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Thread: Accurate drilling - received wisdom

  1. #11

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    I have been reading the last several threads on accurately drilling some holes and to get them to match ie like a flange to an assembly.

    Here is my approach. Part is set up in mill which has a DRO. The reference surface is indicated eg the center of a flange. Holes are indicated using x y. Holes are spot drilled, center drilled, and if small just drilled as long as starting hole is larger than chisel point. This is repeated for each part and then assembled.

    Two recent examples, first was a model crankcase bottom that had 16 - 2 56 holes tapped relative to a reference point. The bottom plate was set up in the mill and reference point found. 16 clearance and countersunk holes were drilled using above method. All screws dropped in just fine. The standard clearance hole was used.

    The second example involved three parts for a sterling engine. They were the cooling fins, the displacer cylinder, and the main frame. The displacer cylinder is about 1.5 long with a flange and a, .400 hole bored in it. The Displacer cylinder was set up in the mill, the center located and 4, 0-80 #52 clearance holes drilled. The main frame was bored so the reference was already present and those 0-80 holes drilled. The cooling fins were machined and a hole bored. It was set up in the mill and the center found. 4 blind 0-80 holes were tapped to .125. The three parts were then assembled and the 0-80 screws went in just fine.

    I have been making models for a long time and find the above to be very successful.

    By the way the second example was completely machined by my 17 year old granddaughter. The only assistance was what material bin to use and where was some of the tooling she needed. She has been making stuff since she was 8 years old. Her sister started when she was 10, and they are both making the same engine. The older one cranked out the same parts last week, same result.


    I tried posting some pictures here but not sure of how to do is right, maybe they came out.

    Bob






  2. #12
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    Quote Originally Posted by Highpower View Post
    Amazon reviews are chock full of complaints from people that have received phony merchandise that is "shipped from and sold by Amazon LLC."
    Yeah, I've seen some of those. The Mitutoyo Digital Caliper page has quite a few. Don't think I have ever seen any for Starrett's better tools though. Starrett's page says they are still made in the US, I figured they may have started making them in China now. The rest of it is fine, but the burr and plain packaging were unusual. The little brown envelope looks like it's sealed with the usual Starrett tape.


    Quote Originally Posted by Forrest Addy View Post
    I can't believe I sucked my self into defending a trivial detail like the proper way to sharpening prick and center punches but everything counts - to a point.
    No need to defend yourself, I believe you. My comment was about Starrett not getting it right.

  3. #13
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    What are folk's preferred methods/tricks for grinding a good point at a specific angle with just a bench grinder with decent rests?

  4. #14
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    I indicate work x,y 0 on the DRO, then move to the X,Y coordinates for the hole location. Often times will use a 90 deg center drill to start.
    I have found that prick punching, etc to be a fools errand. Once you go DRO, theres only moving forward to CNC.

  5. #15
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    Quote Originally Posted by RB211 View Post
    I have found that prick punching, etc to be a fools errand. Once you go DRO, there' only moving forward to CNC.
    a fools errand? You musn't be doing it properly - whats going that its not working for you? I have a newall dro and large(ish) vmc but there are many times that manual layout and punches on the drill press are a lot faster. Same with transfer punches & drill press (done the same way, but a mark from transfer punch instead of scribed lines) heck, a lot of time (like yesterday, making a small bracket) you don't even lay out - eyeball location, punch and drill.

    The trick is to pick the right tools and approach for the job at hand and understand the accuracy capabilities and strengths/weaknesses of each. The more you're capable of, the better able you will be to select the right one.
    Last edited by Mcgyver; 05-25-2017 at 03:27 PM.
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  6. #16
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    Quote Originally Posted by Mcgyver View Post
    a fools errand? You musn't be doing it properly - whats going that its not working for you? I have a newall dro and large(ish) vmc but there are many times that manual layout and punches on the drill press are a lot faster. Same with transfer punches & drill press (done the same way, but a mark from transfer punch instead of scribed lines) heck, a lot of time (like yesterday, making a small bracket) you don't even lay out - eyeball location, punch and drill.

    The trick is to pick the right tools and approach for the job at hand and understand the accuracy capabilities and strengths/weaknesses of each. The more you're capable of, the better able you will be to select the right one.
    Everything I do requires locations within .003" Model making, and small parts have no room for error. I never claimed it was faster, but I insinuated that it is indeed more accurate.
    I do not do this professionally, thank god, I do not like to work fast. I have to admire you guys that can do this stuff accurately AND quickly.

  7. #17
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    Quote Originally Posted by RB211 View Post
    Everything I do requires locations within .003" Model making, and small parts have no room for error. I never claimed it was faster, but I insinuated that it is indeed more accurate.
    I do not do this professionally, thank god, I do not like to work fast. I have to admire you guys that can do this stuff accurately AND quickly.
    I probably can't work to a thou any faster than you can and when making models agree x/y layout (dial or dro) or CNC is great....but if the last job I did was dozens of lag bolt holes 1.5" angle iron welded shelf brackets....then read punch and drill and is a fools errand...I kind of go something is missing here. But we're on the same page, it came across as universal indictment but I get now you meant in the context of your work.

    On speed, I'm not racing a hourly clock either ....thank goodness is right.....just the big clock. Its not pressure that takes the fun away, just I'd rather get more done in a block of time. So....I don't want to use processes that strive for more accuracy than the the job requires
    Last edited by Mcgyver; 05-25-2017 at 04:32 PM.
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  8. #18
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    Select a method suited for the to be accomplished (machining, iron work, carpentry, plumbing, etc,) no more - no less. IOW make the punishment fit the crime...

    here's a musical lesson:

    https://www.youtube.com/watch?v=Ip6czeTuNEU

    There is no one way to do anything, some are ingenious, some preferred, some expedient, some wasteful, lame, or silly. Searing declarations of the Right Way tempts Fate if not heralding a Darwinian loss of face from the emergence of a superior, simpler, lower cost alternative as from the mouth of a child.
    Last edited by Forrest Addy; 05-25-2017 at 08:06 PM.

  9. #19
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    Quote Originally Posted by CalM View Post
    If the subject is drilling on the lathe, Always bore the first 5 mm depth if the hole location is important.
    I've never heard this before. Is it to compensate for tailstock alignment errors?

    David...

  10. #20
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    Quote Originally Posted by boslab View Post
    Same applies to tungsten electrodes.
    There's a further way, use a jig and drill bush, fairly accurate, one jig can have several bushes, you set the jig relative to the datum edges of the job, aka jig drilling
    Mark
    Agreed, but you still have to make the jig

    I did mention that as a way of making parts that will line up with each other.

    Mostly, this is an experiment to see if I can actually communicate something clearly and concisely... without writing my typical 1000 word essay. It's very hard for me to stop writing once I get going

    David...

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