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Shore scleroscope hardness

A measure of hardness on a scale in which tempered steel is rated 100. Measurements are made by a device (the scleroscope) in which a diamond-pointed hammer falls under its own weight within a graduated, vertical glass tube placed above the material whose hardness is to be measured. When the hammer strikes the material it bounces off. The height of the rebound was taken as a measure of the hardness of the surface. The tube was graduated in “shore units.” A.F. Shore invented the device and the Shore Instrument & Manufacturing Company made it.

The advantages of the Shore scleroscope were that it was portable, a workman could easily be trained to use it, and it was cheap relative to other instruments for measuring hardness. In the late 20ᵗʰ century, however, it gradually fell out of use.

The Shore scleroscope should not be confused with the Shore durometer, which measures indentation and is used for testing rubbers and plastics.

1910 patent drawing of sclerometer

sources

Shore Scleroscope Hardness. — Height of rebound of diamond pointed hammer falling by its own weight on the object. The hardness is measured on an empirical scale on which the average hardness of martensitic high carbon steel equals 100. On very soft metals a “magnifier” hammer is used in place of the commonly used “universal” hammer and values may be converted to the corresponding “universal” value by multiplying the reading by 4/7. The scleroscope hardness, when accurately determined, is an index of the tensile elastic limit of the metal tested.

Frederick E. Fowle.
Smithsonian Physical Tables, 7th revised edition, reprint.
Smithsonian Miscellaneous collections, vol. 71, no. 1.
Washington, DC: Smithsonian Institution, 1921.
Page 74.

Some examples of hardnesses as measured by scleroscope,
gathered from 1920's sources
Substance			Shore Units
Aluminum	99%+	rolled sheet, hard, not annealed	14
		sand cast at 700°C	4 - 5
		sheet annealed at 200°C for 2 hours	8
		sheet annealed at 300°C for 2 hours	4.5
		sheet annealed at 400°C for 2 hours	4.5
		sheet annealed at 200°C for 30 minutes	11.8
		sheet annealed at 400°C for 30 minutes	4.5
Aluminum + copper	"alloy No. 12", 92% Al, 8% Cu	sand cast	15 - 18
Aluminum + copper + magnesium	95.2% Al, 4.2% Cu, 0.6% Mg	cast at 700°C	17 - 18
Aluminum + copper + magnesium	95.2% Al, 4.2% Cu, 0.6% Mg	annealed at 500°C	21
Aluminum + copper + nickel + magnesium + manganese	93.5% Al, 3.5% Cu, 1.5% Ni, 1% Mg, 0.5% Mn	cast at 700°C	9 - 25
Aluminum + copper + nickel + manganese	94.2% Al, 3% Cu, 2% Ni, 0.8% Mn	cast at 700°C	9 - 27
Aluminum + zinc + copper	88.2% Al, 3% Cu, 8.4% Zn	cast at 700°C	10
	88.2% Al, 3% Cu, 8.4% Zn	annealed at 500°C	10
	81.1% Al, 3% Cu, 15.9% Zn	cast at 700°C	15
	81.1% Al, 3% Cu, 15.9% Zn	annealed at 500°C	15
Brass	90% Cu, 10% Zn (red metal)	cold rolled hard	20
	90% Cu, 10% Zn (red metal)	cold rolled soft	10
	80% Cu, 20% Zn (low brass, bell metal)	cold rolled hard	28
	80% Cu, 20% Zn (low brass, bell metal)	cold rolled soft	12
	66% Cu, 34% Zn (standard sheet)	cold rolled hard	26
	66% Cu, 34% Zn (standard sheet)	cold rolled soft	12
Bronze	90% Cu, 10% tin (gun bronze or bell metal)	cast	23
	90% Cu, 10% Al (aluminum bronze)	cast	25 -26
	92.5% Cu, 7.2% Al (aluminum bronze)	rolled and annealed	19
	58% Cu, 39% Zn, 0.05% Mn (manganese bronze)	sand cast	18 - 19
Copper	99%+	annealed at 200°C	7
		cast	8
		rolled, annealed at 500°C	6
		cold drawn, 50% reduction	18
Gold	pure	cast	20
Lead		cast	3
Nickel	98.5%	commercial wrought	35
Platinum		drawn hard	24
Platinum		drawn annealed	13
Silver	pure	drawn hard	32
Tin	99.8%	cast	8
Steel, carbon	SAE 1010	annealed	18
	SAE 1010	ht A	24
	SAE 1020	annealed	17
	SAE 1020	ht H, 230°C	35
	SAE 1045	annealed	27
	SAE 1045	ht H, 260°C	45
	SAE 1095	annealed	29
	SAE 1095	ht F, 510°C	75
Steel, nickel	SAE 2315	ht H	43
	SAE 2335	ht H	62
	SAE 2345	ht H	76
Steel, nickel chrome	SAE 3120	annealed	22
	SAE 3120	ht H, 450°C	36
	SAE 3135	annealed	30
	SAE 3135	ht H or D	44
	SAE 3220	ht H or D	50
	SAE 3250	ht M	64
	SAE 3320	ht L	50
	SAE 3340	ht P	64
Steel, chromium	SAE 51120	ht M or P	66
Steel, chromium	SAE 52120	ht M or P	70
Steel, chrome vanadium	SAE 6130	ht T	59
Steel, chrome vanadium	SAE 6195	ht U	75
Steel, silico-manganese	SAE 9250	ht V	59
Steel, silico-manganese	9 × 30	ht V	63
Steel, tungsten	C-47	quench 1065°, draw 205°C	64
Zinc		crystalline	8 - 10

Notes. Keep in mind that the scleroscope was not a very good way of measuring hardness. The inclusion of an alloy doesn't indicate that it was the only composition given that name (e.g., “gun metal”, “manganese bronze”). “ht” = heat treatment. The letters designate Motor Transport Corps Modified S.A.E. Heat Treatments for Steels. (See S.A.E. Handbook) See SAE steel specification numbers for an explanation of them.