Each thread has a unique linear density and has the ability to cover a piece of fabric in a different way; it is important to establish what the ideal cover density is for an average fabric for each thread you use. Digitising software allows you to choose a density setting normally calculated in stitches per square centimetre.

The same thread will cover different fabrics slightly differently so it is also important to establish - for a particular fabric type - what is the ideal stitch density setting to use - especially if you have a long production run on a particular fabric type.

If you choose too high a stitch density you will increase your use of thread and machine time; possibly resulting in additional thread breaks - all of which are very expensive. If you choose too low a setting then 'gaps' and 'grins' will start to appear where the fabric colour protrudes through the embroidered area.

Coats Embroidery have developed a simple test programme that will allow you to establish the correct stitch density for any type of embroidery thread in Ticket 120 (120 denier/2ply) and any type of fabric - the programme can be downloaded below:

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Instructions:

• run the design on the thread & fabric type you want to test
• the design is in two halves of 8 squares each
• the top half [N] uses no underlay - has cover stitches only
• the bottom half [U] uses underlay as well as cover stiches

The density of each square in stitches per square centimetre is indicated in the illustration above

How to interpret the results:

• choose a square in the top half where the density is perfect - no gaps - just enough cover - this is the ideal density for that thread and fabric combination - this indicates the density to use when you have no underlay
• choose another square in the bottom half - this is the ideal density for the same fabric using underlay
• give this information to your digitiser who will use it to adjust the density settings for that design

• using a combination of underlay and cover stitching uses far less stitches than using cover stitching alone - therefore always use underlay if possible - especially for large fill areas
• using the correct stitch density will result in a significant savings of unnecessary stitches; an area sewn at a density of 0.55mm uses 20% less stitches than a density of 0.40mm - adjusting density depending on fabric can routinely save considerable amounts of machine time as well as save on thread useage
• each fabric will have a slightly different ability to absorb stitches from a particular thread; it can save you many thousands of stitches in a month if you routinely run this test on each new fabric when you start a large job.

Test Design: to download the design (in Tajima format): please click here