1340gt surface finish problem

I'd go through the motor mount and stand first to see if something is loose.

Capacitor is unlikely an issue—this should have a start capacitor, not a run capacitor, and it should drop out of the circuit after the motor comes up to speed.

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rherrell said:
why would the angle of the ridges change direction when you change the feed rate???
Click to expand...

You're dealing with a harmonic, not a physical effect. the vibration causes the progression (or regression) of the "groves", which are really tiny chatters.

Is the drive belt tight? if not it may be flopping around.

A lot transpired between the time I wrote this and the time it got posted, Probably my fault for not checking for recent posts.
 
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The thing that I have always noticed, on the machines where the single phase motor is causing that problem, you get a definite audible hum. And you are saying that it sounds quiet. I run one of these all the time, in single phase, and its not a problem just being single phase. On a Chinese motor, yes possibly, but not on this one, well never yet anyway. Not saying that there couldnt be a bad one, but it will be a first on one of these. Can you post a video of the just the motor running?

And yes of course its under warranty, (Thats not loose bolts though), but if there is something wrong with that motor, yes, absolutely no question about that. There is nothing you have to tear apart.

But if you can answer these:

1. Is it a new problem, or has always happened?
2. Are you sure the motor sounds fine? Maybe send me or post a video of just that? Any time I have seen a machine with that classic single phase hum, you can hear or feel it. Maybe not anything extreme, but if its going in to the work piece, any time I have ever had it, you could hear it right away. Possibly without anything to compare with though, maybe its hard to tell. Maybe a video of the motor itself, and then one of the whole machine running from pretty far back.

I can check that motor out / swap motors that is no problem at all, but just want to get a little more info before. If it didnt do it when new but started later and no change to the sound, or if its been doing it since new, (Not sure when you started using it) Turning with the drill motor can be a good indication, but its also turning at a completely different speed, so there could just be more to it than that. Let me know the answer to these if you can, and we will get it taken care of tomorrow.
 
Actually as I listen to that video again, whats that high pitched noise? Or is that just something in the video that is not really there? (That happens to me all the time when I make videos)
 


Here are a few videos, first of just the motor running, and then of it cutting on about the same diameter alum. This is my 1340GT, Single Phase. Just a quick cut, going away from the chuck so I didnt crash it as I was taking the video ha ha.
 
First picture shows the finish with about the same feeds and speeds you were at, pretty good on that one.

IMG_9413.JPG

The one below was with a much faster feed rate, what I thought the others looked like at first, but thats been ruled out long ago.

IMG_9412.JPG
 
A few more things I thought of to check:

1. Check the bar that tensions the belt (Holds the motor up) Make sure its not loose, if it is add a washer to tighten it up.
2. Make sure the headstock bolts are tight to the bed. (Not sure if you aligned it yet or not)
3. Just a general overall check of the headstock area bolts to make sure its all tight.
4. Also the answer above about if it just started, or it always did it.

My idea is since I have a known good running machine here, we can swap parts back and forth until we get it. Like if you send me your tool and work and I turn it on this one, or we swap motors, or whatever. We will get it, don't worry about that.
 
It's been this way from the start, the reason it's taken so long to mention it is I've been trying to troubleshoot it myself. I'm kinda stubborn and I wanted to try everything I could think of before I asked for help.

When I did the test I ran it with my corded 1/2" drill motor which has a top speed of 800 rpm, I ran the lathe at 770 rpm under power so the two speeds are almost the same.

I'll get a video of just the motor and post it here in the morning
 
Here are the videos you wanted Matt. I checked all the bolts on the motor mount and everything is tight, including the adjusting bar.




 
Have you checked the gear lash on the banjo gears? I'll have to go check mine but I don't remember hearing that much gear "whine". My shop's never that quiet so I could have missed it but it seems louder in the video.
 
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