Consolidated Toledo Drill - America's Finest High Speed Steel Cutting Tools
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HSS Heavy-Duty NAS 907B
Magnum Super Premium vs. Cobalt

The Magnum Super Premium drills will substantially outperform cobalt drills in work hardening stainless steel applications.

This performance advantage is the result of construction differences between the two types of drills. Cobalt drills, manufactured to Type J NAS907 specs, has a very thick web. This web is necessary to limit breakage of the brittle cobalt steel.

Magnum Super Premium drills is made of special Hi-moly tool steel, which is much tougher than cobalt steel. The web on a Magnum Super Premium drill can be thinned considerably due to the toughness of the steel. Consolidated Toledo Drill - Magnum Super Premium A Magnum Super Premium drill with its thin web will penetrate the work hardening stainless fast enough to continually cut beneath the chip which is hardening from deformation.

This means the drill is cutting softer steel. The cobalt drill, with its thick web, cannot be fed at a fast enough rate to cut beneath the area which is hardening. As a result the cobalt drill is continually drilling into hardened steel.


Consolidated Toledo Drill — Drill Feeds and Speeds

Different drilling conditions make it impossible to develop any rigid rules for feeds and speeds.

The following tables contain guidelines which can be utilized when Drilling Standard Materials.
Also, the following "rules of thumb" can be used to determine proper feeds and speeds for drilling
ferrous materials ( NOTE: Varying conditions can easily require adjustments. )

Consolidated Toledo Drill - Feeds and Speeds Calculator

Feed equals .001" per revolution for every 1/16" of drill diameter, plus or minus .001" on the total.
Speed equals 80 surface feet per minute in 100 Brinell hardness material and the speed should be reduced 10 surface feet per minute for each additional 50 points Brinell hardness.
Feed and speed rates should be reduced up to 45-50‰ when drilling holes deeper
than 4 drill diameters.

Feeds and Speeds - Formulas

    R.P.M. = (3.8197 / Drill Diameter) x S.F.M.
    S.F.M. = 0.2618 x Drill Diameter x R.P.M.
    I.P.M. = I.P.R. (feed) x R.P.M. (speed)
    Machine Time (seconds) = (60 x Feed minus Stroke) / I.P.M.
R.P.M. = Revolutions Per Minute I.P.R. = Inches Per Revolution
S.F.M. = Surface Feet Per Minute Feed Stroke = Drill Depth + 1/3
I.P.M. = Inches Per Minute Car Reamer = 1/2 Speed of Drill

Recommended Feeds of Various Diameter Drills

Diameter of Drill - Inches Feed Inches per Revolution
Under 1/8 001 to .003
1/8 to 1/4 .002 to .006
1/4 to 1/2 .004 to .010
1/2 to 1 inch .007 to .015
1 inch and Over .015 to .025

Recommended Speeds for Standard Materials with H.S.S. Drills

Material Recommended Speed (SFM)
Aluminum and its Alloys 200-300
Brass and Bronze (Ordinary) 150-300
Bronze (High Tensile) 70-150
Die Casting (Zinc Base) 300-400
Iron-Cast (Soft)
     Cast (medium hard)
     Hard Chilled
Magnesium and its Alloys 250-400
Monel Metal or High-Nickel Steel, Stainless Steel 30-50
Plastics or Similar Materials 100-300
   Mild .2 carbon to .3 carbon
   Steel .4 carbon to .5 carbon
   Tool 1.2 carbon
   Alloy - 300 to 400 Brinell

High Tensile (Heat Treated) (Consult your material supplier)

Recommended Speeds for Carbide Tipped Holecutters

Size Steel Stainless Steel
11/16 to 13/16 in. 700 - 1000 RPM 300 - 700 RPM
7/8 to 1-3/16 in. 500 - 800 RPM 200 - 450 RPM
1-1/4 to 1-9/16 in. 300 - 600 RPM 175 - 315 RPM
1-5/8 to 2 in. 200 - 500 RPM 120 - 225 RPM
2-1/16 to 2-3/8 in. 200 - 400 RPM 95 - 195 RPM
2-7/16 to 3 in. 150 - 300 RPM 80 - 150 RPM