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Old 04-25-2013, 03:35 AM   #1
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Default Rotary Table Fix

I wanted to share this info with the group as it might help someone who has a similar problem.

I bought this 6" rotary table a number of years ago. I bought it new and it was Chinese made so I got it for a good price. A few weeks after I got it, I was going to put it to use and discovered the table had a tight spot on one side and was loose on the other. It felt like the worm gear wasn't concentric with the spindle. I had disassembled the unit and a cursory examination looked like the worm gear and table were part of the same casting.



I decided there wasn't much I could do about so I put it back together. I have a smaller rotary table so didn't use this 6" model very often. Today, I decided to have another look at it and took it apart. A more careful inspection revealed that the worm gear casting was separate from the table, attached with 4 socket head cap screws.



I mounted the table on my lathe in the 4 jaw chuck and centered it on the spindle in the center. Turning on the lathe at slow speed revealed that the worm gear was not concentric and it wobbled slightly. Removing the worm gear casting revealed a depression in the table that the worm gear was supposed to seat in. However, it was .020" too small and slightly off center and the bottom of the worm gear casting was slightly bevelled which allowed the casting to cock slightly when tightened down. Since the worm gear casting had hole in the center that was designed to fit over and center on the spindle, I enlarged the depression with a boring bar so the worm gear casting would fully seat when tightened down. I rechecked it for concentricity and, Bingo, the worm gear now runs dead true.

I'm hoping when I get it back together tomorrow, my problem will be solved!

Chuck


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Old 04-27-2013, 06:08 AM   #2
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Don't you hate that sort of thing? I fitted a 4 jaw to my old lathe and was really disappointed to see air between the chuck and my backing plate. I assumed i had stuffed something up. After I remade the backing plate, I realised the problem was one of the pins that hold the jaws in was sitting proud of the rear surface of the chuck so the chuck could not seat properly. So I replaced the chuck which i had bought new and it was all good. Shame about the wasted shop time though!

It was good you could isolate the fault and rectify it.


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Old 04-27-2013, 06:40 AM   #3
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I suppose it's worth it in the end. You now have a precision rt at Chinese prices😊
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Old 04-27-2013, 09:00 PM   #4
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I suppose it's worth it in the end. You now have a precision rt at Chinese prices😊
Yeah, it's hard to justify buying the high priced stuff when you're not using it to earn a living. I have more time than money and there's a lot of satisfaction in making something work better.

Chuck
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Old 04-28-2013, 01:13 AM   #5
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Hi there Chuck, I have to agree with you "more time than money" and I got one of those Chinese RT's like you I pulled it down as it didn't seem to be 100% and found the nut that holds the worm "in sitchu", had been tapped on a very off centered angle with a thread that I still haven't found a replacement nut for, it is close to metric M10 so I think I will force a nut onto it and leave it at that. (it's not like I have to remove the nut every day).
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Old 04-30-2013, 12:00 AM   #6
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Originally Posted by gabby View Post
Hi there Chuck, I have to agree with you "more time than money" and I got one of those Chinese RT's like you I pulled it down as it didn't seem to be 100% and found the nut that holds the worm "in sitchu", had been tapped on a very off centered angle with a thread that I still haven't found a replacement nut for, it is close to metric M10 so I think I will force a nut onto it and leave it at that. (it's not like I have to remove the nut every day).
Cheers
Gabby
Maybe try an auto parts place. In Aus they usually have a stand with small packets of both metric and Imperial nuts and bolts with some sample threads to size your nut or bolt on. Maybe it is a M10 fine thread or 3/8". I'd be surprised if it was not a standard thread.
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Old 05-01-2013, 09:11 PM   #7
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thanx RodW, I will try that.
cheers
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Old 05-01-2013, 11:37 PM   #8
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Quote:
Originally Posted by cfellows View Post
I wanted to share this info with the group as it might help someone who has a similar problem.

I bought this 6" rotary table a number of years ago. I bought it new and it was Chinese made so I got it for a good price. A few weeks after I got it, I was going to put it to use and discovered the table had a tight spot on one side and was loose on the other. It felt like the worm gear wasn't concentric with the spindle. I had disassembled the unit and a cursory examination looked like the worm gear and table were part of the same casting.



I decided there wasn't much I could do about so I put it back together. I have a smaller rotary table so didn't use this 6" model very often. Today, I decided to have another look at it and took it apart. A more careful inspection revealed that the worm gear casting was separate from the table, attached with 4 socket head cap screws.



I mounted the table on my lathe in the 4 jaw chuck and centered it on the spindle in the center. Turning on the lathe at slow speed revealed that the worm gear was not concentric and it wobbled slightly. Removing the worm gear casting revealed a depression in the table that the worm gear was supposed to seat in. However, it was .020" too small and slightly off center and the bottom of the worm gear casting was slightly bevelled which allowed the casting to cock slightly when tightened down. Since the worm gear casting had hole in the center that was designed to fit over and center on the spindle, I enlarged the depression with a boring bar so the worm gear casting would fully seat when tightened down. I rechecked it for concentricity and, Bingo, the worm gear now runs dead true.

I'm hoping when I get it back together tomorrow, my problem will be solved!

Chuck
I have one just like this with the same problem (tight & loose spots) I will tear it apart again & see if i can fix mine like you did, Thanks!
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Old 05-03-2013, 03:08 AM   #9
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Mike, if you need more detail on what I did, let me know, happy to help.

Chuck
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Old 05-03-2013, 09:21 AM   #10
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Mike, if you need more detail on what I did, let me know, happy to help.

Chuck

Hi Chuck.

Me allso have the same issue with my RT. If you can give more detailed how you fix yours, it would have been great.

Have a nice day

CS


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