01-29-2018, 07:20 PM
I started the lathe work on the "Delrin" base to which the camera tripod head will be mounted. First step was to reverse the chuck jaws to grip the external edges of the square part.
A 3/8 hole had been drilled through the center of the work at a previous step so centering was quick and easy. With the chuck jaws loose and a center in the tailstock, the tailstock was moved forward until the center was snugly engaged in the 3/8 hole. The jaws were then carefully tightened until the jaws just touched the work edges.
I used a one inch travel dial indicator secured to the lathe carriage to indicate the edges of the work, moving the indicator away from the work to clear it while rotating the chuck for measuring the opposite edge. The part is rocked back and forth while the indicator is in contact with the approximate midpoint of the flat to find the lowest reading. This is the reading that will be compared to the opposite side. The chuck jaws are adjusted until both readings are the same (or within your desired tolerance) tightening a bit at a time until the part is chucked securely.
NOTE: if the edges of the part were already at finish dimension, to avoid marring, I would have placed some scraps of metal between the jaws and the work to distribute the clamping pressure.
After centering, a two inch diameter x two inch deep hole is bored. This is the back side of the part and will never be visible so I fed the boring tool by hand for speed and because I wasn't concerned about tool marks.
The next step is to knock off the corners of the part and turn it circular. Had the part material been metallic, I would have sawed most of the material from the corners before turning. But since the composition is "Delrin" plastic, I skipped that step. Removing the chuck jaws and reversing them (again) the part was flipped and then chucked on the two inch bore which is b-a-r-e-l-y large enough to accommodate the jaws.
Because the cut was an interrupted one and because the chuck jaws extended only 3/4 of an inch, I used a tailstock center. There's no way that the part can work it's way off the chuck with the center applying a little pressure. Recall that there is a 3/8 hole drilled through the middle of the part so again I used it to center the part. After centering, I countersunk it just enough to provide a seat for the tailstock center.
Here's the setup:
I was concerned about high spindle RPM causing melting at the point of the tool (I've been warned about this). So I used a moderate speed and fed the cutting tool by hand for roughing. I did this because I was using very aggressive cuts, so aggressive in fact that I could hear the motor slow down, LOL, and I wanted to "feel" the cut, adjusting my feed until it felt comfortable.
And because this surface is external and visible, I used a fine longitudinal power feed to make the final finish pass.
I don't like to spend more than an hour or two in the shop so I quit at this point. Tomorrow I will reverse the part for some work on the other side. This seems like a lot of switching back and forth and it is. But it is also necessary because there must be a means of gripping the part for each operation and this sequence of operations provides for secure chucking at every step.
A 3/8 hole had been drilled through the center of the work at a previous step so centering was quick and easy. With the chuck jaws loose and a center in the tailstock, the tailstock was moved forward until the center was snugly engaged in the 3/8 hole. The jaws were then carefully tightened until the jaws just touched the work edges.
I used a one inch travel dial indicator secured to the lathe carriage to indicate the edges of the work, moving the indicator away from the work to clear it while rotating the chuck for measuring the opposite edge. The part is rocked back and forth while the indicator is in contact with the approximate midpoint of the flat to find the lowest reading. This is the reading that will be compared to the opposite side. The chuck jaws are adjusted until both readings are the same (or within your desired tolerance) tightening a bit at a time until the part is chucked securely.
NOTE: if the edges of the part were already at finish dimension, to avoid marring, I would have placed some scraps of metal between the jaws and the work to distribute the clamping pressure.
After centering, a two inch diameter x two inch deep hole is bored. This is the back side of the part and will never be visible so I fed the boring tool by hand for speed and because I wasn't concerned about tool marks.
The next step is to knock off the corners of the part and turn it circular. Had the part material been metallic, I would have sawed most of the material from the corners before turning. But since the composition is "Delrin" plastic, I skipped that step. Removing the chuck jaws and reversing them (again) the part was flipped and then chucked on the two inch bore which is b-a-r-e-l-y large enough to accommodate the jaws.
Because the cut was an interrupted one and because the chuck jaws extended only 3/4 of an inch, I used a tailstock center. There's no way that the part can work it's way off the chuck with the center applying a little pressure. Recall that there is a 3/8 hole drilled through the middle of the part so again I used it to center the part. After centering, I countersunk it just enough to provide a seat for the tailstock center.
Here's the setup:
I was concerned about high spindle RPM causing melting at the point of the tool (I've been warned about this). So I used a moderate speed and fed the cutting tool by hand for roughing. I did this because I was using very aggressive cuts, so aggressive in fact that I could hear the motor slow down, LOL, and I wanted to "feel" the cut, adjusting my feed until it felt comfortable.
And because this surface is external and visible, I used a fine longitudinal power feed to make the final finish pass.
I don't like to spend more than an hour or two in the shop so I quit at this point. Tomorrow I will reverse the part for some work on the other side. This seems like a lot of switching back and forth and it is. But it is also necessary because there must be a means of gripping the part for each operation and this sequence of operations provides for secure chucking at every step.