- Joined
- Dec 18, 2013
- Messages
- 2,337
Issue: The surface finish when the lathe was new was pretty decent, but quickly deteriorated as the lathe broke in to the point that this is what it looked like after about 15 hours run time. Yikes, this was at 70 rpm about .002 per revolution. It was less severe at 220 rpm but still very poor, mediocre at 320 rpm, not bad at 800 rpm at the finest feed .001 per revolution but even then still had spiraling showing up in the surface finish. Facing also had this spiraling showing up in the surface finish.
There are numerous reports from G4003G owners regarding this issue, some reporting its an issue with the motor and suggested replacing the motor, others reporting that isolating the motor from the lathe improved or resolved the issue.
My take on this after methodical step by step testing is, this is the result of a combination of issues.
1. Poor motor mount design. The factory motor is mounted directly on the lathe bed casting, metal to metal which transmits buzz and hum from the motor directly into the lathe. You can feel this with your hand everywhere on the lathe, headstock, chuck, tailstock. Its accurate to describe it as a buzzing humming type vibration. This is with the belts removed, just the motor spinning in mid air. You can measure this with a .0001 indicator on the chuck and watch the needle buzz back and forth .0001 to .0002 with an occasional spike. So its not the V belts (though using a link belt does reduce V belt vibration).
2. The factory motor itself did develop a WHA WHA WHA Wooo harmonic which was a contributing factor but primarily it was the buzz/hum into the lathe causing the problem.
3. Since the lathe initially didn't exhibit this problem my theory is when the headstock was brand new and tight it was able to deal with this motor buzz. But as the headstock broke in and loosened up it became susceptible.
I decided to replace the factory motor to test some peoples theory that it was just the motor that was the problem. This was not the case.
As you can see I did make half an attempt to isolate the motor but there was still some metal to metal contact between the motor and the lathe via the edge of the bolt and again you could feel the whole lathe buzzing/humming from headstock to tailstock even with the Baldor Motor. While this did get rid of the WHA WHA WHA Wooo issue on the factory motor, the Baldor spinning true and even, mostly the surface finish issue remained.
Here's the test I ran after installing the Baldor motor with the above rubber washers. From right to left I turned 3 sections, at 70 rpm, 220 rpm, and 320 rpm. While the surface finish/spiraling issue was reduced, it remained.
So I ordered some real isolation mounts from McMastercarr. These completely isolate the motor from the lathe, there is no metal to metal contact.
Here you see them installed. This is not ideal as the motor mounts on the lathe sideways putting a shear force on the isolation mounts. They are rated for 20lbs shear but distort a bit and there is some motor vibration, ideally I would redesign the motor mount so that the motor sits flat down on the isolation mounts like in this photo.
Drum roll...with these isolation mounts installed the surface finish issues were eliminated! So was the buzz/hum in the lathe. With just the motor running before installing the belts there was zero buzz/hum and just the very slightest occasional something which was the motor wiggling a bit on these rubber isolation mounts, it was like night and day. So I installed the link belt and even with everything spinning, belt, spindle, quick change gears, carriage feeding turning the OD the lathe felt quiet if you place your hand on it, you could feel something with all that stuff rotating but the best way I could describe it is it felt quiet.
Here's the same test as above, 70 rpm, 220 rpm, 320 rpm, same tool same feed, you can't really tell any difference except for the two lines separating the three turns where I turned off the lathe to change spindle speeds.
And here's a face cut wow, and this is magnified about 4x, no spiral patterns at all.
There are numerous reports from G4003G owners regarding this issue, some reporting its an issue with the motor and suggested replacing the motor, others reporting that isolating the motor from the lathe improved or resolved the issue.
My take on this after methodical step by step testing is, this is the result of a combination of issues.
1. Poor motor mount design. The factory motor is mounted directly on the lathe bed casting, metal to metal which transmits buzz and hum from the motor directly into the lathe. You can feel this with your hand everywhere on the lathe, headstock, chuck, tailstock. Its accurate to describe it as a buzzing humming type vibration. This is with the belts removed, just the motor spinning in mid air. You can measure this with a .0001 indicator on the chuck and watch the needle buzz back and forth .0001 to .0002 with an occasional spike. So its not the V belts (though using a link belt does reduce V belt vibration).
2. The factory motor itself did develop a WHA WHA WHA Wooo harmonic which was a contributing factor but primarily it was the buzz/hum into the lathe causing the problem.
3. Since the lathe initially didn't exhibit this problem my theory is when the headstock was brand new and tight it was able to deal with this motor buzz. But as the headstock broke in and loosened up it became susceptible.
I decided to replace the factory motor to test some peoples theory that it was just the motor that was the problem. This was not the case.
As you can see I did make half an attempt to isolate the motor but there was still some metal to metal contact between the motor and the lathe via the edge of the bolt and again you could feel the whole lathe buzzing/humming from headstock to tailstock even with the Baldor Motor. While this did get rid of the WHA WHA WHA Wooo issue on the factory motor, the Baldor spinning true and even, mostly the surface finish issue remained.
Here's the test I ran after installing the Baldor motor with the above rubber washers. From right to left I turned 3 sections, at 70 rpm, 220 rpm, and 320 rpm. While the surface finish/spiraling issue was reduced, it remained.
So I ordered some real isolation mounts from McMastercarr. These completely isolate the motor from the lathe, there is no metal to metal contact.
Here you see them installed. This is not ideal as the motor mounts on the lathe sideways putting a shear force on the isolation mounts. They are rated for 20lbs shear but distort a bit and there is some motor vibration, ideally I would redesign the motor mount so that the motor sits flat down on the isolation mounts like in this photo.
Drum roll...with these isolation mounts installed the surface finish issues were eliminated! So was the buzz/hum in the lathe. With just the motor running before installing the belts there was zero buzz/hum and just the very slightest occasional something which was the motor wiggling a bit on these rubber isolation mounts, it was like night and day. So I installed the link belt and even with everything spinning, belt, spindle, quick change gears, carriage feeding turning the OD the lathe felt quiet if you place your hand on it, you could feel something with all that stuff rotating but the best way I could describe it is it felt quiet.
Here's the same test as above, 70 rpm, 220 rpm, 320 rpm, same tool same feed, you can't really tell any difference except for the two lines separating the three turns where I turned off the lathe to change spindle speeds.
And here's a face cut wow, and this is magnified about 4x, no spiral patterns at all.
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