Saturday, March 14, 2015

Circle Cutter. Segment Marker. Strip Cutter. Seamstress Ruler

The OLFA CMP-1 Compass Circle Cutter is a great tool for cutting circles in card or balsa/basswood sheets. The major advantage is the blade and the pivot point are vertically parallel to each other. Not shown are included 6 extra blades, a protective blade cover and a pad that prevents poking the pivot point into the material (which I'm usually not concerned with).

I do my circle cutting on a scrap piece of 3mm MDF. I drilled a 1.5mm hole and superglued a short 6mm length of 1.5mm brass tubing into it so 3mm sticks up. I then cut some scrap matt board and drilled a 1.5mm in its center. This slips over the end of the tubing, prevents the OLFA from cutting into to MDF and is easily replaceable when worn out. I put a small piece of BluTac under its corner to keep it from rotating during use.

Bear with me on this next part. It's much easier to do than explain...
For each circle I set the OLFA to the correct radius of the circle. I then drill a 1.5mm in the center of scrap card that's larger than the circle I'm cutting. I then put the card over the pin tubing of the MDF/matt board and hold it in place with a finger or two. Next I place the OLFA in the tube and rotate it part way around, cutting part way into the card. I release the card and "unrotate" it as well as the OLFA. I continue to cut and unrotate until I've gone around the circle enough times to cut all the way through and TAA DAA! A NICE CLEAN CUT CIRCLE! When making a ring I simple readjust the OLFA to the correct inner radius cut out the inner circle the same way.

My explanation may make the process seem awkward but it's actually quite simple: Once the OLFA has been set and you've got a stack of card pieces with 1.5mm holes in their centers it takes very little time to cut out a bunch of circles/rings.

WHY GO THROUGH ALL THIS? 1) The pin tube really helps the cutter and card rotate with minimum difficulty and 2) Turning the cutter all the way around the circle in one go is quite awkward, especially when cutting small circles. By only cutting part of the circle at a time it is much easier AND minimizes blade wear and tear.

HINT: When cutting circles out of matt board or balsa/basswood sheet, remove the jig's matt board and put the material directly over the tubing. Once you've cut the circle almost all the way through, flip it over and finish the cut.

I drew this on scrap cardboard. The circles were drawn using a standard compass with a pencil lead (not my OLFA).

Simply place a circle or ring on it and mark segments. Very useful when I need to mark where rivets go.

Updated version of my shingle strip cutter (METHODS: HG WALLS Shingles 1). It's 3mm MDF, is adjustable and has a brass strip to run a utility or Xacto blade against. It has a piece of matt board to cut into with a piece of BluTac underneath the lower left corner to keep it in place.

Handy when marking where repetitive lines go. I added a short tapered dowel to keep the sliding part snug.