Rotation of a part on another part that rotates



I’m sure this is covered in the forum somewhere, and on YouTube, but I haven’t been able to find it.
To describe what I want to do in my table saw might be difficult to visualise, but if you can answer this much simpler question, I’m sure I can transport the knowledge and technique to my project.

How would I model the rotation of a letterbox flap that rotates on a horizontal hinge on a door that rotates on a vertical hinge? I want to be able to set the letterbox flap at a given angle, then rotate the door on its hinge.

For your interest, the table saw has a framework that hinges to change the angle of cut, then the motor and saw assembly hinges on that frame to alter the depth of cut. The motor, saw and mounting components are a group, and the frame on which they rotate is another group. I can rotate them individually, but both rotate with respect to the XYZ Sketchup axes.


The easiest way to manage this is to control what you have selected for each rotation. Is this a contractor’s style saw? If so, to set the bevel angle, select everything that needs to move and rotate them about the axis of rotation. To adjust the height of the blade, Select the blade and the spindle assembly. Rotate the selection as needed. And so on.

How are you using the tablesaw model? What do you need to show with it?


For the letterbox flap, I think you’ll need 3 components as follows:

  1. Fixed pieces - the door frame and the fixed leaf of each hinge
  2. The moving portion of the door - as a subcomponent of #1. This will include hinge leaf that moves and the fixed portions of the letterbox.
  3. The moving portion of the letterbox flap - as a subcomponent of #2.

For #2 and #3, you’ll need to carefully align their axes along the centerline of the hinge pin, then on activate the movement through rot<X, Y, or Z - depending on which axis you aligned>

The above should work for standard, 2 leaves plus a pin hinges. Other hinge types may require more complexity.


Like this?

Draw the door, pushpull a letter box hole. Make it a component.

Draw the flap. Make THAT a component.

Change axes so the flap has its red axis along one top edge. And the door has its blue axis up one edge.

Select both, and make a combined component.

Then you can rotate the door and flap together about the door’s blue axis, And the flap independently about ITS axis.

Door and letterbox flap.skp (23.7 KB)

Like this.


There is an important piece of information missing: are you looking to create a dynamic component that does this, or merely to draw a SketchUp model that has the parts rotated in a particular way?


You are missing 1 degree of freedom=> I assume you want to figure out how to set saw angle and miter gauge angle to get a compound miter cut?? Note that some saw blades tilt right and others left plus some have a sliding table. If that is the case there are spread sheets on net you can get those in fraction of time vs. model.:slight_smile:


Ummm… I’ve been a Sketchup enthusiast for all of about a week, so I’m not sure I can answer your question. I think, the latter - to simply draw a model that will allow me to rotate the parts. I have read that making a dynamic component requires Sketchup Pro. I’m not looking to make a component to use in future projects. The design I’m doing is for a one-off, for my own use - not for a production run.

My idea was to design the saw, then produce the parts from measurements on the Sketchup model. I want to be able to move the parts to be sure that there will be no interference between them, and that everything will work. In all probability, I could have made the table saw without making any plan, and simply cut bits off to relieve any collisions between parts. I’m really enjoying Sketchup, though, and I’m sure I’ll use it in the future to make little drawings of things I want to communicate. A picture says a thousand words.


Thanks to all those who answered this thread, but I was just looking for the principle of how to do it. I think john_mcclenahan comes closest to what I was looking for - though I’m still missing something that is so obvious to you guys that it’s not worth the mention. It’s not to me, though.

I made a door (the letterbox hole isn’t required). I put a select frame around the door and made it into component “Door”. Then, away from the door, I made a letterbox lid, selected it the same way, and made it into component “Flap”. I selected Flap and dragged it onto the face of the door. I changed the axes to put a red axis along the top of the flap. There is already a blue axis up the left edge of the door. I put a selection frame around everything and make component “Door with flap” However, the axes for the flap are relative to the Sketchup axes, not relative to the door itself, because when I open the door, the flap stays where it is and does not move with the door. Somehow, when moving the axes for the flap, they have to get stuck to the door - and I think that’s what I’m missing.


That sounds like you didn’t actually get the flap nested inside the “door with flap” component. You should be able to investigate this by opening the Outliner window and seeing whether the components are listed as an indented tree or all at the same level.


Don’t forget a saw creates alots of vibration. That is one of reasons reason vendors make them “beefy” . If I can get my table saw to deliver .0625 over extended use period I think I am lucky and have cast iron table and wings. Kick back is also a worry so be safe,