Watch this video to learn how to use a reamer to properly and efficiently ream a hole! Tech Team Expert Kurt Repsher walks you through the do's and don't's of reaming a hole with a hand reamer from planning to execution. Subscribe to our YouTube Channel to see more how-to application videos like this one!
Reamers are multi-fluted cutting tools used to enlarge existing holes to a precise diameter. They are available in a variety of shank styles that can be mounted into hand tools, chucks, collets, or other tool holders, and are used in a variety of portable or stationary machines such as drill presses, lathes, screw machines, milling machines and more. The cutting end is ground with a 45° chamfer angle for easy entry into the hole. Straight fluted reamers are best for through holes, left-hand spiral flute models are better in blind hole applications. Available in a variety of materials, to suit the application and workpiece material, and some are available in almost any size imaginable. Light cutting oil or coolant is recommended for reaming operations.
A reamer is a cutting tool that is used to open the size of an existing hole by a small amount. A reamer will leave a smoother finish and a more precise size than a drill. Hand reaming, or reaming a hole without coolant or oil will result in an oversized hole and a rougher finish. Avoid reaming to the bottom of a blind hole.
For the best reaming results, prepare your holes with just the right amount of stock for the reamer to remove. Too little, and the reamer will rub, leaving a smaller diameter than expected. Too much and the hole may be oversized and have a rough finish. Since reaming is about precision, use stub length tools where possible. The following is an example of how to ream a hole in metal. In this example, we are reaming a 5/16" (.3125") hole in soft, mild steel, step by step:
Step 1: Ensure that the workpiece is held securely and will not slide or rock.
Step 2: Locate & spot drill hole using a spot drill with a slightly greater taper than the drill being used. (For best results, avoid using a center drill (combination drill & countersink.)
Step 3:. Subtract 3% (since we’re working in mild steel) from the reamer diameter to determine the best drill size. (For example, .3125 – 3% = .3031"). A good rule of thumb to find the best drill size is to subtract 2% to 4% from the reamer size. 2% for harder metals, and 4% for softer materials.
Step 4: Use the appropriate drilling feed and speed for the tool, material and operation.
Step 5: Keep the drill and hole well lubricated with cutting oil or coolant.
Step 6: Drill the hole with a size N drill (0.302”). Peck drill to prevent chips from jamming and scoring the walls of the hole.
Step 7: Reduce the feed and speed:
RPM: Use 1/2 to 2/3 the speed of the drill that was used.
FEED: Double the feed of the drill that was used.
Step 8: Chamfer top of hole (just to break the edge) with either a 90° or 82° countersink.
Step 9: Since reaming doesn’t require heavy cutting fluids for optimal performance, use lighter oil or coolant. This will help to produce an accurate size hole and a smooth Finnish.
Step 10: Ream hole with a 5/16” reamer. Don’t stop or peck with the reamer until it exits through the bottom of the hole. With the machine turned off and the spindle completely stopped, pull the reamer straight up, out of the hole.
For a complete listing of all reamer types and styles, view or download our comprehensive Holemaking Guide, available via the link below.
Chucking Reamers, or “Machine Chucking Straight Shank Reamers” are used to enlarge existing holes to a very precise diameter. Chucking reamers have round, straight shanks which can be mounted in chucks, collets, or other tool holders, and are used in a variety of portable or stationary machines such as drill presses, lathes, screw machines, milling machines and more. Chucking Reamers are available in almost any size imaginable.
We believe the Right Tool Is Everything™, and we strive to share our experience and expertise in an effort to ensure you select the right tool for your application, follow best practices, and can push your productivity further.