About Graphite

Great information about machining graphite

This article was first published in the November, 2003 edition of EDM Today, and is published with their permission. Tony Mucha has been in the EDM Industry for more than 40 years and he shares his advice about how to machine graphite.

Machining Graphite Article

Our Terminology: Talking About Graphite

Catalog Terms
Size, Finish, and Tolerance

  • Raw block

    • Tolerance: all dimensions minimum

    • This block is oversized from the manufacturer and is at least as large as the nominal published size. Finish is as supplied by the manufacturer

  • Bulk plates

    • Tolerance: all dimensions minimum

    • This plate has been cut from a raw block. It is saw cut on the width and length and is oversized by approx.. 1/8” on these two dimensions. Its thickness (up to and including 6” has a sanded finish) and is oversized by a minimum of +.030”

    • Over 6” in thickness has a saw cut finish oversize by 1/32” min

  • Flat plates

    • Tolerance: +.030”/-.000” surfaced

    • This block has been cut from a raw block. It is saw cut on the width and length and is oversized by approx.. 1/8” on these two dimensions. Its thickness has a sanded finish and is oversize by a maximum of +.030”

    • Maximum thickness of flat plates is 3/4”

  • Precision plates

    • Tolerance: thickness +.001”/-.000” ground

    • This plate has a ground finish and is within +.001” of the listed size

    • The plate is saw cut on the width and length to 4”x 6” and is oversized by approx. 1/8” on these two dimensions

  • Ground plates

    • Tolerance: thickness +.005”/-.000” ground

    • This plate has a ground finish and is within +.005” Of the listed size

    • The plate is saw cut on the width and length and is oversized by approx. 1/8” on these two dimensions

  • Squares

    • Tolerance: +.030”/-.000” surfaced

    • Squares are furnished with a sanded finish on four sides to a maximum of +.030 of the listed size

    • Squares are saw cut to an oversized length of 12” in the

  • Rounds up to 5/8"

    • Tolerance: +.005”/-.000”

    • Rounds are furnished with a ground finish to a tolerance of +.005 of the listed size. (1/8 dia. - 5/8” dia.)

    • Rounds are saw cut to an oversized length of 12” in the Micrograph grades and in both 6” and 12” oversized lengths in the Poco grades

  • Rounds over 5/8"

    • Tolerance: all dimensions minimum

    • Rounds 5/8” dia. And above are furnished with a turned finish to a tolerance that is oversized by a minimum of +.030

    • Rounds are saw cut to an oversized length of both 6” and 12” 

  • Tapping Electrodes

  •     We stock metric and Inch-size tapping electrodes, in standard (not-orbiting) and orbiting sizes, as well as NPT.  Full descriptions of each size are in the catalog section.  Tapping electrodes are also known as Threaded electrodes, threaded taps or EDM taps.  
  • Graphite Blanks

  •     Graphite blanks are ground on six sides to a tolerance of +/-.0002".  These are known as graphite sticks, or carbon blanks or precision blanks.  These are also listed in the catalogue section and can be made to size.