Moving center drilled hole

PITA but possible. You have to set up the shaft with a steady rest and use a tiny boring tool to bore the center hole true. Swivel around the compound and use that to feed it in, of course.

GWE

-cut off the drilled length

-hold the shaft in a chuck and turn a centered hole

-weld fill the hole

-drill a hole where you're started it & plug it

Bob

Guess I'd better add some more info on this. The bar is

1.75" 4140 B7 , rough finish surface, too big to pass through the spindle, 30" long, no extra length. I managed to do it but got curious what others would do. Phil

Brass bush , steadyrest , and a very pointy lathe bit . And as Grant said , a PITA . I've been turning some 4140 lately , what fun ! Almost as much fun as the Ampco 18 ...

Make a kerf with a cold chisel (in the cone) and drill a bit deeper. It will move in the direction of the kerf.

Nick

The type of cold chisel to use is called a Half Round Nose and it cuts a semicircular groove. You can grind a pin punch or nail set on an angle to make a quick one. Sorry, couldn't find a good picture.

jw

"Snag" wrote in message

it

And as Grant said ,

Voi ye, this dumb 'ol Finn went and did it the hard way, again, but then I have a lot of free time sometimes! So what's my story? Ok. The original holes were actually quite close to the center of the bar ends but when the bar was first placed between centers it rotated on its own to a certain spot, time after time. ? Shouldn't do that, eih? The bar is rough all right, lots of fat spots, a belly along its length and a very slight bow. The bow would not come out even in the press at 24 tons and 0.130 displacement! Some tough iron this is but at $24/foot it better be! And I don't plan to shovel off pricey metal to get a good usable bar. So the center holes even though they were good for the ends they were not in the natural centerline of the bar! So they have to be moved to that line but how? heh heh ....... now the fun begins: First thing, replace the spindle dead center with a combined drill / csk ( mine is a #6 mounted directly into a salvaged 3MT drill shank) then move the faceplate dog to the tailstock end but left loose for now. Then a steady rest was mounted close to the faceplate with a DI on it reading at 12 o'clock position. A wood v-block was placed near the tailstock for convenience. Another DTI w/mag base was set on the rear apron for test measurements along the bar. The bar was then set in place, run up on the center drill with the rear on the tailstock center. The bar was turned watching the DI's and figuring where are the errors. The high spot was set at 12 o'clock and the dog set at the tailstock end to stop rotation . At the steady rest the rollers at 4 and 8 were brought in contact then backed off ever so slightly. The roller at 12 was then brought in contact and the DI zeroed. With the gearbox in lowest gear the spindle was started and the top roller turned down hard while watching the drill cut and the DI reading changing. It didn't take a lot of pressure to do this and as soon as the required distance was reached the tailstock was nudged ahead to clean up the hole back to round. Worked pretty good actually and set me to gloating about it. The bar can stay in place and readings can be taken to assess the situation. The bar can be swapped end for end to take care of anomalies at that end if needed. I gotta admit I spent a lot of time playing with this but was worth it! Here I am, 60 years old and still learning a fun hobby! Hope you youngsters out there learned something today too, eih? Phil Kangas

You take the high road ... your setup was more of a milling function , if you think about it . Worked , and that's what matters . And now I have gained the benefit of a different perspective . That's what I like about this NG , you get a lot of different points of view .

My favorite hole moving tool is a block of metal (steel preferred, depends on what you have and the material you're moving the hole in) and a gun barrel drill bit. Drill the hole in the guide block and attach that to your material. It's essentially a drill bushing. A gun barrel drill (IIRC, it's been awhile) only cuts on the face, so will cut without wanting to pull off center too much.

I guess size does matter...

I've tried that in a mill with a #2 (Keo, I think) and broke the tip off in the hole.

jw