Introduction to Speeds and Feeds

Cutting Tool Speeds and Feeds
In machining, “speeds and feeds” refers to the speed at which the tool is turning (usually measured in RPMs), and the rate (the feed) that the tool is being fed into the material being machined.  Speeds and feeds are important.  When optimized there is a greater chance of achieving the desired surface finish on the part being machined with the least amount of wear on the cutting tool. This results in longer tool life.

Feeds and Speeds vary with the material being machined and the hardness of the material in ideal cutting conditions.  Cutting tool manufacturers can provide you with feeds and speeds appropriate for their cutting tools and the material you are machining.  Good examples of this are Super Tool’s Speeds and Feeds Charts for carbide tipped cutting tools.

Many things affect the cutting conditions of an application such as setup rigidity, machine rigidity, horsepower, flood coolant or through coolant to name a few. Therefore, speeds and feeds are usually given in a range suitable to the material machined. The use of through coolant tools can enhance the optimal cutting speeds and feeds in some applications. Check with your cutting tool manufacturer to determine when a through coolant tool is appropriate and use speeds and feeds that account for coolant.  Super Tool’s Drilling Speeds and Feeds Chart and Reaming Speeds and Feeds Chart are good examples of charts that account for the use of through coolant tooling in the machining application. In some applications, flood coolant is not desirable with carbide tools and can ruin the cutting edge.  This can occur when it is not possible to flood the cutting tool with copious amounts of coolant. One such example would be large diameter cutters milling steel. As the tooth exits the cut extreme temperatures are reached within the carbide surface, the coolant splashing the super heated tooth can cause thermal cracking destroying the cutting edge and leading to unacceptable tool life and part quality.  When in doubt contact your tool manufacture for a recommendation.  We will talk more about coolant in a future blog post.

Feeds and Speeds Formulas
Feeds and Speeds can be calculated using information from a speeds and feeds chart (like Super Tool’s mentioned above) and the formulas below.

Speeds and Feeds Formulas
RPM =    (SFPM*3.82)
            (TOOL DIAMETER)

IPM = (IPT)*(RPM)*(#Teeth)

IPR = IPM/RPM

RPM = Rotations Per Minute
SFPM = Surface Feet Per Minute
TOOL DIAMETER = Diameter of the cutter in inches
IPM = Inches Per Minute
IPT = Inches Per Tooth
IPR=Inches Per Revolution

Many modern machine tools accept both Inches Per Revolution (IPR) as well as Inches Per Minute (IPM) in their canned cycles. As a result, many of Super Tool’s Speeds and Feeds Charts list the IPR to aid in machine tool programming for plunge type tooling.

Check back with us next week where we will discuss speeds and feeds for drilling applications.  If you have any questions about speeds and feeds (or any other cutting tool questions) feel free to drop us a line by filling out the form on Super Tool’s Contact Us Page.

Bryan Enander
Super Tool, Inc.