Also I have been questioning the inverted tool post where the parting tool is mounted upside down. An obvious upside would be that the machine keeps running in the same direction so parting off may be done even without switching off after the previous operation. Although parting off is often done on lower speed. There are claims about the tool 'digging in' vs. 'being pushed away' which are vague to me. After all it's the exact same process. It seems like fixing a problem that has its root in insufficient stability. From a standpoint of forces at play, any inverted tool (front or back mounted) will actually try to lift the saddle and everything on it, which is contrary to the machine design intending the forces to be directed downwards into the frame. If an inverted rear tool post is still desired, at the least it should be executed so that the clamping system is also inverted, with the clamping bolts coming from the bottom and the fixed mounting surface is at the top. I have a Colchester lathe of which the manual shows a very nice example.
Hi, dont see the point in mounting the parting blade upside down when as you say the forces are working against the design of the lathe. I have the 3 phase motor hooked up to a VFD so reversing direction is an easy task !, Would be nice to see some vids of the Colchester. Regards Del.
@@machinenutdel6764 Thanks! Actually I own 10 lathes, not all of them in working order. My main machine is a Gema LZ 160. Great mid size machine with some smart features like auto feed cut-off on both longitudinal and cross slide. I like to work with this especially for safety reasons. Another option is to work on real had stops mounted in a similar way, while these are even more accurate it cannot be used on auto feed for obvious reasons. I also have micro adjustable hard stops which makes it even easier. I intend to eliminate the compound slide on the Gema, as Robin Renzetti and Stefan Gotteswinter have shown. Added stability is a bonus and I have noticed (although it never happened) that with the compound, crashing the bottom part into the chuck is a big risk when the compound is retracted and your eyes are on the tool! Another bonus with compound slide elimination is that there is more room for bigger tools. In fact I have a lot of tools with 25 mm shank from a previous bigger machine which currently don’t fit, in the setup I have now the center height is 17 mm. I have also reverted back to an original 4-way indexing tool post from the (expensive) quick-change tool holder system that came with the machine. I have found the quick-change systems to be a huge trade-off, sacrificing stability for convenience. The inherent problem is that there is always air in the force path from the tool mounting interface to the machine. Possibly an even more problematic issue is tool overhang. The tool is placed further outboard and in the worst case, the tool is situated (far) outside of the left cross slide guideway. This will cause the cutting forces to work and tilt everything from the cross slide up, with terrible consequences. Again, as the lathe is originally designed this never happens. You always want metal-to-metal all the way down into the machine bed, no air! With the quick-change system, parting off was practically out of the question on anything in steel. Yes I am now having to shim my tools again but it is well worth the effort. Once set up series can be produced very efficiently and indexing the tool post is in fact a lot quicker than changing tool holders. There is also a lot less bulk to contend with. There are some modifications in the works to further improve, along with the compound slide elimination comes a new, dedicated 4-way indexing tool post of my own design. One last thing about the rear tool post for cutting off. With a 4-way indexing tool post the rear tool post adds a 5th position which can be very helpful. With 4 or 5 tools the vast majority of work can be done. When a boring bar is used, only 3 positions on the indexing tool post remain, so a 4th in the back is a bonus. I regularly use outside and inside turning tool, a parting tool and a chamfering tool. I like the concept of drilling with the carriage but it depends if I can miss another position. Then again, there's always work that is more suited to the turret machines. Finally, machine list: Gema LZ 160 (4) Boxford (2) Schaublin 102 VM Lorch (watchmaker’s) Boley RD 42 Ward 2A
Nice work. Still vibrations though and I'd say your revs are way too high. With a good setup, parting off can and probably should be done on auto feed. Of course there are plenty of other areas where vibration can come from, solve them one by one.
Hi BBB, Im still a newbie when it comes to parting off, and I think a lot of people struggle with it ! having a rock solid set-up is the way to go , never tried the auto feed when parting, its something I need to do, thanks for the comments, Del.
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Also I have been questioning the inverted tool post where the parting tool is mounted upside down.
An obvious upside would be that the machine keeps running in the same direction so parting off may be done even without switching off after the previous operation. Although parting off is often done on lower speed.
There are claims about the tool 'digging in' vs. 'being pushed away' which are vague to me. After all it's the exact same process. It seems like fixing a problem that has its root in insufficient stability. From a standpoint of forces at play, any inverted tool (front or back mounted) will actually try to lift the saddle and everything on it, which is contrary to the machine design intending the forces to be directed downwards into the frame.
If an inverted rear tool post is still desired, at the least it should be executed so that the clamping system is also inverted, with the clamping bolts coming from the bottom and the fixed mounting surface is at the top. I have a Colchester lathe of which the manual shows a very nice example.
Hi, dont see the point in mounting the parting blade upside down when as you say the forces are working against the design of the lathe. I have the 3 phase motor hooked up to a VFD so reversing direction is an easy task !, Would be nice to see some vids of the Colchester. Regards Del.
@@machinenutdel6764
Thanks! Actually I own 10 lathes, not all of them in working order.
My main machine is a Gema LZ 160. Great mid size machine with some smart features like auto feed cut-off on both longitudinal and cross slide. I like to work with this especially for safety reasons. Another option is to work on real had stops mounted in a similar way, while these are even more accurate it cannot be used on auto feed for obvious reasons. I also have micro adjustable hard stops which makes it even easier.
I intend to eliminate the compound slide on the Gema, as Robin Renzetti and Stefan Gotteswinter have shown. Added stability is a bonus and I have noticed (although it never happened) that with the compound, crashing the bottom part into the chuck is a big risk when the compound is retracted and your eyes are on the tool!
Another bonus with compound slide elimination is that there is more room for bigger tools. In fact I have a lot of tools with 25 mm shank from a previous bigger machine which currently don’t fit, in the setup I have now the center height is 17 mm. I have also reverted back to an original 4-way indexing tool post from the (expensive) quick-change tool holder system that came with the machine. I have found the quick-change systems to be a huge trade-off, sacrificing stability for convenience. The inherent problem is that there is always air in the force path from the tool mounting interface to the machine. Possibly an even more problematic issue is tool overhang. The tool is placed further outboard and in the worst case, the tool is situated (far) outside of the left cross slide guideway. This will cause the cutting forces to work and tilt everything from the cross slide up, with terrible consequences. Again, as the lathe is originally designed this never happens. You always want metal-to-metal all the way down into the machine bed, no air!
With the quick-change system, parting off was practically out of the question on anything in steel. Yes I am now having to shim my tools again but it is well worth the effort. Once set up series can be produced very efficiently and indexing the tool post is in fact a lot quicker than changing tool holders. There is also a lot less bulk to contend with. There are some modifications in the works to further improve, along with the compound slide elimination comes a new, dedicated 4-way indexing tool post of my own design.
One last thing about the rear tool post for cutting off. With a 4-way indexing tool post the rear tool post adds a 5th position which can be very helpful. With 4 or 5 tools the vast majority of work can be done. When a boring bar is used, only 3 positions on the indexing tool post remain, so a 4th in the back is a bonus. I regularly use outside and inside turning tool, a parting tool and a chamfering tool. I like the concept of drilling with the carriage but it depends if I can miss another position. Then again, there's always work that is more suited to the turret machines.
Finally, machine list:
Gema LZ 160 (4)
Boxford (2)
Schaublin 102 VM
Lorch (watchmaker’s)
Boley RD 42
Ward 2A
@@bigbattenberg Got a video coming on at 8pm our time, it shows the Belgian lathe I use for hogging hope you can catch it, Del.
@@bigbattenberg Never fancied the QCTP myself, expensive and whats the rush !
Nice work. Still vibrations though and I'd say your revs are way too high. With a good setup, parting off can and probably should be done on auto feed. Of course there are plenty of other areas where vibration can come from, solve them one by one.
Hi BBB, Im still a newbie when it comes to parting off, and I think a lot of people struggle with it ! having a rock solid set-up is the way to go , never tried the auto feed when parting, its something I need to do, thanks for the comments, Del.