Key points of reamer design

The diameter tolerance of reamer has a direct impact on the dimension precision, manufacture cost and service life of the reamer. When reaming holes, the hole diameter will be larger than that of reamer due to the radial run-out of cutter teeth, the amount of reamer and cutting fluid, etc., which is called "expansion" of reaming holes. As the blunt circular radius of the blade squeezes the hole wall, it will cause the hole to recover and shrink, which is called "shrinkage" of the hinge hole. The factors of "expansion" and "contraction" exist simultaneously, and the final result should be determined by experiments. Experience shows that the hinge holes of HSS reamer generally expand, the hinge holes of HSS reamer generally contract with hard alloy reamer, and the hinge holes of HSS reamer often contract when the thin wall holes are hinged.

The nominal diameter of the reamer is equal to the nominal diameter of the hole. The upper and lower deviation of reamer should consider the expansion and shrinkage, and leave the necessary wear tolerance.

If the hinge hole shrinks, the maximum and minimum limit sizes of the design and manufacture of the reamer are:

Domax = d omega Max + Pamin (6-3)

Domin = domax - G, 6-4)

According to the national standard, the manufacturing tolerance of reamer G=0.35(). According to the general empirical data, the HSS reamer can be Pmax=0.15(). The shrinkage after reaming hole of hard alloy reamer is often different due to different workpiece materials, Pamin=0 or Pamin=0.1(). The reliable determination of Pmax and Pamin is determined by experiments.

The number of teeth and tooth groove of reamer

The number of teeth of reamer affects the precision of reaming hole, surface roughness, chip tolerance space and the strength of cutter teeth. The value is generally determined by the diameter of the reamer and the workpiece material. When the diameter of reamer is large, more teeth are preferred. When processing ductile materials, less teeth should be taken. When processing brittle materials, the number of teeth should be more. To facilitate the measurement of reamer diameter, the number of teeth should be even. In the range of do=8~40mm in diameter, the number of teeth is generally 4~8.

The reamer teeth can be equally spaced along the circumference, or equally spaced. In order to facilitate manufacturing, the reamer is generally distributed at the same tooth spacing.

The geometric Angle of the reamer

(1) the main Angle

Machining steel ductile materials generally take = 15 °; Machining of brittle materials such as cast iron generally take = 3 ° ~ 5 °; Coarse hinge and generally take = 45 ° when reaming blind hole; The hand reamer with general = 0.5 ° ~ 1.5 °.

(2) the anterior horn

Generally, when reaming the hole, the residual amount is small, the chip is thin and the contact length between the chip and the front tool surface is short, so the influence of the front Angle is not significant. In order to make convenient, generally take all = 0 °. Processing ductile materials, to reduce the chip deformation and desirable = 5 ° ~ 10 °.

(3) after the Angle

Reamer is a finishing tool, to make it after resharpening radial size does not change is too big, after general reamer Angle = 6 ° ~ 8 °.

(4) the blade Angle

Generally the blade Angle of the reamer = 0 °. But the edge Angle can make the cutting process smooth and improve the quality of hinge holes. Ream in ductile materials, can be in the cutting section of the reamer grinded = 15 ° ~ 20 ° blade Angle, which can make the ream scraps discharge forward, from scratch has been processed surface. When working with a blind hole, a large hole can be made at the front of the reamer with a tip Angle to accommodate chip cutting.