JPH04197548A - Method for precisely finishing shaft part in bolt - Google Patents

Abstract

PURPOSE:To improve the productivity by manufacturing a bolt having a shaft part with smaller diameter than the needed size by a few, crushing projected parts on the surface of shaft part with precision forging, etc., after forming projected and recessed parts by hitting shots on the shaft part and forming the diameter of shaft part to the needed size. CONSTITUTION:The bolt having the shaft part with smaller diameter than the needed size by a few, is manufactured with extrusion working method, etc. The needed size is the precise size for fitting the shaft part of bolt into a fitting hole in a body to be fastened. After executing extrusion-work, heat treatment of the bolt is executed and successively, shot-peening work is executed to the surface of shaft part. On the surface of shaft part, the projected and recessed parts are formed, and the surface is hardened and further, the fatigue limit of the material is increased to develop the peening hardening. The projected parts on the surface of shaft part in the bolt are crushed with the precision forging or minute forming of rolling and the diameter of shaft part in the bolt is formed to the needed size. By this method, plural pieces of bolts are worked to the projected and recessed parts at one time in short time, and the productivity is improved.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a precision finishing method for a bolt shaft.

<Prior art> As shown in Figure 2, in precision machines, bolts a
There is a structure in which the shaft portion of the bolt is fitted into the mounting hole d of the object C to be fastened.

In the case of such a structure, the accuracy of the shaft part is required, so conventionally, precision finishing of the shaft part was carried out as follows.

<A> A method of manufacturing a bolt with a shaft portion slightly larger in diameter than the required dimensions, and polishing this shaft portion to form the required dimensions.

〈O〉A bolt with a diameter slightly smaller than the required dimensions (〈〉, with details) is manufactured, serrations are made on the shaft of ②, screws are carved, and these serrations or convex portions of the screws are carved. A method in which the shaft is formed to the required dimensions by forging and crushing.

<Problems to be solved by the present invention λ The above conventional method has the following problems.

<The in-polishing method involves applying a polisher to each bolt one by one, which takes time, lowers productivity, and increases manufacturing costs.

Even when carving serrations or screws, it is necessary to carve them one by one on each bolt, which takes time, reduces productivity, and increases manufacturing costs.

<Objective of the present invention> The present invention has been made in order to solve the above-mentioned problems, and provides a method for precision finishing of bolt shafts that can improve bolt productivity and reduce manufacturing costs. The purpose is to

Means for Solving the Problem> That is, the present invention manufactures a bolt having a shaft portion with a diameter slightly smaller than the required dimension, and after hitting this shaft portion with a shot to form irregularities on the surface of the shaft portion. This is a precision finishing method for a bolt shaft, in which the convex portion on the surface of the shaft is crushed by precision forging or precision rolling, and the diameter of the bolt shaft is formed to the required dimension.

<Description of the present invention> The present invention will be explained in detail below.

<A> Manufacture of bolt First, a bolt having a shaft portion with a diameter slightly smaller than the required size is manufactured.

The required dimensions are precise dimensions for fitting the shaft of the bolt into the mounting hole of the object to be fastened.

Also, a slightly smaller diameter is -0,005% smaller than the required size.
It is considered that about mm to -0.01 mm is appropriate.

The manufacturing method is, for example, an extrusion method.

That is, in this method, the bolt material placed in a hollow container is extruded by a ram through a hole in a die located at the end of the container to produce the shaft.

After the extrusion process, the bolt is heat treated.

<Mouth> Shot peening is applied to the shaft surface of the bolt that has been subjected to shot peening heat treatment.

Shot peening is performed using a shot (diameter Q, 7 to 0.
This is a type of cold working in which small particles of 9-valent steel or iron are hammered onto the shaft surface at high speed.

When the bolt is hit with a shot, unevenness is formed on the surface of the shaft portion of the bolt.

Then, the surface of the shaft portion is hardened, and the fatigue limit of the material is also increased, which is a so-called peening effect.

Moreover, the oxide film attached to the bolt shaft surface can be removed by heat treatment.

Furthermore, the surface of the shaft is shot to ensure the same surface roughness as polishing.

When forming irregularities on the shaft surface of a bolt by such shot peening processing, a large number of bolts can be processed at once.

<C> Precision finishing of the shaft The convex part on the surface of the bolt shaft, which has been processed into an uneven shape, is crushed by precision forging or precision rolling, and the crushed material is moved to the concave part on the surface of the shaft. Form the diameter to the required size.

As a forging method, for example, roller finishing can be considered.

Roller finishing is a processing method in which a roller is pressed against the convex portion of the shaft to cause plastic deformation on the surface, thereby reducing irregularities and obtaining a smooth finished surface.

Roll-finished products undergo work hardening, which increases wear resistance and fatigue limits.

<Effects of the present invention> Since the present invention has been described above, the following effects can be expected.

That is, in the conventional polishing method and the method of carving serrations or screws, it is necessary to process each piece by machine, which takes time, reduces productivity, and increases manufacturing costs.

In contrast, the present invention is a method of forming irregularities on the surface of the shaft portion of the bolt by using shots, so that it is possible to process the irregularities on a large number of bolts at once and in a short period of time.

Therefore, manufacturing time can be shortened, productivity can be improved, and manufacturing costs can be reduced.

Also, since the shaft surface is shot processed, the surface roughness equivalent to polishing is ensured.

[Brief explanation of the drawing]

Figure 1: Explanatory diagram of the manufacturing flowchart Figure 2: Explanatory diagram of the fitting structure between the bolt and the object to be fastened Applicant: Sannohashi Seisakusho Co., Ltd.

Claims (1)

[Claims] (1) Manufacture a bolt with a shaft portion that is slightly smaller in diameter than the required dimensions, and after hitting this shaft with a shot to form irregularities on the surface of the shaft, precision forging or A precision finishing method for bolt shafts that uses precision rolling to crush and form the diameter of the bolt shaft to the required dimensions.