LATHE OPERATIONS - OD1645 - LESSON 1/TASK 1
The depth of cut can be gauged with the use of the micrometer
collar located on the compound rest.
(i) When using the taper attachment, there is a certain amount of "lost
motion" (backlash) which must be eliminated or serious problems will result.
In every slide and every freely revolving screw there is a certain amount of
lost motion which is very noticeable if the parts are worn. Care must be
taken to remove the lost motion before proceeding to cut or the piece will
be turned or bored straight for a short distance before the taper attachment
begins to work.
To take up lost motion when turning tapers, run the
carriage back toward the deadcenter as far as possible, then feed it forward
by hand to the end of the workpiece where the power feed is engaged to
finish the cut. This procedure must be repeated for every cut.
(j) The best way to bore a taper with a lathe is to use the taper
Extreme care must be exercised that the lost motion, or
backlash, is removed when tapers are being bored with the taper attachment,
otherwise the hole will be bored straight for a distance before the taper
starts. Since the power feed can be used with this method it is preferable
to using the hand-fed compound rest method. Two important factors to take
into consideration are: the boring tool must be set exactly on center with
the workpiece axis; and it must be small enough in size to pass through the
hole without rubbing at the small diameter. A violation of either of these
factors will result in a poorly formed, inaccurate taper, or damage to the
tool and workpiece.
(4) Checking Tapers for Accuracy.
(a) While the taper is being turned, it is a good practice to stop the
lathe after a complete cut of the taper has been made and measure the
diameters at each end to determine if the taper is being cut to the required
dimensions. An error in calculation must be discovered early because it may
be too late for corrective measures after the workpiece is completely rough
turned. Also, lay a straightedge along one side of the taper to assure that
the taper is uniform. Lack of uniformity can be caused by lost motion in
the taper attachment or by play in the compound rest, if the compound rest
method is being used.