Big Compass Kit
Overview of the big compass kit
The big compass kit is a great addition to any woodwork shop. If you draw your projects full size you can quickly mark out curved components with this tool.
The kit is made in aluminium and delrin with the legs made in wood. The hole for the marking device in the delrin discs is 8mm.
The pivoting delrin discs mean that the centre point and pencil can always be set at a right angle to the surface no matter how wide the compass legs are.
The main pivot point is tightened with an m8 bolt to ensure no movement in action along with m5 bolts that securely hold the delrin discs in place.
The legs provided when you buy the compass kit are 450mm (17 3/4″) long which allows a 1550mm (61″) circle to be drawn.
If you need to draw a larger circle simply make longer legs to suit your needs.
When the circle becomes too large to draw with a compass the shoes can be removed and attached to a piece of wood to form a trammel set.
Dismantling the big compass to show the individual parts.
Using longer legs.
Drawing the smallest circle possible with 450mm legs.
With the deluxe big compass kit one of the delrin discs has the same clamping system as the UBB Scriber see (UBB Scriber page).
You can clamp any marking tool with a diameter of between 5.5 and 10mm. Ideal if you want to use a marking pen.
If you need to score a line in the work piece you can use the Chair Makers Marking Wheel.
By purchasing another scribe you can turn the compass into a pair of big dividers.
When the legs become too long and the compass is unwieldy to use you can turn the compass kit into a trammel set. This allows you to scribe some really big circles. This is a better system than a standard trammel set because the pencil can be set accurately on a mark by pivoting the pencil holder.
The middle image shows the compass shoe screwed to a block which is clamped to the beam. This method allows you to use one beam length for multiple diameter circles.
Drawing showing the dimensions for the compass legs.
Using 1000mm long legs to draw a circle. Any longer than this and the compass becomes unwieldy.
This is when you switch over to the trammel set up.