Drilling into end of bar

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schwabw
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Drilling into end of bar

Post by schwabw »

Hello all,

I need to drill into the end of a "long" bar. The part will be roughly 3" long and 0.5" square in cross section, and the goal is to drill (for tapping) holes into the center line from both ends.

For some time, my only option was to find a way to stand such a things on end and drill them on my mill. Now I see an opportunity to throw it on my lathe for that step.

The only way I see to do it is to use my 4-jaw chuck and center the bar. The problem is that I do not know how to center it :oops: The answer will probably have something to do with an indicator and rotating the spindle 180 degrees? How would one do that?

Bill
Greg B
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Post by Greg B »

First get the part close by eye. Lean a scale against the part with your indicator touching the scale at part center line. Slowly rotate chuck by hand. The corners of the part will push the scale out as you rotate. Adjust chuck to get the part true. Using the scale will stop the corners of the part from banging the indicator tip.
Or depending on just how accurate you need to be, scribe lines on the center of part and line it up with a center held in the tailstock.
I hope this made sense.
GDB
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Harold_V
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Post by Harold_V »

If you have more than a couple to do, you're likely to enjoy faster and better success using a mill. The problem with using a 4 jaw is that it is slow to align, and it can yield parts that have a bit of lean to them.

There was a heated exchange on that very subject just last week. Chucks do not always have parallel jaws, which can complicate aligning parts as may be desired or required.

Here's a slick way to do it, Bill, and it's much faster. Using an angle plate, clamp a parallel to the plate, using the shortest leg of the angle plate that will serve the purpose. Square the parallel with a precision square (off the table), and clamp it securely, using a pair of clamps to avoid rotation.

You can now place your piece against the angle plate and parallel for instant alignment, holding it with a C clamp, or even a finger clamp. Once you locate your first part and lock the table and saddle, all parts will mount easily. The only fly in the ointment is if the material varies a great deal.

You can also make a setup using a V block on end. Clamp it in the vise, then use a soft piece (aluminum) to reach the piece that needs to be held. The clamp will permanently locate the V block, and the jaw will function to hold the part. Same story. Once you locate center, parts are quickly exchanged.

As a side note, if you'd rather use your lathe, duplicate the angle plate setup using a face plate. Try to balance the setup so you can run at a respectable speed.

Hope this helps.

Harold
Jay, Idaho
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Post by Jay, Idaho »

I must be missing something or it is too early in the a.m.
Wouldn't a 1/2" square collet be a simple solution?

Jay, Idaho
CarlD
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Post by CarlD »

For drilling and tapping the end of square stock I usually use a large V block on it's side clamped to the mill table to one side. Clamp the stock in the V then move the head to position it over the stock which I have scribed the center on the end and locate the center point with a wiggler and then drill and tap it. Be sure to have the bar away from the side of the knee so you can use the hand wheels to center the work.

Sometimes I do round stock the same way because it's easier to get it straight in the mill. If the stock is short enough to clear the ground it works great.

As Harold said, the work may be centered in the chuck but running out at the free end sticking out the back of the spindle.
It's only ink and paper.
pkastagehand
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Another possible option is...

Post by pkastagehand »

something I read about somewhere. Not sure if I have it exactly right but something about a tube in the 3 jaw chuck that is slit down the side. The square stock fits in, the jaw is tightened, the tube compresses and it grabs the corners of the square stock. Make the bushing/tube in the chuck and leave under sized, then slit, then cleanup so that the part fits only when the chuck is released a bit but not enough for the tube to fall out. Put the stock in and clamp it tight. Sort of a poor man's collet. Accuracy somewhat limited and if stock varies it might be a problem but useful for many applications.

Paul
kapullen
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Post by kapullen »

schwabw,

If you have a quick change tool holder that will hold a 1/2 inch lathe
bit you're all set.

Chuck a piece of half inch round in the three jaw chuck. clamp a qc block lightly on the round bar (bar well seated in the block) with the base block loose.

Lock the QC base block, and clamp it down on the compound.

Now you can zero and lock your slides for referance, remove the round bar from the chuck, and qc block.

Install your jacobs headstock chuck in the spindle, your square bars in the qc block and drill away.

It's best to have the compound square with the ways, so any movement
won't spoil the setup.

Kap
Fadal Turn, Fadal Vmc 15, Prototrak 16 x 30 Cnc Lathe, Pratt and Whitney 16 x 54 lathe, Pratt and Whitney Vertical Shaper, G & E 16" Shaper, B & O Electric turret lathe, 36" Doall band saw,
Enco B.P. Clone, Bridgeport CNC Mill, Delta 12" Surface Grinder.
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Frank Ford
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Post by Frank Ford »

Kap -

I'm going to remember THAT one - it's an elegant solution, for sure!
Cheers,

Frank Ford
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Harold_V
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Post by Harold_V »

Jay, Idaho wrote:I must be missing something or it is too early in the a.m.
Wouldn't a 1/2" square collet be a simple solution?
(Sheepishly) well, yeah! :oops:

Might not be worth a damn for hot rolled material, though. A two jaw chuck would work perfectly well for both cold or hot rolled stock. Not many have them, However.

Harold
CarlD
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Post by CarlD »

With the collet on a three foot bar you will still have wobble at the free end to deal with. You can make a support that fits in the back end of the spindle to center the stock but not many do. I have stuffed rags in the spindle to somewhat center the stock to keep it from banging around.

It's still faster to do it with a V block on the mill, unless of course, you don't have a mill and V block.
It's only ink and paper.
Jay, Idaho
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Joined: Wed Jul 26, 2006 3:03 pm

Post by Jay, Idaho »

Carl,

The original poster stated that the part was 3" long, not 3'.

It is good to caution folks that the "free" end can really cause problems. I won't allow very much to stick out the left end of a lathe spindle unless it is captured in a tube on a stand or something that prevents it from whipping and possibly causing an injury to someone.

Jay, Idaho
CarlD
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Post by CarlD »

Opps, missed that, when he first stated he had to drill a hole in the end of a long bar I just totally ignored the " behind the 3. :oops:
It's only ink and paper.
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