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Thread: accuracy drilling small holes

  1. #21
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    I think BC rider and Paul Al have shown what my problem is but the solution is a bit problematic. In the case of center punching many of these parts a small and round so it would be difficult if not impossible to do this, that is why I have used the coordinate method. The info on why a spot/center drill dosen't work some times is helpful. Maybe I will just have to start the holes with an end mill (they seem to locate properly) and finish with the drill, at least for those that are to deep for an end mill. Thanks.
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  2. #22
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    I find a ball nose end mill works very well as a spot drill. I have ball nose end mills down to 1/32". They are available in sizes smaller than that.
    Last edited by Toolguy; 02-10-2019 at 11:08 AM.

  3. #23
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    As several of us mentioned, center punch....

    Center punch makes a cone of a good size for the follow drill, if the drill is small. Stoning off the raised area is actually a decent idea for small drills, so they do not "catch in" the raised stuff and either get pulled off center, or break (if quite small).

    BUT, there are center punches and then there are center punches. Some of them still are not pointy, and make a mark that is not a good cone. Plus, punches wear like other tools. I like to have a standard punch, and also one sharpened to a steeper and sharper point, often called in the UK, a "prick punch", because it makes a smaller mark, not like a big and somewhat clumsy punch can. The thinner sharper punch can find the intersection of scribed lines... that is how sharp I mean.

    Now, I do not know why you think a punch is not possible to use. Maybe you do not want to ht the part with a big punch, or the like. Maybe NO punch is good.

    So, the jeweler's flat drill is one possible. Or just make your own.

    Get a small spade drill and stone the end thinner than the tip of the drill you want to use, which would be less work than making a spade drill.

    Now use that to do your spot drilling. If you made it small enough you will get a cone that your small drill will land in nicely.

    The good part about a spot drill that works, iis that you are going to be on-center with the follow drill if you change out the spot drill and put in the follow drill without moving the work.
    Last edited by J Tiers; 02-09-2019 at 09:07 PM.
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  4. #24
    Join Date
    Oct 2002
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    If the drill press spindle upper end can be accessed, put a 60 degree sharpened center punch in and locate the hole. Then LIGHTLY tap the upper end of the spindle, making just enough of a mark to help in locating a larger center punch to deepen the mark before drilling. The second center punch could be used with a guide to keep the punch vertical.

    If the center punch is not perpindicular to the workpiece, it will move from location as it is punched. Using a guide can help maintain location.

  5. #25
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    Jan 2014
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    Edmonton Alberta
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    Their are drill bushes for this thing down to 0.2 mm,I assume their are drill bits that small.I don't think my eyes would see them.

  6. #26
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    Using drill bushings would be awesome. But for one or two holes and not knowing the sizes needed that could end up being a LOT of bushings. And they still need to be placed in some manner of holder which is then located over the work piece. That seems like more of a production situation.

    A lot of the suggestions seem to be aimed at far larger hole sizes than what the OP asked about in the opening post. The focus here is supposed to be small drills of around 1/16 and smaller. Things like drilling with an end mill and spotting with a ball nose mill. Great ideas for larger size options but not so great for sub 1/16".

  7. #27
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    If you're using coordinates to find the 'spot', then why not mount a center and use just a bit of downfeed to place the mark. You can get a decent sized mark in most materials with a reasonably light pressure. For a small hole like that it's likely to be enough.

    For a 1/16 hole, I would make my own center from say 1/8 inch drill rod or music wire. Grinding the point well centered is then the challenge. This isn't that difficult though. You would probably make it about the length of the drill bit you're going to use so you won't need to change any settings- just swap out the center for the drill bit and continue on to drilling.

    Another method which has some merit is to simply drill a hole in some scrap- perhaps 1/8 thick, making sure that when it's started, you allow the drill bit to bring the scrap piece to center before you drill all the way through. Then once you have the coordinates set for the hole location, you slip this jig up onto the drill bit, bring the bit down to barely touch, or not quite touch, then allow the scrap to settle onto the piece you want to drill. The drill bit locates the scrap piece, and you then hold it in place with your fingers while the drill bit starts its location. This has the potential to prevent wander.
    I seldom do anything within the scope of logical reason and calculated cost/benefit, etc- I'm following my passion-

  8. #28
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    Apr 2017
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    Just in wood but this improvised drill guide improved things a lot where it wasnít practical to use a short carbide bit, or spot or center punch first.


  9. #29
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    I would go for the carbide pcb drills, the shortest available, but with a larger shank. Just start the hole with them and then change to regular drills. Spotting drills tend to make a finer starting indent than centre drills which are intended for a different purpose entirely. With the pcb drills, you may not need anything else beforehand. Check runout of the chuck, even 0.003" would be too much for the sizes of drill you are using.

  10. #30

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    To add my 2c, from my experience in drilling small holes is slightly different than the generally held approaches. The small holes I drill are typically between 1/64 (.0156) and 1/32 (.031). Usually on small gas engines. The first thing I learned was runout is the bane of small accurate holes. For example, when drilling a .020 hole and if you have a chuck with .003 runout, you have effectively a 15% runout relative to hole size. Not going to get a round, straight hole. That is the equivalent of .075 runout on a .5 hole. The .5 bit would look like it was shaking all over the place.
    Get rid of runout and you at least have a start. I have a special chuck that can be made to run at 0.00 runout, ie none. It is special Dumore chuck. So strive to get the runnout as good as you can. Most of the time I use a good small chuck and I am fine with the larger holes above .025.

    Next I spot the hole with a center drill that has a point smaller than the diameter of the drill I am using. For a .020 hole I would use a 5/0 center drill with a point of .015. That way the bit is not just dropping in the hole it is hitting the tapered side. Even though the taper is not the same it seems to center very well. Most of the time I am dialing in the hole position from a reference with a DRO. If the hole has no reference edge, I have just spotted the cross marks. Usually in that kind of a setup being off by several thousands is not an issue.

    Next is what was told to me by a production engineer many years ago. When running a small drill at high RPMís you must have a method of controlling the feed rate based on the material being drilled. The concept is easy to understand if you have ever drilled stainless with even a 3/16 drill. If you do not feed it fast enough it work hardens the stainless and you destroy the bit. The point he made to me was I could not feed a #76 (.020) bit properly at high speed so donít bother.

    I drill the above size holes at about 100 Ė 200 rpm sometime a lot less. If you watch the cut with some degree of magnification you will see the chip forming. With practice you get a feel for the feed and you end up with real nice holes. Since I do not drill small holes enough to develop a touch, I just take my time on each occasion.

    I use the Dumore see pictures for about half the holes I drill, the rest are done on a Clausing 8530. The special chuck works like edge finder , you use your finger nail against the bit to center the magnetic holder and its base in the drill chuck.

    Bob




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