I needed a knob with 1/4-20 threads for the band saw circle cutting jig I was building. The fastest option was turning one from 3/4" aluminum round stock. The following instructions assume basic knowledge of metal lathes.
Step 1: Materials and Tools
- 3/4 inch aluminum round stock or other material to make the knob from (enough to hold in the lathe and cut a 1 inch long knob from)
Drill chuck that fits the lathe
#7 drill bit
1/4-20 tap and handle
Knurling tool with your favorite pattern
- Parting tool
Step 2: Turn Diameter
Calculate the next smallest diameter to work with your knurling tool. I just took off enough material to clean the surface as perfect knurls were not important. Turn down the diameter along a 1.25 inch length of the rod using the right-hand cutter. All the turning and drilling was done at about 1500rpm.
Step 3: Turn Face
Using the left-hand cutter, turn the face to achieve a clean surface.
Step 4: Center Drill
Use the center drill on the end of the rod to create a start mark for the next drilling step.
Step 5: Drill
Chuck the #7 drill bit and drill to a depth of 3/4 inch. Adding some lubricant to the bit will help with chip removal.
Step 6: Tap
Chuck the 1/4-20 tap in the tap handle and add a little lubricant to the tap threads to prevent sticking. Use a center in the tailstock to align the rear of the tap handle with the drilled hole (I used a center drill). Tap the hole until it bottoms out.
Step 7: Turn Base Diameter
Reduce the diameter at the base of the knob for about 1/4 inch along the rod using the right-hand tool. The dimensions are a visual choice, so you decide. Leave enough material to support the threads.
Step 8: Knurling
Use the knurling tool to apply some grip to the knob. I textured a little over 3/4 of an inch. (about 200rpm)
Step 9: Parting
Cut off the knob using the parting tool at a little over an inch.
Step 10: Turn Other Face
Secure the knob in the lathe with the parted face out. Take a finishing pass on the face using the left-hand tool. Round the edge using a file or other tool.