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Thread: New Lathe - AL-346V ?
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22nd Apr 2019, 08:58 PM #31Diamond Member
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In my case, I'm looking to keep the thread cutter lined up with the threads I've already cut by leaving the feed engaged all the time - at the end of a pass, I stop the machine, withdraw the tool and then run the lathe backwards to feed the tool back to the start, then feed in deeper and take another pass. It works well provided you can stop the lathe quickly at the end of the pass.
For this kind of thread cutting, the variable speed comes in handy, as I can temporarily speed up the machine while running backwards, making it quicker to reset for the next pass.
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22nd Apr 2019, 09:02 PM #32Golden Member
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22nd Apr 2019, 10:13 PM #33Member: Blue and white apron brigade
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22nd Apr 2019, 10:24 PM #34After hearing (and seeing for myself) buying additional toolholders that aren't purchased with the QCTP [despite identical part no.s] -- may not fit. So good to see yours actually fitted on.
Local joint up my way has a couple (one of which I scored to try at home) he ordered for a cust. You guessed it, so far out wont fit. Was hoping it would just need a skim on the flats. No such luck, dist between both sides of dovetail too small to fit tool post.
DRO --yeah lots of bells and whistles, don't see myself even learning half of what it can do anytime soon.
Like that toolholder mounted mill slide. Cant say I have seen one of those.Frisky wife, happy life. Then I woke up. Oh well it was fun while it lasted.From an early age my father taught me to wear welding gloves . "Its not to protect your hands son, its to put out the fire when u set yourself alight".
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23rd Apr 2019, 04:03 AM #35
Hi Rusty Arc,
The danger of running into the shoulder or even worse the chuck, is one reason I try and cut threads away from the chuck towards the tailstock running the lathe in reverse. I'm soon about to cut a left hand threadBest Regards:
Baron J.
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23rd Apr 2019, 07:58 AM #36Most Valued Member
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That is a sensible practice Baron makes sense
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23rd Apr 2019, 11:05 AM #37Diamond Member
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Kind of, as mentioned, it's a looser fit, meaning I have to make sure to crank down on the top lever extra hard to make sure it's solid.
Like that toolholder mounted mill slide. Cant say I have seen one of those.
That was a particularly sketchy setup - I just managed to clamp the edge of the vice in a spare toolholder, and was able to clamp the work at the right height for a single pass through the 3/8" endmill. That said, it all felt surprisingly solid.
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23rd Apr 2019, 11:07 AM #38Diamond Member
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23rd Apr 2019, 07:51 PM #39Diamond Member
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Had a chance to remove the back plate and look at the variable speed drive that's in there. It's a Shinlin SS2 1.5kW vector drive with a 100R 600W braking resistor.
Closer inspection shows that I was wrong about the closed loop operation - the RPM display on the lathe (and its sensor) is completely independent of the drive.
I shot a video of the lathe stopping and went and counted frames - at 500 RPM it took 0.43 seconds to stop. At 1,000 RPM it took 0.9s.
Having found the manual online, I tried changing the odd setting, but got an error message each time - there doesn't seem to be a password set, so not sure what's stopping it.
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23rd Apr 2019, 08:59 PM #40Member: Blue and white apron brigade
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Assuming uniform deceleration, that's 7.5 completer revs at 1000 rpm and about half that at 500 rpm
PLUS
Reaction time, for a pedal while standing, unless you are prewarned something might happen, is around 0.5s (and this will be at full at full RPM) so you are looking at ~16 revs at 1000 and half that at 500 rpm.
I doubt you will get that much better with a mechanical foot brake.
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15th Aug 2019, 06:05 PM #41Novice
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Very pleased to find this thread. Im looking at the 336D and contrasting it to to the 346V. Given the extra time with the new lathe how have you found it? Is the electronic brake delivering? From the discussions it should be stopping on a dime at threading speeds? How are you finding the accuracy on turning? How parallel is it turning over ~200mm? How is the torque? Are you able to manage ~2-3mm depth of cuts okay across a range of speeds? ie not torque issues with the VFD control?
Appreciate any info, views, learning on this machine.
Cheers,
J.
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15th Aug 2019, 10:08 PM #42Senior Member
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Does the lathe have a saddle lock?
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16th Aug 2019, 01:57 PM #43Diamond Member
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Really happy with it, but am still learning a lot. I am disappointed with the VFD brake - you can't really use it to stop the machine quickly enough if you're threading up to a shoulder, so I've now taken to threading in reverse (away from the chuck) with the cutting tool upside down on the other side of the work. I am confident I could stop the machine considerably faster with a mechanical brake.
That said, for routine use, the quick stop that you always get with the electric brake is nice, rather than waiting for the machine to coast to a stop.
I've done a few tests for taper where I adjusted the tailstock offset slightly, but apart from that, the machine seems to be very accurate. It's me that needs to learn/practise a lot more to get adept at turning to a diameter.
I haven't really pushed it on DOC - with no experience on other lathes, I don't really have a yardstick for sensing how the machine is coping. With time I'll push it harder and probably start to find its limits.
Very happy with the flexibility of the VFD, the DRO is great, and if they had included the mechanical brake with the VFD brake it would have been ideal.
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16th Aug 2019, 01:59 PM #44Diamond Member
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16th Aug 2019, 07:13 PM #45Novice
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Thanks for the response. Hope you don't mind if I ask some more questions and perhaps through some ideas about.
Interested to understand this threading/braking side of things some more.
Heres what I have found: I currently have an AL320G which is also metric leadscrew and has a chasing dial. When I am threading to a shoulder for metric threads and I can't (for whatever reason) use the safer running in reverse method I disengage the half nut. Wind the saddle back, wait for the correct chasing dial mark to line, re-engage the the half-nut to start the next pass. Obviously when doing imperial threads on a metric leadscrew lathe its a different story. However I would encourage you to look at Tom Liptons video on this. https://youtu.be/HXt4TWa382Q Even though he is using imperial leadscrew to cut metric the principle is the same You could use when dealing with Imperial would be exactly the same approach and allow you to use the half nut to actually stop saddle movement which is instant and the foot brake brings the spindle under rapid control. Another entertaining youtube is This Old Tony. He also has some threading video(s) that might be worth a watch. Remember what they do with Imperial and chaser dials you can do with metric and your chaser.
So thinking about things and the way the electronic brake would seem to be operating when you thread what RPM you running at? I'm conservative and still tend to use 80-100rpm. So with the constant deceleration of that VFD (which would seem to have been programmed to drop 1Hz every 0.036 secs, again assuming it us using 50Hz as its base not 60Hz) that should be about 0.36 secs. Pretty quick stop. About half a turn. If running at 100rpm in low gear that should be around 0.45secs which is around 0.75 of a turn. If the electronic brake is delivering that performance things should be good for imperial threading to a shoulder as well. Again assuming you are not able to do the much better system of the reverse threading trick ala Joe P.: https://youtu.be/Z-dqOi_z5bk
I've done a few tests for taper where I adjusted the tailstock offset slightly, but apart from that, the machine seems to be very accurate. It's me that needs to learn/practise a lot more to get adept at turning to a diameter.
I haven't really pushed it on DOC - with no experience on other lathes, I don't really have a yardstick for sensing how the machine is coping. With time I'll push it harder and probably start to find its limits.
Very happy with the flexibility of the VFD, the DRO is great, and if they had included the mechanical brake with the VFD brake it would have been ideal.
I had a good look at at 346V at Machinery House today. Really pocked all over it and compare it to the 336D. Really hard to choose between them.
Cheers,
J.
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