Project: Lathe Centering Tool
Wednesday, May 10 2017
I have a chunk of 3/8" steel plate. From that I cut off a piece a bit more than 1/2" wide along the 6" side of the plate. Why? Because I’m going to make a lathe centering tool and need about 1/2" of material to drill and tap the 8 mm holes that will hold the bearings in place. Why 8 mm? That is the ID of the bearings I have. Why 6"? That was the size of the steel plate. I know that it is too long. Not sure how much too long.
After squaring the piece on the mill the bar was about 3/8" x 1/2" x 6". It will fit in one of my tool holders. Good enough.
I drilled and tapped holes in both ends and mounted some bearings with a washer to keep the bearing from rubbing on the holder. 6" is WAY too big. I’m going to cut it in half (which might be too small). I will find out.
Thursday, May 11 2017
I cut the bar in half and prepared the cut end by milling it flat then drilling and tapping a new hole. I spent a few minutes with files to slightly round the end. If I had a rotary table I’d have milled the end with a nice radius. Some day. I blued the bar to inhibit corrosion. Finally the bearings were re-mounted.
It is just large enough to fit into a tool holder without interference from the ends of the screws holding the bearings in place. I could have shortened the screws but there was no need.
The way I usually have my compound slide configured means I have to use the centering tool on the back side of the part when mounted parallel to the ways as pictured. I can use it mounted perpendicular to the part if the part is about 1" in diameter or less. Or I could adjust my compound slide. The lack of cross slide travel is one of the down sides to using a mini-lathe.
No matter. It works. The tool is fed into the part. Pressure of the bearing against a part lightly clamped by the chuck jaws brings the part into alignment. Tighten jaws. Get to work. That is much faster than using an indicator and tapping the part with a hammer until happy.