Drilling straight centered holes in a rod without a lathe
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  1. #1
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    Lightbulb Drilling straight centered holes in a rod without a lathe

    Hello. I have some Ø0.6”, 4.5” long steel bars that need to be drilled with straight and centered holes. I don’t have a lathe to do this with, so I was planning on using my drill press to get the job done.

    So, I wounder what is the best method of doing this? I saw some different methods on youtube on how it could be done, here’s an examples of how to make a centered pilot hole: YouTube

    And this guy is using the drill press as a lathe, but my drill press chuck is to small to do this YouTube

    So my initially though was to go with the first method to create a centered and straight pilot hole, combined with securing the rod by using another chuck (like the second example video secured the drill bit) making the rod aligned and the hole straight. Since I’m using a chuck for straight alignment, maybe a knockout punch to guide the drillbit into the center is enough?

    What’s your thoughts?

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    1) Get a lathe
    2) Pay someone with a lathe to do it
    3) Accept very poor drill press results

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    How straight and how centered?

    A proper jig holding as close to the top of the part as is practical, and an accurate setup should work.

    Can be as simple as a right angle plate bolted to the table, a plate bolted to the angle plate][to create a corner] clamp part in place

    getting it set up will be a pita

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    Buy a bigger chuck for your drill press.

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    Make a wooden jig that holds the rod firmly. Clamp 2 pieces of hardwood together, square up all 4 sides.
    Make it wide enough so it sits on the vice bottom and as high as the rod. Tighten the vice and check that the rod is square to the jaws. Lay out the center, use a spotting drill and bore the hole about 17/32. Clamp the rod between the wood, the hole is about 1/16" smaller than the rod so it should clamp tight. Check with an engineers square that the rod is square to the jaws. Add a clamp or two to the wooden portion above the jaws. After the center is marked I use a "pin" in the chuck jaws to locate the center. Switch to a spotting drill. Depending on the bore you may need to bore a pilot drill first. I would bore from both sides as I have reservations that your machine drills will bore straight thru that deep.
    mike

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    Another method would be to use a v-block.

    You could chuck the largest diameter pin your drill chuck will allow (assume 1/2” diameter). Subtract the diameter of the pin from your rod diameter and divide by two. Place two shims (.050” thick if you use a 1/2” diameter pin) on each face of the v-block. Next hold the v-block with the shims up against the pin held in the drill chuck and clamp the v-block to the table. Now the v-block is positioned so that when the 0.60” diameter rod is held in place it will be on center.

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    No way, pay a machine shop...Phil

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    check your eyecrometers, .6" would be a bastard size.
    I second the v-block clamping, only without shims. put v in vice and lock it down dead center to drill bit, dead parallel. clamp block in v, drill, peck, drill. flip and repeat. then you can ream final bore. don't move vice or v once you have it set up. Using a drill chuck to hold bar is inviting drift, a collet would be better-still the bar is going to flex in a triangle pattern. the block should help support it.

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    Depends how straight and centered is good for you but im with Phil, take it to a shop if you want something decent. Remember you cant make chicken salad from chicken $hit but you can make chicken $hit salad.

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    You better have a darn good drill press and a perfectly sharpened drill bit to do this. 4-1/2” is a long way to go. Be prepared to scrap a few pieces. Simple job for a lathe, but the average cheapo drill press is going to make a difficult and frustrating ordeal out of it.

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    Did some similar as a desperation move: I mounted a small 1/2" diameter ACME screw in a battery drill mounted on a plywood stand with it's chuck aimed upwards at the drill press chuck and had the screw turned by the battery drill in the opposing direction to the drill, while the drill press drilled the hole. It functioned like a jury rigged gun drill and gave a very straight and true hole only an inch deep.

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    1. Mount a vise to your drill press table sand then rotate the table by 90 degrees to the drill chuck travel (Z).
    2. Put you stock in the vise and hold a indicator in the drill chuck. Rotate the indicator around the stock.
    Swing the table for X alignment. Tap in the vise for Y alignment. Extend indicator down the length of stock to check Z alignment.
    3. Now you can drill whatever holes you want with repeatable results.

    The alignment will be a iterative process with successive tap movements being smaller. Sounds like a lot of work but it won't be that bad.

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    Hard to predict what your outcome will be - depends a lot on factors you haven't specified (what "steel"? what dia hole?, what degree of "straight" are you after?, etc.). I wouldn't be too optimistic unless your tolerances are really loose. With the right approach, drill-start on center is the lesser problem, drilling straight is the greater. Drilling from both ends is good, but carries no guarantees of meeting in the middle. Any chance of making do with commercial tube? Lots of sources, such as
    McMaster-Carr
    If the ID is suitable, 15 mm OD tubing is only a quarter of a mm smaller than your 0.6".

    -Marty-

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    What's my thought?

    Even a cheap POS 7 x 10 Chinese lathe will do a better job than even a high quality drill press.

    Sad fact of life but when ambitions exceed capabilities the choices are pay someone else to do it or pay to expand your capabilities.

    PS: Inexpensive cutoffs of tubing etc are often found on ebay. It would be easier to enlarge an existing bore than to center drill that length without a lathe.

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    Drilling a 0.050 inch diameter hole over that distance will be really tough with a drill press.

    Er, that *is* the size hole you need, right?

    And, you need it to be within 0.001 inch when it exits the workpiece, right?

    Or was there some other hole size and tolerance you wanted, maybe share those.

  22. #16
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    Please refer to the Op's prior threads.

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    A tough job even with a lathe. For example let a part hang way out toward the tail stock and see all the wobble at the out end of the part. Many fair lathes will wobble the part .010 or more. How close do you need both ends to near center. For very exact one could 4 jaw the part center at the out end indicated near the out end to center drill a spot. . Then move the out end with the center drill to be held in the steady..next 4jaw and true the last (rear) end with the out end in the steady. Then drill from the out end, you might get .001 this way.

    Standing in a drill press lucky to get .025 or worse.
    Yes having a Pratt or the like one might get less that .025 with a careful set-up.

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    A few more details I forgot to mention. The size of the holes I need to drill are 10-11mm in diameter and the length of the holes are 4.3”, it’s bottom holes so I can’t drill from both sides.

  26. #19
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    Being a blind hole certainly helps lol

    This thread has a sort of McGuyver air to it....I somehow feel a hairpin, Q-Tip, or duct tape might help.

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    There is no way to do a decent job as the OP described it.

    Endless people here could rig temporary powered spin-jigs on the drill press to make decent holes.

    A lathe is cheaper than a makeshift kludge, mostly.
    For the part, any spare decent lathe would work.


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