Lathe Guide Bushing

This part named “Guide Bushing” will have some profiling on the OD (Outside Diameter), a 1/4-28 UNC external thread, and a 0.126” reamed through hole.

  • Select MODE to get to the control’s Main Menu. 
  • From the Main Menu – select DRO to enter manual operation mode.

To make the part, we are going to separate it into two sections as shown below. This approach is due to part and tool geometry. The right-hand face tool that will be used for turning operation cannot perform undercuts defined by the part.

We will start by machining Side A profile.

The following are steps for machining Side A.

Step 1 – Setting Raw Material

  • Calibrate the right-hand face tool (tool #1) as specified in Setting Up Tools Tutorial.
  • Obtain 0.5” diameter brass stock from stock area, about 1.5” long.
  • Hold stock in 0.5” collet and secure collet on chuck using ratchet. About 0.95” stock should stick out from collet/chuck. Use a chuck key to secure collet firmly.
  • Select tool #1 by pressing tool # soft key then enter [1] and press Abs Set.
  • Press Spin Speed, enter [1000], and press Inc Set to set the spindle speed to 1000 revolutions per minute (RPM)

  • Turn on spindle and face part as demonstrated in Setting Up Tools Tutorial and set Z = 0 on faced side
  • Move tool away from part and turn off spindle

Now we move on to the process of defining the part contour.

This step resembles an “Etch-A-Sketch” like process of identifying the endpoints of line segments that define our contour.

Note that Z coordinates are negative and X coordinates are given by the diameter of the part.

We will utilize the GO TO function to machine the part profile.

Step 2 – Machining Side A Profile

Since we are using manual operations, the following steps will be iterative. Nonetheless, they require the machinist to observe discipline by verifying instructions prior to machining.

  1. Press GO TO, then press x coordinate key. Enter [0.25] and press Abs Set. Press z coordinate, enter [-0.89], and press Abs Set.
  2. Start Spindle and move tool to Z = 0.2, X = 0.5 by turning the hand wheels. Ensure jog keys are set to fine feed by pressing F key on the computer panel.
  3. Turn 0.04” increment in the –X direction to about 0.46”.
  4. Turn Z hand wheel to machine along the z direction to the set Z GO TO limit of Z = -0.89.
  5. Move tool away from part in +Z direction to about Z = 0.5 or until tool is clear off part in the Z direction.
  6. Using X hand wheel, make another 0.04” decrement in the –X direction from last machined position. For instance, move tool to X = 0.42 for the second cut.
  7. Repeat steps 4 to 9 until the set X GO TO limits. NOTE: Spindle should be spinning whenever tool is in contact with part to preserve tool life and minimize damage to tool holder. Move tool away from part in case you pause operations. 
  8. When finished, move tool away from part

Step 3 – Machining Chamfer

To machine the chamfer at the edge of Side A, we will use the TAPER function.

  1. Press GO TO, then press x coordinate key. Enter [0.22] and press Abs Set. Press z coordinate, enter [0], and press Abs Set.
  2. Start Spindle and move tool to Z = 0, X = 0.22 by turning the hand wheels. Ensure jog keys are set to fine feed by pressing F key on the computer panel.
  3. Press RETURN to exit GO TO function.
  4. Press DO ONE TAPER then enter [45] to set chamfer angle to 45 degrees.
  5. Turn the X hand wheel clockwise to machine fillet. Turn hand wheel until tool clears the part.
  6. Press RETURN, move tool away from part, and stop the spindle

Using a micrometer, inspect the final diameter of side A. Make necessary adjustments as required.

The following are steps for machining Side B.

Step 4 – Setting Raw Material

  1. Remove collet from chuck using the ratchet. NOTE: You may have to use the chuck key to loosen the collet before using the ratchet. 
  2. Hold Side A of part in a 1/4” collet and secure collet on chuck using ratchet. Side not machined should stick out from collet/chuck. Use a chuck key to secure collet firmly. 
  3. Select tool #1 by pressing tool # soft key then enter [1] and press Abs Set.
  4. Press Spin Speed, enter [1000], and press Inc Set to set the spindle speed to 1000 revolutions per minute (RPM)
  5. Start spindle and face off about 0.03” from the side sticking out.
  6. Move tool away from part and stop the spindle.
  7. Unscrew collet to remove part and measure the length of the 0.5” diameter side remaining. Write this dimension down as we’ll use it to dimension Side B.
  8. Hold part again in collet with Side B facing away from the chuck.
  9. Turn on spindle and touch off tool #1 on the side sticking out and set Z=0.
  10. Since we want length of Side B to be 0.3” long, subtract 0.3” from the measured length.
  11. Press GO TO then press x coordinate key. Enter [0] and press Abs Set. Press z coordinate, enter the difference between the measured length and 0.3” and press Abs Set. We aim to cut-off excess material and dimension part as specified on part drawing.
  12. Start Spindle and move tool to Z = -0.03, X = 0.55 by turning the hand wheels. Ensure jog keys are set to fine feed by pressing F key on the computer panel.
  13. Turn the X hand wheel ONLY to face off part to X = 0. Turn hand wheel continuously at a slow rate.
  14. Move tool away from part in +X direction to about X = 0.55 then make another 0.03” increment along –Z direction to about Z = -0.06. Turn the X hand wheel ONLY to face off part to X = 0. Turn hand wheel continuously at a slow rate. Repeat this to the set Z GO TO limit.
  15. After last pass, press RETURN to exit GO TO function then press Z coordinate key and enter [0] and press Abs Set. This sets a new origin for the part.
  16. Move tool away from part and stop the spindle.

Step 5 – Machining Side B Profile

Since we are using manual operations, the following steps will be iterative. Nonetheless, they require the machinist to observe discipline by verifying instructions prior to machining.

  1. Press GO TO, then press x coordinate key. Enter [0.248] and press Abs Set. Press z coordinate, enter [-0.3], and press Abs Set
  2. Start Spindle and move tool to Z = 0.2, X = 0.5 by turning the hand wheels. Ensure jog keys are set to fine feed by pressing F key on the computer panel.
  3. Turn 0.04” increment in the –X direction to about 0.46”.
  4. Turn Z hand wheel to machine along the z direction to the set Z GO TO limit of Z = -0.3
  5. Move tool away from part in +Z direction to about Z = 0.5 or until tool is clear off part in the Z direction.
  6. Using X hand wheel, make another 0.04” decrement in the –X direction from last machined position. For instance, move tool to X = 0.42 for the second cut.
  7. Repeat steps 4 to 9 until the set X GO TO limits. NOTE: Spindle should be spinning whenever tool is in contact with part to preserve tool life and minimize damage to tool holder. Move tool away from part in case you pause operations.
  8. When finished, move tool away from part

Step 6 – Machining Chamfer

To machine the chamfer at the edge of Side A, we will use the TAPER function.

  1. Press GO TO, then press x coordinate key. Enter [0.22] and press Abs Set. Press z coordinate, enter [0], and press Abs Set
  2. Start Spindle and move tool to Z = 0, X = 0.22 by turning the hand wheels. Ensure jog keys are set to fine feed by pressing F key on the computer panel.
  3. Press RETURN to exit GO TO function.
  4. Press DO ONE TAPER then enter [45] to set chamfer angle to 45 degrees.
  5. Turn the X hand wheel clockwise to machine fillet. Turn hand wheel until tool clears the part.
  6. Press RETURN, move tool away from part, and stop the spindle

Using a micrometer, inspect the final diameter of side B. Make necessary adjustments as required.

Step 7 – Machining Threads

To machine threads, we will use a ¼-28 UNC die.

  1. Get a ¼-28 UNC die and a threading guide from the tool crib threading cabinet. 
  2. Mount the die on holder.
  3. Move tool holder away in the +X direction.
  4. Slide the lathe tailstock forward. To slide tailstock, unlock the quill by pulling it towards you while facing the chuck then push the tailstock forward. Once the tailstock is within 3” of the part, lock it in place by pushing the quill up. 
  5. Secure the threading guide on the drill chuck.
  6. Align the die with the chamfered edge of Side A and rotate the tailstock hand wheel to hold the die holder firmly in place using the threading guide.
  7. Turn the die holder clockwise to create threads on the .248” diameter. Rotate the die once or twice clockwise then half turn anti-clockwise to remove chips from the die. Adjust the tailstock hand wheel as you thread to keep the die aligned.
  8. Cut threads until the die rests flat against the .5” diameter edge of the part.
  9. Once finished, turn the die handle counterclockwise with the holder still aligned to remove the die.
  10. Get a ¼-28 UNC thread gauge from the thread measurement cabinet and inspect the cut threads. You may have to redo the threads again in order to clear off chips and cut the threads to the accurate size.
  11. Remove the tap guide from the drill chuck.

Step 8 – Drilling and Reaming

To make the 0.126” reamed hole, we will use a #1 center drill, #32 drill bit, and a 0.126” reamer.

  1. Get the #1 center drill, #32 drill bit, and a 0.126” reamer from the tool crib. 
  2. Secure center drill on the drill chuck. Turn the tailstock hand wheel until the center drill touches the part to confirm it’s centered on part with spindle off. Retract the drill from part.
  3. Press Spin Speed, enter [2000] and press Inc Set to set the spindle speed to 2000 rpm.
  4. Turn spindle on and center drill a hole for the #32 drill size. 
  5. Turn spindle off and replace the center drill with the #32 drill bit. Turn the tailstock hand wheel to confirm the bit is centered on the part. Retract the drill from part.
  6. Turn the coolant and spindle on. Drill part by turning the hand wheel. Retract the drill bit after each peck to evacuate chips and to prevent the drill from breaking.
  7. Drill through and take care not to crash the drill chuck on to the rotating part. You can extend the drill stick out length to avoid crashing. 
  8. Once finished, retract the drill and turn off the spindle.
  9. Replace the drill bit with the 0.126” reamer. Turn the tailstock hand wheel to confirm the bit is centered on the part. Retract the drill from part.
  10. Press Spin Speed, enter [600] and press Inc Set to lower the spindle speed to 600 rpm. 
  11. Turn the spindle on and ream through once.
  12. Retract the spindle reamer and turn off the spindle. Remove the bit from the drill chuck and slide the tailstock to the rear of the lathe.

Your part is done

 

Reference

(TRAK TRL SX Lathes, PROTOTRAK SLX CNC - Safety, Programming, Operating and Care Manual)

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