that will allow reverse.

 

A nice hack for a drill press is a washing machine motor that has a two-speed gearbox controlled by a solenoid. As for reverse:
https://www.hunker.com/13414114/how-to-reverse-the-direction-of-a-single-phase-ac-motor