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API Spec. 7, 30 Edition, April 1975, specifies that “Tool
joints shall be of the weld-on type and shall be furnished in the
sizes and styles shown in API table 4.2 as specified on purchase
order.”(See Table 3-2).

Kelly and drive bushings

Of all the peculiar terminology found in the oilfield perhaps
none finds its origin as remote from this sphere of activity as does
the kelly joint, first known as the griefstem.
The latter name was given to the joint because of the trouble
drillers had in keeping their grip rings adjusted as it slidе through
the rotary table.
According to the story told by oil writer and author Jerry
Robertson, there was a baseball player named Michael J. (King)
Kelly with the Cincinnati team in l878. He reached his pinnacle of
fame with Chicago from 1880 to 1887 as a great base runner who
made long slides. King Kelly was encouraged in his trips around
the bases by his fans yelling "Slide, Kelly slide." Although he
never saw a rotary rig, his name has been given to this square
forged joint of pipe, developed by an engineer who doubtless
could recall the great King Kelly.
This joint has made great strides through the years in
keeping with the advancements made in accurate machining,
precision forging and hardening of fine steel. The kelly has
become straighter, tougher and made with closer tolerances—truly
a precision instrument.
Kelly substitutes, or short, extra hard joints, above and below
the kelly have been added to prolong its life many times. Kelly
drive bushings have been, and are being, improved. This bushing,
as it revolves the kelly joint in the rotary table, holds the key to its
success and the safety of the entire drill string. A sudden drop
caused by hanging up will be sufficient to ruin a core bit or drill, or
cause damage to the wireline. Drill pipe subjected to shock has a

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