SMOOTHING PLASTICS

Question 0

What files are used for working plastics?

Answer 0

Metalworking files, particularly suitable for use with acrylics

Question 1

Name the 3 main ways of smoothing plastics

Answer 1

1. Filing
2. Scraping
3. Rubbing with abrasive papers

Question 2

Describe files that are typically used for plastics - 3 points

Answer 2

1. 250mm in length
2. Second cut or smooth
3. Have double-cut teeth

Question 3

What are hand files used for when smoothing plastics?

Answer 3

Smoothing flat surfaces

Question 4

What are half-round files used for when working with plastics?

Answer 4

For smoothing inside curves

Question 5

What are needle files?

Answer 5

Small files of different cross-sections

Question 6

What are needle files used for?

Answer 6

Very fine work and getting into awkward places. They are very delicate.

Question 7

Name the 2 main methods of filing

Answer 7

Cross filing and

Draw filing

Question 8

Explain cross filing

Answer 8

The file is moved across at 90 degrees to the edge of the work
Your work should be held in a vice to prevent marking from the hard steel vice jaws
You can also use accurately positioned smooth steel strips instead of wood. These also act as a guide to greeting a flat edge and prevent removal of too much material.

Question 9

Explain DRAW filing

Answer 9

The file is placed across the work and then moved parallel with the edge.
Draw filing provides a much smoother finish
The work is held in the same way as for cross filing

Question 10

What is a file card?

Answer 10

It is like a small wire brush.

Question 11

When would you use a file card?

Answer 11

When your files become clogged between the teeth with waste material.
Coating your file with chalk will help to reduce pinning in the first place.

Question 12

Explain scraping

Answer 12

A scraper is a steel blade which has sharpened and BURNISHED edges.
The burnishing is achieve by rubbing under pressure with a hard piece of steel to produce the slightly turned cutting edge. The scraper is held with both hands and angled forwards. It needs expert sharpening.

Question 13

What do you know about abrasive paper?

Answer 13

Abrasive papers consist of a strong paper base on which particles of abrasive are bonded.

Question 14

What type of abrasive paper is normally used for smoothing plastics?

Answer 14

Waterproof SILICON CARBIDE which is available in several grades of particle size.

Question 15

Why should coarser grades of abrasive paper not be used unless necessary?

Answer 15

Because the scratches are difficult to remove

Question 16

Why is silicon carbide paper often called ‘wet and dry’ paper?

Answer 16

It can be used when wet or dry.
It is best when wet because the water washed away the waste that may otherwise clog up.
It is more convenient to hold the work and rub it on a fixed sheet of abrasive paper.

Question 17

Why would you use a block of wood as a guide?

Answer 17

It will help you keep the edge of your work at 90 degrees to its surface.