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Recommended Rotational Speeds (RPM’s)

Based on the peripheral speeds specified above, the following table defines the recommended rotational speed ranges for various common bit sizes:

Bit Size	Recommended Rotational Speed (Rev / Minute)
	Impregnated Diamond		Surface-Set Diamond		PCD (TSP)-Set and “Carbide-Chip” Type Tungsten-Carbide		“Saw-Tooth” Type Tungsten-Carbide
	Max	Min	Max	Min	Max	Min	Max	Min
E	2027	1221	1243	466	-	-	-	-
A	1589	957	978	367	733	244	-	-
B	1271	766	782	293	586	195	293	68
N	1005	605	618	232	464	155	232	54
H	792	477	487	183	366	122	183	43
P	620	374	382	143	286	95	143	33
36mm	2103	1267	1294	485	-	-	-	-
46mm	1643	990	1012	380	759	253	-	-
56mm	1351	814	832	312	624	208	312	73
66mm	1147	691	706	265	529	176	265	62
76mm	996	600	613	230	460	153	230	54
86mm	880	530	541	203	406	135	203	47
101mm	749	452	461	173	346	115	173	40
116mm	652	393	401	151	301	100	151	35
131mm	578	348	356	133	267	89	133	31
146mm	518	312	319	120	239	80	120	28

Calculation of Rotational Speed (Imperial System)

The following formula may be used to determine the required rotational speed range (S) for any bit or casing shoe:

Where:

“ D “ represents the mean outside diameter of the bit crown in “inches”. Normally, this value is considered to be the mid-point of the outside set diameter tolerance.

“ P “ represents the peripheral speed of the outside diameter of the bit crown in “feet per minute”. In order to establish the rotational speed range, it is necessary to perform this calculation twice: where one calculation is used to determine the minimum recommended rotational speed and the other calculation is used to determine the maximum recommended rotational speed. The value of “ P “ is a function of the bit or casing shoe type and the normal minimum and maximum values are given in the table below:

Bit or Casing Shoe Type	Normal Peripheral Speed Values (“P”)
Bit or Casing Shoe Type	Minimum	Maximum
Impregnated Diamond	470 feet / minute	780 feet / minute
Surface-Set Diamond	180 feet / minute	480 feet / minute
Geotechnical Triangular-TSP Set	180 feet / minute	480 feet / minute
Geotechnical Cubic-TSP Set	180 feet / minute	360 feet / minute
Geotechnical Pax (PCD)-Set	120 feet / minute	300 feet / minute
Geotechnical TSP Sawtooth	42 feet / minute	180 feet / minute
Tungsten-Carbide (“Carbide-Chip” Type)	120 feet / minute	360 feet / minute
Tungsten-Carbide (“Sawtooth” Type)	42 feet / minute	180 feet / minute

Calculation of Rotational Speed (Metric System)

The following formula may be used to determine the required rotational speed range (S) for any bit or casing shoe:

Where:

“ D “ represents the mean outside diameter of the bit crown in “millimetres”. Normally, this value is considered to be the mid-point of the outside set diameter tolerance.

“ P “ represents the peripheral speed of the outside diameter of the bit crown in “metres per minute”. In order to establish the rotational speed range, it is necessary to perform this calculation twice: where one calculation is used to determine the minimum recommended rotational speed and the other calculation is used to determine the maximum recommended rotational speed. The value of “ P “ is a function of the bit or casing shoe type and the normal minimum and maximum values are given in the table below:

Bit or Casing Shoe Type	Normal Peripheral Speed Values (“P”)
Bit or Casing Shoe Type	Minimum	Maximum
Impregnated Diamond	140 metres / minute	240 metres / minute
Surface-Set Diamond	54 metres / minute	144 metres / minute
Geotechnical Triangular-TSP Set	54 metres / minute	144 metres / minute
Geotechnical Cubic-TSP Set	54 metres / minute	108 metres / minute
Geotechnical Pax (PCD)-Set	36 metres / minute	90 metres / minute
Geotechnical TSP Sawtooth	12 metres / minute	54 metres / minute
Tungsten-Carbide (“Carbide-Chip” Type)	36 metres / minute	108 metres / minute
Tungsten-Carbide (“Sawtooth” Type)	12 metres / minute	54 metres / minute

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	Operational Effects of Rotational Speed for Impregnated Diamond Core Bits and Casing Shoes

	Operational Effects of Rotational Speed for Surface-Set Diamond Core Bits and Casing Shoes

	Operational Effects of Rotational Speed for Geotechnical Bits and Tungsten-Carbide Core Bits

	Calculation of Rotational Speed (Imperial System)

	Calculation of Rotational Speed (Metric System)

	Download Section Tables in PDF (335kb)



	Bit Load

	Bit Hydraulics

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