Selecting a Magnetic Indicator Base and Arm
Dial indicators are one of the main tools used in precision machining. Whether it is to measure a crank shaft or concentricity, you won’t be able to get the job done without a tool in which you can mount the indicator, aka a magnetic indicator base.
An indicator base is the box that supports the arms which hold the indicator itself. This setup is absolutely essential in conducting an accurate reading. It is important to select a base of quality, as not all indicator bases are made the same and you will want the base to have optimal rigidity for a secure hold on the indicator.
There are three main indicator base types, all of which include a magnetic base which allows the inspection tool to latch onto the machine.
Whichever type of arm you decide on, it is recommended to consider trusted brands or spend a bit more money because the quality will almost always be better. Choosing a cheap indicator base can lead to frustration as you will most likely be sacrificing a rigid hold of the indicator and thus an accurate reading.
Standard Magnetic Indicator Base
Magnetic bases are the traditional option. This standard base is comprised of two “arms.” One of which is screwed directly into the magnetic base, the other attached to it in order to hold onto the dial indicator itself. There is a clamp that connects the two arms together and allows the user to change the position of the indicator along that base arm.
Hydraulic Magnetic Indicator Base
Hydraulic magnetic bases technically have a single arm connected to the magnetic base. The movement is enabled from a ball and joint that allows the arm to pivot. What makes this mechanism unique, is the knob between the joints that creates high hydraulic pressure to develop the arms rigidity and strength.
Flexible Arm or “Goose Neck” Magnetic Indicator Base
Flexible arm bases feature the same magnetic box that characterizes the standard bases we described above. Unlike standard models, however, this type of base only have one “arm”. This arm, aka the goose neck, is a tubular system comprised of joints that allows it to bend and move with extreme flexibility. These arms are the absolute best for applications with harder to reach areas that a standard base would have difficulty reaching.
How the Magnetic Base Works
A magnetic base is used because it is the most efficient way to connect the inspection tool to the machine. The way this works, is the base of the stand has a magnet placed directly in the core of the box. This magnet is able to be turned on and off with a switch, which is what allows the base to stick to and be removed from metal surfaces.
If you’re interested in fully understanding exactly how the magnet mechanism works. Check out this video.
Below you will find different indicator bases currently on the market, including models of each type mentioned above.
Recommended Magnetic Indicator Bases
The 657P magnetic base is has a push-button on/off switch for one-handed operation. The base has three precision-ground, magnetic contact points. This allows the base to grip horizontally, vertically, and upside-down. The V-step structure holds the base to arbors, shafts, and other cylindrical items.
The Fowler 52-585-005-0 Magnetic Base is available with both flat surfaces and a V-step structure specifically for round surfaces. With 85 lbs of pull, this indicator base can mount all AGD indicators as well as test indicators.
Both the 110 lbs of permanent magnetic holding power and fine adjustment arm support quality and accurate readings. Featuring the typical and easy on/off switch, the dimensions of this base are 2-1/2” x 2-1/8” x 2”.
The 360-degree articulated arm of the Noga magnetic base is capable of reaching every possible position – even upside down. Its strong magnetic base and superior holding power clings firmly which supports the indicator to achieve highly accurate measurements. The base supports up to 176 lbs.
This indicator base features two arms that are adjustable in any position by twisting the knob. The V-grooved base allows the base to achieve a secure mounting on cylindrical surfaces. This magnetic base is compatible with all branded dial indicators.
The Fowler 72-641-300-0 Flex Arm Base and Indicator Combo features 85 lb. pull and is desired for its ability to hold rigidly in any position desired. The magnetic indicator base style features the flexible tubular arm, an on-off lever release magnet and a V-base for placing on round surfaces.
This flexible arm indicator base is great for attaching to uneven steel surfaces as the magnetic base can adapt to almost any shape or contour. This arm features a chrome plated flexible shaft that has a single lock lever to ensure secure locking of the segments.
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