TABLE XII
HARDNESS OF 32 WOODS IN GREEN CONDITION, AS INDICATED BY THE LOAD REQUIRED TO IMBED A 0.444-INCH STEEL BALL TO ONE-HALF ITS DIAMETER
(Forest Service Cir. 213)
COMMON NAME OF SPECIES Average End surface Radial surface Tangential surface
Pounds Pounds Pounds Pounds
Hardwoods



1 Osage orange 1,971 1,838 2,312 1,762
2 Honey locust 1,851 1,862 1,860 1,832
3 Swamp white oak 1,174 1,205 1,217 1,099
4 White oak 1,164 1,183 1,163 1,147
5 Post oak 1,099 1,139 1,068 1,081
6 Black oak 1,069 1,093 1,083 1,031
7 Red oak 1,043 1,107 1,020 1,002
8 White ash 1,046 1,121 1,000 1,017
9 Beech 942 1,012 897 918
10 Sugar maple 937 992 918 901
11 Rock elm 910 954 883 893
12 Hackberry 799 829 795 773
13 Slippery elm 788 919 757 687
14 Yellow birch 778 827 768 739
15 Tupelo 738 814 666 733
16 Red maple 671 766 621 626
17 Sycamore 608 664 560 599
18 Black ash 551 565 542 546
19 White elm 496 536 456 497
20 Basswood 239 273 226 217
Conifers



1 Longleaf pine 532 574 502 521
2 Douglas fir 410 415 399 416
3 Bald cypress 390 460 355 354
4 Hemlock 384 463 354 334
5 Tamarack 384 401 380 370
6 Red pine 347 355 345 340
7 White fir 346 381 322 334
8 Western yellow pine 328 334 307 342
9 Lodgepole pine 318 316 318 319
10 White pine 299 304 294 299
11 Engelmann pine 266 272 253 274
12 Alpine fir 241 284 203 235
NOTE.—Black locust and hickory are not included in this table, but their position would be near the head of the list.

Tests for either form of hardness are of comparative value only. Tests for indentation are commonly made by penetrations of the material with a steel punch or ball.[16] Tests for abrasion are made by wearing down wood with sandpaper or by means of a sand blast.

CLEAVABILITY

Cleavability is the term used to denote the facility with which wood is split. A splitting stress is one in which the forces act normally like a wedge. ([See Fig. 21].) The plane of cleavage is parallel to the grain, either radially or tangentially.

Figure 21

Cleavage of highly elastic wood. The cleft runs far ahead of the wedge.