Introduction: Shopsmith Hack #1: Tapping Straight Holes
If you have a Shopsmith, you already know about using it as a drill press, but you can also use it to keep your tap straight when tapping threads. Tapping crooked can break a tap as it tries to straighten itself in the hole, or leave you with a crooked screw when you assemble.
This video (click here) follows these instructions very closely. You can watch it through to get the idea, then you still have the rest of these instructions to follow without having to stop and rewind, etc.
You can buy your tap and drill bit as a set:
For best results when tapping holes:
1. Use the right tap drill size from the drill chart.
2. Use cutting oil on the tap.
3. Use a sharp tap. A dull tap puts excessive radial stress and torque on your workpiece and the tap, which can break either of them.
4. Chamfer the hole slightly before tapping.
After drilling, when you are ready to tap...
Step 1: Unplug Your Machine
You're going to put a wrench on the drive shaft and you do NOT want to forget and turn on the motor before you remove the wrench.
In the video, you see me putting a painter's tape reminder on the plug to make sure I don't forget and leave the wrench on the shaft when I want to use the motor again. Alternatively, you could tie the cord to the wrench. Use whatever works for you, but don't dismiss the need to remove the wrench. Serious consequences await the careless.
Step 2: Attach a Wrench to the Accessory Drive Shaft
I have a 1/2" router bit adapter. The old Shopsmith motor is too slow for use as a router, but I can fit a 3/8" socket wrench extension in it. I put this on the accessory shaft, which is on top when the machine is in the drill press configuration.
If you don't have a router adapter, you could use a piece of pipe with a couple of holes drilled in the side, tapped for set screws. Be creative.
Step 3: Insert the Tap in the Drill Chuck and Align It With the Workpiece
I put the Jacobs chuck on the drive end and insert my tap.
I find the hole in my workpiece with the tap and lower it to the table with the quill feed.
Before tapping, I put some cutting oil on the tap.
Step 4: Cut Threads
Now, maintaining light pressure on the quill feed, I turn the tap with the wrench. When I'm done cutting threads, I maintain light pressure with the quill feed and loosen the chuck with the chuck key. Then I let the quill feed up and remove the tap by hand with a tap handle. Don't try to back the tap out while held in the drill chuck to prevent damage to the thread.
If you're tapping a through-hole, you might be done tapping. If it's a blind hole, you might want to follow up with a flat-bottom tap to get full threads further in. At this point, you have already established straight threads, so you can easily follow the existing threads with another tap by hand with a tap handle.
Step 5: Remove the Wrench!
Remove your wrench IMMEDIATELY after you're done tapping and definitely BEFORE you plug the machine in.
Now you're done!
You're part is ready to have a screw installed.
Step 6: P.S.
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