VU20961 – Levelling Page 17.

CHECKING THE ACCURACY OF A SPIRIT LEVEL Spirit levels lose their accuracy if they are dropped or stored incorrectly, so it is best practice to check that your spirit level is accurate before use.

ASSESSMENT 1: CHECK YOUR SPIRIT LEVEL

How: Use the following steps to check that your spirit level is accurate.

Step 1 Hammer two nails into a piece of timber that is longer than your level.

Hammer in two nails

Step 2 Place one end of the spirit level on one nail and the other end of the level on the other nail and check for level. If it is not level, hammer in one nail until it is. Check for level and adjust by hammering in one of the nails

Step 3 Turn the spirit level 180° so that the opposite end of the spirit level is on each nail.

Turn the spirit level 180°

Step 4 Check for level.

Check for level

Step 5 If your spirit level is accurate, the reading should be the same.

The reading should be the same Check the spirit level for plumb Use a plumb bob to check bubbles for ‘plumb’ position. Use the same process but set the nails to height with a ‘plumb bob and line.

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AUTOMATIC LEVEL

Nicon AC-2S automatic level

Carpenters in the Building and Construction Industry will normally have an automatic (or dumpy) level, to assist them in the setting of site levels and to measure distance.

Automatic levelling equipment Using an automatic level Setting up the tripod You need to set up the tripod so that it is secure, the head is approximately level and the instrument telescope is at eye level. To achieve this use the following steps:  Undo carrying straps  Extend legs  Set tripod in position (if the ground is sloping place two legs on the downhill side).  Firmly press in two of the tripod feet into the ground using your own foot on the tripod's foot plate.  Move the third leg so that the head looks level and the instrument

telescope will be at a comfortable height when this leg is firmly pushed into the ground. Tripod legs set up  Fine adjustments can be made by changing the length of each leg to level the head. Make sure that the clamp or locking screw is tightened when finished.

22216VIC – Certificate II in Building and Construction (Carpentry) Copyright LAPtek Pty. Ltd. VU20961 – Levelling Page 25.

Setting up an automatic level Setting up an automatic level is a relatively easy task. To set one up use the following steps.  Attach the dumpy level to the legs and tighten the base plate screw.  Turn the dumpy so it is parallel with two of the levelling screws  Turn both screws either away from each other or towards each other simultaneously until the bubble in the spirit level is centralised.

 Turn the dumpy 90° so the level now points towards the levelling screw Level attached to that has not been touched and then use this to complete the bubble the tripod levelling by putting the bubble in the middle of the bulls-eye.

The ‘dumpy’ should now be perfectly level and you are ready to start to take spot heights.

Reading a levelling staff The staff is simply a large ruler, available in lengths of 3, 4 or 5 metres and usually made of aluminium with telescopic sections. Measurements are in metres and cm (10mm blocks) which enable heights to be estimated to 1 mm. Alternating colours are used to differentiate each metre length, the most common being black and red on a white background. Major graduations occur at 100 mm intervals and are denoted by figures. Minor graduations are at 10 mm intervals and form coloured squares or intervening Field of view spaces. The lower 50 mm of any 100 mm block are joined by a band to form the distinctive E pattern which is designed to make reading a small section of the staff in the telescope easier.

How to use an automatic level to determine distance To enable you to determine distance the automatic level (dumpy level) has stadia cross hairs. These are the two short cross hairs above and below the main cross. To determine how far the staff is from the level, you multiply the distance between the two by 100. So in this example on the right, the lower cross hair is at 855mm and the upper cross hair is at 1.0 m, (1000mm) so the difference is 145 mm So the distance from the level to the staff is:

145 x 100 = 14.5 m Stadia crosshairs, the top mark is at 1.0m (1000mm) and the lower is at 855mm

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Check that the staff is vertical It is essential to take readings when the staff is vertical. If the staff is not vertical (leaning right, left, forward or backwards) the reading will be larger than it should be, this is because you are measuring a slope distance, and this will give you errors.

Holding a staff straight

ASSESSMENT 7: DETERMINE AUTOMATIC LEVEL READINGS

1. Reading: ...... 2. Reading: ......

3: Reading: ...... 4. Reading: ......

22216VIC – Certificate II in Building and Construction (Carpentry) Copyright LAPtek Pty. Ltd. VU20961 – Levelling Page 37.

Student Learning Guide & Record DATE INSTRUCTOR’S TASK PAGE NAME COMPLETED SIGNATURE

Assessment 1 17 Check your spirit level

Assessment 2 18 Summarise spirit levels

Assessment 3 18 Check walls for plumb

Assessment 4 19 Check window sills for level

Transferring levels with a straight Assessment 5 20 edge and spirit level

Assessment 6 22 Use a plumb bob to check for plumb

Assessment 7 26 Determine automatic level readings

Use an automatic level to transfer Assessment 8 27 height

Assessment 9 28 Testing an automatic level

Transferring a given datum with a Assessment 10 29 water level Explain the hazards of using a rotary Assessment 11 32 laser level Use a rotary laser level to transfer Assessment 12 32 height Identify the parts of an automatic Assessment 13 33 level

Assessment 14 33 Review questions

Assessment 15 35 Reflection – Levelling

Copyright LAPtek Pty. Ltd. 22216VIC – Certificate II in Building and Construction (Carpentry)