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I'm trying to drill a centered, straight hole in a piece without a big drill press and a bunch of clamps and brackets, which seems to be the usual way to do it. I can manage straight, but centered is eluding me.

I'm very new to working wood and I'm working on an umbrella swift for my partner to wind yarn on. Part of this involves an axle (in this case, simple dowel) and a couple of square-sided blocks that rotate around it. A bit of friction is actively desirable, so this isn't even going to get a sheave bearing, let alone anything fancier.

I'm having a lot of trouble drilling a straight, centered hole down the square stock, and tend to get a hole that's off center and/or not straight.

With a basic drill guide (collar style) I can get it pretty straight, but setting the work piece perfectly perpendicular is tricky since the edges from where it's cut off the bar stock aren't quite square after hand-sawing. (Maybe I should be using a mitre box?). I'm dealing with this by mounting it in a vise and measuring it carefully before tightening.

Getting the hole centered is just not working though. I drill a small pilot hole with a 2-bit, but it still tends to wander half a mil off center once it bites and starts drilling. I suspect it might be because of the soft pine I'm working with and the fact that I'm drilling down the line of the grain, not across it, but I don't have much choice about that. Widening the hole tends to make the situation worse, as the bit again tends to wander before biting properly.

If I go straight to the 12mm spade bit for the full width cut it tends to wander more, rather than less.

I'm also getting a hole that's usually not quite round - slightly distorted on three sides. Is this because I'm drilling with the grain?

Please forgive my ignorance. I've been hunting around for info, but mostly finding things focused on drilling down the center of round stock like dowel, where you can spin the stock in a drill and use a fixed bit. That's not an option here.

(I suspect this is like those programming questions I get on SO, where someone wants to know "how to build a dynamic website with PostgreSQL", where the answer is "let me write a book" or "where do I start"... but I'm hoping there are just a few simple tricks I'm missing here.)

Current results:

hole1 hole2

Craig Ringer
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  • It's the centering that's giving me the most trouble, and since I don't have a full on drill press it's hard to prevent the bit wandering when it first bites, even if the drill guide is bolted down and the work piece is temp screwed into the same base board. – Craig Ringer Jun 21 '15 at 10:44
  • Updated with pics of the current awful results. Hole is straight, but waaay off center and not quite round. No idea how it manages to drill not-quite-round... – Craig Ringer Jun 21 '15 at 10:49
  • I retracted my dup vote. This is a good question.If you run your spade bit in the air does it move around its axis? Do you see it shaking a lot? It would not take much to get a small variance. Guessing the drilling is following the grain a little maybe – Matt Jun 21 '15 at 10:54
  • Yes, there's some shake. Unsure if that's normal for the bit, the bit is bent, or the drill its self is off true. Both power drills I have seem to shake the same amount and it's a new bit, so I suspect it's just fairly normal. – Craig Ringer Jun 21 '15 at 14:38
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    Consider cutting your blocks oversize, drilling the hole, then recutting the blocks so the holes are centered. – FreeMan Jun 21 '15 at 19:23
  • @freeman add a bit more and that is an answer. A good solid approach – Matt Jun 21 '15 at 21:25
  • That is NOT round. – Treow Wyrhta Jun 22 '15 at 02:40
  • @FreeMan Good thought; in this case I'm using a fair few blocks that need to be very close in size and shape so I'm using 30mm x 30mm square cut DAR as a starting point, and I suspect using larger stock and cutting down would be a lot harder than getting a good centered hole. I can see that being useful when doing one-offs or when ideal regular stock isn't available though. – Craig Ringer Jun 22 '15 at 03:23
  • In my experience non-round drilled holes are not unusual. I have even managed to drill a square(ish) hole with a round drill. I blame blunt tools. – LosManos Jun 22 '15 at 06:00
  • A brace and bit might be the perfect solution for this hole-drilling problem. – Ast Pace Jun 23 '15 at 04:58

6 Answers6

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You may want to try drilling the hole with a lip and spur (brad point) type of drill bit. When using it do not start with the smaller pilot hole.

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If you had a drill press then a Forstner bit may be the ticket for a clean hole.

enter image description here

Craig Ringer
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Michael Karas
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  • Interesting. That should be more stable than a spade bit? The spade bit has a center point too. As for the drill press, I have a router and a drill guide, but no access to a drill press alas. – Craig Ringer Jun 21 '15 at 13:38
  • Looking up lip and spur bits, they sound like they'd potentially be ideal. https://en.wikipedia.org/wiki/Drill_bit . – Craig Ringer Jun 21 '15 at 14:11
  • You might also consider a hole saw or a hole cutter. Both use a twist bit as a guide, so assuming your drill guide makes your pilot hole correctly and they're deep enough, they may give you a better cut and they will certainly give you a more circular hole. – Daniel B. Jun 22 '15 at 08:27
  • Yeah, I'd likely do so for a larger hole, but 12mm is a bit small for a holesaw. The lip and spur / brad point bit did a great job, and looks to be the way to go. Massively more stable than the twist bits I was using, especially cutting from the end grain. – Craig Ringer Jun 22 '15 at 08:50
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Guides, clamps drill presses are things that are needed to get the precision you are looking for. In my opinion your first picture is very good for a hand drilled hole.

Simple cheap miter boxes can be found (at least here in the US for under $50). Might be worth the investment.

Another option is the lathe. Most people don't think of a lathe for drilling but it can be done. There are chucks that can be put in the tail stock to hold drill bits. then when the wood is spinning the chuck is extended into the wood.

So at least in my opinion, to improve on your first picture, you likely need to invest in some more equipment, or find a place you could rent some time to get it done, like a Maker Space.

bowlturner
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  • Yeah, I'd use a lathe if I had access to one, as I've done a little with wood lathes before... but then I'd probably also have a drill press and so on too. Maybe time to look for an accessible makerspace; the main one I know of is a long way off. – Craig Ringer Jun 21 '15 at 14:11
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Really good effort, but you've chosen an incredibly difficult task to accomplish with hand tools.

I suggest you skip over the bothersome accuracy and go straight to the metal shop. Buy 2 of these: http://www.amazon.com/dp/B00IG7PBNA (amazon asin: B00IG7PBNA, described as "Item # 101260, Oilube® Powdered Metal Bronze SAE841 Sleeve Bearings / Bushings - INCH"). You could even hit the plumbing supply aisle and get a "copper coupler without stop" and find a dowel that'll suit the inside diameter.

Drill an oversized hole and simply epoxy the sleeves at each end. You'll be able to center them perfectly with a bit of shimming, and you'll have a slop-free half inch for your dowel/axle.

Aloysius Defenestrate
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  • I believe bushings might not give the friction OP is looking for, but this is certainly worth considering. – Daniel B. Jun 22 '15 at 08:17
  • Yup, though I can always use a bushing like that then add separate adjustible resistance any number of ways. In this case it looks to be unnecessary as a brad point bit did the job beautifully. – Craig Ringer Jun 22 '15 at 08:52
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Cut the block in half lengthwise. Use your router to cut 1/2 of a hole in each piece lengthwise (like a trench). Glue the blocks back together. Alternatively, if you have a plunge router, and the hole you need is not too deep, very carefully, a little at a time, cut the hole with that.

Chuck
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With any work you need to define tolerances so we know how big everything is and what degree of error is permissible.

Using a softwood dowel as an axel seems like an unrewarding plan. Why not metal?

Normally woodworkers use "auger" bits to bore holes. You need a stable setup to use them, meaning usually a drill press or a bushing. If all you have is a hand drill, then you will need to make a bushing, which can be a short piece of pipe, the same diameter as the hole. This needs to be mounted 90-degrees in a flange. If you don't want to make the bushing, you can buy them (search drill guide bushing). There are also devices called "doweling jigs" that serve a similar function.

Treow Wyrhta
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  • Good point. In this case, 30mm x 30mm x 40mm, centered on the 30x30 face, target tolerance is about +- 0.5mm off center bore at both start and finishing ends, though I can probably live with 1mm off-center if it's not diagonal through the piece. So far I'm achieving about 1mm - ugly, but usable - with a brad point bit. The main challenge now is keeping the work piece steady and centered while drilling. Bah. This must be what starting programming for the first time feels like... – Craig Ringer Jun 22 '15 at 12:54
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With a basic drill guide (collar style) I can get it pretty straight, but setting the work piece perfectly perpendicular is tricky

  1. Start with oversize stock large enough for a drill guide.
  2. Mark the cut lines for the square faces.
  3. Mark the diagonals. They intersect in the centre of your hole.
  4. Drill.
  5. Cut.

since the edges from where it's cut off the bar stock aren't quite square after hand-sawing. (Maybe I should be using a mitre box?).

Get a compound mitre slide saw. And a drill press.

Peter Wone
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    Get a compound mitre slide saw. And a drill press. Those are excellent tools, but I'm not sure telling someone to spend $500-$1000 to fix a problem they may never run into again is the ideal solution. Of course, if OP has the cash and is getting into wood working, this is a nice starter set. ;) – FreeMan Mar 02 '16 at 21:00
  • @FreeMan - Going by the question he and she are makers at heart. – Peter Wone Mar 03 '16 at 02:04