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Home  >>  Products  >>  Hardness  >>  H501 Pencil Hardness Gauge
H501 Pencil Hardness Gauge

Meets ASTM D 3363

H501 Pencil Hardness Gauge

The Pencil Hardness Gauge is practical for use in the laboratory, or the production line, or in the field to assess quantitatively the rigidity or firmness (elastic modulus) of organic coatings applied to rigid substrates such as metal.

Hardness values may define requirements for particular coatings applications, or may be used to evaluate state-of-cure or aging of a coating.





The gauge is composed of a set of eight mechanical drawing lead holders (pencils) permanently mounted in a circular array on a plastic cylinder. A small metal tube through the center of the cylinder provides storage for spare leads and is a guide for positioning pencils for a test. Alternate pencils in the assembly point in opposite directions, so that in either direction four pencil tips define a square around a guide tube, and each pencil may be precisely positioned instantly to perform a test. Pencil positions are identified by numbers 1 to 8 on the plastic holder.

The Pencil Hardness Gauge is unique only by the fact that it provides a compact single unit for performing this test rather than a set of easily lost individual pencils. The importance of this advantage should not be discounted, especially when several individuals may be working with a single instrument. Leads supplied with the unit, softest to hardest, are as follows: 6B, 5B, 4B, 3B, 2B, B, HB, F, H, 2H, 3H, 4H, 5H, 6H.

The leads are supplied in a holder that identifies each lead (individual leads may come without identification, or the identification mark may be difficult to read). Choosing and installing the eight leads most appropriate to the surface(s) being tested will allow the most commonly used leads to be always “at the ready.”

A plastic dressing disk is provided with five adhesive-backed sandpaper disks to facilitate dressing the lead points while they are in place in the gauge. The Pencil Hardness Gauge is supplied in a plastic carry case with niches for the gage, the dressing disk plus spares, the lead set in its case, and a niche for a pen or pencil.


Technical Data

Technical Data
Size: Diameter 1.75 inches; overall length 7.50 inches.
Weight: 7.0 oz. (199 g)
Material: Blends of graphite, clay and binders.
Grades: 6B, 5B, 4B, 3B, 2B, B, HB, F, H, 2H, 3H, 4H, 5H, 6H, (8H sold separately)
Weight: 0.5 oz. (14 g) total.

Pencil Scale


Measurement Procedure

Remove the gauge and sanding disc from the carrying case. Using the disc face as a guide, adjust the exposed lengths of lead uniformly to approximately 1/8". Square the ends of the leads, four at a time by gently rotating an abrasive paper supported by the plastic disc until all squared edges of the leads are sharply defined. Load the eight lead holders with leads in the most used hardness. (It is recommended tht a list is kept which leas is in which holder.) This completes the preparation for testing.

Begin testing using the hardest pencil (normally mounted in position number 8). Grasp the holder firmly and bring the metal tube end down onto the test surface. Rotate until the selected pencil is nearest the operator, and then incline the assembly downward until the lead point and the tube end are simultaneously in contact with the surface. This defines the correct lead angle of 45° to the surface. Push the gauge forward (away) about one-half inch. Observe the pencil track. Sufficient pressure must have been applied either to cut or mar the film or to crush the sharp corner of the lead. If neither marring nor crushing is observed, repeat the test with greater pressure applied until a definite observation is made. If crushing of the hardest lead should occur, the film is extremely hard and is beyond the measuring range of the test. If scratching or marring of the film occurs, proceed with the next softer pencil grade and repeat the testing process until a test lead is found which crushes and does not mar the film. Confirm the result with duplicate observations of the last (crushing) lead and the next harder (marring) lead.

In addition to the mar or scratch hardness described above, ASTM Specifications D3363 defines a “Gouge Hardness” as “the hardest pencil that will not cut through the film to the substrate for a distance of at least 1/8 inch.” This severe test is more applicable as a service simulation of coatings expected to receive heavy mechanical abuse.



  1. Smith, W. T., “Standardization of the Pencil Hardness Test, “Official Digest”, 28, p. 232, ff (1956).
  2. ASTM D3363, Method of Test for Film Hardness by Pencil Test.
  3. Pencil Hardness Tests. Sherwin Williams Industrial Test.
  4. NACE, TPC Publication No. 2 “Coatings and Linings for Immersion Service”, p. 22, (1982).



Prices subject to change    Prices listed in US dollars for domestic shipments within US, Canada, & Mexico only    Export orders require quotations - click here for a quote     For more info call us 1-800-762-2478 or 954-946-9454.
Item Number Item Prices

14 leads, Vinyl carrying case, Dressing disc
HA-H501 Pencil Hardness Gauge $395.00
HA-H501A Extra Lead Set, 14 pieces 6B-6H 54.00
HA-H501B Extra Dressing Disc (with 5 sandpaper disks) 38.00
HA-H501-08 8H Lead (Each) 12.50
HA-H501-20R Replacement sand paper disc kit (5 discs) 20.00


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