Ken Wines
Member
This was my first attempt at making threads on an all wood (except for the nib) rollerball pen. I received my thread mill cutter for the CNC and wanted to immediately try it out (it's a boy and their toys thing). Admittedly black palm is not the best candidate for taking threads but it was already rounded and ready to go.
Ebony was used for the nib section because the blank wasn't long enough to accommodate it in black palm. M12 x 0.8 triple start threads for the body to cap mating. 3/8" - 40 threads were used for the section to body mating. M6.5 x 0.5 threads used for the Schmidt Refillable Rollerball nib. No taps and dies were used in the making of this pen. The thread mill cutter pictured below cut all the threads that are used in the pen. Using it, you are able to cut full depth threads very close to the shoulder on the tenon. There is no end to end play in the threads, so I have to believe they are cut pretty close to the tolerances listed in the Machinery Handbook. The threads fit and move great straight of the machine. When cutting threads with taps and dies (and maybe it could be the adjustment on my dies), I've always had to "work" them for a little while to get smooth movement.
You will notice an extra 1/2" tenon cut below the the M12 tenon. It is there for a purpose. To center the bit with collet chuck, I have a routine that "touches off" on the inside taper of the collet chuck on 8 differ points every 45 degrees around the circle. The X and Y values are recorded and the average X and average Y are called the 0, 0 coordinates. The routine runs at least 2 times and continues to run until the deviation between the current run and the last run is 0.001" or less. This could take up to 5 iterations to meet that criteria. The centering routine doesn't have to be run after each blank is cut. Many blanks could be cut but the routine should be run periodically. Anyway getting back to the extra tenon... because I know that the setup is probably not perfect. the extra tenon is cut and should be concentric with the threads that were just cut. This allows me to chuck the extra tenon up in a collet chuck and make the rest of the blank concentric with the threads.
Now for the disclaimers.
I don't intend to sell all wooden pens. This was an experiment to see if wood could be threaded and black palm was probably one of the worst case scenarios to try it on.
I'm not saying that this is the best way to cut threads. Personally, I doubt if I use my taps and dies much in the future. I see some advantage to cutting threads using this method when it comes to difficult materials such as polyester resins, acrylic acetate, etc. If you wanted to cut left handed threads just to mess with that special someone in your life, it could be easily done without bearing the expense of additional taps and dies.
I'm pretty happy with the results from the experiment and time will tell as to the longevity of the threads.
Ebony was used for the nib section because the blank wasn't long enough to accommodate it in black palm. M12 x 0.8 triple start threads for the body to cap mating. 3/8" - 40 threads were used for the section to body mating. M6.5 x 0.5 threads used for the Schmidt Refillable Rollerball nib. No taps and dies were used in the making of this pen. The thread mill cutter pictured below cut all the threads that are used in the pen. Using it, you are able to cut full depth threads very close to the shoulder on the tenon. There is no end to end play in the threads, so I have to believe they are cut pretty close to the tolerances listed in the Machinery Handbook. The threads fit and move great straight of the machine. When cutting threads with taps and dies (and maybe it could be the adjustment on my dies), I've always had to "work" them for a little while to get smooth movement.
You will notice an extra 1/2" tenon cut below the the M12 tenon. It is there for a purpose. To center the bit with collet chuck, I have a routine that "touches off" on the inside taper of the collet chuck on 8 differ points every 45 degrees around the circle. The X and Y values are recorded and the average X and average Y are called the 0, 0 coordinates. The routine runs at least 2 times and continues to run until the deviation between the current run and the last run is 0.001" or less. This could take up to 5 iterations to meet that criteria. The centering routine doesn't have to be run after each blank is cut. Many blanks could be cut but the routine should be run periodically. Anyway getting back to the extra tenon... because I know that the setup is probably not perfect. the extra tenon is cut and should be concentric with the threads that were just cut. This allows me to chuck the extra tenon up in a collet chuck and make the rest of the blank concentric with the threads.
Now for the disclaimers.
I don't intend to sell all wooden pens. This was an experiment to see if wood could be threaded and black palm was probably one of the worst case scenarios to try it on.
I'm not saying that this is the best way to cut threads. Personally, I doubt if I use my taps and dies much in the future. I see some advantage to cutting threads using this method when it comes to difficult materials such as polyester resins, acrylic acetate, etc. If you wanted to cut left handed threads just to mess with that special someone in your life, it could be easily done without bearing the expense of additional taps and dies.
I'm pretty happy with the results from the experiment and time will tell as to the longevity of the threads.
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