Reamers are rotary tools with one or more teeth, used to remove a thin layer of metal on the surface of a machined hole, and rotary finishing tools with straight or helical edges for reaming or repairing holes.
What is a Reamer?
There are many types of reamers, including tapered pins and hand reamers. High-precision mechanical reamers are often used in lathes or machining centers. A reamer is a precision tool, and its precision depends on the machine itself and the operator's ability to operate, and on the functional characteristics of the tool itself. Reamers can be produced from carbide, high-speed steel, or metal-ceramic composites.
The reamers are designed to slightly enlarge the size of the drilled hole, but with high precision, ensuring a smooth surface finish on the sides of the hole. With the correct use of reamers, thousands of holes can be reamed to high-precision holes without compromising performance. Reamers are the most accurate hole-making tools currently available, and if used in metalworking, they are usually used for high tolerances of H6/H7 according to ISO standards. Both ISO and ANSI metric standards refer to fasteners that can be freely assembled and disassembled.
The Purpose of the Reamer:
A reamer has one or more teeth, a rotary tool used to remove a thin layer of metal from the machined surface of a hole. The holes processed by the reamer can obtain precise size and shape. The reamer is used to ream the drilled (or reamed) hole on the workpiece, mainly to improve the machining accuracy of the hole and reduce the roughness of its surface. It is a tool for finishing and semi-finishing holes. The machining allowance is generally small. Hand reaming is often used to finish dowel or pinholes to allow an interference fit between the hole and the dowel. When used properly, hand reamers can only remove a small amount of material at a time, usually only .005 to 0.008 inches. Therefore, hand reaming is ideal for producing a high-quality finish on the hole surface.
Reamers used to machine cylindrical holes are more commonly used. The reamer is used to machine the tapered hole in the tapered reamer, which is rarely used. According to the usage, there are hand reamer and machine reamer, and machine reamer can be divided into straight shank reamer and taper shank reamer. The hand used is a straight handle type.
Operation of the Reamer:
A reamer has one or more teeth, a rotating tool used to remove a thin layer of metal on the surface of a machined hole. Reamers cannot remove large amounts of material. The amount of material removed depends on several factors, including the material to be machined and the size and quality of the pre-drilled holes. For mechanics, this is a process that requires careful balancing. For the reamer to work efficiently, it is critical to have the correct allowance in the hole. Too much allowance and the reamer may struggle to run and the hole may be deformed. Too little allowance and the reamer will rub and wear, resulting in poor hole quality. The cutting edge of the reamer needs to have a certain hardness to prolong the service life; it also needs to have good toughness so that the tool will not fail during normal use. Proper use controls a small amount of material allowance to ensure long reamer life and a high hole finish.
Also, if the workpiece is not held securely when reaming, chattering can result, the finish of the part will be poor and the cutting edge will become dull. Friction and extreme heat can also cause problems during reaming, which means that effective lubrication is essential not only to cool the tool but also to extend the life of the reamer. Lubrication also increases cutting speeds, reduces cycle times, and removes chips, helping to improve the finish of the workpiece.
Types of Reamers:
- According to the way of use, it is divided into hand reamer and machine reamer.
- According to the shape of the reaming hole, it is divided into cylindrical reamer and conical reamer.
- According to the direction of the chip groove, it is divided into the straight groove and spiral groove.
- The shank parts are straight shank and taper shank.
- According to the material, there are high-speed steel and cemented carbide inserts.
Several teeth and tooth slots of the reamer:
The number of teeth of the reamer affects the reaming accuracy, surface roughness, chip space, and tooth strength. Its value is generally determined according to the diameter of the reamer and the material of the workpiece. When the diameter of the reamer is larger, a larger number of teeth can be selected. When machining ductile materials, the number of teeth should be smaller. When processing brittle materials, the number of teeth is preferable. To facilitate the measurement of the diameter of the reamer, the number of teeth should be an even number. In the range of common diameter do=8~40mm, the number of teeth is generally 4~8.
Design Points - Reamer Diameter and Its Tolerances
The diameter tolerance of the reamer directly affects the dimensional accuracy of the machined hole, the manufacturing cost, and the service life of the reamer. When reaming, due to the radial runout of the cutter teeth, the amount of reaming, and the cutting fluid, the aperture will be larger than the diameter of the reamer, which is called reaming expansion. And because the blunt radius of the blade squeezes the hole wall, the hole will recover and shrink, which is called reaming shrinkage. Reaming with a high-speed steel reamer generally expands, and reaming with a carbide reamer generally shrinks, and shrinkage often occurs when reaming thin-walled holes. The nominal diameter of the reamer is equal to the nominal diameter of the hole. The upper and lower deviation of the reamer should consider the amount of expansion and contraction, and leave the necessary wear tolerance.
