Dial Indicators
Dial indicators are precision measuring tools with a myriad of applications in the machine shop. Once you move beyond the basic machining operations you will definitely want to have one or more of these in your workshop. On this page I will describe the instruments and holders, but the how-to-use-them information will be added to my other pages as I have time.
A plunger moves in and out from the body of the indicator and rotates the measuring needle on a dial face. Dial indicators usually have either a 1" or 2" range and are calibrated in increments of .001". A smaller dial reads each revolution of the larger dial in increments of 0.100".
The outer bezel rotates and turns the numeric scale with it so that you can set the indicator to zero at any plunger position. Most D/Is have two little movable markers on the outside of the dial face that can be used as reference points. I have removed them from mine, since I rarely use them.
Applications
• To check for runout when fitting a new disc to an automotive disc brake. Runout can rapidly ruin the disc if it exceeds the specified tolerance (typically 0.05 mm or less).
• In a quality environment to check for consistency and accuracy in the manufacturing process.
• On the workshop floor to initially set up or calibrate a machine, prior to a production run.
• By toolmakers (moldmakers) in the process of manufacturing precision tooling.
• In metal engineering workshops, where a typical application is the centering of a lathe's workpiece in a four jaw chuck. The DTI is used to indicate the run out (the misalignment between the work piece's axis of rotational symmetry and the axis of rotation of the spindle) of the work piece, with the ultimate aim of reducing it to a suitably small range using small chuck jaw adjustments.
• In areas other than manufacturing where accurate measurements need to be recorded (e.g., physics).
Probe indicator
0.1–20 mm dial indicator
Probe indicators typically consist of a graduated dial and needle (thus the clock terminology) to record the minor increments, with a smaller embedded clock face and needle to record the number of needle rotations on the main dial. The dial has fine gradations for precise measurement. The spring-loaded probe (or plunger) moves perpendicular to the object being tested by either retracting or extending from the indicator's body.
The dial face can be rotated to any position, this is used to orient the face towards the user as well as set the zero point, there will also be some means of incorporating limit indicators (the two metallic tabs visible in the right image, at 90 and 10 respectively), these limit tabs may be rotated around the dial face to any required position. There may also be a lever arm available that will allow the indicator's probe to be retracted easily.
Dial test indicator
Dial test indicator
A dial test indicator, also known as a lever arm test indicator or finger indicator, has a smaller measuring range than a standard dial indicator and therefore has the ability to measure in smaller increments. A test indicator measures the deflection of the arm, the probe does not retract but swings in an arc around its hinge point. The lever may be interchanged for length or ball diameter, and permits measurements to be taken in narrow grooves and small bores where the body of a probe type may not reach. The model shown is bidirectional, some types may have to be switched via a side lever to be able to measure in the opposite direction.
These indicators actually measure angular displacement and not linear displacement. If a force is perpendicular to the finger, the linear displacement error is acceptably small within the display range of the dial. However, this error starts to become noticeable when the force is as much as 10 degrees off the ideal 90.[1]
Some cheaper models of test indicators may come with a pear-shaped contact point in an attempt to compensate for cosine error.
Contact points of higher end test indicators come with a standard carbide sphere at 1, 2, or 3 mm diameter. More usable materials are available for contact points such as ruby, teflon and PVC. These are more expensive and not available OEM, but, are extremely useful in applications where surfaces are easily scratched or damaged.
Dial indicator calibration
The fast, economical and accurate way to calibrate a quantity of dial indicators is to invest in a Dial Indicator Calibrator. These mechanical devices are available in inch or metric models from several manufacturers. They are in effect a micrometer head with a large 3.5" diameter, .00005" accuracy and 0-1" range. The dial indicator is positioned in front of the spindle. The micrometer head is rotated and readings are compared. Ideally, readings should be taken at every numeral printed on the indicator dial, or as your quality manual requires. In practice, a reading taken every half revolution is sufficient. It will be necessary to have this unit regularly calibrated by a calibration lab to maintain traceability.
If you need to calibrate large quantities of analog and/or digital indicators you may want to invest in the electronic i-Checker which is hooked up to a computer system and generates inspection certificates.
Gage blocks are an accurate but time consuming way to check your dial indicators. Fasten the indicator in a stand on a granite plate. Lower the contact point to the surface and set the indicator at zero. Now it's a simple procedure to insert gage blocks under the contact point and take the readings. Be certain that the blocks are clean and wrung to the surface, that the indicator is perpendicular to the surface, and that it's securely fastened. Blocks should be used which will allow a reading at every half revolution or as your calibration manual stipulates. Obviously, the gage blocks will need to have their accuracy certified on a regular basis (annually is the norm).
The indicator is deemed accurate if it does not deviate more than one graduation over the first 2-1/3 revolutions and not more than one additional graduation per revolution thereafter. Most manufacturers offer better accuracy than this, particularly on the short range indicators. Check with the manufacturer for specific details.
Repeatability should be less than half a graduation in all cases. Allow the contact point to come down several times onto the same gage block. Any variation in readings will indicate a problem with repeatability. If this occurs, check once again that your indicator is firmly attached to an indicator stand of some substance. Check that the screws on the indicator back are tightened (if you're holding the indicator by its lug back) and check that the contact point is tight as well. The indicator will need to be serviced if repeatability is unacceptable.
Gage blocks: investing in eight gage blocks (.020" .025" .050" .100" .250" .400" 1.00" and 2.00") will allow you to calibrate all your inch reading dial indicators with ranges up to 2" travel. With these blocks you'll be able to check each indicator at the 2-1/2 revolution mark as well as the full range mark. This will serve as the absolute minimum requirement for indicator calibration. NIST certificates included. Calibration Grade 0.
Digital indicator
With the advent of electronics and LCDs the clock face and analog display has been replaced with digital displays, these have the added advantage of sometimes being able to record and transmit the data electronically to a computer. This process is known as statistical process control (SPC) and involves a computer recording and interpreting the results, this also reduces the risk of the operator introducing recording errors. Digital indicators can also be switched between imperial and metric units with the press of a button, thereby increasing the DTI's versatility.
Dial Indicator
800 في 1148 - 232 كيلو بايت - jpg
mini-lathe.org.uk Product Name: Dial
500 في 466 - 42 كيلو بايت - jpg
saame.com Dial Indicator
372 في 480 - 89 كيلو بايت - jpg
littlemachineshop... Typical dial
303 في 386 - 16 كيلو بايت - jpg
tpub.com
العثور على صور مشابهة
DIAL INDICATOR
896 في 592 - 122 كيلو بايت - jpg
lathemaster.com
File:Dial
724 في 1205 - 425 كيلو بايت - jpg
commons... Image of Dial
250 في 235 - 13 كيلو بايت - jpg
ptreeusa.com Metric Dial
500 في 500 - 26 كيلو بايت - jpg
toolstation.com Standard type dial
381 في 437 - 33 كيلو بايت - jpg
advic.co.th Dial Indicator,
480 في 318 - 81 كيلو بايت - jpg
littlemachineshop...
Dial Indicators
300 في 263 - 18 كيلو بايت - jpg
benchmark.20m.com digital dial
750 في 730 - 48 كيلو بايت - jpg
boeckeler.com Dial Indicator
500 في 728 - 89 كيلو بايت - jpg
made-in-china.com Dial Indicator
400 في 235 - 17 كيلو بايت - jpg
johnsmachine.com A dial
400 في 334 - 33 كيلو بايت - jpg
diracdelta.co.uk
العثور على صور مشابهة
with a dial
305 في 517 - 17 كيلو بايت - jpg
tpub.com
العثور على صور مشابهة
1" dial
288 في 288 - 25 كيلو بايت - jpg
mini-machine.com Dial Indicators
340 في 509 - 15 كيلو بايت - jpg
shan-usa.com This shows the dial
480 في 640 - 41 كيلو بايت - jpg
w6rec.com 1010 Series Dial
330 في 296 - 37 كيلو بايت - jpg
mytoolstore.com
Dial indicators are precision measuring tools with a myriad of applications in the machine shop. Once you move beyond the basic machining operations you will definitely want to have one or more of these in your workshop. On this page I will describe the instruments and holders, but the how-to-use-them information will be added to my other pages as I have time.
A plunger moves in and out from the body of the indicator and rotates the measuring needle on a dial face. Dial indicators usually have either a 1" or 2" range and are calibrated in increments of .001". A smaller dial reads each revolution of the larger dial in increments of 0.100".
The outer bezel rotates and turns the numeric scale with it so that you can set the indicator to zero at any plunger position. Most D/Is have two little movable markers on the outside of the dial face that can be used as reference points. I have removed them from mine, since I rarely use them.
Applications
• To check for runout when fitting a new disc to an automotive disc brake. Runout can rapidly ruin the disc if it exceeds the specified tolerance (typically 0.05 mm or less).
• In a quality environment to check for consistency and accuracy in the manufacturing process.
• On the workshop floor to initially set up or calibrate a machine, prior to a production run.
• By toolmakers (moldmakers) in the process of manufacturing precision tooling.
• In metal engineering workshops, where a typical application is the centering of a lathe's workpiece in a four jaw chuck. The DTI is used to indicate the run out (the misalignment between the work piece's axis of rotational symmetry and the axis of rotation of the spindle) of the work piece, with the ultimate aim of reducing it to a suitably small range using small chuck jaw adjustments.
• In areas other than manufacturing where accurate measurements need to be recorded (e.g., physics).
Probe indicator
0.1–20 mm dial indicator
Probe indicators typically consist of a graduated dial and needle (thus the clock terminology) to record the minor increments, with a smaller embedded clock face and needle to record the number of needle rotations on the main dial. The dial has fine gradations for precise measurement. The spring-loaded probe (or plunger) moves perpendicular to the object being tested by either retracting or extending from the indicator's body.
The dial face can be rotated to any position, this is used to orient the face towards the user as well as set the zero point, there will also be some means of incorporating limit indicators (the two metallic tabs visible in the right image, at 90 and 10 respectively), these limit tabs may be rotated around the dial face to any required position. There may also be a lever arm available that will allow the indicator's probe to be retracted easily.
Dial test indicator
Dial test indicator
A dial test indicator, also known as a lever arm test indicator or finger indicator, has a smaller measuring range than a standard dial indicator and therefore has the ability to measure in smaller increments. A test indicator measures the deflection of the arm, the probe does not retract but swings in an arc around its hinge point. The lever may be interchanged for length or ball diameter, and permits measurements to be taken in narrow grooves and small bores where the body of a probe type may not reach. The model shown is bidirectional, some types may have to be switched via a side lever to be able to measure in the opposite direction.
These indicators actually measure angular displacement and not linear displacement. If a force is perpendicular to the finger, the linear displacement error is acceptably small within the display range of the dial. However, this error starts to become noticeable when the force is as much as 10 degrees off the ideal 90.[1]
Some cheaper models of test indicators may come with a pear-shaped contact point in an attempt to compensate for cosine error.
Contact points of higher end test indicators come with a standard carbide sphere at 1, 2, or 3 mm diameter. More usable materials are available for contact points such as ruby, teflon and PVC. These are more expensive and not available OEM, but, are extremely useful in applications where surfaces are easily scratched or damaged.
Dial indicator calibration
The fast, economical and accurate way to calibrate a quantity of dial indicators is to invest in a Dial Indicator Calibrator. These mechanical devices are available in inch or metric models from several manufacturers. They are in effect a micrometer head with a large 3.5" diameter, .00005" accuracy and 0-1" range. The dial indicator is positioned in front of the spindle. The micrometer head is rotated and readings are compared. Ideally, readings should be taken at every numeral printed on the indicator dial, or as your quality manual requires. In practice, a reading taken every half revolution is sufficient. It will be necessary to have this unit regularly calibrated by a calibration lab to maintain traceability.
If you need to calibrate large quantities of analog and/or digital indicators you may want to invest in the electronic i-Checker which is hooked up to a computer system and generates inspection certificates.
Gage blocks are an accurate but time consuming way to check your dial indicators. Fasten the indicator in a stand on a granite plate. Lower the contact point to the surface and set the indicator at zero. Now it's a simple procedure to insert gage blocks under the contact point and take the readings. Be certain that the blocks are clean and wrung to the surface, that the indicator is perpendicular to the surface, and that it's securely fastened. Blocks should be used which will allow a reading at every half revolution or as your calibration manual stipulates. Obviously, the gage blocks will need to have their accuracy certified on a regular basis (annually is the norm).
The indicator is deemed accurate if it does not deviate more than one graduation over the first 2-1/3 revolutions and not more than one additional graduation per revolution thereafter. Most manufacturers offer better accuracy than this, particularly on the short range indicators. Check with the manufacturer for specific details.
Repeatability should be less than half a graduation in all cases. Allow the contact point to come down several times onto the same gage block. Any variation in readings will indicate a problem with repeatability. If this occurs, check once again that your indicator is firmly attached to an indicator stand of some substance. Check that the screws on the indicator back are tightened (if you're holding the indicator by its lug back) and check that the contact point is tight as well. The indicator will need to be serviced if repeatability is unacceptable.
Gage blocks: investing in eight gage blocks (.020" .025" .050" .100" .250" .400" 1.00" and 2.00") will allow you to calibrate all your inch reading dial indicators with ranges up to 2" travel. With these blocks you'll be able to check each indicator at the 2-1/2 revolution mark as well as the full range mark. This will serve as the absolute minimum requirement for indicator calibration. NIST certificates included. Calibration Grade 0.
Digital indicator
With the advent of electronics and LCDs the clock face and analog display has been replaced with digital displays, these have the added advantage of sometimes being able to record and transmit the data electronically to a computer. This process is known as statistical process control (SPC) and involves a computer recording and interpreting the results, this also reduces the risk of the operator introducing recording errors. Digital indicators can also be switched between imperial and metric units with the press of a button, thereby increasing the DTI's versatility.
Dial Indicator
800 في 1148 - 232 كيلو بايت - jpg
mini-lathe.org.uk Product Name: Dial
500 في 466 - 42 كيلو بايت - jpg
saame.com Dial Indicator
372 في 480 - 89 كيلو بايت - jpg
littlemachineshop... Typical dial
303 في 386 - 16 كيلو بايت - jpg
tpub.com
العثور على صور مشابهة
DIAL INDICATOR
896 في 592 - 122 كيلو بايت - jpg
lathemaster.com
File:Dial
724 في 1205 - 425 كيلو بايت - jpg
commons... Image of Dial
250 في 235 - 13 كيلو بايت - jpg
ptreeusa.com Metric Dial
500 في 500 - 26 كيلو بايت - jpg
toolstation.com Standard type dial
381 في 437 - 33 كيلو بايت - jpg
advic.co.th Dial Indicator,
480 في 318 - 81 كيلو بايت - jpg
littlemachineshop...
Dial Indicators
300 في 263 - 18 كيلو بايت - jpg
benchmark.20m.com digital dial
750 في 730 - 48 كيلو بايت - jpg
boeckeler.com Dial Indicator
500 في 728 - 89 كيلو بايت - jpg
made-in-china.com Dial Indicator
400 في 235 - 17 كيلو بايت - jpg
johnsmachine.com A dial
400 في 334 - 33 كيلو بايت - jpg
diracdelta.co.uk
العثور على صور مشابهة
with a dial
305 في 517 - 17 كيلو بايت - jpg
tpub.com
العثور على صور مشابهة
1" dial
288 في 288 - 25 كيلو بايت - jpg
mini-machine.com Dial Indicators
340 في 509 - 15 كيلو بايت - jpg
shan-usa.com This shows the dial
480 في 640 - 41 كيلو بايت - jpg
w6rec.com 1010 Series Dial
330 في 296 - 37 كيلو بايت - jpg
mytoolstore.com
