3. Recommendations for practical vocational training in the working technique of “Manual Sawing”

The following paragraphs comprise proposals on conducting trainee instruction, the demonstration of the working techniques as well as exercises and tests. We recommend the following way of conducting the course:

Introductory instruction with demonstrations from the “Trainees’ Handbook of Lessons”.

Exercises in sawing from “Instruction Examples 4.1. - 4.6.” and subsequent evaluation.

Final test of theory knowledge based on the contents of the “Examples for Recapitulation and Tests”.

The exercise associated with “Instruction Example 4.7.” can follow later as a complex work, because it is necessary to acquire other working techniques first.

Practical skills should be tested immediately after handing over the finished workpiece. Knowledge of theory should be constantly checked. However, it is recommended that a final test paper should be written after the conclusion of the exercises.

3.1. Introductory instruction

If possible, this instruction should be given in a classroom. Make sure that the trainees put down necessary supplementary hints or answers to questions in their “Trainees’ Handbook of Lessons”.

Instruction can be carried out on the basis of the main points contained in the “Trainees’ Handbook of Lessons”. The main subjects of “Purpose of Sawing” and “Tools and Accessories for Sawing” are to be taught with the employment of all the teaching aids available.

Purpose of sawing

This subject should be illustrated by presenting workpieces which were cut by sawing or which show kerfs. The trainees should recognize the single-piece nature of this work.

Tools and accessories

Transparencies nos. 4.1. and 4.2. can support the demonstration of original tools and accessories. The design of a hand hacksaw and the fixing of the saw blade is to be explained.

Vice

Most important clamping device for any locksmith work. It consists of a fixed part screwed onto the work bench and a movable part.

By means of a handle the movable part (clamping Jaw) is screwed towards the fixed clamping jaw (both jaws are hardened). The clamping jaws may be of flat or vee type.

Figure 7 Vice

Vee clamps

Vee-shaped attachments for the vice permitting horizontal clamping of cylindrical workpieces.

Figure 8 Vee clamp

Angle clamps

Simple angles to be vertically attached to the vice permitting long metal sheets to be firmly clamped.

Figure 9 Angle clamp

Protective jaws

Soft-metal attachments for the vice to protect coated or sensitive surfaces of workpieces from damage when being clamped.

Saw blades for different cross sections of workpieces and degrees of material hardness

Type of saw blade	cross section of workpiece	material hardness	tooth pitch (number of teeth on 25 mm)
coarse	- solid sections (round, square and hexagonal steels)	soft steel, non-ferrous metals	14
normal	- normal sections (angles, sectional steel) - thick sheet metal	steel of normal hardness, harder light metals	22
fine	- light-steel sections - thin sheet metal	harder steel, cast iron	32

The instructor has to stress the importance of the free cutting action of saw blades.

For the purpose of demonstration one trainee is to be given the task to perform a sawing cut on any workpiece using a saw blade with free cutting action first, and then a saw blade without (or with poor) free cutting action. The trainees have to register the required times for sawing and to draw the necessary conclusions.

They will recognize that more time and energy is necessary for the use of saw blades without or with poor free cutting action due to the frequent jamming.

Subsequently, the trainees have to answer the questions contained the “Trainees’ Handbook of Lessons”.

The following order is recommended when introducing the accessories:

- vice
- vee clamps
- angle clamps
- protective jaws.

It must be stated quite clearly why these accessories have to be used - this should be supplemented by employing transparency no. 4.3.

If some of these tools and accessories should not be available as originals, the respective illustrations in the “Trainees’ Handbook of Lessons” could supplement the instruction.

Effects of sawing, posture and
saw guidance

Demonstrations should show these effects when cutting a broad and a narrow workpiece each. The trainees will see that the saw will cut better when many teeth are cutting at the same time. This requires a different handling of saws.

Figure

In this context the trainees should be shown the proper posture and guidance of the saw.

The “Trainees’ Handbook of Lessons” contains specific hints for this subject which must be taken into account.

How to handle the saw

The trainees have to be shown the close connection between a vertical guidance of the cut and the proper clamping of the workpieces. The following examples need particular explanation:

- Clamping of flat workpieces for sawing on their broad side.
- Clamping of sheet metal and sawing with upward pushing direction.
- Clamping and repeated re-clamping when sawing tubes.
- Fixing of angle sections and sawing on the broad side only.
- Sawing of deep cuts with the saw frame swivelled by 90°.

These facts should be further illustrated when working in the workshop.

3.2. Exercises

If it was not possible to include the individual demonstrations into the instructions, they should be performed right now before the exercises.

If the trainees avail of only little practical skills, they should do some preliminary exercises on any small workpieces:

- simple cutting of flat and square steel
- cutting of tubes and angle sections
- sawing of straight and angular recesses.

But it is also possible to begin with the first exercises contained in the “Instruction Examples for Practical Vocational Training” at once.

However, it is necessary to prepare any individual exercise by a brief “job-related instruction”. Within this context the trainees are shown a finished workpiece in order to make them familiar with the aim and purpose of this exercise.

The instructor must have completed such a workpiece by himself so as to know the problems involved in manufacturing it.

This makes it possible to determine the main points in evaluating the trainees’ performance and to advise the trainees on problems involved.

During these lessons of special instruction the trainees have to place the sequences of operations and working drawings of the training examples on their desks so that they can make notes therein.

All the trainees can carry out these exercises simultaneously, if the required number of working tools is available. If this is not the case, the trainees will be divided into groups based on the respective tasks and the number of the working tools available.

Those trainees who cannot start their practice of sawing immediately should do some other jobs in the workshop first:

- selection and preparation of the initial materials.

- checking and minor repair work on working tools under supervision of an instructor; other exercises can reinforce the skills of working techniques acquired earlier.

3.3. Examples for recapitulation and tests

This section comprises questions for consolidating and testing the acquired knowledge and skills. Each question is provided with the respective answer. Questions which are also contained in the “Trainees’ Handbook of Lessons” are marked with the letter “A”.

1. What is the purpose of sawing?
(Cutting of workpieces in a narrow saw kerf in order to divide them or to provide them with slots or cuts.)

2. How do the various types of saw blades differ?
“A” (Design of angles at the saw tooth, number of teeth on a length of 25 mm.)

3. What saw blade do we use when sawing steel of normal hardness?
(Saw blade with medium tooth pitch and cutting-type chip formation.)

4. Why is the free cutting action necessary for saw blades?
“A” (This is to prevent them from jamming in the kerf.)

5. Which are the common design-based ways of achieving the free cutting action?
(Raker-setting of saw teeth, wave-setting of teeth.)

6. What is to be taken into consideration when clamping a workpiece for sawing purposes?
“A” (The workpiece is to be clamped in a way that allows a vertical sawing cut and prevents the workpiece from springing and slipping.)

7. Which is the most important clamping device for workpieces?
“A” (Vice.)

8. Which types of workpieces have to be clamped in vices by means of protective jaws?
(Workpieces with coated or sensitive surfaces.)

9. Why must we guide the saw in such a way that as many teeth as possible are cutting at the same time?
“A” (If only a few teeth are cutting, there will be the danger of hooking in and breaking out of teeth.)

10. What is to be taken into consideration when sawing off workpieces?
“A” (Immediately before the workpiece is sawn off, the pressure on the saw must be reduced so that the saw blade will not be damaged by a torn off workpiece.)

11. How is the saw to be handled when sawing thin metal sheets?
"A" (Saw must be held slightly upwards in the pushing direction.)

12. How is the saw to be handled when sawing tubes and sectional steel?
“A” (Tubes and steel sections must not be sawn off in one pass, but they have to be reclamped during sawing so that as many teeth as possible will be cutting at the same time.)