Palm Size Leeb Hardness Tester (Recaliber,Test Any Angle)

Additional Information

Applications:

Configuration

Measuring and Converting Ranges

Structure Feature and Testing Principle
Structure Feature

1 Calibration mode                 8 Average Symbol

2 Measuring value                 9 Measuring symbol

3 Average times set                10 Battery indicator

4 nth measuring value           11 Hardness scale

5 Impact type                           12 Material

6 Measuring state                  13 Direction

7 Browsing state                   14 Number of memorized data

Leeb Hardness Testing Principle

An impact body with a spherical test tip made of tungsten carbide is propelled against the sample surface by a spring force and then rebounds back. At a distance of 0.03 in (1 mm) from the sample surface, the impact and rebound velocity of the impact body are measured by the following method: A permanent magnet embedded in the impact body, when passing through the coil in its coil holder, induces in the coil an electric voltage proportional to the velocities of the magnet. Leeb hardness is expressed by the following formula:

HL=1000 × (VB/VA)

Where: HL is Leeb Hardness

VB is the rebound velocity of the impact body

VA is the impact velocity of the impact body

The voltage characteristic of the output signal, when the impact body passes through the induction coil is illustrated in the following figure:

Voltage Characteristic of output signal

A Leeb Hardness Tester measures the hardness of sample material in terms of Hardness Leeb (HL), which can be converted into other Hardness units (Rockwell B and C, Vicker, Brinell and Shore D).

When measuring the hardness of a sample material using the traditional static hardness testing method, a change of applied pressure will result in a change in the hardness reading. This will also happen during a Leeb’s Hardness test when you change the impact device. In measuring the hardness of the same test sample with different impact devices, the Leeb’s hardness values obtained will vary.

For example, 760 HLD≠760 HLC≠760 HLG

Symbols and illustrations of Hardness Scale

Symbols of Materials

Preparation

Selection of the workpiece to be tested and preparation of its surface prior to testing will help ensure accuracy. Magnetism of the sample itself should be avoided. The surface temperature of the sample should be less than 248 °F (120 °C).

Weight Requirement

To achieve correct test results, select thick, heavy, and solid workpieces for testing whenever possible. The surface area where the impact body strikes should have an even hardness. A solid workpiece that weighs more than 11 lbs (5 Kg) can be tested on directly with this hardness tester. Support is not necessary for the heavy sample. A workpiece that weighs 6 lbs to 11 lbs (3 Kg to 5 Kg) should be fixed to a bearing or support weighing over 11 lbs (5 kg) to avoid bending, deformation, and displacement during testing.

A workpiece that weighs less than 4 lbs (2 Kg) should be secured to a workbench or a stable support. The surface between the workpiece and the support must be hard, clean, and smooth. To secure the workpiece, apply petroleum jelly or yellow grease to the adjoining surfaces of the workpiece and support, press the workpiece firmly onto the support, and eliminate any air between the two surfaces by moving the workpiece back and forth. Proper coupling requires a little experience. Insufficiently coupled samples produce large variations of individual measurements, HL-values which are too low and the operation is characterized by a rattling noise upon impact of the test tip.

For the coupling operation, the following prerequisites must be fulfilled:

Roughness Requirement

To eliminate measurement errors which could result from the roughness of the test surface, the surface should be polished so that a metallic luster appears. The roughness (Ra) of the surface must be limited to ≤ 2µm. Note that the rougher the surface of the workpiece, the lower the hardness test results.

Cleanliness Requirements

To ensure test accuracy, the test surface of the workpiece must be clean and free of any oil stains, rust, and remains from electroplating or paint.

Stability Requirements

To avoid displacement during testing, the workpiece should be firmly fixed with its test surface perpendicular to the impact direction. Due to the impact of the Impact Body, the test area may deform or vibrate, even for some workpieces with suitable weight and thickness.

The tested hardness may be lower than normal. This is especially true for workpieces such as a large plate, a long bar or a rod, and workpieces with a curved surface. Some testing recommendations for these workpieces are shown in the figure given below.

Samples with Curved Surfaces

The larger the curvature of the workpiece’s surface, the easier the testing operation. Under normal conditions, testing can be done directly with the standard support ring to a curvature with the radius of 1 3/16″ (30 mm) or longer.

For a workpiece with a radius of less than 1 3/16” (30 mm), a special support ring should be used for testing.

For impact device type D, Rmin=30 mm

Test Sample Properties

Operation of the Tester

Power on/off

Setting your Impact Direction

Use the DIR/SHIFT button to move the cursor until you reach the desired direction.

Selecting a material

Press the DIR/SHIFT key first and not release it. Then press RD/▲ key to scroll down the list until the desired material is reached.

Choosing a hardness scale

Press the DIR/SHIFT key first and not release it. Then press DEL/▼ key to scroll down the list until the desired hardness scale is reached.

Average Times Setting

After pressing POWER/MENU key for 6 seconds into item AVE, press RD/▲ key or DEL/▼key, in turn, to select the average times from 2-9, selecting 0 means no mean values. Press POWER/MENU key finally to exit from the operation. This function allows you to view the average of the amount of tests you entered. Example: If you chose “3”, the tester will show the average after 3 consecutive tests.

Measuring Procedure

Use standard test block to check your hardness tester prior to a hardness test.

If the test results are outside the ranges listed in the table – Measuring and Converting Ranges, the screen will display E. Each measure area of the sample usually needs 3 to 5 times of testing operation. The result data dispersion should not be more than mean value ±15 HL. The distance between any two impact points or from the center of any impact point to the edge of the testing sample should conform to the regulation of the table given below.

Data Memorizing

When taking measurements, all values will be stored automatically in memory and the number of stored reading is accordingly increased by 1. The tester can store up to 50 groups of data with measurement conditions. If the memory is full, the tester will auto save the new reading and discard the oldest one. That means the tester only hold the last 250 groups of data in memory.

Memory Recall

Under measuring mode marked by ‘M’ on the display, press RD/▲ key to enter into the mode of viewing stored values marked by ‘R’. Press RD/▲ key or DEL/▼ key to recall stored values forwards and backward. To return to the measurement state, just press the POWER/MENU key.

Delete data in memory

In the measurement state marked by ‘M’ on the display, the new reading can be deleted by pressing key DEL/▼, and the number of stored reading is accordingly decreased by 1. To clear memory, just press and hold DEL/▼ key for 3 seconds till the number of stored reading becomes 000.

Download to PC

This tester can communicate with a PC by optional USB or RS232C cable and software. All the memorized data can be downloaded to your PC every time when in a measurement state, you press RD/▲ key to enter the viewing memorized state.

Auto Power Off

The instrument features an auto power off function designed to conserve battery life. If the tool is idle (neither measuring nor any key operation) for 3 minutes, it will turn itself off.

Battery Replacement

When the battery symbol appears on the display, it is time to replace the batteries. Slide the Battery Cover away from the instrument and remove the batteries. Install batteries paying careful attention to polarity.

Calibration

After a long period of use, especially for measuring harder materials, the ball tip of impact body will be worn which may lead the tester have more or less error on accuracy. At this moment, this tester is designed to allow recalibration. The calibration can be made in the following way.

Maintenance & Servicing

After the impact device has been used for 1000 to 2000 times, please use the nylon brush provided to clean the guide tube and impact body. When cleaning the guide tube, unscrew the support ring first, then take out the impact body, spiral the nylon brush in a counter-clock direction into the bottom of the guide tube and take it out for 5 times, and then install the impact body and support ring again.

Table A

No.	Type	Sketch of non-conventional Supporting ring	Remarks
1	Z10-15		For testing cylindrical outside surface R10~R15
2	Z14.5-30		For testing cylindrical outside surface R14.5~R30
3	Z25-50		For testing cylindrical outside surface R25~R50
4	HZ11-13		For testing cylindrical outside surface R11~R13
5	HZ12.5-17		For testing cylindrical outside surface R12.5~R17
6	HZ16.5-30		For testing cylindrical outside surface R16.5~R30
7	K10-15		For testing spherical outside surface SR10 ~ SR15
8	K14.5-30		For testing spherical outside surface SR14.5 ~ SR30
9	HK11-13		For testing spherical outside surface SR11 ~ SR13
10	HK12.5-17		For testing spherical outside surface SR12.5 ~ SR17
11	HK16.5-30		For testing spherical outside surface SR16.5 ~ SR30
12	UN		For testing cylindrical outside surface, radius adjustable R10 ~ ∞