any suggestions on selecting a surface plate?

The Shars surface plate has two ledges. That is really useful for clamping things to the plate. The stated accuracy of Chinese surface plates is often quite good, but can never be trusted because of the lack of valid quality control and quality assurance programs. Still, more than good enough for shop work unless you get one made at the end of the shift, or whatever. The price is excellent, less than half that of an equivalent US made plate. You will probably never know if you got a good one or a bad one, that sort of testing is not able to be done in nearly all hobby shops. So the grades are pretty much meaningless. If you really want one that is tested and vetted by the book and better, look to a company like Standridge Granite and get ready to pay much more, but you will know for sure what you are getting. I own the Woodcraft one and I agree with Bob, not sure about the accuracy. They do include a surface map of the plate and for whatever its worth, it is a grade A plate so good enough for the shop floor. I bought this in lieu of a certified plate because to ship something like that to Hawaii would leave me in shock. This will have to do unless Bob wants to send me a Standridge plate for free (hint, hint)! You can use the plate to scrape in a straight edge, and then use the straight edge, truly flat or not, to check the plate. They're "self proving" in that regard. The process is described in Connelly's Machine Tool Reconditioning book, but it essentially boils down to scraping the straight edge in using the plate, and then rotating it 180 deg and checking the bluing pattern. If the pattern repeats, then the plate is flat. If it doesn't, it's not. Almost impossible to tell where and by how much using this method, but it will at least get you some information.

You can use the plate to scrape in a straight edge, and then use the straight edge, truly flat or not, to check the plate. They're "self proving" in that regard. The process is described in Connelly's Machine Tool Reconditioning book, but it essentially boils down to scraping the straight edge in using the plate, and then rotating it 180 deg and checking the bluing pattern. If the pattern repeats, then the plate is flat. If it doesn't, it's not. Almost impossible to tell where and by how much using this method, but it will at least get you some information.

That is indeed in Machine Tool Reconditioning, and surprised me. It is not really a proof, it is an ad hoc means to an end where the straight edge is "judged" accurate. There are multiple ways for that test to not give a true result, but is used for ad hoc adjustment in the workshop (section 9.11). It is no doubt useful enough for 'machine tool reconditioning' if done carefully, but not for some other uses of a surface plate.

My work in inspection, and as a quality management system auditor, provides numerous opportunities to acquire knowledge. It also provides areas of risk for ensuring valid and reliable results. One risk that keeps repeating itself in my audit findings is the treatment of surface plates. Instead of being treated as a precision device, they are treated as an area to stack tools, parts and other debris. The root cause of this treatment is the lack of knowledge about the surface plate and its mistaken identity as just a table. Let&#;s take a journey of the history and recommended care for the surface plate.

Check now

The surface plate was designed and developed as a precision tool by Henry Maudslay and Joseph Whitworth in order to ensure the production of identical tool parts. The first surface plate was composed of cast iron. The first surface plates were sold in by the Crown Windley company. During World War II, metal was in high demand which resulted in the introduction of using granite, a non-corroding metal that is extremely hard and non-magnetic.

A flatness check of a surface plate. Source: ASQ

Engineering and manufacturing specifications are demanding tighter tolerances, which elevate the importance of accurate measurements. To deliver measurements, each piece of metrology equipment requires a base plate.

Hengfeng are exported all over the world and different industries with quality first. Our belief is to provide our customers with more and better high value-added products. Let's create a better future together.

Granite is the most common material used for surface plates. The surface plate does require maintenance. The following are recommendations for maintaining these precision instruments:

• Practice proper installation methods
  • Use the support system that came with the surface plate, which includes a hard rubber pad attached to the bottom of the plate. These pads are critical for the accuracy of the surface plate. Some large plates may have more than one support system to assist in controlling vibration.
• Perform regular service and calibration procedures, including regular inspection of the surface for dents, scratches
  • Resurfacing may be required if damage risks reliable and accurate measurements with a compromised table (not properly flat)
  • To verify flatness, periodic inspections can be made on the surface using a repeat reading gage with a manual indicator (move the gage across and identify if there are any deviations more than 0. inches for AA plate, 0. inches for A plate and 0. inches for B grade plate)
• Maintain a clean table
  • Use granite cleaners to clean plates prior to use, and after. (Using a dirty surface plate will result in inaccuracies in tool readings and cause the plate to wear faster)
  • A cover should be utilized to prevent debris from settling on the table
  • Only use soft cloths to prevent scratching the surface
  • Do not use metal straps of chain for large or heavy parts
  • Do not drop the plates when positioning them on the table
• Rotate table or table location
  • Rotate your position around the table to minimize wearing the table in one location
  • Do not lift or move a table by the granite (keep forks or lifting device away from the granite), be sure you are under the rubber pad.
• Do not use surface plates for storage
  • Surface plates must not be used for storing tools, food, and parts
  • coffee will stain plates
  • food will contaminate the surface with a grease residue
  • storing on plates will accelerate the wear of the surface and promote uncertainty of measurements
  • A cover should be utilized to prevent debris from settling on the table
• Avoid overload
  • Ensure you have the correct size of surface plate for the size of the parts and measuring equipment you need to use
  • Ensure even distribution across the surface plate to prevent issues with accuracy and serious damage
• Use threaded insert correctly
  • A surface plate may have threaded inserts to hold fixture gages or other tooling
  • The bolts should be torqued at a minimum setting
  • Do not ignore the warning labels included with these plate types

A surface plate on a CMM (r) and other surface plate devices (l). Source: ASQ

Along with checking the flatness of parts, surface plates can identify part warpage. The surface plate is the &#;0&#; reference point. If a height gage is used on the plate, the inspector can place the gage anywhere on the plate and zero the gage. This can be completed in conjunction with a gage block. The gage block is removed, and small parts can be accurately measured. This is also a technique to verify small parts for flatness.

The surface plate is an underrated metrology tool. It has been more than 80 years since granite was identified as an alternative to cast iron. Granite surface plates have become foundation for many standards in metrology. The coordinate measuring machine (CMM) does represent the acceptance of granite as the only material used in this vital area of metrology. Hopefully, you were able to obtain knowledge and insight on why I feel it is critical to properly maintain surface plates. Valid and reliable results must be acquired in order to make proper decisions on the disposition of parts.

For more Inspection Surface Plateinformation, please contact us. We will provide professional answers.