5. Preparation of work
The prophylactic health and fire protection and labour safety
are an essential requirement for carrying out this technique. Therefore, the
following is to be observed:
- Keep your workplace always clean and in order.
- Use only such working tools which are in a good condition.
- Use appropriate protection for your body (safety glasses,
protective gloves).
- For cleaning, checking and clamping place the machine out of
operation. Do not make safety devices ineffective.
- Use appropriate aids for chip removal (brush, broom, etc.).
- In case of defects which affect the operational reliability of
the machine do not start the machine and eliminate the defects.
Prepare the work in such a manner that all necessary working
tools and objects of work can immediately be used without losing any time. This
includes above all:
- Receive the work order, instructions and
workpieces to be machined. Check the workpieces for completeness and accuracy to
size, i.e. check the premachining quality.
- Study the technical drawings (working drawing) and data sheets
- Lay out and check the necessary working tools (tools,
measuring and testing means, clamping equipment) according to the instructions
for work or your own decision.
- Determine cutting values.
- Fix sequence of operations.
Choice of cutting values
When determining the cutting values, pay attention to the
following hints:
As a rule, the tools for centring, drilling, counterboring and
countersinking, reaming and tapping consist of tool steel or high-speed steel.
The choice of cutting values will depend on this.
The required speed (n) is calculated by rearranging
The machining recommendation for v (cutting speed) is as
follows:
The feed can be effected both mechanically (by using the feed
gear) and manually. When tapping, consider the thread lead. Choose such a feed
that the surface finish required is guaranteed. Always choose clockwise rotation
as direction of rotation of the tools. Maintain this clockwise rotation also for
returning the tools (with the exception of tapping).
A bore with a diameter of 20 mm is to be machined into a
work-piece by means of a twist drill. What speed is to be chosen?
Setting of the machine places high demands on the knowledge and
skills of the operator. This includes:
In view of these factors the techniques are carried out in the
following sequence and show a degree of technological unity:
In order to reduce the wear of the tool cutting edges, it is
necessary in most cases to use a coolant or lubricant. In this connection the
following should be considered:
