No manual interruption is required at any stage, which makes the back spot facing tool most ideal for machines with auto-cycle like VMC:

D.E. Specialty Tool & Manufacturing is a complete manufacturing facility that has served its customers since 1962.  We offer CNC drilling and tapping; CNC turning, machining and milling; light stamping, large quantity automatic machining, welding and assembly.  Our primary focus is contract machining of large job lots, but we have not lost sight of the need for customers smaller sized and prototype orders that have been the backbone of our company's business throughout its 40-year history.  In our operation, we can hold very close tolerances.  Our goal has always been quality first and we have enjoyed great success in our quest for zero defects, zero rejections and on-time delivery.

Note: This program is as per Siemens Sinumerik CNC Standards, some G codes and M codes may vary for CNC of other makes. Please use this only as a reference to make CNC programs for your machines. The parameters like feeds and speeds need to be manipulated as per your  requirement.

• Co-axially jig-bored pivot holes & blue-matched wing seating transferring the cutting load to the shank, thereby preventing damage to the wing.

We offer CNC Drilling and Tapping, CNC Turning, CNC Machining, CNC Milling, Light Stamping, Large Quantity Automatic Machining, Welding and Assembly.  Our main focus is Contract Machining of large job lots but we have not lost sight of the smaller orders that have been the backbone of our growth. We also serve customers with smaller sized orders and Prototype orders. In our operation, we can hold very close tolerances and have in the past.

We proudly supply the railroad, automotive, trucking, electronics, farm equipment and paper processing industries, among others, and are approved suppliers to Navistar International, John Deere, General Motors, Harley Davidson and other large and mid-size companies.

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. The rear counter boring tool is meant for producing one specific back spot facing dia through one specified bore. Therefore, these back spot facing tools are ideal for a large batch production or mass production.

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, 0.2 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.

The below given graph shows for a particular sized hole, upto which size of back spot face can be done. It also shows which kind of wing and inserts will be used. Click on the image to view a larger picture

Make the axis of guiding pilot shank of the automatic rear counter boring tool true to the axis of the pilot hole. Use cotter / drive-key for preventing the tool from falling down while cutting. The back spot facing 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 back spot facing tool little away from the job; then reverse the spindle rotation to anti-clockwise and pull the automatic back spot facing tool out of the bore. The wing automatically folds into the pocket on coming in contact with the job in anti-clockwise rotation.

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.