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Shop Tips & Tricks #11: MORE than you ever wanted to know about HOLES!

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Blog entry by GnarlyErik posted 04-09-2013 09:06 PM 2163 reads 1 time favorited 9 comments Add to Favorites Watch
« Part 10: Clamping Big Stuff Part 11 of Shop Tips & Tricks series Part 12: Making Long, Round Things in Wood - with the Norwegian Dowel Cutter »

Don’t get too excited – this isn’t an article on porn or sex, but only about making holes in wood! There are times when you need a hole in wood which becomes a challenge, even with the right sort and size bit. Here’s how to deal with some of the more common challenges:

1. Drilling long holes accurately:

 A. By far the easiest way is by making a shallow saw kerf in the “Faying Surface”①. These are then joined together by glueing or other means, with the kerfs mirroring each other, i.e., face to face. After joining, the hole is made using a spiral auger with a lead screw entering the saw kerfs. The lead screw will follow the kerf unless it encounters a knot or irregular spot. Needless to say, you must go slowly and carefully and clear the chips often. If the bit starts to bind it may mean it is getting off track. This works with brad point bits too up to a point (pardon the pun!), but these are more likely to wander since the bit is not supported on its sides its full length, which seems to be an important requirement for any tool drilling long, deep holes. Regular machinist type twist bits do not work nearly as well as augers unless the saw kerfs are quite wide.

 B. Of course there are times you must drill a long, deep hole when you don’t have the option of glueing two pieces together with sawn kerfs. Here, you might use a ‘Barefoot Auger’; A barefoot auger is a special bit used by shipwrights and is similar to a spiral auger with no lead screw. These can drill quite long holes, but must be very carefully started in exactly the right direction. Even then, it the bit hits a knot or hard place it can change direction on you. Shipwrights often make a special ‘guides’ to get the bits started in the proper direction usually consisting of two pieces of wood at right angles to each other and squared at the bottom (or beveled, if the hole is to be at an angle). Other sorts of guides ‘sandwich’ the part to be drilled with drill guides to keep the bit centered along its length. You can make a sort of barefoot auger from an old auger by cutting off the lead screw, but it will not have the same ‘foot’ as a bit intended and manufactured as barefoot, and therefore will not work nearly as well.

C. Use a ‘Spoon Bit’ or ‘Shell Auger’; A spoon bit is an ancient type still used by chair, lamp, and instrument makers to bore long holes in things like chair backs, lamps and flutes. These are usually carefully hand driven with a bit stock, or twist handle. Spoon bits today are fairly expensive. Lee Valley sells one type.② You can also make your own and here is an article which shows how in detail.③ If you find yourself making a lot of long, deep holes it would be worthwhile to explore this type of bit. Obviously, there is some skill and patience required to use these accurately.

D. There are also a number of speciality (and expensive) bits used with lathes to make long holes in gun barrels, lamps, etc. These are somewhat similar to shell bits and are called ‘D’ bits. Those are beyond the scope of what I am trying to present here.

And, just for giggles, I’ll mention something called a ‘boring bar’ which boatbuilders use to drill out for propeller shafts, but these are not properly drill bits in themselves as they need a pilot hole which must first be drilled with one of the above mentioned type bits.

2. Drilling ‘part of a hole’:

Here are some common-sense tips for drilling ‘parts’ of a hole, i.e. half or other fraction of a hole’s diameter at the edge of something. For example, you may need a series of half circles in the edge of a plank to hold bottle necks in a wine rack or something like that. You can use a jig saw, or band saw and try to deal with the irregular hole which results,  Or, 

You can cut or drill your holes down the middle of a plank and then cut that through the holes into two equal width pieces with a saw; Or you can,

Clamp a piece of waste material of the same thickness next to your stock, locate the center of your hole so your drill cuts away as much as you need for the partial hole in your stock. This works with augers, twist drill bits, Forstner bits, hole saws or whatever and is very accurate. See illustration and photos following:

If you need to make ‘part holes’ of longer lengths, you can use the same method at the edges of your working stock. The nice thing about this is you can produce partial holes limited only by the depth capacity of your bit or hole saw.  See illustration and photos following:

Links to pertinent information:
http://www.answers.com/topic/faying-surface
http://www.leevalley.com/us/wood/page.aspx?p=57713&cat=1,180,42240,53317&ap=1
http://toolmakingart.com/2011/02/27/how-to-make-an-octagonal-handle-shell-auger-and-straight-drilling-guide/

-- Candy is dandy and rum sure is fun, but wood working is the best high for me!



9 comments so far

View shipwright's profile

shipwright

5221 posts in 1518 days


#1 posted 04-09-2013 10:50 PM

Good tips Eric.
When I saw your title it made me think of the first day I walked into North Arm Boat Works and asked if they were hiring. I had no experience except building a ferro cement hull but the boss took me out under a timbered stern he was working on and showed me the setup below. After a bit of instruction I was drilling1/2” X 3 1/2’ holes, cutting and threading the rod bolts and driving them home. At the end of the day he came out to see how I was doing and when I said I’d have the last one in in ten minutes, he said “It’s OK you can finish it up tomorrow.” That’s how I got started as a boat builder. The boat was a 50 foot seiner and the stern was an “igloo” of 4 X 12 Yellow Cedar. That man taught me more in two years than I’ve learned in any ten years since.

-- Paul M ..............If God wanted us to have fiberglass boats he would have given us fiberglass trees. http://prmdesigns.com/

View Dave G's profile

Dave G

178 posts in 768 days


#2 posted 04-10-2013 12:54 AM

The boring bar sounds like what metalworkers call a reamer.

-- Dave, New England - “We are made to persist. that's how we find out who we are.” ― Tobias Wolff

View shipwright's profile

shipwright

5221 posts in 1518 days


#3 posted 04-10-2013 01:45 AM

Boring bar:

-- Paul M ..............If God wanted us to have fiberglass boats he would have given us fiberglass trees. http://prmdesigns.com/

View GnarlyErik's profile

GnarlyErik

209 posts in 854 days


#4 posted 04-10-2013 02:03 AM

Dave G -

See Shipwright’s comment above.

The ‘reamers’ I am familiar with are cylindrical tool bits with ridges, sometimes slightly cone shaped and some with parallel sides – although machinists may know and use a different type.

The boring bar a shipwright uses is a 10’ or so length of rod – usually a piece of propeller shafting. This has a square keyhole cut at about a 20 degree angle through its diameter a few feet from one end. A sharp machinist’s lathe tool bit is set in the keyhole with a set screw to control how far it projects outside the shaft. This apparatus is threaded thru a pilot hole however drilled. It is then precisely aligned, then supported by bearings – flange or pillow block – and sometimes just holes drilled through blocks of wood. Once aligned and all securely clamped or bolted down, power is applied to one end of the shaft – usually something like a 1/2” drill motor. The shaft is advanced into the pilot hole and the cutter bit accurately trues and sizes the hole. The bearings allow the turning shaft to pass back and forth through the pilot hole. Usually, several passes are made with the cutter bit being advanced beyond the shaft a little at a time. A very accurate bore is the result.

-- Candy is dandy and rum sure is fun, but wood working is the best high for me!

View GnarlyErik's profile

GnarlyErik

209 posts in 854 days


#5 posted 04-10-2013 02:07 AM

Yes, Paul -

We called those timbered stern vessels ‘floating national forests’ in the shipyard – they had so many cubic feet of timber in them – and those sterns are the devil to repair as you know. Frost can really work on them.

-- Candy is dandy and rum sure is fun, but wood working is the best high for me!

View shipwright's profile

shipwright

5221 posts in 1518 days


#6 posted 04-10-2013 05:36 AM

I built a few, but never had to repair one Erik, but I’ll take your word for it.
I can imagine it would not be easy.

-- Paul M ..............If God wanted us to have fiberglass boats he would have given us fiberglass trees. http://prmdesigns.com/

View Dave G's profile

Dave G

178 posts in 768 days


#7 posted 04-10-2013 09:11 AM

Nice picture and description. I can see that the boring bar would make a nice straight hole.

Sometimes I wonder how oil well drillers can snake the hole any direction they want.

-- Dave, New England - “We are made to persist. that's how we find out who we are.” ― Tobias Wolff

View Dave G's profile

Dave G

178 posts in 768 days


#8 posted 04-10-2013 09:18 AM

http://www.eia.gov/pub/oil_gas/natural_gas/analysis_publications/drilling_sideways_well_technology/pdf/tr0565.pdf

pipe stabilizers bottom of page 2. If you want to turn the hole you reach down and use a block to nudge the bit the direction you want to go. Similar reason a pilot hole nudges a bit straight.

We could use that idea to straighten a hole that’s headed crooked. Seems like we woodworkers have developed good ways to stay straight.

-- Dave, New England - “We are made to persist. that's how we find out who we are.” ― Tobias Wolff

View stefang's profile (online now)

stefang

13528 posts in 2054 days


#9 posted 04-10-2013 12:05 PM

Great blog with lots of good info Eric. I have a long shafted spoon bit for my lathe which I bought to make cord holes for turned lamps. It works great. When I have two boards glued up with a hole running lengthwise I just rout half holes on each piece providing I have a round nosed bit that will do the job, otherwise the sawkerf is the way to go. I wish I had some boat building experience. There sure is a lot to learn about woodworking there.

-- Mike, an American living in Norway.

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