Analytical Test Procedures (Cont)

TM 38-260

place snug enough to keep it from falling out of the spindle. Place the indicator approximately one inch from the spindle

nose and rotate it under power to obtain readings. Use a slow speed as high speeds will whip the test arbor and false

readings will be obtained. Move the indicator set up to the free end and repeat the procedure. Total indicator reading is

recorded for each position. If the readings are out of tolerance, recheck the internal taper for dirt or nicks. Check

several times before reaching a decision when the readings obtained are out of tolerance.

(7) Spindle parallel with table travel. To obtain accurate readings on this check, it is important that the previous

inspections in (6) above, check within tolerance. When rotating the arbor and indicating the free end, mark the test arbor

at the high or plus indicator reading. When inspecting position turn the high spot 90 degrees. Place the indicator either at

the top or bottom of the test arbor. The readings should be identical. Move the table to the extreme inboard position.

Using approximately 0.005 inch (0.01m) pressure on the indicator, set the dial on zero with the contact point on the

vertical center line. Move the table to the extreme out position to obtain the readings. For position 2, repeat the above

procedure making sure that the high position is 90 degrees away from the indicator travel. Connect the indicator on the

horizontal center line. Upon completion of the test, remove the high spot mark.

(8) Checking T-slot is used quite often for the locating of fixtures. The slot should be inspected in relation to

wearing of the ways. It is recommended that the T-slot should not be indicated directly, as T-bolt clamping during

production may have burred the slot. Use hardened keys and small toolmaker knees. Make sure that the knees are tight

against the keys by the use of the Jacob chuck, attach the indicator and contact the knee. Move the table so that the

indicator moves from one knee to the other. This check is similar for various types of machines, and the indicator should

be kept as close to the table as possible. Tramming checks for T-slots are used quite often on horizontal machines

utilizing approximately the same setup. Move the sweep or tramming rod out as far as possible. Be sure that the

indicator is mounted rigidly. Use approximately 0.005 inch (0.01m) pressure and set the indicator at zero. Manually

rotate the spindle to contact the other knee and obtain the reading.

(9) Vertical alignment of head and tail centers. For this check, use a straight test arbor.

Master centers that are concentric on all diameters shall be used to accomplish an accurate inspection. Clean the

centers thoroughly and insert the test arbor between the centers. The arbor shall be tightened between the centers to

eliminate end play, but at the same time must be loose enough to be rotated by hand. Using a magnetic base holder with

an indicator attached, contact the test arbor on each end and check for concentricity. When concentricity is established,

contact the vertical center line of the arbor by moving transversely, and apply approximately 0.005 (0.Ol mm) inch

pressure. Then move the carriage from one end to the other. Check the transverse on each end to make sure of the

contact on the crown of the arbor.

(10) Spindle travel square with table surface. Inspections of this type are usually accomplished on vertical

machines.

(a) Move the working table to the center of travel.

(b) Use a fine abrasive stone to remove all nicks and burrs from the table.

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