Drilling centers in round stock, "Lathe work"

[BHD]

I realize this is more of a welding forum, but for any one who has a lathe

how do you get (drilled) centers in longer shafts centered?
and IN the good old days, when they jsut used a face plate and a dog, how did they do it?

Just interested in your methods, thank you.

[RonMar]

I have a machinest square set that has a device that looks like a drawn arrow. It is basically a "V" with a ruler comming out of it. One edge of the ruler is aligned with the center of the "V". You set the round stock into the v with the ruler flat across the end, and scribe a line. Then you rotate the stock 90 degrees and scribe another line. Where the lines cross you apply the center punch. I am not sure how you could bore a hole using a plate and dog, as the opposite center on the tailstock supports the other end of the workpiece.

If I just want to bore a hole in the center, I chuck the material in the lathe, then confirm it is centered and running true using a dial indicator at several places along the materials length, and looking for runout while rotating the lathe chuck. The beauty of boring from the end of a spinning piece of stock, is that the drill really wants to find the center of the rotating stock.

[flathead]

The headstock spindle is hollow. If the stock you want to drill is narrow enough, you just feed it in through the outboard end of the headstock and hold it in a chuck just sticking out a bit. Use a center drill in a drill chuck in the tailstock ram to poke the center hole while the work is spinning. If the OD of the shaft is fatter than the spindle hole, then one end is held in the lathe chuck while the other is supported by a steady rest for drilling with the tailstock. In the absence of a 3 or 4 jaw chuck, you would have to mark and drill the center hole manually with a drill press. Even with a face plate and a drive dog, you first have to have the center holes drilled since the stock is located between the headstock and tailstock centers. They did have lathe chucks back in the "good old days" however.

flathead

[BHD]

those are all things I do, do. it jsut seems like many times I am off a few thousands, and normally it is not a problem as I am usually turning more off than that, and the part is not that percison.

but I do not think I have ever been able to take a clean shaft and get an exact center in it with in few thousands.
unless it is small or short and can fit totally in the chuck, (and I realize that even three jaw chucks not not always the most accurate.

Thank you for your replies, some times when some one is self taught, one wonders if your jsut not figuring out how to accomplish some thing or what is the situation.

[scott_vt]

Good Afternoon BHD,
On long shafts that are to large in diameter to fit inside the headstock you can use what is called a steady rest. It is a device that has three ball bearings that the shaft runs on and it is clamped to the ways on the bed, obviously the two lower bearings need to be adjusted properly and then the top of the steady rest is flipped down and the top bearing is then adjusted. The old time steady rests had brass supports rather than ball bearings.

In the event that the shaft has a rough finish not suitable for using a steady rest, you could use a vee block on a Bridgeport miller and hang the shaft off of the side of the table and swivel the head on the miller, and then use a dial indicator to indicate the end of the shaft !

There are some other methods but thats the just of it !

[scott_vt]

Originally Posted by BHD

how do you get (drilled) centers in longer shafts centered?
and IN the good old days, when they jsut used a face plate and a dog, how did they do it?

Just interested in your methods, thank you.

BHD,
Your question about the face plate and dogs, the face plate was used rather than a 3 or 4 jaw chuck, obviously to run the shaft on centers, the shaft needed to have the centers on both ends first, and then the dog would be used on the headstock end of the shaft and would be driven by a slot in the faceplate !

Hope that helps !