TABLE OF CONTENTS The discussion on maintaining large part accuracy will be handled by folllowing the development of high accuracy for a specific family of parts.
This chapter begins with a discussion of temperature control and goes on to discuss the following areas of resolution of a specific accuracy problem:
Statement of the problem
Drill jig accuracy and limitations
Development of precision drilling centers
Finding other precision machines to handle production overload
Development of a test fixture to predict machine capability
Results and findings of testing
The chapter concludes with a brief summary.
Drill Jig: Tooling fixture with bushings for each hole location that guides drilling operations. Drilling is usually accomplished with portable drills.
Large parts: For purpose of this report, large parts are parts that measure a minimum of two meters long.
True Position (TP): See the following sample calculation of TP
TP is the diameter of the circle in which the center of the produced hole must fall.
Diameter equals radius times two.
Radius equals the hypotenuse of the triangle that has two sides of 0.010 in. (0.254 mm).
So radius = hypotenuse = 0.014 in. (0.356 mm), and diameter (TP) equals radius times two or 0.028 in. (0.711 mm).
This 0.028 inch TP was often rounded to 0.030 in. (0.762 mm) TP by engineering a nice round figure to work with.
Temperature is a variable that must be considered on all large parts. Air-conditioned rooms have been...
