3 Jaw Chuck issues (and the fix)

[cfellows]

I've avoided using my 11" Logan lathe of late because the runout on the 3 jaw chuck has become intolerable. I finally measured the runout tonight and it was close to .020" out. My first thought was that the scrolls or the teeth on the jaws were getting badly worn... the chuck is 16 years old and was made in India.

On a lark, I decided to check for runout on the chuck body, and to my surprise, it was also out by more than .015". I removed the chuck from the back plate, leaving the backplate mounted on the spindle and when I checked it, the face was close to .015" high on one side. So, I made a couple of passes across the face of the back plate where it meets the back of the chuck. I also turned down the register lip that fits inside the back of the chuck since it was also out. This, of course, meant that the chuck no longer fit tightly over the register but that didn't matter. I plan to make a ring that will let me adjust the chuck for center but in the mean time, I just snugged down the bolts, then used a rubber hammer to tap on the side of the chuck until it was exactly centered. I was able to get the runout down to under .001", so, needless to say, I'm deliriously happy with my Logan again.

Chuck

 

[mosedawg56]

Good job! I may have to check the 3 jaw on my Heavy 10 to see if I can make it a little more accurate. It is much like your's was, but I have a brand new 4 jaw that was fit to it's new backplate on this lathe, so I just quit using the 3 jaw.

A complete set of 5C collets makes life somewhat easier as well.

Thanks for the reminder that most times it is the smallest things that cause the biggest problems.

Pat
Raytown, MO

 

[n4zou]

I have a 6" 3 jaw chuck that I salvaged from a scrap heap. It was worn past the shops tolerance so they threw it out. I paid the going scrap metal price at the time which was something like 35₵ a pound. After a few days of thinking about what to do with it I suddenly had a "light bulb above the head" moment. I took an old 8" face plate and mounted it on the spindle and faced it flat. I then took it over to the mill and slotted it matching the 6 mounting holes in the chuck. Whenever I need to make a run of parts that need to be offset turned or bored I just offset that 6" 3 jaw chuck on the 8" face plate and tighten down the 6 mounting bolts after getting the offset correct for the parts to be machined. Now instead of taking time to make sure each and every part is correctly set in a 4 jaw chuck and just clamp the part in my offset 3 jaw chuck and make chips fly.