2.4 Component Connections

Bench Vice

The vice assembly is used as the basis for dimensioning individual parts of various geometries and functions. The component should always be considered as a whole in order to ensure later joining and operation. The exploded view shows four individual parts whose dimensions are explained below.

Pins

Functionality: The bolt serves as a lever for adjusting the vice on the workbench. To make the adjustment handy, a ball head is attached to the bolt. This requires an oversize fit (see also chapter "3.3.1 Selection and calculation of fits"), which enables the ball to be firmly seated. In order to be able to produce these, an undercut is screwed onto the heel which allows grinding without any permanent rounding in the edge. The bolt is then inserted into the pressure spindle, which then tightens the vice on the workbench with the pressure plate by turning it. The bolt should be able to move easily in the pressure spindle, therefore the remaining diameter is manufactured with a backlash fit (see chapter "3.3.1 Selection and calculation of fits"), which on the one hand enables this movement and on the other hand prevents "wobbling".

Procedure for dimensioning a shaft:

When dimensioning a shaft, production must be considered. Shafts are produced on lathes and, depending on the shape of the sections, are therefore often re-clamped, i. e. a shaft is always dimensioned from two reference edges.

Bolt dimensioning:

The manufacturing method of the bolt and the resulting dimensions are explained below:

First the raw material is sawn off to a length of 83 mm, then clamped on one side and the heel is manufactured with an undercut. The fit is then ground. Now change the side of the clamping and grind the clearance fit. Therefore, it makes sense to specify the total length and the length of the interference fit. The length of the clearance fit then results automatically. The length of the fit 6 s6 is also important for the fitting of the ball head on the heel. Therefore, this was measured with a negative tolerance. If no tolerance is specified directly on the dimension, the previously selected general tolerance defines the range of dimensions (see chapter "2.2 View, Sections and Hatching"). The undercut is manufactured here in compliance with the DIN standard (DIN 509), which is why it can be dimensioned by the abbreviated marking.

Threaded Bolts

Functionality: The threaded bolt is used to adjust the clamping jaw in order to clamp the workpiece to be machined later. Therefore, a motion thread, i. e. a trapezoidal thread, is chosen. For a trapezoidal thread, the nominal diameter is always indicated with a gradient (see chapter "3.2.1 DIN 13 Part 1: Metric ISO thread").

alt — Technical Drawing of the Threaded Bolt

Threaded bolt dimensioning: The procedure for dimensioning the threaded bolt is identical to the dimensioning of a shaft. The total length of the threaded bolt is 168 mm. The shaft is clamped on the left side and first the diameter 13 mm is roughly pre-turned. In order to be able to produce the fit, an undercut is manufactured at the heel which is not in accordance with DIN 509 and must therefore be dimensioned separately. In order to make the dimensioned lengths recognizable, the undercut is displayed as a detail (see chapter "2.2 View, Sections and Hatching"). The thread length is pre-defined, therefore a thread outlet is manufactured in order to separate the thread and fit neatly from each other.

The two holes for the dowel pins cannot be dimensioned in the front view because they are not completely visible. Therefore, cuts are made through the axes of the holes. In these sectional views, the inner contour of the holes becomes visible.

The most important installation dimension in this drawing is the distance between the two bolts, which defines the seat of the threaded bolt.

Jaws

The jaw is attached to the guide with screws. The threaded bolt is inserted through the central hole in the jaw. The clamping jaw is attached to the jaw.

In the front view you can see that the jaw is a symmetrical part.

Dimensioning of symmetric bodies: The symmetry is used when dimensioning individual parts or assemblies. This means that all hole spacings are dimensioned above the center. There is therefore no reference to an outer edge, as is necessary for a casting, for example.

This symmetry is also used for the jaw.
First of all, the main dimensions such as height, width and depth are entered.

Insertion of main dimensions:Main dimensions, such as height, width and depth, should be entered on a view, if possible.

The lower edge is selected as the reference edge for the height dimensions unless there is a good explanation for the deviation.

In this part it is important to dimension the hole pattern correctly and above all with regard to each other. The dimensions that are corresponding with the counterpart should be selected, i. e. the individual parts that follow must also be taken into account.

Screwing from the jaw to the clamping jaw: In this case, an example for the dimensioning of bolting is the bolting of the clamping jaw to the jaw. The distance of the hole must be the same, otherwise the parts cannot be joined. We therefore dimension the distance 40 and tolerate it with +/- 0.1 on both parts to ensure that the dimensional deviations are within a certain range.

In this case it is important that the clamping jaw fits into the paragraph. For this reason, the height dimension 6 is tolerated with + 0.1 for the jaw and -0.1 for the counterpart and -0.1 for the jaw. This prevents overlapping during joining.

Clamping Jaw

The procedure for dimensioning the clamping jaw is similar to the procedure for dimensioning the jaw. The dimensions associated with the clamping jaw are explained in the section "Dimensioning of the jaw".

alt — Technical Drawing of the Clamping Jaw

Dimensions of countersinks for screw heads according to DIN 74

Countersinks for screws are standardised. In order to select the correct countersink, you first have to select the type of bolt (cylinder head, countersunk or oval head bolts) and then look for the dimensions for countersinks in the corresponding table (see chapter "3.2.8.: Countersinks for screws").

In our case, a cap screw according to DIN EN ISO 1207 was selected. The corresponding dimensions for the screw countersink according to DIN 974-1 are 8 mm in diameter and 3.2 mm in depth.

Clearance holes for screws according to DIN EN 20273

The situation is similar for clearance holes for threads. For each thread according to DIN 13 series 1 there are tables with the corresponding clearance hole diameters (see chapter "3.2.7 DIN EN 20273: Through holes for screws").

In our example, the thread is M4 and the corresponding through hole in the medium tolerance zone corresponds to a diameter of 4.5 mm.

Main and connecting dimensions in an assembly drawing

alt — Technical Drawing of the Assembly Bench Vice

The main dimensions correspond to the outer dimensions in an assembly drawing. These are important for the further use of the assembly. They are used, for example, to define the packaging size or space requirement in the usage phase. The end user also receives information about the installation space of the module. Main dimensions include height, width and thickness. In the case of a vice, the width of the lever is not dimensioned as its position is variable.

Connecting dimensions are important for the buyer in order to be able to take the appropriate precautions for assembling or installing the product at a later date. This usually includes connection holes for certain screws. In the case of a vice, it is important to know how thick the workbench can be so that the vice can still be clamped to it. Therefore, a range of 0-45 is given here. Furthermore, it is important to know which sizes can be clamped on workpieces. Again, an interval is specified here.