[1369]. Ordinary centre pin, with split pin and washer.

[Larger plate.]

Section 78.—SCREW GEAR, BOLTS, &c.

[1370]. Square thread screw. Single, double, or multiple thread.

[1371]. V thread screw.

[1372]. Enlarged section of V thread.

[1373]. Strongest thread when the strain is always in one direction.

[1374]. Round thread screw.

[1375]. Geared thread, to be used with ordinary wheel teeth, the section of thread being that of a rack of the same pitch as wheel.