There are dozens of different dial indicators on the market, in this review I will explain what I consider to be the best dial indicators for a cnc hobbyist.
What is a dial indicator?
A dial indicator is a measuring instrument that amplifies a distance so that it can be read on the ‘face’ of the indicator.
The face of the indicator resembles a clock face with two arms that give large and smaller increments of the distance the plunger travels.
You read both the large dial face and the smaller inset dial face to read the total distance the plunger travelled. The larger dial face gives the reading of the smallest increments.
What are the different types of dial indicator?
The two most common types of indicator are the dial indicator (as shown above) and the dial test indicator also known as the finger dial.
Test Indicators differ from dial indicators by having a lever arm instead of a plunger.
The arm pivots back and forth about a hinge point and can measure in both directions.
This arm can be positioned where you need it, just carefully push the arm to the to overcome the friction that holds it in place.
Test indicators have less movement than plunger dials and are physically smaller as well.
What is a dial indicator used for?
When dial indicators are used for machining their main function is to check that a workpiece is running parallel to the axis of movement. Also to confirm if a rotating part is running true to the center of rotation when used in a lathe or rotating axis on a mill.
They do have many other uses however, such as measuring sizes. This would be common in an inspection department where they can be used to quickly measure a large batch of identical parts.
Readout on manual micro lathe
I have a dial indicator with 2” of travel setup on my Taig Lathe as a readout. It allows me to accurately travel an exact distance in the Z axis. The plunger on the dial is set against the carriage on the lathe.
Dial indicators are used in engine rebuilds or for maintenance. When mounted on a magnetic stand they can be used for finding top dead center of a piston or measuring the amount of lateral movement or ‘play’ in a crankshaft.
How to use a dial test indicator
Among the most common dial test indicator use for a machinist is clamping them in the spindle.
Mounting them on an arm in the spindle enables the Z column to be swept to ensure it is perpendicular to the table.
Using a finger dial in the spindle also lets you pick up the center of a part to set your X and Y axis datums and to dial the center of a hole.
Dialing the center of a hole is done by positioning the dial in the hole so the dial arm is contacting the circumference. Then rotate the spindle by hand and adjust the X and Y axes until the readout stays on zero all around the circumference of the hole.
The machine will now be positioned on the center of the hole.
How do You set up a dial Indicator?
I usually mount my small finger dial in the spindle to square up the vice on my taig mill or alternatively a small magnetic base can be used to hold it against the Z axis column.
Test indicators are smaller than a standard dial indicator, making them perfect for use in a small benchtop cnc milling machine.
How does a dial indicator work?
A basic dial indicator works using a rack and pinion system. The plunger has teeth ground into one side which rotates a series of gear wheels, which in turn rotate the arms on the dial.
The plunger is also spring loaded to make it return to its fully extended position and keep the tip in contact with the surface being measured.
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Khcraft dial test indicator
This is a small dial indicator and is identical to the one I bought for my Taig cnc mill. The build quality and supplied attachments are not as good as a mitutoyo or starrett but I have not had any issues with it and it does the job. It is also more compact than the more expensive dials making it ideal for a small mill.
All industrial supply dial indicator
This is a typical generic dial indicator and magnetic stand. Similar to the one I own. (I am pretty sure they all come from the same factory). It will do what you need and will last a long time if you look after it. Even if it does get damaged the dials can be bought individually and are really inexpensive.
This set includes a box of interchangeable heads. The thin ones are really useful although I am not to sure what the bent one can be used for….
Clockwise tools digital dial indicator
Just like micrometers and calipers there are digital versions available. The main advantage is the ability to switch between metric and imperial measurements. I don’t own one of these so if you want one, check out the reviews on Amazon before you buy. I prefer the reliability of an analogue gauge.
Mitutoyo dial test indicator
I use this dial test indicator at work, it is pretty much the gold standard for test indicators. If you want the best, this is what you have to buy.
HFS(R) 0-2″ Precision Travel Dial Indicator
This is the Dial Indicator I bought for my Taig Lathe. I choose this one specifically for the 2” travel as opposed to the typical 1” travel on most indicators. It is reasonably priced and works perfectly as an analogue readout on my micro lathe.
I made an aluminum stand off to mount it to a small dia bar which I was using as a stop to prevent the carriage from hitting the chuck. I can now set the stop and then slide the dial along it to position it where needed.
Anytime Tools Dial Indicator Extension Stem Rod Set
I had to add these to my recommended list. They are perfect for a setup similar to my lathe where I am using a dial indicator as a readout. Just add or remove the extensions to the dial to position it on the Z axis. This enables me to move the ‘readout’ to measure the carriage movement where It is needed.