logan 820 runout

[Redlineman]

Hey Frank;

You're building a good body of evidence. This kind of poking around is how the first guy learned to fix this stuff after all. You're repeating of "dummying through it" will give you more understanding than just reading it in a book and following the directions.

I have a mint 3-jaw chuck that showed the same kind of wobble on a no center mounted 12" bar. Kind of disappointing, but then you don't ever turn anything setup like that anyways... and for good reason!

Keep blundering along and you will have a good setup head on your shoulders when you are done! I'm right behind you.... one of these days.

 

[Franklyn]

Redlineman, will do! Your right on the money as to how much I've learned.I'll post the results as soon as they are available. Will try to get some pictures as well. Thanks for the encouragement.

 

[Franklyn]

Re: logan 820 runout Pictures added

I removed the original chuck from the Logan (which was surprisingly easy) and turned 3/4 round between centers. There was about .002 runout per 11 inches Next I placed a 5" Bison 3 jaw chuck(from ENCO) and started turning some stock. On a 12 inch length of rod I measured .0015 per foot which is better than I ever thought I would get. I also took some of the rod that had been turned with the old chuck and produced wavy irregular gouges in the metal and was able to get runout of .002.

I'e posted some pictures of the end results. So the problem was with the jaws of the chuck or the scrolling mechanism. An indicator on the outside of the old Logan chuck would have a runout of .003.




This is a picture of the lathe with the new chuck . I'm measuring the run out at the headstock.


Indicator at tailstock:



The carriage with the indicator was run along the length of the car with .0015 deviation along its entire length.

These are some pictures of the results I was getting.

turned with old chuck. Close up



Rod turned on old chuck (top) and Bison chuck below. Stock diameter didn't matter with the old chuck, wavy irregular lines were often present along with run out measured in the .01 at its worst.



. this is .75 rod that was originally turned in the old chuck. I turned it again in the bison chuck leaving the top portion as it was for comparison.




Same thing here, different view of the rod.



Turned between centers. Good results obtained this way, as long as the center wasn't held in the jaws of the old chuck. If I did, wavy irregular turning resulted. The spindle has an internal 3 MT. The dead center was held in the spindle with the chuck removed.


Here's the problem. Can't tell at all by looking at it or by placing an indicator on the circumference of the chuck. The jaws had to contact and turn the work.

 

[burtonbr]

That's some great info there, I think I'm finding exactly the same issues.

 

[Franklyn]

That's some great info there, I think I'm finding exactly the same issues.

I'm glad to help. If anything I posted is not clear or needs more explaining, just ask.
Frank

 

[Redlineman]

Indeed;

Excellent discovery work, Frank. Invaluable experience created in a systematic scientific way. It will stand you well and make a good foundation for the future. My project is going no where lately. I hope to be where you are at... some day.

Now it would be interesting to see where the issue in the old chuck stems from.