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Thread: Drill, Bore, Ream...how to drill a hole

  1. #1
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    Default Drill, Bore, Ream...how to drill a hole

    Greetings:
    I'm looking for a tutorial or similar information on drilling accurate holes.
    Specifically, with a final hole size in mind, how to select the correct size of Drill, Bore, and Reamer.
    Thanks.

  2. #2
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    There's probably a few generalities that would more or less cover it. One is that the pilot drill size should be about the same diameter as the web diameter on the following drill bit, or maybe a tad larger. Obviously the final size of the drilled hole has to be larger than the effective diameter of the boring tool. Then for reaming you want to only be taking out a few thou.

    One of my most prized books had been Technology of Machine Tools, which is a high school textbook. It pretty much covers all those questions. Maybe check with a school and see if they have even an obsolete version of something similar. My version is dated 1976. Quite a few charts in it too.
    I seldom do anything within the scope of logical reason and calculated cost/benefit, etc- I'm following my passion-

  3. #3
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    Pilot drill--not too large, drill 1/64 undersize and ream. If you need anything better than that you need to
    use a boring tool...
    Keith
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    Just one project too many--that's what finally got him...

  4. #4
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    Keith:
    Please clarify what you mean. Remember: I'm BRAINDEAD

    I'm looking for guidance on drilling the most accurate holes I can get.

    Thanks.

  5. #5
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    When you say 'accurate', do you mean just roundness and diameter or are you including accuracy in location? Drilling is, under normal circumstances (using a common twist drill), not accurate in either. Reaming can give accurate hole size, but won't correct location. Like Keith said, boring yields the best results in all ways, but is more time-consuming.

    So, the biggest factors affecting common drilling are proper drill grind, proper starting (center-punch, spot drill etc.) proper holding of the work and a good drill press (a milling machine is even better).
    Last edited by chipmaker4130; 09-13-2019 at 11:21 PM.

  6. #6
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    Braindead... There are several measures of "accuracy" when it comes to holes. Hole placement is one. Perfectly vertical is often needed. Taper can be a problem. Roundness. And lastly, size. LKiethR gave you the right way to get a hole that is not tapered and is the correct size.

    You asked for "guidance on drilling the most accurate holes I can get". That depends on the tools you have or are willing to get. A jig borer (very heavy equipment) is often thought of as the best way to make a hole in the right spot and right angle.

    Please give us a quick description of either a) What you are trying to do or b) how accurate you need to be in one or more of the above categories. Seriously, someone will then be able to tell you what you asked for or guide you to a youtube video that already has that information.

    Dan
    At the end of the project, there is a profound difference between spare parts and extra parts.

  7. #7
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    And the size of the hole is another important factor. A 1/4" hole is one thing. A 3" hole is quite another. And then, there would be sizes like 1/16", 1/64", and smaller. Somewhere around 1/2" or so, the question of drill and reamer vs. boring bar comes into play. Some may even have boring bars that can fit in even smaller holes.

    Oh, and what are you drilling these holes in?

    One job where I was very careful about the position and location of a series of holes was for an indexing back plate for a lathe chuck. Sixty holes in all and I wanted them all accurately sized and located as closely as possible to 6 degrees apart. I used about five operations to make them: a center drill to establish the position, a small diameter drill to drill the center to depth, a tap drill for some threads at the bottom, a NEW drill that was a about ten thousandths smaller than the final size, and finally an exact size reamer (around 3/16" if I recall correctly). Oh, and somewhere in there a countersink to debur the edge: I think that was just before the final reaming. That actually made it six operations, not five. I had to index that plate to intervals of six degrees six times: 360 individual movements. Can you say tedious work? Needless to say, I gave the sequence a lot of consideration before doing it. But other jobs could be different. For one thing, I used a center drill as the first step because the final diameter was so small. That way, the center drill (1/16" or 3/32" or so) was larger than the hole created by the small center part of the center drill while still being significantly smaller than the drill that preceded the reamer. For a larger final hole, I may have chosen a spotting drill for the first operation instead. There is no one, single procedure for every job. Even the decision to only change tools after all 60 holes were operated upon with each tool was made with carefull thought. In some circumstances I may have located each position only once and changed from one tool to the next while at that location. That would involve more tool changes, but may have produced better location accuracy.

    Or not. each job is different.



    Quote Originally Posted by danlb View Post
    Braindead... There are several measures of "accuracy" when it comes to holes. Hole placement is one. Perfectly vertical is often needed. Taper can be a problem. Roundness. And lastly, size. LKiethR gave you the right way to get a hole that is not tapered and is the correct size.

    You asked for "guidance on drilling the most accurate holes I can get". That depends on the tools you have or are willing to get. A jig borer (very heavy equipment) is often thought of as the best way to make a hole in the right spot and right angle.

    Please give us a quick description of either a) What you are trying to do or b) how accurate you need to be in one or more of the above categories. Seriously, someone will then be able to tell you what you asked for or guide you to a youtube video that already has that information.

    Dan
    Last edited by Paul Alciatore; 09-14-2019 at 01:41 AM.
    Paul A.

    Make it fit.
    You can't win and there is a penalty for trying!

  8. #8
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    Quote Originally Posted by darryl View Post
    One of my most prized books had been Technology of Machine Tools, which is a high school textbook. It pretty much covers all those questions. Maybe check with a school and see if they have even an obsolete version of something similar. My version is dated 1976. Quite a few charts in it too.
    I just bought a copy of that on eBay. I should have read the fine print carefully. They had a picture of an old edition, but in a bunch of other stuff the eBay ad said "picture doesn't show the edition you will get". I got a latest version from India. It's pretty thin paper, and it has all sorts of stuff on JIT, Kaizen manufacturing, CNC, computers, etc...

    It doesn't even have "Shaper" in the index, and the information on mill bits was so short I could have written it.

  9. #9
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    I can drill,ream and countersink with my home built contraption,it's real handy to use.

  10. #10
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    Quote Originally Posted by Tundra Twin Track View Post
    I can drill,ream and countersink with my home built contraption,it's real handy to use.
    A bunch of gangsters .Tundra thats a thing of beauty.Was this for a specific task that you repetitively do.?

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