Reaming Blind Holes vs. Reaming Through HolesCarbide Tipped Coolant Fed Reamer - Flute Fed - Straight Flute

Knowing the difference between the two types of holes is important when reaming with coolant.  A blind hole is a hole that does not have an opening on the other end.  If you were to put your eye up to the hole, all you would see is darkness.  In a sense, you would be “blind” while looking in the hole.  A through hole has an opening on the other end.  If you put your eye up to the hole, you would be able to see out of the other side.  Coolant fed reamers come in two styles coolant through the center of the tool and coolant through the flutes of the tool.  Reamers with coolant through the center should only be used on blind holes.  This is because when the reamer shoots the coolant out of the front of the tool it will hit the back of the hole and come back towards the reamer forcing the chips back up through the top of the hole and at the same time flood the cutting edges.  If a reamer with coolant through the center is used on a through hole, the coolant will shoot out the front of the tool and out the other side of the hole without flooding the cutting edges rendering the coolant ineffective.  Reamers with coolant through the flutes should be used on through holes.  This enables the coolant to flood the cutting edges as the coolant is shooting out the side rather then the front of the reamer.

Right Hand Spiral vs. Left Hand Spiral Coolant Fed Reamers

The principle behind a left hand spiral reamer and a right hand spiral reamer concerning coolant is simple. A left hand spiral pushes the chips ahead of the reamer.  A right hand spiral pulls the chips towards the back of the reamer.  It is typically best to use a center fed coolant reamer with right hand spiral flutes on blind holes.  The force of the coolant is “pushing” the chips towards the back of the reamer and is complimented by the right hand spiral that is also “pulling” the chips towards the back of the reamer.  Conversely, it is best to use a flute fed coolant reamer with a left hand spiral on through holes.  The force of the coolant is “pushing” the chips ahead of the reamer as the coolant floods the left hand spiral cutting edges. This action is complimented by the left hand spiral which is also “pushing” the chips ahead of the reamer out the other side of the through hole.  This contributes to better hole finishes because the chips are being flushed away from the reamer/workpiece interface. Flushingthe chips away reduces the chances of scarring the workpiece and reduces the chance of damaging the reamer by previously cut chips. (Note: there are other advantages to using right or left hand helixes, which we will discuss in a future blog).

 Coolant Pressure

Inadequate coolant pressure or volume can lead to tool failure.  For more on coolant pressure see the previous post Drilling with Coolant as the principles regarding coolant pressure is similar for reamers and drills.

Reaming Speeds and Feeds Using Coolant

Use the same formulas for speeds and feeds that you use for reaming without coolant.

Speeds and Feeds Formulas

RPM =     (SFPM*3.82)
            (TOOL DIAMETER)

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


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

Here is a link to a reaming speeds and feeds chart.  There are two charts one for reaming dry and one for reaming 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.



  1. Hello,
    Bryan Enander,
    This the most usful site for me!
    I am working in cutting tool (Global Sourcing)
    Procurement section at M/S. ASB INT.PVT. LTD
    We are using huge varities of Cutting tools.

    My query is –
    A. Can we use blind hole reamer for through hole application?
    B.Can I get formulas for costing of Tools ?
    (Reamer , End mills, Drills, )

  2. Larry says:

    Hello good day,I will like to know if you do carry coolants for sell,can you kindly let me know the types you do have instock with pricing now so that we can proceed.

    Larry Bones
    1301 19th Street North,
    Humboldt Iowa 50548
    785 505 7250

  3. Itzhak Rosenthul says:

    Good morning!
    We would like to receive your best prices for follow reamers for our new product.

    Our requirements for reamers are:
    Dia. 5.54 mm
    Dia 5.55 mm
    Dia. 5.56 mm
    Dia. 7/32″

    The length of our piece is 330 mm.

    Shape of reamers :
    We will be very pleased to receive your recommendation. We need left hand reamer rotation and chip ahead

    The material has 45-50 HRC hardness, brittle.

    Have a nice day,