Since my Bison 6" set tru needs some serious cleaning (about a year in service!), here is some "hands-on" explanation of how a set tru chuck works ... Will's style, with TONS of photos :devil:
Here is the dirty Chuck. I am using a pad to protect the ways, and a 1" drill rod clamped on the jaws to provide a holding point while removing it:
To disassemble the chuck there are 3 small screws from top, and 3 larger ones from the bottom:
Each jaw is marked, and each slot is marked as well:
And this is why it was not working as smoothly as when new - it was just dirty after a year of use:
After cleaning:
Ready to go back on the lathe:
To set the chuck using the set-tru feature, you mount the chuck, but do not fully tighten the 3 mounting bolts - I would say to use about 75-80% of the actual mounting torque - you basically need to allow for small radial movement by using the 4 set-tru screws. In this picture, one has the key and my finger is pointing to another one:
The idea is to measure about 2" inches away from the chuck's face, and adjust the 4 radial screws until you get the smallest possible reading. I first tried using the same 1" drill rod, but it's surface was not smooth enough, and not round enough - that Brown and Sharpe "BestTesT" (Ebay - used for $25) can sure pick up small movements 😉 . I am using my NOGA holding arm (highly recommended!), to hold the indicator:
I then used a smaller diameter drill rod that I used in the past that is much smoother surface-wise, and after a while, I got the following two shots, describing the total range of movement after going a full revolution, which is less than 0.0005" - not bad :twothumbs
You then finalize the installation by fully applying torque on the mounting bolts, check once again that things did not move (run the indicator again a couple of revolutions), and then pat yourself in the back for a job well done 😉
Will
Here is the dirty Chuck. I am using a pad to protect the ways, and a 1" drill rod clamped on the jaws to provide a holding point while removing it:
To disassemble the chuck there are 3 small screws from top, and 3 larger ones from the bottom:
Each jaw is marked, and each slot is marked as well:
And this is why it was not working as smoothly as when new - it was just dirty after a year of use:
After cleaning:
Ready to go back on the lathe:
To set the chuck using the set-tru feature, you mount the chuck, but do not fully tighten the 3 mounting bolts - I would say to use about 75-80% of the actual mounting torque - you basically need to allow for small radial movement by using the 4 set-tru screws. In this picture, one has the key and my finger is pointing to another one:
The idea is to measure about 2" inches away from the chuck's face, and adjust the 4 radial screws until you get the smallest possible reading. I first tried using the same 1" drill rod, but it's surface was not smooth enough, and not round enough - that Brown and Sharpe "BestTesT" (Ebay - used for $25) can sure pick up small movements 😉 . I am using my NOGA holding arm (highly recommended!), to hold the indicator:
I then used a smaller diameter drill rod that I used in the past that is much smoother surface-wise, and after a while, I got the following two shots, describing the total range of movement after going a full revolution, which is less than 0.0005" - not bad :twothumbs
You then finalize the installation by fully applying torque on the mounting bolts, check once again that things did not move (run the indicator again a couple of revolutions), and then pat yourself in the back for a job well done 😉
Will
