10.19 Tapping
Micky R. Jennings
What is it?
Tapping on a lathe can be completed by a couple different methods. One is similar to tapping by hand on a drill press, using the tailstock to support the tap with a center, while twisting the tap with a tap wrench or adjustable wrench. The second method is power tapping. Power tapping on the lathe is slightly more complex of a setup than on the drill press. It involves a little more timing and coordination. Power tapping on a lathe utilizes the power of the lathe’s spindle, turning at a slow speed, to pull a tap through the workpiece. The end of the tap is stabilized by the tailstock spindle, while a long standard tap handle is applied to the tap and placed against the compound rest, where it will make contact and apply pressure during the cutting action.
Step by step process for power tapping:
- On the lathe, drill the required TDS into the end of a part.
- Install a center into the tailstock.
- Remove the tool post.
- Select a slow spindle speed, generally, about 100 RPM or slower works well for beginners.
- Select the correct tap and a long tap handle.
- Apply oil to the inside of the hole.
- With the tap handle on the tap, insert it into the beginning of the hole, and bring up the tailstock to support the end of the tap.
- Rest one end of the tap handle against the compound rest. Make sure there is enough room for the tap handle to move along the compound rest without catching or falling into the tee slot. It needs at least enough distance for the length of the tap.
- Tighten the tailstock against the back of the tap, and get ready to crank on the handle to match the infeed of the tap. It is critically important that the center remain secure in the end of the tap throughout the entire operation. If the center comes out, the tap could go crooked, overcutting the internal thread or breaking the tap.
- Simultaneously, turn on the spindle and start cranking the tailstock handle until the tap depth is reached.
- Turn off the spindle.
- Remove the tailstock.
- Back out the tap by hand or with an adjustable wrench.
“Step 8: Rest one end of the tap handle against the compound rest. Make sure there is enough room for the tap handle to move along the compound rest without catching or falling into the tee slot. It needs at least enough distance for the length of the tap.”
“Step 10: Simultaneously, turn on the spindle and start cranking the tailstock handle until the tap depth is reached.”
Attributions
- Figure 10.218: Power Tapping Setup by Micky R. Jennings, courtesy of Wenatchee Valley College, for WA Open ProfTech, © SBCTC, CC BY 4.0
- Figure 10.219: Power Tapping Setup by Micky R. Jennings, courtesy of Wenatchee Valley College, for WA Open ProfTech, © SBCTC, CC BY 4.0
- Video 10.107: Micky R. Jennings, courtesy of Wenatchee Valley College, for WA Open ProfTech, © SBCTC, CC BY 4.0
The process of using the spindle power of a machine tool to drive a tap into the workpiece.