Page 3 of 3 FirstFirst 123
Results 21 to 30 of 30

Thread: Accurate drilling - received wisdom

  1. #21
    Join Date
    Oct 2002
    Location
    Bremerton Washington
    Posts
    5,731

    Default

    Quote Originally Posted by fixerdave View Post
    I've never heard this before. Is it to compensate for tailstock alignment errors?

    David...
    Nope, it's to give the drill or reamer the most concentric start possible.

  2. #22
    Join Date
    Mar 2011
    Location
    Troy, Mi
    Posts
    91

    Default

    It is looking like I'm the only one that does not center punch any thing to be drilled on a no-dro mill. I locate the scribe line cross section with a 20 degree sharp pointed rod held in the drill chuck. Then start the normal drilling process. It seems to me to be easier and more accurate than to locate the in the center of a punch crater which may or may not be accurately placed to begin with.

    Come to think about it I don't use punch marks on the drill press since I added an x-y mounted vice there.

  3. #23
    Join Date
    Sep 2013
    Posts
    1,046

    Default Good enough is good enough, but take a look at the drill point

    Quote Originally Posted by rickyb View Post
    It is looking like I'm the only one that does not center punch any thing to be drilled on a no-dro mill. I locate the scribe line cross section with a 20 degree sharp pointed rod held in the drill chuck. Then start the normal drilling process. It seems to me to be easier and more accurate than to locate the in the center of a punch crater which may or may not be accurately placed to begin with.

    Come to think about it I don't use punch marks on the drill press since I added an x-y mounted vice there.
    Then take a look at the "spot" the drill point leaves when you just touch down and go into steel about .005"
    Have a look with magnification.

    There are good reasons why wigglers and center punch methods were developed. Twist drills are much too flexible to be relied on to hold position.

    Drill a piece of hot rolled with a 3/32 jobber drill. With no center punch divot to follow, the drill tip will walk around like a drunk. '=))

  4. #24
    Join Date
    Mar 2011
    Location
    Troy, Mi
    Posts
    91

    Default

    Quote Originally Posted by CalM View Post
    Then take a look at the "spot" the drill point leaves when you just touch down and go into steel about .005"
    Have a look with magnification.

    There are good reasons why wigglers and center punch methods were developed. Twist drills are much too flexible to be relied on to hold position.

    Drill a piece of hot rolled with a 3/32 jobber drill. With no center punch divot to follow, the drill tip will walk around like a drunk. '=))
    I didn't expand on it, but to me the "normal drilling process" is to first center drill a pilot.

  5. #25
    Join Date
    Oct 2002
    Location
    Bremerton Washington
    Posts
    5,731

    Default

    Sounds like some people want to converge on a single "approved" way of drilling holes; no deviation allowed. I thought about the ways and requirements I use for drilling holes and gave up at a dozen from hanging pictures to roughing holes undersized for later boring to precision size and location.

    An as-drilled hole is seldom a precision cylinder. Its size is inevitably 0.003" to 0.010" larger then the drill, the finish is a usually a bit rough and seldom very round, and it may be lobed, bell-mouthed, rainbowed, or mis-located because of walk before actual penetration. An as-drilled may be used for clearance on bolts, as an initial step for reaming or boring, tapped or bored for threaded fasteners, passage for liquid, to reduce weight, waste out excess material, etc. And that's just in general machine shop applications

    Aint no one rule for drilling from layout by hand or machine any more than one size drilled hole fits all. I like to think I pick the simplest, handiest, and most efficient way to make a hole that suits the job and the available equipment. If you have a preferred way to drill holes, well and good but don't sneer at a fellow who uses a slightly different method - or many. If it works for the other guy, well and good. If the guy is a noob or not so experienced and off on a tangent for some reason, a polite suggestion is plenty.

    However I'm an old fart of 75 with long and diversified experience in most forms of metalworking so naturally I can throw my weight around. When I do it, i'm an adorable, delightful grouch. If you guys try it, people think you're a PITA.
    Last edited by Forrest Addy; 05-28-2017 at 08:09 AM.

  6. #26
    Join Date
    Oct 2006
    Location
    Victoria BC, Canada
    Posts
    846

    Default

    Quote Originally Posted by Forrest Addy View Post
    Sounds like some people want to converge on a single "approved" way of drilling holes...
    Actually, my goal was to differentiate between 2 different approaches, while not saying either was better nor that they were the only ways.

    I suspect I'm not alone in doing a reasonably precise layout, getting a nice center punched mark, then cramming a center drill into it by eyeball, locking everything down to drill, and then wondering why the stupid hole isn't in the place I wanted it. I was stupidly mixing approaches, taking a little from both ways, and not getting the results I wanted. If I had left it at a fine punch mark and then used that with a measuring tool, like a center finder, before locking everything down for the center drill (the index method) OR if I had used a jobber-length drill in that center mark and let everything float, the hole would have ended up closer to where I wanted it. Just an "aHA!" moment that I'd figure I'd write down in an coherent way. That, and a few other tips I've come across in reading.

    David...

    Edit: now posted: Drilling Holes in all the Right Places
    Last edited by fixerdave; 05-27-2017 at 09:46 PM.

  7. #27
    Join Date
    Apr 2017
    Location
    Poway CA
    Posts
    82

    Default

    Here is to old farts!

    I have not obtained such august status yet. But I can see it from where I am standing.

    I began my engineering career in a company that had a shop filled with experienced machinists and tool and die makers. Most were close to retirement in the early 80's. I learned so much from them. I still remember Max Pfluger saying with his thick German accent, "The hole is not complete until it has bin deburrrrrrrrrred" Last step is always a counter sink or a deburring tool depending on hole diameter.

  8. #28
    Join Date
    Oct 2006
    Location
    Victoria BC, Canada
    Posts
    846

    Default

    Quote Originally Posted by Erich View Post
    ..."The hole is not complete until it has bin deburrrrrrrrrred"
    THANKS...

    I was drilling some holes today... that just kept running through my head, over and over and over and over and over, in my best German accent, which I must admit probably sounds more like Swedish. Never was any good at fake German, even in my head.

    I wonder how long that's going to last??

    David...

  9. #29
    Join Date
    Sep 2009
    Location
    Sacramento, CA
    Posts
    1,167

    Default

    I do it old school. Layout on surface plate with a height gage, prick punch, then punch. Inspect punch marks with a magnifier for accuracy, adjust if needed. Then my personal touch is to go over it with a flat file to remove the ridges. My thought there is that if I have to move a punch mark the ridges might be uneven and cause the drill to wander, especially in soft material.

  10. #30
    Join Date
    Feb 2012
    Location
    Metcalfe, Ontario, Canada
    Posts
    1,025

    Default

    I do it the old school way too. Then, when I try to bolt the carefully laid out and drilled parts together, the bolts don't go. So I drill all the holes oversize.

    There, fixed!

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •