Nice demos. Thanks. Have you found any significant difference between straight plunge in vs the approx 26 degree cuts? And won't the final cuts being a plunge in throw off the form of the threads by altering the load at the almost full depth of the threads? Or the amount of movement you would need to make to get to the final size?
Thanks for the questions. Cutting on a flank is recommended by the insert manufacturers, these methods follow their advice in several simple ways. While plunge cutting can be ok, tool load is increased and tool life is compromised. The idea is that as the method is so simple, a quick advance on the compound becomes a small addition to plunging. There is no need for high precision compound moves, just enough to load the tool by the amount preferred in the direction required. These methods attempt to show a decreasing depth of cut and proportional tool advance / retract so any later steps are small and removed by a small plunge cut to size. There should be no steps as the tool always cuts on both sides just loaded one side or the other. I hope the process is clear and you never have to set your compound again for screwcutting.🙂
@@machinists-shortcuts Appreciate the thorough reply. And if I may add, keeping the compound at 0 (or is it 90 deg 😎) makes it much easier to get the tool to the other side and cut away from the chuck.
@@7alfatech860 Thanks, I like to use a boring bar on the other side, It's basically a left handed tool when used on the O/D. This is easier to set up and cutting forces are down into the bed, no need to turn any tools upside down.
The insert has a full form & this is what dictates the finished thread profile. The reason that 26.5 degrees is used is because it is simply the angle that is achieved when advancing the compound slide half the depth of cut. This formula is simple to remember and providing the angle is less than 30 degrees it will always shave a bit off one flank. 29.5 degrees gives a load split ratio of 99:1 - 26.5 degrees gives a load split ratio of 93:7 the difference between them translates to very small differences in chip widths.
@@machinists-shortcuts thanks for the detailed explanation, much appreciated. I think I get it now, going to give this a crack on my tiny little lathe.
@@machinists-shortcuts tested it and works a treat. I get nice curly chips instead of the usual crud. Since I'm not using full form inserts, it looks like I need to reduce the final depth otherwise it overshoots and destroys the thread form in the final pass.
@@HM-Projects Glad it worked out. When using a partial form tool I always deburr the crests of the thread before trying it on a gauge. Failure to do this will allow the thread to run on the crests and not the flanks giving a false indication. Then when the thread is deburred it will be loose. Hope this helps.
@@machinists-shortcuts just uploaded a video with my electronic leadscrew thread cutting function updated to use your suggestion. I've tried it a few times now and it produces excellent results every time, especially with smaller diameter and pitches. In hindsight it's such a simple and effective approach than setting the compound slide to an angle, thanks!
👍
Nice demos. Thanks. Have you found any significant difference between straight plunge in vs the approx 26 degree cuts? And won't the final cuts being a plunge in throw off the form of the threads by altering the load at the almost full depth of the threads? Or the amount of movement you would need to make to get to the final size?
Thanks for the questions.
Cutting on a flank is recommended by the insert manufacturers, these methods follow their advice in several simple ways. While plunge cutting can be ok, tool load is increased and tool life is compromised.
The idea is that as the method is so simple, a quick advance on the compound becomes a small addition to plunging. There is no need for high precision compound moves, just enough to load the tool by the amount preferred in the direction required.
These methods attempt to show a decreasing depth of cut and proportional tool advance / retract so any later steps are small and removed by a small plunge cut to size. There should be no steps as the tool always cuts on both sides just loaded one side or the other.
I hope the process is clear and you never have to set your compound again for screwcutting.🙂
@@machinists-shortcuts Appreciate the thorough reply. And if I may add, keeping the compound at 0 (or is it 90 deg 😎) makes it much easier to get the tool to the other side and cut away from the chuck.
@@7alfatech860 Thanks, I like to use a boring bar on the other side, It's basically a left handed tool when used on the O/D. This is easier to set up and cutting forces are down into the bed, no need to turn any tools upside down.
Interesting approach, why 26.5 degree as opposed to 29.5 for example ?
The insert has a full form & this is what dictates the finished thread profile. The reason that 26.5 degrees is used is because it is simply the angle that is achieved when advancing the compound slide half the depth of cut. This formula is simple to remember and providing the angle is less than 30 degrees it will always shave a bit off one flank. 29.5 degrees gives a load split ratio of 99:1 - 26.5 degrees gives a load split ratio of 93:7 the difference between them translates to very small differences in chip widths.
@@machinists-shortcuts thanks for the detailed explanation, much appreciated. I think I get it now, going to give this a crack on my tiny little lathe.
@@machinists-shortcuts tested it and works a treat. I get nice curly chips instead of the usual crud. Since I'm not using full form inserts, it looks like I need to reduce the final depth otherwise it overshoots and destroys the thread form in the final pass.
@@HM-Projects Glad it worked out. When using a partial form tool I always deburr the crests of the thread before trying it on a gauge. Failure to do this will allow the thread to run on the crests and not the flanks giving a false indication. Then when the thread is deburred it will be loose. Hope this helps.
@@machinists-shortcuts just uploaded a video with my electronic leadscrew thread cutting function updated to use your suggestion. I've tried it a few times now and it produces excellent results every time, especially with smaller diameter and pitches. In hindsight it's such a simple and effective approach than setting the compound slide to an angle, thanks!
Very interesting. It never even crossed my mind that these methods were options.
Thanks, Keeping the compound at zero degrees allows these extra options. The load can be split to suit your requirements.