Page images
PDF
EPUB

is much more expensive than by ship but the difference is largely offset by customs broker's charges. An added advantage of air transportation is very great decrease in the time the gages are away from the owner's factory. The Bureau's charges for calibrations or tests will be billed separately from those of a customs broker. Prepayment of all NBS charges is required.

212.221 Length and diameter dimensional metrology.

The length and diameter standards and gages, with the exception of thread and gear measuring wires, are in general intended to be used as comparison masters. In addition to the items listed, high quality components requiring gage tolerance inspection of length or diameter may be calibrated as special measurements.

212.221.1 End standards of length.

flat, or pointed

The listed end standards, having spherical, ends normally are used as instrument or machine tool setting standards. End standards up to 20 feet in length can be calibrated. As a special test, end measuring bars with flat ends of gage block quality can be calibrated with higher accuracy than listed below. Lengths are reported with a 21⁄2 pound measuring force unless otherwise requested.

Item

212.221.la

212.221.1b

212.221.1c

212.221.1d

212.221.le

212.221.1f

212.221.1g

212.221.1h

Description

Determination of length to ±0.000 05 inch for lengths of 0.25 inch up to and including 4 inches.

Determination of length for lengths over 4 inches up to and including 20 inches. Estimated accuracy is ±0.000 05 at 4 inches and porportionaly larger to ±0.000 12 at 20 inches. Determination of length for lengths over 20 inches up to and including 40 inches. Estimated accuracy is ±0.000 12 at 20 inches and proportionaly larger to ±0.000 20 at 40 inches. Determination of length for lengths over 40 inches up to and including 80 inches. Estimated accuracy is ±0.000 20 at 40 inches and proportionaly larger to ±0.000 35 at 80 inches. Determination of length to ±0.000 020 inch for lengths of 0.25 up to and including 4 inches.

Determination of length for lengths over 4 inches up to and including 20 inches. Estimated accuracy is ±0.000 020 inch at 4 inches and proportionaly larger to ±0.000 060 inch at 20 inches.

Determination of length for lengths over 20 inches up to and including 40 inches. Estimated accuracy is 0.000 060 inch at 20 inches and proportionaly larger to ±0.000 100 inch at 40 inches.

Determination of length for lengths over 40 inches up to and including 80 inches. Estimated accuracy is ±0.000 100 inch at 40 inches and proportionaly larger to ±0.000 200 inch at 80 inches.

[blocks in formation]

Step gages gages having flat parallel faces along a common center ne are calibrated as special measurements. The test is made horizontally lengths up to 40 inches. Step blocks having flat parallel adjacent ces also are calibrated as special measurements.

[blocks in formation]

2.221.2z Fee depends on accuracy, number of steps, and amount of labor required.

212.221.3

External diameter standards and gages: Plug gages. In addition to the scheduled plug and wire gages, ameters of other products may be accepted for measurement.

external

[blocks in formation]

2.221.3a

2.221.3b

2.221.3c

2.221.3z

average

Plain cylindrical plug gages-determination of
diameter, taper, and roundness to +0.000 05 inch for sizes up
to and including 4 inches.

Plain cylindrical plug gages-determination of diameter at a specific location, taper, and roundness to +0.000 010 inch for sizes up to and including 2 inches.

Plain cylindrical plug gages-determination

of diameter at specific location, taper, and roundness to +0.000 005 inch for sizes up to and including 2 inches.

Special measurements not covered by this schedule.

212.221.4 Measuring wires for threads and gears.

Thread measuring wires for 60° and 29° threads are tested for mpliance with the latest specifications in commercial use given in NBS ndbook H-28 and USASI B1.2. These wires, which àre supplied in 3-wire ts, are calibrated and the pitch diameter correction factor is computed r the average diameter of the 3 wires in the set. Special thread asuring wires for unusual sizes and for threads finer than 80 tpi are asured in a manner consistent with current commercial practice. as a ecial test. Fee is for a single set of 3 wires. Gear measuring wires in Le 1 92"/P, 1.728"/P, 1.44"/P, and 1.68"/P series supplied in sets of 2 are tested for compliance with the latest specifications in

res

[ocr errors]

Reference master wires for threads and gears are supplied as single wires which are intended as transfer standards of diameter for the calibration of working sets of thread measuring and gear measuring wires. Wires are measured using standard measuring practice. Fee is for single wire of standard size.

Item

212.221.4a

212.221.4b

212.221.4c

Description

Thread measuring wires-determining diameter, taper, and round-
ness for each of 3 wires in a set in accordance with wire
specifications. Determining mean diameter and pitch diameter
correction for best size wire for standard 60° threads
between 2 and 120 tpi and supplying label
this infor-

mation. Determining mean diameter for best size wire for
standard 29° threads between 1 and 20 tpi and supplying label
with this information. Mean diameter is reported within an
uncertainty of +0.000 010 inch on labels. See minimum fee
under 212.220 (c).

Gear measuring wires-determining diameter, taper, and roundness for each of two wires in a single set and reporting mean diameter within an uncertainty of +0.000 010 inch on label. See minimum fee under 212.220 (c).

Reference master wires-determining average diameter, taper, and roundness and reporting average diameter with an accuracy of +0.000 005 inch on individual labels.

212.221.4z Special sizes not covered by this schedule or other measuring requirements.

[blocks in formation]

Balls used in precision bearings. and master balls used as transfer diameter standards are calibrated according to current commercial practice. The ball diameters reported are the undeformed sizes as calculated with the Hertz relations to maintain a consistency in reported sizes. The following schedule is based on steel and carbide balls only; other materials require special measurements.

[blocks in formation]

212.221.5a Steel or carbide balls-determination of diameter to +0.000 050 inch for sizes from 1/16 to 1 inch, each.

212.221.5b Steel or carbide balls-determination of diameter to +0.000 010 inch for sizes from 1/16 to 1 inch, each.

212.221.5c

Master balls-determination of diameter to +0.000 005 inch by
comparison with NBS master and measurement of roundness of
two equators, for sizes from 1/8 to 1/2 inch by 1/32
1/32 inch
steps and 1/2 to 1 inch by 1/16 inch steps. Measurements ap-
plied only on balls with diameter variation of 0.000 005 inch
or less and deviation from nominal size within +0.000 030
inch, each.

2.221.5d

2.221.5z

Master balls-determination of mean diameter from three interferometric readings to an accuracy of ±0.000 003 inch and measurement of roundness on three equators. For sizes up to 1 inch in diameter. Measurements made only on balls with diameter variation of 0.000 003 inch or less, each.

Special measurements not covered by this schedule.

212.221.6

Internal diameter standards: Ring gages.

In addition to the scheduled items, larger ring gages and holes precision products can be calibrated as special measurements.

[blocks in formation]

2.221.6a Plain cylindrical ring gages-determination of diameter, taper, and roundness to ±0.000 01 inch for sizes 0.035 inch up to and including 2 inches.

2.221.6b Plain cylindrical ring gages determination of diameter at specified location, taper, and roundness to ±0.000 005 inch for sizes 0.035 up to and including 2 inches.

2.221.6c

Plain cylindrical ring

[ocr errors]

gages determination of diameter at specified location, taper, and roundness to ±0.000 003 inch for sizes 0.25 inch up to and including 1 inch.

2.221.6z Special measurements not covered by this schedule.

212.222 Complex standards of length and diameter.

Gages which control two or more dimensions are considered to be mplex standards. The listed items are for screw threads and gears as 11 as plain conical plug and ring gages. Other complex gages, tools, and oducts can be made as special measurements.

212.222.1 Plain conical plug and ring gages.

Plain conical plug and ring gages are tested for angle and ameter at a specified position.

[blocks in formation]

2.222.1z Because of the variety of taper angles, diameters, and lengths, only special measurements are made in this category.

Threaded plug and ring gages are tested in accordance with current commercial practice as outlined in NBS handbook H-28 and USASI B1.2. Threaded plug plug gages can be tested for pitch diameter, major diameter, flank angle, lead, and taper. Threaded ring gages must be submitted with the setting plug gage for test and are set for fit and tested for minor diameter, flank angle, lead, and taper, and standoff if applicable. API gages are not covered in this Section, see 212.222.3.

[blocks in formation]

212.222.2a Straight thread plug gages and setting thread plug gagesdetermination of flank angle with uncertainty depending on pitch and diameter; lead error and pitch diameter to 0.000 1 in., major diameter to 0.000 2 in. thread form as to clearance, for sizes 1/4 to 6 in.

212.222.2b

212.222.2c

Straight thread ring gages-determination of flank angle with uncertainty depending on pitch and diameter, lead error to 0.000 1 in., minor diameter to 0.000 2 in., thread form as to clearance, and fit on setting plug, for sizes 1/4 to 6 in. Must be submitted with setting plug.

Taper thread plug gages having 60° threads (except API Cable and Rotary gages) - determination of flank angles with uncertainty depending on pitch and diameter, lead error, pitch diameter and taper to 0.000 1 in., major diameter to 0.000 3 in., and thread form as to clearance, for sizes up to and including 10 in.

of

212.222.2d Taper thread plug gages having 60° threads-determination flank angles with uncertainty depending on pitch and diameter, lead error and taper to 0.000 1 in., pitch diameter to 0.000 2 in., major diameter to 0.000 4 and thread form as to clearance, for sizes over 10 to 24 in., inclusive.

212.222.2e

in.,

Taper thread ring gages having 60° threads (except API Cable and Rotary gages)-determination of flank angle with uncertainty depending on pitch and diameter, lead error to 0.000 1 in., taper to 0.000 2 in., minor diameter to 0.000 5 in. (or truncation of thread crest), thread form as to clearance, and standoff from mating plug to 0.000 2 in., for sizes up to 10 in. Must be submitted with mating plug.

212.222.2f Taper thread ring gages having 60° threads determination

of

angle to 3 to 15' depending on pitch and diameter, lead error to 0.000 1 in., taper to 0.000 2 in., minor diameter to 0.000 5 in. (or truncation of thread crest), thread form as to clearance, and standoff from mating plug to 0.000 2 in., for sizes over 10 to 24 in., inclusive. Must be submitted with mating plug.

212.222.2z Special measurements not covered by this schedule.

« PreviousContinue »