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A compass ruler, why when you can use a standard compass.
The standard compass still requires the ruler to measure the appropriate radius for the circle to be drawn and has a limited useful radius.
While a beam compass is more specialised offering a greater range than the standard compass, possibly including graduations and extension pieces but is a relatively expensive option.
A ruler is a must have in the workshop and is relatively inexpensive in comparison to the former.
But the size of the circle is only limited by the length of the ruler and is infinitely adjustable along its length without recourse to extension pieces.
The elements to be designed to accomplish the function are inexpensive, few in number and can be scaled to the appropriate ruler size.
Materials and methods
Only two elements are required to be made for the compass ruler these are made to fit a 12mm x ~0.5mm steel ruler
These are the pivot element and the slider which holds the pencil and are designed to be 3D printed.
Both elements have a slot which is compatible with the ruler allowing them to slide up and down.
The pivot element sits at the end of the ruler and is held in place with a screw, a hole at the extreme is the pivot point.
This point has two options.
1: Fixed with a grub screw that will be the circle centre.
2: Placed over a fixed point (i.e. Nail), that is the centre of the circle to be drawn.
For greater flexibility two pivot elements can be made for interchangeability subject to requirements simply swapping the elements as required for the task.
The slider that holds the pencil needs to be able to slide up and down the ruler and locked in placed with a thumb screw at the required point to set the circle radius.
Screw holes are M3
Thumb screws - 10mm in length
The design would be created using BlocksCAD.
The orientation of the elements in relation to the bed is critical as a result of the slots and the impact of gravity.
As a result the slots are orientation vertically and short arcs are used in non supportive horizontal runs to eliminate sagging.
Due to the small size of the elements and that they will have threaded bolts fitted the infill was set at 100% to add strength.
Layer Height - 0.15mm
Infill type - Tri-Hexagon
Base adhesion - Brim
Filament - PLA
Size 13 x 19 x 29 mm
Weight - 6g
Filament length - 2m
Print time - 1hr 20min
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