Walk into nearly any mold making, tool-and-die or precision machine shop and you will find numerous granite surface plates with at least one surface gage or transfer stand; read on…
Surface gage or transfer stand
Personally, I’ve yet to figure out what the difference is between a surface gage and a transfer stand, except that the former is generally not as large, accurate or expensive.
Whatever you might call this precision measurement tool, it is indispensable in the tool shop. How else can you use a dial indicator, gage blocks or height gage to measure your workpiece? If you have an electronic height gage, you can do without the surface gage, though there are many setups that just don’t lend themselves to the use of an electronic height gage.
The typical style is the Starrett no. 57 series or the Fowler Xtra-Surf surface gage. Other companies have manufactured similar styles, though some have long ago gone out of business. You can still find Brown and Sharpe or Lufkin models in shops around the world, mostly in the tool box of old-timers.
This style is satisfactory for basic measuring on a granite surface plate or other flat surface, but is not nearly as stable as the more expensive, heavier styles. If you are working in the .001 in range these work just fine. Once you start working in the .0002 in range, they just don’t repeat very well.
One exception to this is the Hermann Schmidt tool. This is a simple, but very reliable gage and is quite commonly used in mold making shops the world over. They are expensive, but worth it, if you need a good, reliable surface gage.
The Metrology Handbook, Second Edition
An authoritative book, “The Metrology Handbook, Second Edition” provides a foundation for understanding basic metrology and calibration principles and practices.
As the name implies, these are used to transfer the measurement taken with a dial indicator to a height stand for comparison. The simple surface gage does exactly the same thing, just not as reliably.
Transfer stands must be rigid, smooth when sliding on the surface plate, have fine adjustment for the final reading, be versatile and easy to use. Some models have tiny screws for the fine adjustment, which makes it difficult to control, so look for one with a user-friendly mechanism.
Dial Indicator Manufacturers
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An authoritative book, “Basic Metrology for ISO 9000 Certification
”gives a nice introduction to ISO 9001 requirements for calibration of test and measuring instruments.
Recommended surface gages or transfer stands
Some recommended models include Hermann Schmidt, Fowler Workshop , the Mitutoyo series 519, and the Mahr 815 GN.
When selecting a quality transfer stand, look for the following:
- Rugged, heavy base
- Good hand grip
- Ability to move easily over surfaces without vibration
- Ground surface on front or back to enable moving along ruled edges
- Stable 3 point support on bottom of base
- Fine adjustment capability
- Flexibility of movement so you can reach difficult spots
It is also important to have enough attachments so you can use a variety of indicators. You may want a dovetail attachment, another for different size indicator stems, as well as one for drop indicators.
With proper care and common sense, your surface gage or transfer stand will easily last a lifetime. Keeping it clean and rust free is about all the maintenance required.