Drilling With Coolant

Drilling with Coolant
There are many benefits to drilling with coolant. Directing the coolant through the tool to the cutting edge improves lubricity and reduces the temperature at the point of contact. Reduced heat build-up and improved lubricity lead to lower wear and tear on the drill that improves the tool life and reduces the cost per hole. Depending on the application, the introduction of through the tool coolant may enable the operator to increase feeds and speeds as well as reducing or eliminating the retract cycle (pecking) which contributes to a lower cost per hole. Hole finishes are improved due to the flushing of the chips away from the drill/workpiece interface which reduces the scarring of the workpiece by previously cut chips.

Coolant fed drills should be used for production drilling of holes greater than three tool diameters deep. They offer high penetration rates, reduced cycle times and straighter/rounder holes with better finishes often eliminating secondary finishing operations such as reaming or boring. Coolants fed drills typically have longer flutes to facilitate deep hole drilling. They perform well in a wider range of materials then a non-coolant fed drill.

Why use Carbide Tipped Coolant Fed Drills?
Carbide tipped coolant fed drills have an advantage over solid carbide coolant fed drills. When using carbide tipped coolant fed drills the tool steel body can absorb shock loads better than a solid carbide coolant fed drill with the same dimensions. Carbide is brittle and has a tendency to break rather then bend. The tool steel body of the carbide tipped drill has more of a tendency to bend slightly rather than just breaking. Here is a link to Super Tool’s straight fluted carbide tipped coolant fed drills.

Coolant Pressure
Inadequate coolant pressure or volume can lead to tool failure. High coolant pressure results in higher stock removal rates and longer tool life. High coolant pressure is required to break through the point vapor barrier created by chip forming heat at the drill point. High coolant pressure is required to effectively evacuate the high volume of chips produced by faster feeds and speeds. Coolant pressure requirements decrease with an increase in drill diameter but require more volume of coolant. The reverse is also true. Coolant pressure requirements increase with a decrease in drill diameter but require less volume of coolant. Super Tool strongly recommends automatic drilling operation shutdown if coolant flow is interrupted. Use of a continuous coolant pressure system (non-pulsating) is also recommended. Contact Super Tool for recommendations on coolant pressure.

Drilling Speeds and Feeds Using Coolant
Use the same formulas for speeds and feeds that you use for drilling without coolant.

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

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

IPR = IPM/RPM

Here is a link to a drilling speeds and feeds chart. There are two charts; one for drilling dry and one for drilling with coolant.

Check back with us next week. We will be discussing reaming speeds and feeds. If you have any questions about drilling with coolant (or any other cutting tool questions) feel free to leave us a comment here on our blog or fill out the form on Super Tool’s Contact Us Page.

Bryan Enander
Super Tool, Inc.