Precision Mensuration
Last updated on Thursday, February 02, 2012 06:45:42 PM Eastern US Time Zone

Indicators, Z-Offset Gages, Height Gage, Inside Diameter Gages, Pin Gages, Runout & Bore Gages, Calipers, Micrometers,
Dial Test Indicators, Coaxial, Indicator Holders, Thread Gages, Angle Meter, Angle Gages, Radius Gages, Infrared Thermometer

Mensuration - The act, process, or art of measuring. Measurement of geometric quantities.
Resolution - Smallest difference between indications of a displaying device that can be meaningfully distinguished.
For a digital display device, this is the change in the indication when the least significant digit changes by one step.
Measurand - A quantity that is being determined by measurement.
Accuracy - Closeness of the agreement between the result of the measurement & the true value of the measurand.
I'm a scientist, I like to quantify things. So, you can't have too many measurement tools.

Indicators

Mitutoyo electronic indicator (½" range). Resolution is 0.00005" (50 millionths). A linear encoder, it always
displays the spindle's absolute position from the origin at power-on. Digimatic indicator manual & drawing.

Mitutoyo electronic indicators (½" range) with a Noga magnetic base indicator holder (all from Japan).
See digital indicator manual.

A wooden holder for ⅜" stemmed digital & dial indicator gages. Many tools are supplied with their
own indicator. Two came with dial indicator comparator stands & two with gun cartridge measurement
fixtures. The second gage was my first digital style which is upgraded by the front gage that has much
higher resolution. The gages vary by their respective measurement ranges, accuracies, & resolutions.


Their positions are offset to accommodate the lug back mounts.
The plungers of  the more costly units are not compressed while stored.

Two, dial indicator comparator stands. Used for quality assurance (QA) size
measurements of many parts. Serrated anvils are purportedly more accurate.

Several two-inch range gages were used on various machines before changing to advanced DROs.
For example, I used two gages just for the Taig micro lathe & to good effect, providing excellent control.
I liked it so much I went digital for both X & Z-axes but later extensively modified the lathe to be CNC.
Surprising accuracy & repeatability though low durability, but given the cost, acceptable if on a budget.

A two-inch range digital indicator that reads to 0.0005" resolution. It has an 8mm stem.

The fine adjustment mechanism for the stand.

A collar was made to adapt the 8mm stem to ⅜". The screw is threaded through to directly contact the stem.

An old, heavy, Brown & Sharpe No. 731 10" x 3" x 1¾" (L x W x H) inspection holder (USA).

Note the robust adjustments.

Different types of dial gage interchangeable 4-48 threaded indicator points.
To keep from straining or breaking a gage's internal alignment pin, completely depress the plunger
so the rack absorbs the loosening & tightening forces before changing the points. Never use Loctite.

Z-Offset Gages


4.000" height, Z-axis tool length setting gage (USA). One-inch contact face picks-up all the flutes of
large end mills, easy to read 2.2" dial face, a setting repeatability of 0.0002", & hard, red anodize.
Needle-based Z-setting gages are not damaged by over travel like some electronic types.
The unit's overall ergonomic & mechanical design is excellent & has a good, heavy feel.

Z-axis offset animation showing a ¾" end mill being set at 4.000" above the vise bed.

A 3.000" height offset gage using a 40 mm (1.5") diameter face Mahr dial indicator (GER) that reads to 0.0005".
Stem is 8mm (.315"). The 7.5mm (0.295") diameter flat tip is an ideal shape. The bracket is all steel construction.
All critical surfaces of the parts, including the round post ends, were precision surface ground for high accuracy.
An adjustable, brass, over-travel stop was added so the needle can only turn about one revolution.

Starrett also makes a superior 4-inch special dial depth gage for Z-height setting.

The bottom of this Z-offset gage needed lapping which was performed on a granite surface plate first using
320 followed 400 & 600 grit silicon carbide papers. Move the part in a figure-8 pattern to insure an even
removal of material. Significant surface improvement resulted. The edges were deburred with an India stone.

This offset gage has a magnetic bottom which attracts debris. The spring is too strong for very small end mills.

This Z-offset gage is 2" high. A 3" micrometer & a 123 Joe block were used to set the gage's zero at 2.0000".
The micrometer was first locked at 3.0000" using the gage block.

Mill Z-offset gage (instructions) used to set tool lengths. Needle-based, Z-offset gages set the
 mill more quickly & accurately than illuminated types plus they are not damaged by over travel.

Animation showing a 2.000" tool Z-offset height being set on the Taig CNC Z-axis using the MPG in step mode.


Baker dial depth indicator (India) with a 0" to 10" range & where one gradation = 0.001". Rod extension chart.

Height Gage
  
A carbide-tipped (Mitutoyo) 10", dial height gage on a granite surface plate (± 0.0001"). High accuracy can be achieved using gage blocks to set specified heights.
Use layout die to make the scribe marks easier to see. Mitutoyo height gage manual. Surface plates are useful for precision alignment when assembling parts, too.
See Height Gages in Layout Tools for descriptions of accessories.

Inside Diameter Gages

Telescoping & half-ball Mitutoyo inside gage sets. The half-ball type can get into a shallow, blind hole
better than a ball type. Expand into hole, lock & then measure the gage with a micrometer or caliper.

Left: The small hole gage is expanded by the center wedge.
Right: The telescoping inside gage posts spring outward, self-center & are then locked.
They can then be measured with a micrometer or caliper.

Full-ball, small hole gage set.

Pin Gages

 Pin/plug Gage Sets - ID type gages for measuring hole diameters & slot widths.
0.011" to 0.060" x 0.001" minus Class ZZ pin-gage set (50 pieces).
Tolerance +.0000" -.0002".  10µm finish or better.  Hardness 60-62 RC.

 0.061" to 0.250" x 0.001" minus Class ZZ pin-gage set (190 pieces).
Tolerance +.0000" -.0002".  10µm finish or better.  Hardness 60-62 RC.

Detail of the 0.061" to 0.250" x 0.001", minus pin gage set (still in the grease). Two-inches overall lengths.

 
0.251" to 0.500" x 0.001", minus Class ZZ pin-gage set (250 pieces).
Tolerance +.0000" -.0002". 10µm finish or better. Hardness 60-62 RC.

0.501" to 0.625" x 0.001", minus Class ZZ pin-gage set (125 pieces).
Tolerance +.0000" -.0002". 10µm finish or better. Hardness 60-62 RC.

Go/no go pin gage handles. Shown holding 0.25" & 0.050" pin gages.

Runout & Bore Gages


Baker back-plunger dial indicator set (India) with 'G' clamp, universal clamp, swinging-arm assembly, tool post holder,
 holding rod, Tommy bar & anvil. Swinging-arm assembly enables the back-plunger dial gage for use on internal
work to a depth of 1.6" (40mm); similar to a lever-type gage. Allows multiple types of mounting possibilities for
gaging applications like concentricity checks, alignment of machine tools, testing parallelism & surface plate work.

Back-plunger dial gage with swinging-arm attachment.


A self-centering, 1.4" to 6" cylinder bore gage (instructions).
The gage is first set up to measure a specific size (zeroed) then run through the bore to measure its variation.
To keep the extensions in order, a vibrator engraver was used to label each size on a non-critical surface.

The dial gage must be inserted deep enough to preload (or move) the needle about 1 revolution (0.050").
The black plastic shroud can be installed after calibration to protect the head under heavy shop use.

These ½" travel digital indicators, preloaded to 0.050" depth, can also be utilized but others may not work.

Exploded view of the 1.4" to 2" measurement head, the 1.4" range anvil & knurled anvil lock nut.
The pointed rod end (at the lower left) engages a rod inside the handle.

Anvil installation animation.

The center measurement anvil moves in & out.
The outside mechanism depresses under spring tension to center the head.

Small anvil animation.
 

Assemble the appropriate anvils & spacers (left side) for the target measurement size.
Then, using a gage block, set a micrometer (e.g., 2") to the bore size & zero the dial scale.
The gage is then run through the cylinder & the variation from set size, noted.

Bore gage measurement animation.
Note the small measurement anvil (left) depresses & the self-centering guide mechanism slides to the right.

Calipers

Mitutoyo Absolute Digimatic caliper (Japan).
An excellent digital caliper that is very accurate throughout its entire measurement range.
Always maintains zero, large LC display, greater than 3 years battery life. No irritating auto-off.

Mitutoyo digital caliper manual.

Hardened & precision ground depth base attached.


A digital caliper (manual) that measures & displays inches, millimeters & fractions to 1/64th inch.
Handy for wood work & sifting through raw stock. This LCD has a somewhat narrow optimal viewing angle.

Digital depth gage with a large base. See digital caliper manual.

8-inch digital linear scale for instrumenting tools like mills, lathes, & drill presses.

This open-weave drawer liner has (Microban) antimicrobial properties that prevent bacterial growth.
The non-slip black cushion protects the instruments & keeps them from moving (banging) around, too.

Mitutoyo digital measurement tools: depth gage, caliper & micrometer (older models).

Micrometers

Superior quality Mitutoyo (Japan) digital micrometer that reads down to 0.00005" or 0.001mm.
The scales are engraved, not chemically etched thus have superior readability & durability.
Even if the battery is removed, the micrometer's scales allow it to be used as a standard instrument.
Micro-polished, carbide-faced working surfaces & an effective spindle lock.
DO NOT store a micrometer (any style) with its measurement anvils touching.

See micrometer manual.

The holder adjusts to different angles & has rubber pads that protect the instrument from clamping damage.

Another style micrometer stand/holder.

Small, 0.6" (non-locking) & standard 1" micrometers. The smaller micrometer's scales are chemically etched,
the larger micrometer's scales, engraved. Superior instruments have engraved scales for clarity & durability.

2-inch micrometer.


Micrometer set zero through six inches with its wooden storage case (import).
One, two, three, four & five-inch sized standards plus adjustment wrench are included.
The plastic insulating grips on the standards reduce warming effects (expansion) due to handling.
Acquired for use mainly on the 9x20 lathe. Excellent accuracy, engraved scales, & a good value.
All micrometers read to 0.0001". The wooden case was re-glued in places & then sanded.
See micrometer scale reading instructions.

Though low-cost, the scales are engraved, the positive locking lever is metal, & the ratchet thimble is precise.
A good value for light use.

Detail of the 1" to 5" standards for the 0" to 6" micrometer set.

6" to 12" micrometer set. The smaller wooden case holds size standards 6" through 11".
All micrometers read to 0.0001".

6" micrometer, shown.

12" micrometer shown with the standards case, open. The holes lighten the instrument for easier handling.
I needed the 7", 8", & 9" micrometers (for e.g., a flywheel) so it was more economical to buy the whole set.

Two micrometer sets covering the 0" through 12" range. Eleven size standards; 1" through 11".
Two separate sets can make handling/storing the boxes easier than one big heavy 0" ~ 12" set.

A 0.6" micrometer compared to a 12" micrometer.

A micrometer head that can be incorporated into other devices e.g., an adjustable lathe carriage stop.
½" range. The tip of the 0.2" diameter anvil is rounded & hardened. The collar is ⅜" diameter x 0.32" long.

Hub micrometer that measures 0-1" to 0.0001" & designed to clear through a ¾" hole.
Handy in tight places especially in milling setups. A spindle lock would have been better.

A 6" throated micrometer having a measurement range of 0 to 1" maximum with a 0.0001" scale.

Locking levers made of metal are a plus for durability & precision of the mechanism movement.

Caliper-type micrometer measures to 0.0001".  Measuring anvils are approximately ¾" above the micrometer.
The thread mechanism that keeps the anvil from rotating also acts as a somewhat effective lock.

Disk micrometer with a 0.0001" scale.

0-1" range, 0.07" diameter anvil, tube wall thickness micrometer that measures to 0.0001".

0-1" range, 0.19" diameter anvil, tube wall thickness micrometer that measures to 0.0001".

Carbide-faced electronic blade micrometer for measuring in narrow slots & recesses.
The thread mechanism that keeps the anvil from rotating also acts as a lock.
 A 0.00005" minimum readout. Non-critical parts are plastic. Digital blade micrometer manual.

The blades are 0.030" thick.

1 to 2-inch blade micrometer supplied with a 1-inch standard & adjustment wrench.

Carbide-tipped, small faces or spline micrometer for measuring in tight areas. 0-1" range with 0.0001 scale.
The anvils are 0.0775" diameter.

Carbide-tipped, point micrometer for measuring in very tight areas. 0-1" range with 0.0001 scale.
Points have a radius of approximately 0.012".

Screw thread micrometer with five different anvil pairs measure both unified & metric external pitch diameters.
0" to 1" measurement range with a 0.0001" scale. The left anvil holder floats back & forth to allow zeroing then
 it is locked into place. However, the anvil itself always floats rotationally to maintain ease of measurement.

SCREW THREAD MICROMETER ANVILS
ANVIL #	1	2	3	4	5
TPI RANGE	64 - 48	44 - 28	24 - 14	13 - 9	8 - 5
METRIC RANGE	0.4 - 0.5	0.6 - 0.9	1 - 1.75	2 - 3	3.5 - 5

Anvil pairs are clearly marked for pitch range.

Example measurement of a ¼-20 screw. The micrometer reading is 0.2160". Table pitch value is 0.2164" max.
A fast & accurate thread measurement tool. The bolt can freely rotate around the micrometer's anvil axis.

Carbide-faced inside micrometer gages with locking mechanisms. The top gage range is 1"-2" & the bottom
gage range is 0.2"-1.2". Supplied with 1" & 0.2" inside ring standards, respectively. One gradation = 0.001".

Micrometer depth gage with a 0-6" range & where one gradation = 0.001".

Dial Test Indicators (DTI)

Interapid 312B-1 (Swiss). Best in class dial test indicator having: a monobloc metal housing with two dovetails,
jeweled movement, ball-bearing lever system, micro-polished carbide tip, large tilted dial face, & an additional
revolution counter. Bi-directional measuring with automatic reversal inside the movement & extra wide ±0.060"
range makes it especially versatile. True readings when the angle between the stylus & workpiece surface is 12°.

This Starrett Model No. 711 DTI has a small side lever to select the needle direction. No dovetail mounts.


The carbide tips have multiple spring-loaded detent positions. Quick & easy tip changes.

Rugged LS Starrett No. 711 Last Word DTI & attachments (USA). One gradation = 0.001".
If needed, fast & easy to send back to Starrett for repairs. They stand behind their products.
I have damaged it twice & Starrett quickly repaired it charging only a nominal price for return postage.

Starrett 711-49 attachment: 2⅝" OAL, ⅛" x 5/16" x 1⅞" rectangular shank, & a ¾" long x 15/16" round tip.
Used to affix the Starrett 711 Last Word DTI to either the 3715 height gage or the 995E Universal Gage.

Gem DTI (USA). One gradation = 0.001". Rod & dovetail mounting.  Gem dial indicators & accessories.
See instructions on how to set tip geometry & illustration. Essentially a copy of the
Starrett No. 711 but with slightly different dimensions so accessories are not interchangeable.

Federal Testmaster DTI (USA). One gradation = 0.0001". Note needle reversing lever & dovetail mounting.

Various DTIs showing dovetails. Top to bottom: Brown & Sharpe (Swiss), Federal, & Gem (USA).

Fowler DTI set (import). Moderately low quality. One gradation = 0.0005". Dovetail mounts.

Using Dial Test Indicators - Test indicators are primarily used for the testing or checking of parts & for machine setups.
Test indicators come in two types; the plunger style & the lever style. The lever style is more adaptable to smaller,
confined working areas. The lever style differs in measuring because the lever contact moves in an arc rather than in a
straight line, as in the plunger style. This can cause a slight inaccuracy called cosine error, if reasonable care is not
 used in setting the angle of the lever to the work piece. If, for example, a lever was set off 20º more at the start of a
reading than it should have been, there could be an error of .0006” in a .010” range (0.012mm in a 0.2mm range).
This is not important when zeroing-out, but only when looking for a measurement. It is best to keep the contact at or near
90º to the direction of movement unless the manufacturer specifies another angle (see illustration.) Test indicators
 should always be “loaded” 1/10 to ¼ of a turn before measuring. Test indicators are not hand-held absolute measuring
tools. They are comparative instruments that check & compare to known standards or that are used to zero-out setups.

Coaxial Indicator


Coaxial indicator (import) that takes measurements while the spindle is spinning (800 RPM maximum).
The point can be used to locate a punch mark. See centering indicator instructions.
Different length probes affect the scale's absolute readout values. Good for large parts.

Indicator Holders

Sparro 1^st Word dial test indicator holder (USA).

Using a Sparro 1^st Word holder & a LS Starrett Last Word DTI
to check the alignment of the mill/drill. Nicely made, very rigid indicator holder.

Animation showing how to check alignment by indicating the Rong Fu RF-25 mill table.

Noga indicator holder (Japan) for both dovetail & ⅜" stem types. Note the fine adjustment mechanism.


Noga NF1018 indicator arm (Japan) with ⅜" & dovetail clamp.
This style arm is very quick & easy to set up plus it has very good rigidity.


Noga arm held by a modified, V-groove tool post, mounted off the headstock side T-slot of the Taig mill.
Setup shows indicating a work piece before rotating to a specific cutting angle.
The Noga arm is good for aligning mills, lathes & rotary tables.

Zero-set universal dial test gage attachment (import).

A Federal 0.0001", dovetail mount, DTI being used to indicate the Parlec vise's solid jaw.

This style universal DTI holder gives a broad sweep of the small 18" mill table.

IndicOL #178 (USA) DTI holder attaches an indicator to the mill's spindle. Best in class attachment.
Dovetail or stem-style test dial indicators can be attached to this holder.

Half-round combination DTI (dovetail & stem) with a ¼" shank.

Modified an indicator clamp to hold various stemmed DTIs; close to the center; rigid, compact, & quick.
Reamed two, 3/16" holes & the thumbscrews are 6-32 SS cap-head screws with pressed-on plastic caps.

Added another setscrew to hold the half-round combination DTI holder.

Detail of the close-fitting brass bushing (⅜" OD, ¼" ID) that is held in using red Loctite.
Added a 5/32" hole & setscrew for the Interapid stem size.


Tramming a 6", 4-jaw chuck on a rotary table.

A Mighty Mag (USA) magnet holds ⅜" (or smaller) stemmed indicators.

Ultra low-cost 2" range analog positional readout; quite accurate, though.

Thread Gages

Imperial & metric (yellow) screw thread gages (2), fractional & numbered drill size gages.
These plate-type thread gages would be more accurate if they were twice as thick.
Having just a few threads, it is easy to make an error.

These gages check both nuts & bolts. Metric have black oxide & imperial have galvanized coatings.
Superior to plate-type gages which use only a few threads per size for testing.

Standard imperial & metric thread gages.

Angle Meter

Starrett AM-2 angle meter (USA). The RF-25 mill X-axis is shown being level.

Back label of the AM-2 angle meter.

Angle Gages

Angle gage set 5° to 90° every 5°.

Multiple edges provided for a given angle.

Radius Gages

Radius gage set 1/64" to 17/64" by 1/64" & 9/32" to ½" by 1/32" with handle.

Multiple edges provided for a given radius.

Infrared Thermometer

 

The red laser beam is used solely for aiming. An infrared (IR) sensor actually measures the temperature.
The distance to spot ratio is 8:1., so for e.g., at a 16" (407mm) distance the measurement area is 2" (51mm).

Indicators, Z-Offset Gages, Height Gage, Inside Diameter Gages, Pin Gages, Runout & Bore Gages, Calipers, Micrometers,
Dial Test Indicators, Coaxial, Indicator Holders, Thread Gages, Angle Meter, Angle Gages, Radius Gages, Infrared Thermometer