GAOTek Palm Size Leeb Hardness Tester (Recaliber, Test Any Angle) measures the hardness of metal workpiece material in the range from 200 L to 900 L. It is a powerful hardness tester for different kind of metallic materials including cast aluminum, grey cast iron, steel and cast steel, brass, cold work tool steel, nodular cast iron, and stainless steel with high accuracy. Manual or automatic shutdown, low battery indication, powerful battery and 0.49 in (12.5 mm) LCD with backlight are some of the important features of this instrument. This portable device can be used on a heavy work piece, steam generator and other equipment, installed machinery and permanently assembled parts, die cavity of molds, bearings and other mass produced parts on a production line.
- Palm size for narrow space.
- The Large memory could store 50 groups including single measured value, impact direction, material and hardness scale etc.
- Manual or automatic shutdown.
- Test at any angle, even upside down.
- Direct display of hardness scales HRB, HRC, HV, HB, HS, HL.
- Low battery indication.
- User recalibration function allowed.
- Can communicate with PC computer for statistics and printing by the optional cable.
|Measuring Range||200 L – 900 L|
|Accuracy||Display error ±0.8 %|
|Display||0.49 in (12.5 mm) LCD with back light|
|Materials||9 different common materials.
Steel and cast steel, C.W. Tool, Steel, Stainless Steel, Gray, Cast iron, Nodular cast iron, Cast aluminum, Brass, Bronze and Copper)
|Power Supply||2×1.5 V AAA size battery|
|Impact Device||Probe D
Weight: 0.16 lbs (75 g)
|Memory||50 data can be stored and re-readable|
|Dimension||5.74 in×2.55 in×1.41 in (146 mm×65 mm×36 mm)|
|Weight||0.28 lbs (130 g) (without batteries)|
|Working Temperature||14 °F ~ +122 °F (- 10 ℃ ~ +50 ℃)|
|Storage Temperature||– 22 °F ~ +140 °F (- 30 ℃ ~ +60 ℃)|
- Die cavity of molds.
- Inspection of bearing and other mass produced parts on a production line.
- Failure analysis of pressure vessel, steam generator, and other equipment.
- Inspection of installed machinery, permanent parts of assembled systems and heavy work pieces.
- The testing surface of a small hollow space.
- Material identification in the warehouse of metallic materials.
- Rapid testing in a large range and multi-measuring areas for the large-scale work piece.
|Standard Configuration||1||Main unit||1|
|2||Standard test block||1|
|3||Small support ring||1|
|Optional Configuration||1||Other type of impact devices and support rings|
|2||RS232C or USB cable +Software|
Measuring and Converting Ranges
|30 D2||10 D2|
|Steel & Cast St.||300 ~ 900||20.0 ~ 68.0||38.4~99.5||80 ~ 647||80~940|
|C.W. Tool Steel||300 ~ 840||20.4 ~ 67.1||80~898|
|ST.STEEL||300 ~ 800||19.6 ~ 62.4||46.5~101.7||85 ~ 655||80~802|
|Gray Cast Iron||360 ~ 650||93 ~ 334|
|Nodular Cast Iron||400 ~ 660||131~ 387|
|Cast Aluminium||174 ~ 560||20~159|
|Brass||200 ~ 550||13.5 ~95.3||40~173|
|Bronze||300 ~ 700||60~290|
|Copper||200 ~ 690||45~315|
Structure Feature and Testing Principle
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
|LD||Leeb hardness value used with impact device D|
|HB||Brinell hardness value|
|HRB||Rockwell B hardness value|
|HRC||Rockwell C hardness value|
|HSD||Shore hardness value|
|HV||Vicker hardness value|
Symbols of Materials
|1||Steel and cast steel|
|2||Cold work tool steel|
|3||Stainless steel and high temperature-resistant steel|
|4||Cast iron with lamellar graphite (grey cast iron GG)|
|5||Cast iron with spheroidal and nodular graphite (GGG)|
|6||Cast aluminium alloys|
|7||Copper – zinc alloys (brass)|
|8||Copper-alu/copper-tin alloys (bronze)|
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).
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:
- The contact surface of the sample and the surface of the base plate must be flat, plane parallel and ground.
- The direction of the test impact must be perpendicular to the coupled surface.
- The minimum thickness of the sample for coupling 0.11 in (3 mm).
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.
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.
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
|Sample||Impact Device D|
|Sample Weight (kg)||Needs Support||0.05-2|
|Needs to be stabilized||2.5|
|Min. Thickness (mm)||Sample||3|
|Max. Roughness (or Min. Fineness)||ISO||N7|
Operation of the Tester
- Press the POWER/MENU key, now power is on. The instrument is in working mode.
- The LCD will display the same settings that were previously set. If the display meets your current testing requirements, you can start the test immediately. If not, you can enter your required settings using the keypad.
- The tester can be turned off by pressing the POWER/MENU key for 3 seconds while OFF shows on the display.
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.
Use standard test block to check your hardness tester prior to a hardness test.
- Loading: Push the Loading Tube towards the support ring to lock the impact body. Then, while still holding on to the loading tube, slowly return it to its original position. Caution: Returning the Loading Tube back to its original position too quickly may damage the tester’s parts. ALWAYS hold onto the Loading Tube and slowly guide it back in a controlled fashion.
- Placement: Hold the tester between your thumb and index finger, hold the tester against the work piece. Please note: the impact device must be firmly against the surface and the impact direction should be vertical to the testing surface or you may get unsatisfied value.
- Releasing: Press the release button lightly on top of the tester and take the measurement. The measuring value will be displayed on LCD. Ensure that while releasing the triggering button, the work piece, the impact device, and the impact body are all stable and the starting force coincides with the axis of the impact device.
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.
Type of Impact Device
|Distance of center of the two indentations||Distance of center of the indentation to sample edge|
|Not less than (mm)||Not less than (mm)|
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.
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.
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.
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.
- Press POWER/MENU key for 8 seconds into item CAL and the tester now is in the calibration mode.
- Take measurements on the standard test block.
- Use RD/▲ key or DEL/▼ key to adjust the reading on the display to the standard value.
- Repeat 2 till the measurement readings are accurate.
- Press POWER/MENU key to quit from the calibration mode and return to the measurement mode.
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.
- Release the impact body after use.
- Any lubricant is absolutely prohibited inside the impact device.
- When results from repeated testing on a standard hardness test block are consistently higher than the actual hardness value, the Impact Body is probably worn. In such a case, it is necessary to replace an impact body.
|Sketch of non-conventional Supporting ring||
|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|
|For testing spherical outside surface SR10 ~ SR15|
|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|
|For testing cylindrical outside surface, radius adjustable R10 ~ ∞|