5 months by cncdivi

If you want to learn more, please visit our website.

Surface Plate 2024 Complete Guide [Granite, Cast Iron, Steel]

Grade A Black Granite Surface Plate, 18' x 12'.  About $160 on Amazon&#

Surface Plates are crucial flattened structures employed to simulate an ideal 2D plane, ensuring utmost accuracy for various measurements made atop that plane. These plates are typically utilized in precision inspection, marking out for machining guidance, and for setting up tooling.

Height Gauges are often used for common measurements. A Surface Plate complemented by a height gauge is invaluable for CNC operators or machinists, making it wise to invest in this essential set early in your career.

Surface Plate Material: Granite, Cast Iron, Steel, or Glass

Most surface plates are crafted from granite, available in various sizes and grades. Although cast iron, steel, and glass plates can be found in the market, granite remains the preferred choice for many users.

The adoption of granite for surface plates gained traction during World War II when it became necessary to conserve metal for vital uses. This innovative idea stemmed from Wallace Herman, who owned both a monument and metal fabrication shop in Dayton, Ohio.

Granite brings numerous benefits compared to cast iron, including enhanced durability and resistance to rust. These benefits ensured granite surface plates continued to thrive even post-World War II.

You will notice black and pink granite used for surface plates, with black being the favorite. Pink granite, which contains more quartz, offers superior wear resistance; however, its lack of strength compared to black granite necessitates a thicker profile for optimal usage. Black Granite, on the other hand, showcases excellent stiffness, vibration damping, and machinability.

Before the prevalence of granite, cast iron was the material of choice for surface plates. Today, it remains popular for specific applications due to its relative ease in achieving high precision. In fact, cast iron plates can even assist in resurfacing granite plates during maintenance.

Surface Plate Grades and Precision

Surface Plate Grades dictate their level of flatness, which can be classified as follows:

• AA (Most accurate): Referred to as laboratory grade, their flatness is calculated as (40 + diagonal (inches) of surface plate squared / 25) x 0.'.
• A: Inspection Grade, which is twice as accurate as AA specifications.
• B: Toolroom Grade, four times less accurate than AA.
• Workshop Grade (Least accurate): Not suitable for CNC applications; specifications are generally omitted.

When possible, purchase an A grade granite surface plate in the largest size suitable for your workspace. This grade is explicitly designed for inspection tasks, making it the most versatile option.

The American Society of Mechanical Engineers (ASME) has established ASME B89.3.7 as the standard for granite surface plates.

Regular calibration of surface plates is essential to maintain accuracy. This ensures that no wear, chipping, or warping compromises their performance.

Surface plate flatness is defined by two parallel planes—the base and the roof—and the distance between them determines overall flatness.

Standard Surface Plate Sizes

Typical sizes for surface plates include 18 x 24 in., 24 x 36 in., 36 x 48 in., and 48 x 72 in., but custom sizes are widely available if required. My A Grade 24 x 36 in granite surface plate serves my metrology needs quite well. However, larger operations may necessitate even larger plates and access to multiple units.

Reducing Wear, Cleaning, and Extending Life of Granite Surface Plates

Maintaining the cleanliness of a granite surface plate is key to reducing wear. The main culprit of wear is airborne abrasive dust, which can also embed itself into workpieces and the contact points of gauges.

To protect your plate, cover it against dust and damage and rotate its use to prevent localized wear. Where possible, employ carbide pads to minimize the risk of abrasive dust embedding during gauging work.

Keeping the surface plate clean is a must, as swarf and debris can hinder accurate measurements. Dedicated surface plate cleaners are commercially available, roughly priced at $30 for a gallon on Amazon, and should be employed to avoid any potential chemical erosion of the granite.

It is ideal to clean your plate at the start and end of each day, using the appropriate cleaner. Be aware that the evaporation of cleaner can lead to temperature changes that distort the surface—allow about an hour for small plates and two hours for larger plates to normalize.

Based on the porosity of your granite plate, retaining moisture from cleaning may lead to rusting in precision tools.

Surface Plate Calibration

Visit Hengfeng for further information.

Given that surface plates are susceptible to chipping, warping, and wear, regular calibration is crucial. Often, wear will occur in specific areas due to repetitive tool use, such as a height gauge.

A fascinating video detailing surface plate testing and calibration in the field can greatly enhance your understanding of the process.

Lapping is a technique utilized to enhance the flatness of a plate when necessary.

Don't Use Your Surface Plate as a Counter!

Remember, surface plates are not for storing items. Only gauges and pieces intended for measurement should be placed on the surface plate.

Consider the repercussions if someone places an item like a Coke can on your surface plate. Any spilled liquid could harm the plate, causing irreversible damage.

Placing miscellaneous objects on the plate can introduce harmful debris, disrupting delicate precision and leading to surface abrasion.

Surface Plate Accessories

A wide variety of accessories complement surface plates, but we will focus on the most commonly utilized ones.

Ledges and Threaded Metal Inserts

Specify ledges when ordering your surface plate, as they facilitate work clamping.

Threaded metal inserts can be embedded within the granite to aid clamping, but must remain below the surface level for accuracy.

Surface Plate Stands

Proper support for surface plates is essential to minimize potential warping. Granite surface plates should ideally be supported at three points, positioned about 20% of the plate length from either end. This allows for accurate support, unlike configurations using four or more points.

A variety of stands are available for all surface plate types. Smaller plates can rest on any appropriate bench, while larger plates benefit from dedicated support.

Temperature Controlled Room

Using a laboratory-grade surface plate in a non-temperature-controlled room undermines its accuracy. For maximum precision and consistency, temperature stability is crucial, hence why many shops store their surface plates in temperature-controlled inspection areas.

Surface Plate Covers

To protect your surface plate during idle periods, using a fitted cover is recommended.

Surface Plate Cleaner

Dedicated surface plate cleaners, priced around $30 for a gallon on Amazon, should be employed to prevent chemical erosion on your plate.

Height Gauges, Sine Gauges, and Gauge Blocks

Height gauging, gauge blocks, and sine gauges (including sine bars and sine plates) are among the most frequently used measuring accessories alongside a surface plate, though the list of measurements tools is extensive.

This article forms part of our Complete Guide to Metrology.

JASH C.I. Surface Plates and Tables serve as a precision reference base for inspection, tool making, gauging, spotting marking and layout operations. Granite or Cast Iron Surface Plates are supported on suitable stand called Surface Tables Stands enable proper levelling of plate and also provide the top surface at a convenient working height of approx. 850 to 900 mm from the floor. The adherence to high quality standards and precise configurations makes JASH a leading surface plate manufacturer and supplier in the industry and one of the best Cast Iron and Granite surface plate manufacturers globally.