Expression of Engineering Creativity
Automatic Back Spot Facing Tool
No manual interruption is required at any stage, which makes the tool most ideal for machines with auto-cycle like VMC:
a) Anti-clockwise spindle rotation, wing folds in & tool enters the bore.
b) Clock-wise rotation, wing opens up due to centrifugal force & the tool cuts with feed.
c) Reverse the tool rotation to anti-clockwise; wing folds in and the tool retracts.
> Can also be used on conventional radial drills, milling & boring machines.
> Available for holes from Ø 7 mm onwards.
> Tools From Ø 7 mm to Ø 12 mm, offered with solid HSS wing
> Tools from Ø 12 mm onwards, offered with inserted carbide
> e7 tolerance on the guiding shank for a good guide as well as
entry & rotational clearance
> Coolant through offered optionally
> Co-axially jig-bored pivot holes & blue-matched wing seating transferring the
cutting load to the shank, thereby preventing damage to the wing.
> Case hardened shank & hardened wing & other parts for
wear-resistance & longer life
Generally, the ratio of maximum back spot facing dia with respect to the corresponding pilot dia is 2:1. Since a back spot facing tool is normally custom-built, there is no general thumb rule for the back spot facing dia with respect to the corresponding pilot dia. The holding shank can be cylindrical (suitable for side lock holders), Morse taper, ISO, BT, and Metric, depending upon the machine spindle taper. An automatic back spot facing tool is meant for producing one specific back spot facing dia through one specified bore. Therefore, these tools are ideal for a large batch production or mass production.
Duplex back spot facing tool
Back chamfering tool
Combination tool
Operation
Make the spindle / tool axis true to the axis of the pilot hole. Use cotter / drive-key for preventing the tool from falling down while cutting. The tool enters the pre-drilled pilot bore in an anti-clock wise rotation of the spindle. The wing is so designed that even if it is open, it folds into the pocket on touching the job in anti-clockwise rotation. After the wing come clear of the pilot bore in anti-clock wise rotation, reverse the spindle rotation to clockwise; due to centrifugal force, the wing automatically opens up; with feed it cuts. After the spot facing is over, take the tool little away from the job; then reverse the spindle rotation to anti-clockwise and pull the tool out of the bore. The wing automatically folds into the pocket on coming in contact with the job in anti-clockwise rotation.
Cutting Parameters
SPOT FACE DIA (in mm)
|
SPINDLE
SPEED
(RPM)
|
SPOT FACE DIA (in mm)
|
SPINDLE
SPEED
(RPM)
|
SPOT FACE DIA
(in mm)
|
SPINDLE
SPEED
(RPM)
|
9 to 11 *
|
575
|
18to 21*
|
285
|
36 to 45
|
320
|
12 to14*
|
450
|
22 to 25
|
550
|
46 to 55
|
260
|
15 to17*
|
360
|
26 to 35
|
450
|
56 to 65
|
215
|
*Tools for this range of back spot facing are generally with HSS wings and feed rates of 0.05 & 0.03 mm per rev. in CI & MS are generally recommended. For the rest, 0.02 and 0.15 mm per rev in CI & MS, respectively are recommended, since Carbide inserts are generally used in this range. Cutting parameters depend on machine condition, clamping rigidity, hardness of job etc. For intermittent cutting, spindle speeds may almost be doubled, while feed rates are to be reduced by 30%. These are indicative parameters. Actual parameters are to be established only by trial and error.
Assembly
Press the pivot pin in the bore, provided on the tool shank. Position the wing in the pocket through the pivot pin. Screw on the pivot screw through the tapped hole till its point enters the cone, provided in the bottom of the wing. Tighten the pivot screw till the clearance between the pivot pin and pivot screw is just sufficient for the wing to freely swing in and swing out of the pocket, at the same time avoiding any axial and radial play. Lock this position by tightening the lock screw through the aluminum binder. It is advisable to release the pivot screw by about 30° before locking, so as to nullify the possible thermal expansion during cutting. Do not over tighten the insert clamping screw. Solid HSS wings are with integral pivot pin. Regrind the blunt cutting edges of HSS wings.
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