Beam Compass & Marking Gauge

Compasses, marking gauges - all different shapes and sizes, of which I have one or two myself.

But this started out as needing to draw a line 5mm away from a routed channel that was oval - no straight edge. Yes I could have tried various methods and cobbled something together but I had an idea and needed to try it out, and like most things I like it to do more than just one thing, hence the compass.

• Scrap recycled wood - preferably a hardwood
• 6mm Acrylic if available
• Brass or steel bolts - 4,5 or 6mm depending on what you have
• Steel, brass or aluminium 5 or 6mm diameter rod - about 50mm long
• Wax to finish it off and make it smell nice
• A saw of some kind - a bandsaw is useful
• A square & rule
• In my case I used a router but there are ways around this.
• ...and a pencil - always useful

The aim of this it to have 2 pieces of wood that slide parallel to each other, can be locked in position and will secure a pencil in the end of one piece (the carrier) and 2 bolts (one in each end) of the other piece (the beam).

This can be made of one piece of solid wood or where a router is not available then laminate pieces together - this method can create the 'slot'.

In theory you could make this any length and width you desire with flamboyant shaping ... but for me a clean tidy tool is required - 'minimalist' design. I made something approx 30x40x300mm.

The bottom piece - the beam - has holes drilled in each end to secure bolts. One is pointed to be a compass point, the other is screwed in from below to be a 'stop'. This butts up against an edge.

The top piece - the carrier - is drilled to secure a pencil or scribe in the end.

When both pieces are placed together they can slide but can be locked via a knob, and through this the distance between the compass point or the stop and the pencil end can be adjusted.

So I have 2 pieces of iroko hardwood 20x30x300. I set up my palm router with a piece of wood to be the guide fence to route a 6mm groove. This width depends on what router bits you have and also the width you want your slide strip. In this case I'm using 6mm thick black acrylic (scrap) - 10mm wide.

• The beam - route a slot the full length - 5mm deep, in the top. Drill a 4mm hole vertically in each end - this is to screw in 5mm brass bolts - one from above, one from below, approx 4mm from the end.
• The carrier - route a slot the full length - 5.5mm deep, in the bottom. In the top you need to route a slot the full depth but leaving material at both ends. Approx 15mm at one end and about 30mm the other. This through slot is for the locking bolt.

• The beam - I cut the end off approx with10degree angle and screwed in a brass bolt from the underside. This is a stop. The angled end allows for the pencil to then be adjusted within 2mm. I used a sharpened bolt (done on the grinder) and screwed this in from the top. This can't be too long as it needs to retract up when not required.
• The carrier- I drilled 3 holes - one for the pencil, the other for a scribe - so 8mm and 5mm, and another for the 'flex' slot - about 3mm. Using the bandsaw I then cut a 2mm slot and also shaped the end enough to allow the wood to flex to allow for the pencil to be clamped. I drilled another 4mm hole all the way through and a recess hole to accept the bolt head just behind the pencil. The bolt was screwed in and the pencil or scribe could then be clamped in place. I then cut off (8mm) and shaped the top section where the locking bolt sits to take some weight off.

I had found an internally threaded 6mm knob and glued in a threaded bolt and cut the hex head off. This was my locking bolt.

The acrylic strip was cut and glued into place to allow for the end bolts.

Once dry it was all placed together and aligned and then another 5mm hole was drilled down into the slot so the locking bolt could be screwed in.

I then smoothed it all down and waxed it for a smooth operation.

Using it in the compass mode I found it a little difficult to see where to place the centre point. Also the scribe rod had no home when not in use.

So the beam section was modified by shaping the sides and undercutting the bottom. This allowed better visual positioning. I also drilled a hole (length wise) into this end to take the scribe rod and to keep it in place, fixed a magnet to the underside (4mm hole for a 4x5mm magnet).

• Compass mode - screw the top bolt down to use the point. Screw the bottom bolt up so it is out of the way. Fix in the pencil - adjust the beam to desired length and away you go. Works well and allows me a range between 290-515mm. I don't need smaller than this as a standard compass will do it.
• Marker gauge mode - the minimum distance I can draw a line away from an edge is 2mm. The pictures show I can draw lines various distances away from a routed slot, therefore so long as the slot is approx.6mm wide the bolt head will fit in.

I'm looking at how it can design just one arm that you make twice and mirror the items, both having the capability of clamping pencils or scribes(compass points). But thats for another day.

Thanks for looking