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accuracy drilling small holes

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  • Tundra Twin Track
    replied
    Originally posted by old mart View Post
    Most of the holes we drilled in bolt heads were 1/32", and most likely in all six corners. Sometimes the holes were drilled flat to flat, it depended on the drawing instructions, and all were deburred. Even twelve point heads were drilled, and nuts if they weren't castellated, or self locking. Large batches warrant the cost of jigs with quick replaceable bushes. Our driller was highly skilled in drilling and tapping, to get it right 99.99% of the time, you don't want just anyone.
    The guy must have been pretty talented and have soft hands to control something that small.

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  • old mart
    replied
    Most of the holes we drilled in bolt heads were 1/32", and most likely in all six corners. Sometimes the holes were drilled flat to flat, it depended on the drawing instructions, and all were deburred. Even twelve point heads were drilled, and nuts if they weren't castellated, or self locking. Large batches warrant the cost of jigs with quick replaceable bushes. Our driller was highly skilled in drilling and tapping, to get it right 99.99% of the time, you don't want just anyone.
    Last edited by old mart; 02-12-2019, 08:31 AM.

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  • BCRider
    replied
    Originally posted by MattiJ View Post
    Hard on the drill bit even with guide bushing, end mill works better.
    That could be. But where time is money and lots of them need to be done I'd bet that the jig in the drill press is both faster and allows the shop to put the less skilled guy to work so the mill can be doing other more demanding things that bring in more money.

    Back when I prepared the old motorcycle for track days and some club level racing (part of the "Rider" username) I had to safety wire a lot of key areas of the bike. I cross drilled between opposite flats just to avoid this nasty angled adjacent flat issue.

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  • Tundra Twin Track
    replied
    Originally posted by MattiJ View Post
    Hard on the drill bit even with guide bushing, end mill works better.
    I agree, a little tough on bits but can be done on simple drill press was surprised how easy it drilled just have to be gentle on the start.Drill bits are cheap and kinda of a consumable item around my shop especially the small ones.

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  • MattiJ
    replied
    Originally posted by old mart View Post
    One of the most difficult small hole drilling is for wire locking holes in bolt heads when they go through the corners. My old firm always used to jig drill them in custom bushed blocks on the manual drills despite having lots of NC mills.
    Hard on the drill bit even with guide bushing, end mill works better.

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  • Tundra Twin Track
    replied
    Originally posted by old mart View Post
    One of the most difficult small hole drilling is for wire locking holes in bolt heads when they go through the corners. My old firm always used to jig drill them in custom bushed blocks on the manual drills despite having lots of NC mills.
    Are you meaning like the bolt in pic on post#36 ?

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  • old mart
    replied
    One of the most difficult small hole drilling is for wire locking holes in bolt heads when they go through the corners. My old firm always used to jig drill them in custom bushed blocks on the manual drills despite having lots of NC mills.

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  • fixerdave
    replied
    I've read about but never needed to try this:

    If you want to cross-drill a rod, take an extra short chunk of it and drill the hole size desired in a lathe down through the center, being as accurate as you feel necessary. Then, clamp that section vertically in a vice over where you want the hole drilled in your rod... can't help but at least start in the right position, side to side anyway.

    Quick and easy for the one-offs that need to be right.

    Oh, being a jig, the drill should be long enough to flex so that it can follow rather than try to lead.

    That's the theory anyway.

    David...

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  • Tundra Twin Track
    replied
    Originally posted by BCRider View Post
    Your drill jig reminds me of a similar product that was showcased in a YT video. Sure enough I found it. Mr Pete222 showcasing the Heinrich Cross Hole Drill Jig.

    Not to try to compare mind you. But it IS an interesting idea. Could be a good home shop project. Proper hardened bushings aren't cheap though. And we'd need the same tools in a couple of sizes to let us cross drill from your 1/8" example up to something like 1/2 to 3/4".

    Yes the Heinrich Jig is pretty cool and is real cheap to purchase new compared to Reglus.I contacted Reglus in Switzerland to get a price on a Lettered&Numbers set.I just about $hit myself $65.00 for EACH DRILL BUSHING and nearly $4000.00 for Drill Jig with all the Bells&Whistles.

    This thing will do more than I will ever need(Thanks to past member JC Hannum for parting with it) but is very versatile.It will take round stock up to 1-3/4" dia. And can hold flat material as well.I think the Small Engine Builders could use it to it's potential.

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  • BCRider
    replied
    Your drill jig reminds me of a similar product that was showcased in a YT video. Sure enough I found it. Mr Pete222 showcasing the Heinrich Cross Hole Drill Jig.

    Not to try to compare mind you. But it IS an interesting idea. Could be a good home shop project. Proper hardened bushings aren't cheap though. And we'd need the same tools in a couple of sizes to let us cross drill from your 1/8" example up to something like 1/2 to 3/4".

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  • Tundra Twin Track
    replied
    This 1/16" hole drilled in 1/8" ER 308 SS Tig rod dead center,rotated 180 deg after drilling bit slid right thru.Sir John swore by these Reglus Drill Jigs,I have to agree with him.

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  • BCRider
    replied
    I suspect it would be fair to warn about chuck runout if using the carbide PCB drills. As mentioned even .003, which may or may not be visible, will be a large part of the hole size and likely enough to snap a really small solid carbide drill. So we're talking about swapping from our usual drill chuck over to a really good small size chuck or a good collet setup.

    And I also suspect that making up a sensitive drive chuck and arbor to fit the drill press would not be a bad option too. My DP is pretty good even down to working with 1/16 and 3/64 size drills. It's well enough broken in that I can "feel" those drills back through the quill and arms. But a couple of holes I've done which were smaller were in brass and pretty much a case of trust.

    I think I'd prefer the solid carbide drills for this. But there again it would cost a small fortune to amass a complete small number collection. Not so bad to buy a few sizes but we're talking about special ordering rather than using what is on hand.

    Depending on the material and setup I really like that suggestion for a small hardened point punch in the drill press used to mark a center. And along that line the idea of perhaps grinding away half to form what is essentially a sharp pointed engraver cutter?

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  • J Tiers
    replied
    They made things to do this co-ordinate based drilling...... Jig borers. Drill the hole, then bore it out to size, all on location to a tenth or maybe less.

    If you DID use bushings, you could do the job with a drill press, outfitted with a bushing holder, and an x-y table. X-Y table to be as accurate as your needs require, possibly with a DRO or the like.

    Of course your mill could do that too, and already has an X-Y table attached to it, all you need is the drill bushings and holder. I betcha you could make the holder, and choose a suitable size drill to use as the pilot for your holes. Then you could drill pilots for all holes, and maybe that is good enough.

    If not, make more bushings for the sizes you need, and drill all the holes with them.

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  • PStechPaul
    replied
    You might also try small carbide end mills like these:





    They all have a standard 1/8" shank so you can use a collet, which will usually have much better runout than a chuck. I haven't used these yet, but they look pretty good, and the entire set was (IIRC) well under $10 from Banggood. Like these from AliExpress:

    https://www.aliexpress.com/item/10Pc...AbTest=ae803_4

    Or get a set of 10 pieces 0.8 mm (0.031") PCB bits for under $2:
    https://www.aliexpress.com/item/10Pc...AbTest=ae803_4



    A 90 degree chamfering end mill might be useful as a spotting drill or in place of a center punch:

    https://www.aliexpress.com/item/1pc-...AbTest=ae803_4

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  • PS4steam
    replied
    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 RPM’s 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 don’t bother.

    I drill the above size holes at about 100 – 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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