What is floating carriage micrometer
Measurement of minor diameter by using floating carriage micrometer: The minor diameter is measured by a comparative method by using floating carriage diameter measuring machine and small V pieces which make contact with the root of the thread. These V pieces are made in severalsizes, having suitable radii at the edges. V pieces are made of hardened steel. The floating carriage diameter-measuring machine is a bench micrometer mounted on a carriage.
PROCEDURE :-
-A calibrated setting cylinder having nearly same diameter as the minor diameter of the thread to
be measured is used as setting standard.
-the setting cylinder is held between the V anvils and readings are taken.-the cylinder is then replaced by the threaded work piece and again the micrometer reading is noted.
If , D= diameter of the setting cylinder,
R1= reading of micrometer on setting cylinder.
R2= reading of micrometer on screw thread.
Then minor diameter of screw thread, = D ± (R2-R1)
Floating carriage micrometer is also called screw thread measuring machine or bench
micrometer.
Principle of floating carriage:
It works on Principle of Nut & Bolt /Screw threads. As drum of micrometer rotates by one revolution, it will move forward by one pitch of interval thread.
The movement will be measured using number of division on drum and main scale i.e.
Micrometer principle.
Floating carriage consist of:-
1)Two centers held on pillars of base
2) These centers are used for holding the job.
3) Lower slide is kept on the base, and the top slide is placed over the lower slide
4) Top slide has two pillars.
5) One pillar consists of micrometer drum having least count of 0.0002 mm.
6) The other pillar consists of a fiducial indicator which senses the pressure applied on the anvil end.
Advantages:
More accurate measurements
More versatile
Disadvantages:
More expensive
More difficult to use
Applications :-
1) Measurement of Major diameter of screw thread
2) Measurement of Minor diameter of screw thread
