Manufacturers strive to avoid difficult gaging situations by enforcing strict quality control processes that begin with ensuring their gages are properly calibrated to international standards of measurement. For best gaging practices, manufacturers start with applying primary standards for measurement and inspection that will ultimately lead to consistent, reliable gaging results. Further, they use proper care and maintenance procedures to maintain accuracy and provide long tool life.
Precision gage blocks are the primary standards vital to dimensional
quality control in the manufacture of interchangeable parts. These
blocks are used for calibrating precision measuring tools and for
setting numerous comparative type gages used in incoming, production
and final inspection areas. Gage blocks provide the most economical,
accurate method of setting dial test indicators and other gages used in
conjunction with surface plates for inspecting parts with exacting
tolerances.
Essentially, gage blocks consist of a hard stable material with a flat, parallel gaging surface on each end. The measuring surfaces are ground and lapped to an overall dimension with a tolerance of plus or minus a few millionths of an inch. Gage blocks may be stacked or “wrung” together to form accurate standards of practically any length.
Gage blocks are made in several grades or degrees of accuracy. Grade 0 is the most popular grade of gage blocks, as this grade is usually suitable for most applications and is a grade that offers the best combination of accuracy and cost. Higher accuracy grades of blocks, such as Grade 00 are primarily used as masters to check other gage blocks and for applications that require extreme accuracy. Grade B (±50 microinches) blocks are relatively inexpensive but are limited to workshop use where exacting accuracy is not required.
Gage blocks are available in various materials including Starrett-Webber croblox, ceramic, and steel. Steel is the most economical gage block material available, and steel’s thermal and mechanical properties are adequate in typical workshop environments. The main disadvantage of steel is its susceptibility to corrosion.
Various styles of gage blocks are available including rectangular, square and Starrett-Webber Heavy Duty. The use of gage blocks can also be extended by means of accessories that can be used with height gages, snap gages, scribers and dividers.
Even Work Surfaces
Every linear measurement depends on an accurate reference surface from which final dimensions are taken. Precision granite surface plates provide the best reference plane for work inspection and layout prior to machining. They are also ideal bases for making height measurements and gaging surfaces, parallelism etc. A high degree of flatness, stability, overall quality and workmanship also make them ideal bases for mounting sophisticated mechanical, electronic and optical gaging systems.
Surface plates without work clamping ledges are recommended for sustained accuracy and reliability. Ledges are for work clamping purposes only. If excessive torque is used when applying clamps to ledges, it can adversely effect measurements taken near the plate edges. If clamping is important, T-slots and threaded metal inserts may also be installed in the surface.
Granite surface plates are manufactured in three grades of accuracy including AA-Laboratory Grade (for precision operations in constant temperature gaging rooms and metrology departments), A- Inspection Grade (for general work in quality control) and B-Toolroom Grade (for production checking work throughout the shop).
Even Work Surfaces
To properly care for gage blocks, wringability is a key test for evaluating the integrity of the surface condition of a gage block. Wringability is the ability of two surfaces to adhere tightly to each other in the absence of external means and it is an important property of gage blocks. Blocks that don’t wring may give erratic and unreliable results and are recommended to be replaced.
The granite surface plate is a precision piece of equipment and as such, must be properly installed and maintained. Before use, the plate should always have a reliable support system furnished with the plate. Typically this a hard rubber pad attached to the bottom of the plate forming a non-distortable 3-point support system. The pads are a critical factor in surface plate accuracy and must not be removed. Plates up to and including 6’ wide x 12’ long should be furnished with this non-distortable 3-point support system. When mounting the plate on a stand, be sure only the pads are resting on the stand. Never support the plate by the ledges or under its four corners, as this will completely void guarantee of accuracy. Plates larger than 6’ wide x 12’ long are supported on multiple support points (6 or more points) consisting of granite pedestals and leveling wedges.
Once set-up, plates do not require extensive care and maintenance. Primarily, keeping the surface clean and free from buildup of dust, dirt, grease, grime and other foreign particles will maintain accurate tool readings and extend the life of the plate.
Surface plates should be checked on a regular basis for wear using a repeat reading gage with a manual indicator. Generally, long before a surface plate has worn beyond specifications for overall flatness, it will show worn or wavy spots, which will produce measurement errors. The reading gage will readily detect these error-causing areas.
Manufacturers that produce the highest quality products use the best quality control practices. The quality of products is only as good as the accuracy and reliability of measurements. This begins with relying on primary standards to ascertain that gages are properly calibrated and are being used to check parts on optimal work surface conditions.
This article was supplied by the L.S. Starrett Co., Athol, MA.
www.starrett.com
Essentially, gage blocks consist of a hard stable material with a flat, parallel gaging surface on each end. The measuring surfaces are ground and lapped to an overall dimension with a tolerance of plus or minus a few millionths of an inch. Gage blocks may be stacked or “wrung” together to form accurate standards of practically any length.
Gage blocks are made in several grades or degrees of accuracy. Grade 0 is the most popular grade of gage blocks, as this grade is usually suitable for most applications and is a grade that offers the best combination of accuracy and cost. Higher accuracy grades of blocks, such as Grade 00 are primarily used as masters to check other gage blocks and for applications that require extreme accuracy. Grade B (±50 microinches) blocks are relatively inexpensive but are limited to workshop use where exacting accuracy is not required.
Gage blocks are available in various materials including Starrett-Webber croblox, ceramic, and steel. Steel is the most economical gage block material available, and steel’s thermal and mechanical properties are adequate in typical workshop environments. The main disadvantage of steel is its susceptibility to corrosion.
Various styles of gage blocks are available including rectangular, square and Starrett-Webber Heavy Duty. The use of gage blocks can also be extended by means of accessories that can be used with height gages, snap gages, scribers and dividers.
Even Work Surfaces
Every linear measurement depends on an accurate reference surface from which final dimensions are taken. Precision granite surface plates provide the best reference plane for work inspection and layout prior to machining. They are also ideal bases for making height measurements and gaging surfaces, parallelism etc. A high degree of flatness, stability, overall quality and workmanship also make them ideal bases for mounting sophisticated mechanical, electronic and optical gaging systems.
Surface plates without work clamping ledges are recommended for sustained accuracy and reliability. Ledges are for work clamping purposes only. If excessive torque is used when applying clamps to ledges, it can adversely effect measurements taken near the plate edges. If clamping is important, T-slots and threaded metal inserts may also be installed in the surface.
Granite surface plates are manufactured in three grades of accuracy including AA-Laboratory Grade (for precision operations in constant temperature gaging rooms and metrology departments), A- Inspection Grade (for general work in quality control) and B-Toolroom Grade (for production checking work throughout the shop).
Even Work Surfaces
To properly care for gage blocks, wringability is a key test for evaluating the integrity of the surface condition of a gage block. Wringability is the ability of two surfaces to adhere tightly to each other in the absence of external means and it is an important property of gage blocks. Blocks that don’t wring may give erratic and unreliable results and are recommended to be replaced.
The granite surface plate is a precision piece of equipment and as such, must be properly installed and maintained. Before use, the plate should always have a reliable support system furnished with the plate. Typically this a hard rubber pad attached to the bottom of the plate forming a non-distortable 3-point support system. The pads are a critical factor in surface plate accuracy and must not be removed. Plates up to and including 6’ wide x 12’ long should be furnished with this non-distortable 3-point support system. When mounting the plate on a stand, be sure only the pads are resting on the stand. Never support the plate by the ledges or under its four corners, as this will completely void guarantee of accuracy. Plates larger than 6’ wide x 12’ long are supported on multiple support points (6 or more points) consisting of granite pedestals and leveling wedges.
Once set-up, plates do not require extensive care and maintenance. Primarily, keeping the surface clean and free from buildup of dust, dirt, grease, grime and other foreign particles will maintain accurate tool readings and extend the life of the plate.
Surface plates should be checked on a regular basis for wear using a repeat reading gage with a manual indicator. Generally, long before a surface plate has worn beyond specifications for overall flatness, it will show worn or wavy spots, which will produce measurement errors. The reading gage will readily detect these error-causing areas.
Manufacturers that produce the highest quality products use the best quality control practices. The quality of products is only as good as the accuracy and reliability of measurements. This begins with relying on primary standards to ascertain that gages are properly calibrated and are being used to check parts on optimal work surface conditions.
This article was supplied by the L.S. Starrett Co., Athol, MA.
www.starrett.com
Published in
News
Latest from Rob Colman
Latest Videos
-
On May 2nd, Sandvik Coromant introduced its new drilling event, called "See the whole picture." See what you can expect from the program in this video. To find out when… -
Chiron's Russel Pollack introduces the machine at Ferro Technique during the machine tool distributors' Joint Open House in Mississauga, ON. -
DMG's Nicholas Piccione introduces the machine at DMG Canada's facility during the Joint Open House in Mississauga, ON.
Digital Edition
