High-Speed Steel Drill Speeds and Feeds Chart

Revolutions per minute and feed per revolution for high speed steel twist drills, by drill diameter and by the material being drilled, with the factors that trade cutting speed against the time a drill runs between regrinds. A reference summary of published practice and not an Aobo Steel specification.

How the drill table was built

The table is a shop standard from the period rather than a modern recommendation, and it is worth knowing how its figures were set before they are used. Its basis is a peripheral speed of 60 to 65 feet per minute in soft steel at the medium diameters, and the peripheral speed is raised as the diameter falls. That is the reason a small drill turns so much faster than a large one, and it is the reason the same table cannot be read as a single cutting speed. Feed is given per revolution for a two lipped drill. The source prefers the lighter figure of each pair and allows the heavier figure where the machine and the setup are rigid. Two adjustments carry the table onto a shop floor. Running without a lubricant costs 15 to 20 per cent of the speed, and rose reamers, threading dies and taps run at about half the speeds tabulated here for drills.

Speeds and feeds for high speed steel drills

Revolutions per minute and feed per revolution, by drill diameter

Source, speeds and feeds for drills, printed page 249, and the cutting speed factors for a longer run on printed page 241.

The five speeds are for a high speed steel twist drill and the column headings are the material being drilled, not the material of the drill. All values are revolutions per minute, and the feed is given per revolution for a two lipped drill. The table is based on a peripheral speed of 60 to 65 feet per minute in soft steel at the medium diameters, and the peripheral speed rises as the diameter falls. Without a lubricant the speeds should be reduced by 15 to 20 per cent. The lighter figure of each feed pair is the preferred value, and the heavier figure is usable where the machine and the setup are rigid. For rose reamers, threading dies and taps about half the speeds shown are to be used. A reference table only, it is not an Aobo Steel recommendation, and the figures should be read against your own machine, holder and coolant.

The feed deserves as much attention as the speed. The source is explicit that a feed that is too light is what shortens drill life on work of this kind, because a chip that is too thin is pulverized under the edge and the powder then grinds the cutting edge away from behind. The feed quoted for each diameter is the figure the drill needs in order to bring up a sound chip, and a drill will carry a slightly higher speed on a moderately heavy cut than on a cut that removes almost nothing. On cast iron the source records 65 to 70 feet per minute as satisfactory practice for an average job, with a feed per lip of 0.008 to 0.02 inch depending on the size of the drill and the rigidity of the machine.

Drill breakage is more often a machine problem than a speed problem. The source records that the frequent failure of a drill just as the point breaks through the far side of the work, usually blamed on high speed or on heavy feed, is really spring and slack in the machine, and that the remedy is to stiffen the setup rather than to slow the drill down. That reading still holds on a drill press or a lathe with worn spindle bearings, and it is the reason a drill that survives in one machine fails in the next.

Trading cutting speed for a longer run between regrinds

Tool life is bought with cutting speed. The factors below are adapted from the work of Taylor and they carry a drill from one regrind to the next. They are used one direction at a time. A drill that is set to cut for 20 minutes between regrinds will run for 40 minutes if the tabulated speed is divided by 1.09, and for 80 minutes if it is divided by 1.19. Read the other way round, the same figures multiply the speed and shorten the run, which is what a shop does on a job that has to come off the machine today.

Factors that carry a tabulated speed to a longer run

Source, cutting speed factors for a longer run between regrinds, printed page 241, adapted from Taylor.

The factors are adapted from Taylor and they carry the run of a drill from one regrind to the next. Dividing the tabulated speed makes the cut last longer and multiplying it makes the cut shorter, so the two directions are the same factor read opposite ways. The middle pair takes the run straight from twenty minutes to eighty minutes, which is a slower cut than the two step change through forty minutes.

Related reference data

The grades this table is used with are collected on the high speed steels catalog, with M2 set out on the M2 tool steel page and selection for cutting work on the high speed cutting tool steel selection guide. Turning and milling speeds for the tool steel grades are on the tool steel cutting speeds and feeds page, and the rating that decides how a grade machines at all is on the tool steel machinability rating chart. Hole sizes for threading are on the tap drill size chart, and the speeds for a specific cold work grade are worked through on the A2 tool steel machining and fabrication guide.

Reference data compiled from High-speed Steel (Otto Matthew Becker, McGraw-Hill, 1916). The drill table is printed on page 249 of that edition and the cutting speed factors on page 241. Both were read from the page image and not from an automatic text layer.