Rotary subs

OTI’s Rotary Subs are made from modified AISI 4145H chromium molybdenum alloy steel that resemble material specifications of drill collars.

Rotary subs have two primary applications. They can be used to crossover from one connection size to another. They can also be used as disposable component to extend the connection life of a more expensive drill stem member. Rotary subs are available with box x pin, box x box or pin x pin connections. The connections are protected by a phosphate surface coating that minimizes galling on initial make-up.

When rotary subs are ordered to conform the API specifications, OTI is authorized to apply the API Monogram on them.

The following rotary subs are available:

Straight OD Sub is used to connect drill stem members that have a similar outside diameter. The drill bit, downhole tools, heavy weight drill pipe and drill pipe can be crossed over using a straight OD sub.

Reduced Section Sub is used to connect drill stem members that have different diameters that warrant the cross-sectional change necessary to accommodate different connections. This sub would be used to crossover large OD drilling tools or a tapered drill collar string

Saver Sub is used to extend the life of the Kelly by taking the connection wear each time it is make-up to a drill stem component. The saver sub connection is sacrificed because it can be easily repaired or inexpensively replaced. The saver sub can be equipped with a rubber protector to reduce BOP equipment and casing wear resulting from contact damage with a lower Kelly connection.

Bit Sub is used to connect the drill bits to the component / equipment above it in the BHA. Because drill bits are “Pin –Up” and all other BHA components are generally “Pin-Down”, the bit sub functions as a crossover for BHA attachment.


When ordering or requesting quotations, please specify the following –

  1. Identify sub use
    Example: Kelly Sub, X-over drill pipe to drill collar, X-over drill collar to drill collar, bit sub etc.

  2. Nominal Size (A)
  3. Bore ID
  4. Overall Length / Shoulder to Shoulder Length
  5. Size and type of upper and lower connections, indicating pin or box
  6. On reduced section subs, add:
    Diameter of reduced section,
    Length of reduced section – 8”, 12”, 18” or 24”

  7. On bit subs, add: float bore, size and type
  8. On Kelly saver subs with protector, add: casing OD and weight for sizing casing protector
  9. Cast-steel or pressed-steel thread protectors