Calibration labs and manufacturing facilities around the world are using Tru-Stone precision granite standards. Our procedure is to produce surface plates that exceed federal specification GGG-P-463c; at minimum, they will meet the required specifications. Inspections are performed by staff members who have completed a stringent training program and participate in annual proficiency testing just one of our many efforts to produce high quality products. Our metrology accessories exceed standards set by the industry.
All standard metrology products are supplied with a NIST traceable calibration certificate. If requested, an A2LA accredited certificate will be issued for any calibrations that are within our ISO/IEC 17025 scope. Along with these precision granite products, we supply stands to properly support our surface plates, covers to protect the plates when they are not in use and cleaners to help lengthen the life of the accuracy of your product. We strive to provide you with the highest quality products combined with excellent customer service and fast turnaround on products in stock at the time of order.
Whether your precision granite product weighs a few pounds or a few tons, we will crate it with care. Our crating personnel have developed expertise after many years of experience and testing.
Tru-Stone offers calibration and certification services for both surface plates and accessories. These services are not limited to only granite nor do we require the product be manufactured by Tru-Stone. We will resurface and/or certify both granite and ceramic products regardless of where or by whom the item was manufactured. You may have old granite products that are in very poor condition and think there is no chance of restoration. We can grind and lap your old products in our factory, making them appear like new. As with new products, our calibrations are accredited by A2LA (for perpendicularity, parallelism, flatness and repeat reading).
The majority of our surface plates are produced with charcoal black granite. Upon request, we can also manufacture black diabase, pink or gray plates as well. Plates are produced to meet or exceed federal specification GGG-P-463c. Final inspection of our surface plates is done with an autocollimator or electronic levels and Repeat-O-Meter. Black and pink plates are engineered to support a loading weight of 100 pounds per square foot, loaded in the center of the plate; which is twice that required by federal specification. This means that the designated load may be placed in the center of the plate without deflecting the overall accuracy more than 50%. Special loading and size considerations can be quoted upon request.
In surface plates, flatness is very important; however, repeat reading is equally important. The flatness and repeat readings of Tru-Stone plates are unilateral, not bilateral. The term unilateral accuracy means that all points on the work surface are contained between two parallel planes, separated by a distance greater than the distance specified for each size and grade. The term bilateral accuracy means twice (+ or the accuracy stated) as much flatness deviation may exist. The values specified on Tru-Stone calibration certificates are the TIR (total indicator reading).
In addition to our standard surface plate sizes, we will quote any other size requirements you may have. We can also make modifications to your plate, which includes t-slots, inserts, holes, etc.
To insure accurate readings, you need to support your granite surface plate properly on three or four points as specified in GGG-P-463c. Tru-Stone offers several options for supporting your plate. The standard work height for all stands is 36” unless otherwise specified.
Floor locks are available for all castered stands.
Tubular Steel Surface Plate Stands:
Our stands are constructed from welded square steel tubing to provide exceptional strength and durability. Steel crossbeams are located at the proper support points to ensure maximum surface plate accuracy. Stands are supplied with a scratch and abrasion resistant industrial painted finish. Our standard color is gray; however, other colors are available upon request and at an additional charge. Stands require no assembly. Stationary stands come with leveling adjustors with the typical adjustment being 2”. Rolling stands are fabricated with two stationary and two swivel casters.
Cabinet Support Stands:
Cabinet stands are constructed with square steel tubing and heavy gauge steel. Leveling screws are provided on the bottom of each leg, adjustable to obtain the standard work height of 36”. Roomy cabinet space is provided with a shelf and locking doors.
Stanley-Vidmar drawer stands are available upon request. Please note that these stands are not made specifically for our surface plates and are, therefore, not an exact match in size.
Block and Wedge Systems:
By using a block and wedge system, you remove the need for a large steel stand to support your granite base. This system is comprised of three granite blocks, cut and honed to provide the desired work height. An adjustable wedge is placed between the top of the block and the bottom of the surface plate. This system provides maximum support with minimal cost. Standard blocks are 12”x12”, with a height based on the thickness of your surface plate.
Master Square: Master squares are ideal for inspecting the X, Y and Z axes of machine tools. This product is very stable and rigid, providing the ultimate in squareness references. Our master squares have 5 finished faces (1 large face and 4 edges) finished flat, square and parallel to either laboratory grade AA (.000025” per 6”) or inspection grade A (.000050” per 6”). All six faces can be finished upon request.
Master Angle: These triangular shaped master angles are ideal for checking X, Y and Z axes of machine bases or parts. They are very rigid and stable and come with either 2 or 3 finished faces. The 2-face master angle has 2 perpendicular edges finished flat and square. The 3-face has a large triangular face finished flat and square to those two edges. Our master angles come in laboratory grade AA (.000025” per 6”) or inspection grade A (.000050” per 6”).
Angle Plate: Angle plates provide a convenient and practical means of clamping and holding work in a vertical position. Their excellent finish and flatness make them very compatible for use with granite surface plate accuracies. The angle plates are available with either 2 or 4 finished faces. The 2-face angle plate has the bottom and the adjacent square face finished flat and square to one another. The 4-face is similar to the 2-face, but has the two adjacent sides finished flat and square to the other two faces, as well as being parallel to each other. The laboratory grade AA has a tolerance of .000025” per 6” and the inspection grade A has a tolerance of .000050” per 6”.
Inserted Angle Plate: Inserted angle plates are available upon request. This product is the same as our standard angle plate with the addition of metal discs inserted into one side. The inserted angle plates also have a main gauging face for magnetic chucking purposes and threaded inserts for clamping purposes.
Straight Edge: Our straight edges are produced from impala black granite, as are all of our accessories. Straight edges have a single long, narrow face finished flat. Laboratory grade AA accuracy is .000025” per 12” and inspection grade A accuracy is .000050” per 12”. Lifting holes are provided on sizes 48” or larger.
Parallels: These precision tools can be used to elevate work above the surface of a plate to enable quick and easy inspection of piece parts with shoulders or steps, along with many other uses. Our parallels are provided in matched pairs with either 2 or 4 finished faces. 2-Face parallels have the 2 narrow faces finished flat and parallel. 4-Face parallels have the wide faces finished flat and parallel as well as the two narrow faces. Parallels are available in laboratory grade AA (.000025” per 12”) or inspection grade A (.000050” per 12”).
V-Blocks: V-Blocks are ideal for supporting or holding cylindrical pieces during manufacturing or inspection. They are provided in matched pairs and have 5 finished faces. V-blocks have a nominal 90-degree “V”, centered with and parallel to the bottom and two sides and square to the ends. V-Blocks come in either laboratory grade AA (+/- .000050” per 6”) or inspection grade A (+/- .000100” per 6”).
Bench Comparators: The bench comparator is a highly accurate inspection tool used for checking roundness, diameters, lengths, steps, flatness, angles and parallelism. Bench comparators come with a stainless steel post and indicator holder (lug mount is standard, stem mount is available upon request).
Keeping your precision granite products clean and in the best condition can lengthen your calibration intervals and help ensure that your readings are accurate. Tru-Stone provides two types of cleaner: liquid and waterless.
Our pink liquid cleaner is furnished in plastic bottles. Cases containing (12) quart containers or (4) gallon containers are available.
Our waterless cleaner is a product that is extremely popular. This product was once a valuable item in the offerings of Rahn Granite Surface Plate Company. Since the consolidation of our two companies, Tru-Stone now offers this cleaner. The waterless cleaner is packaged in 1-pound containers, with there being (12) per case.
Cleaners are sold in case quantity only.
We highly recommend the usage of surface plate covers to protect your precision granite investment. Prevent abrasive build up on your plates with our covers made from heavy gauge black vinyl with a soft interior lining. Our covers provide a tough, durable, protective outside with a soft cushion inside.
Tru-Stone offers two types of cases: travel and storage.
Our travel cases provide maximum protection for shipping or transporting accessories. They are constructed with a polyurethane exterior, reinforced steel edges and aircraft-style locks along with a padded interior for the ultimate protection.
Our storage cases have a vinyl exterior cover with a padded interior to keep your granite accessories safe and clean while they are not in use.
Federal Spec GGG-P-463c dictates that the proper methods for determining the overall flatness of a granite surface plate. In section 4.5.9, it states, “A…system of diagonals, perimeter and center lines may be calibrated on plates, and especially on small ones, by using a precision calibrated straight edge, adjustable supports and a suitably mounted indicator…”. This is a basic description of the Planekator.
The Planekator kits consist of a granite straight edge, a set of supports (one fixed height and one adjustable), a calibrated .000020” dial indicator with indicator carriage and a storage case. The straight edge is supplied with a correction tape.
When selecting your Planekator, consider the size of the plate(s) you will be inspecting. The straight edge should be at least equal to the full width of the plate and at least equal to 50% of the length of the plate. For example, a 36” Planekator straight edge can be used to calibrate any surface up to 36”x72”.
The Repeat-O-Meter is used to scan visually the work surface of the plate. The range of the indicator readings shall not exceed the values shown in Table II of section 3.3.3 in Federal Specification GGG-P-463c. The Repeat-O-Meter performs the same function as a height gage and gage block, but is more dependable and easier to use.
In a short amount of time, you can check the repeat measurement accuracy of a surface plate by moving the Repeat-O-Meter over the work surface, noting the full indicator range (F.I.R.). In just a few more minutes, by zeroing the R-O-M at the center along a diagonal or centerline and then recording readings at 5” intervals, you can chart the readings from the plate. The difference between the greatest plus and minus readings is the maximum measurement error possible on the plate.