Techniques for Measurement of Threaded Hole …

1 Techniques for Measurement of Threaded hole PositionTony BryceSandia National LaboratoriesSandia is a multiprogram laboratory operated by Sandia Corporation, a Lockheed Martin Company,for the United States Department of Energy under contract DE-AC04-94AL85000. The funny part of metrology is that we're never right, we just have to tell people how wrong we are, and hope the wrong part is right enough! Joseph CeremugaSandia National Laboratories (Livermore, CA)How should the position be established? ANSI Section Each tolerance of orientation or position and datum reference specified for a screw thread applies to the axis of the thread derived from the pitch cylinder. Figure 5-6 Note that the length of the tolerance zone is equal to the length of the feature, unless otherwise specified on the drawing.

2 Projected tolerance zone applicationsTo comply with ANSI Measure the feature or gage as a cylinder in multiple circle sections Line generated between circle centers serves as the axis Axis is used to determine pierce points at ends of feature or evaluation length Zeiss UMESS UX will evaluate these points as L1 & L2 for TP calculations and report worst case deviationCMM Methods Direct probing of the thread form Issues Chips, burrs Establishing pitch cylinder Not able to probe pitch diameter directly Probing a Threaded /cylinder gage Issues $ - Cost of gage Inconvenience of installing (time = money $) Establishing pitch cylinder Various gages each using a different method to locate the pitch cylinderHow did we get interested in this? Threaded Holes on a Curved SurfaceThreaded Holes on a Curved SurfaceThreaded Holes on a Curved SurfaceOff-Line CMM Programming Silma CimStation Inspection Curved Surface Issue Standard Threaded /cylinder gage does not seat properly?

3 Rocking MotionTechnique is needed that is not influenced by the surface the hole is on!What to do? Evaluate Techniques Perform R & R tests using various Techniques on a flat surface Test pieces having a 2 inch outside diameter with -20 thread in center Aluminum part Diameter and face turned on lathe Drill and tap hole Steel part Gage quality lapped thread with outside diameter and face ground to pitch diameter axisTest Piece Datum s Datum A = Top surface Datum B = 2 outside diameter Datum C = through hole Establish DRF - ABCT hreaded / Cylinder Gages Obtain all available types on the market Jo-Plug Cylinder with straight thread and shoulder face perpendicular to axis Tru-Pos Tapered thread for interference fit CL Flex Plug Split thread for compliance fit Multi-Ball Gage Expanding balls fit to pitch diameterJo-Plug (Spence)

4 Industries Inc.)CL Flex Plug (Glastonbury/Southern Gage)Tru-Pos Locator (LaVezzi Precision Inc. )Multi-Ball (True Precision Corp. )R&R Test Parameters for Threaded / Cylinder gages Using UMESS UX with PCM routines, probe a total of 32 points* on the cylinder 8 equally spaced points at 4 different levels over the length of the cylinder * 24 points (8 equally spaced points at 3 levels) used on CL Flex Gage due to short cylinder lengthR&R Test Parameters Establish pierce points of cylinder axis with Datum A (top surface) and at below Datum A Record X & Y position at both pierce points Should show repeatability of not just Datum A location, but of the cylinder orientation (tilt).Jo-Plug (Spence Industries Inc.)CL Flex Plug (Glastonbury/Southern Gage)Tru-Pos Locator (LaVezzi Precision Inc.

5 Tru-Pos Locator (LaVezzi Precision Inc. )Multi-Ball (True Precision Corp.)Multi-Ball (True Precision Corp. )Multi-Ball (True Precision Corp. )Direct Probing of Thread Use Zeiss PCM thread routine Measure circles at both ends of Threaded hole . (8 equally spaced points) Construct a line through the centers of both circles Establish pierce points at Datum A (top surface) and at below Datum APCM MeasurementPCM MeasurementPCM Measurement Many CAD models show Threaded holes as plain cylinders (minor diameter) and could be programmed in a helical path to establish pitch cylinder Use pass through commands via Silma Cim Station InspectionOff-Line CMM ProgrammingTest Parameters CNC Program written to measure datum features and establish W-Pos Measure position using each of the five Techniques Loop program for a total of 10 runs Loop includes establishing W-Pos Run the CNC program on 3 different CMM sCMM s Used & Specifications Prismo (9/12/7)

6 1D = microns + L / 300 3D = microns + L / 300 Contura (7/10/6) 1D = microns + L / 300 3D = microns + L / 300 UPMC 550 (CAA) 1D = microns + L / 400 3D = microns + L / 300 L = Length in millimetersCMM Software UMESS UX Version 550 Test Results Steel Test PieceJo-PlugPosition Std. Dev. position Std. AProjected "ConturaResults In InchesTest Results ConturaSteel Test Piece TPResults In TPGagesPCMTest Results Steel Test PieceJo-PlugPosition Std. Dev. position Std. AProjected "Results In InchesTest Results PrismoSteel Test PieceResults In TPGagesPCMTest Results Steel Test PieceJo-PlugPosition Std. Dev. position Std. 550 Projected "Dat um AResults In InchesTest Results UPMC550 Steel Test Piece Results In TPGagesPCMTest Results Steel Test PieceJo-PlugPosition Std.

7 Dev. position Std. AProjected "Average All CMM'sResults In InchesTest Results Average of all CMM sSteel Test Piece Results In TPGagesPCMTest Results Aluminum Test PieceJo-PlugPosition Std. Dev. position Std. AProjected "ConturaResults In InchesTest Results ConturaAluminum Test Piece Results In TPGagesPCMTest Results Aluminum Test PieceJo-PlugPosition Std. Dev. position Std. AProjected "PrismoResults In InchesTest Results PrismoAluminum Test Piece Results In TPGagesPCMTest Results Aluminum Test PieceJo-PlugPosition Std. Dev. position Std. AProjected "UPMC 550 Results In InchesTest Results UPMC550 Aluminum Test Piece Results In TPGagesPCMTest Results Aluminum Test PieceJo-PlugPosition Std.

8 Dev. position Std. AProjected "Average All CMM'sResults In InchesTest Results All CMM sAluminum Test PieceResults In TPGagesPCMTest Result SummaryManufacturer s Jo Plug Spence Industries Inc. 800-991-1396 http:// Multi Ball True Precision Corporation 317-899-0899 s CL Flex Plug Glastonbury / Southern Gage 800-229-4243 Tru-Pos LaVezzi Precision Inc. 800-323-1772