The following abstract of records of experiments on the holding power of nails may be useful : -

Holding Power of Wrought Iron Tenpenny Nails, 77 to the lb., about 3 inches long, nailed through a 1-inch board into a block, from which it was dragged in a direction perpendicular to length of nails.1

No. of

Nails in

Square

Foot.

Kind of Plank.

Kind of Block.

Average Breaking Weight per Nail.

lbs.

8

Pine

Pine

380

8

Oak

>>

415

8

,,

Oak

465

4

Pine

Pine

341

4

Oak

,,

446

4

,,

Oak

551

12

Pine

Pine

612

12

Oak

,,

555.5

No. of

Nails in

Square

Foot.

Kind of Plank.

Kind of Block.

Average Breaking Weight per Nail.

lbs.

12

Oak

Oak

542.5

6

Pine

Pine

463.5

6

Oak

,,

332.5

6

,,

Oak

437.5

16

Pine

Pine

289

16

Oak

,,

420

16

,,

Oak

433

The surfaces in contact were from 1 to 2 square feet. The average strength decreased generally with the increase of surface.

Adhesive Force of Nails forced into dry Christiania Deal at right angles to grain of wood.2

Number to the lb.

Length in inches.

Length forced into the Wood.

Force in lbs. required to extract.

Fine sprigs ....

4,560

0,44

0.40

22

,, ....

3,200

0.53

0.44

37

Threepenny brads .

618

1.25

0.50

58

Cast-iron nails

380

1.00

0.50

72

Wrought iron 6d. nails .

73

2.50

1.00

187

,, ,,

..

..

1.50

327

,, ,, ,,

..

..

.2.00

530

,, 5d. ,,

139

2.00

1.50

320

The relative adhesion when driven transversely and longitudinally is in deal about 2 to 1, in elm about 4 to 3.

To extract a common sixpenny nail from a depth of 1 inch required -

lbs.

Beech, dry, across grain .

167

Deal, Christiania, dry, do.

187

Do., do., with grain

87

lbs.

Elm, dry, across grain .

327

Do. do., with grain

257

Oak, do., across grain .

507

Sycamore, green, do.

312

From experiments by Lieutenant Fraser, E.E., it appears that the holding power of spike nails in fir is 460 to 730 lbs. per inch in length.

1 Haupt's Military Bridges.

2 Tredgold, Bevan's Experiments.