drill

Bits and pieces
by

Bits and pieces

I’ve been preparing for social distancing since 1975. My barely-repressed nerd is now coming to the fore. If this is what happens in the first week imagine what I’ll be investigating by the peak? Comparative awl sharpening anyone? I could set up the microscope and look at the scratch marks made by each sharpening medium. In the meantime here’s a post about drill bits. Keep your puns to yourselves…

This is what we’re looking for: a clean hole bored at a slight angle. Most of the others are chipped. Now guess which bit made this hole and see if you’re right.

I probably make more  ⅝” holes in cylindrical bits of wood than all other woodworking joints combined. Given that I’m in the middle of a set of grates for my boat with more than a thousand half laps that’s saying something.

Because of this I’ve put quite a bit of time and testing into drill bits. About ten years ago I bought a forstner bit with a square shank that fits my brace. Brendan Gaffney has written extensively about these and there’s no point repeating it. I was so taken with that bit that I started collecting them with an eye to one day teaching ladderback classes. In ten years I’ve managed to accrue a grand total of… 2.

So a couple of years ago I decided to start testing other bits. Covid-19 has given me the time to apply a veneer of objectivity.

We need a scoring system:

  • Clean, consistent holes: very important. Chipped edges and scratches left by wandering bits are disappointing. If they don’t consistently bore the same diameter hole they’re no use. I’m double weighting this by giving a score for holes at 90° and another at about 80° – roughly the angle of stretchers into back posts.
  • Ease of use: they have to be easy to locate on a cylindrical chair leg, cut without a herculean effort and not stall. If they bind and need to be cleared the score goes down.
  • Speed: I’m measuring this in revolutions, not time. More points – lower time.
  • Cost: I’m including postage. Some of these are hard to find. More points – lower cost.
  • Availability: I thought about making this a binary score or combining it with cost. But I’ll keep it simple.

I use three species of timber most of the time: ash, oak and chestnut. Ash is disappearing from our woodlands but not yet from our timber yards. Oak is a perennial favourite and chestnut, whilst a bit prone to dents, is a great timber for chairs. If you want to know how these bits perform in your favourite species send me a piece and I’ll run the test again.

I bored four holes, 3/4″ deep with each bit in a 1 3/8″ leg blank from each species. I counted the number of revolutions each took and compared the holes. Halfway through I realised that I was using a 9/16″ Jennings bit and did them all again with the 5/8″. Then I did another set at an angle.

All holes are bored with a brace. The bits with a square shank are in an old extension. Those designed for an electric drill are in a Famag extension. None of the bits slipped in the extensions when properly tightened and the Famag extension didn’t slip in the brace.

Let’s meet the contestants.

Spade bit. The cheapest bit here. Lots of people do good work with these but I’ve never seen one used like this..

Centre bit. I threw this in because I happened to have one about the right size. In fact it’s a bit bigger than 5/8”. I had very low expectations on turned parts.

Stanley Powerbore. Jenny Alexander’s favoured bit for green wood. This isn’t green wood and these are really hard to find new. They also have only one cutter so are likely to be slow.

Gedge or Cooke’s pattern auger bit. Designed for end grain but liked by Windsor chair makers because they leave a clean hole. Interesting to sharpen.

Jennings pattern auger bit. Ubiquitous. One of my most used bits. But not for chairmaking.

Forstner bits designed for a brace. Rare, no longer made. I’ve got two so I tested both.

Famag Forstner bit. Excellent in a drill press. Saw tooth edge. I’ve been using these in a brace for a while.

Fisch Wave Forstner bit. Less saw tooth to the edge. Again, excellent in a drill press. I hoped that the wave edge gives some advantage over the saw tooth.

Wood beaver power auger bit. The most aggressive bit here with four cutters.*

Spoon bit. I didn’t even test this bit. I can make it work in flat stock. I’ve practiced with it enough so that it doesn’t wander around the workpiece but I couldn’t get it started anywhere near the mark in round stock. It’s here to say: don’t bother.

There’s one obvious bit missing: the brad point. Lots of chairmakers like these in electric drills. Curtis Buchanon and Pete Galbert both recommend they be used at full speed. Given that I’m using a brace they’re not really relevant. They’re also fiendishly expensive this large so I didn’t put them in the test. That said – if you’re using an electric drill big brad point drill bits are worth getting or grinding yourself.

Many boring hours later I had some surprising results:

BitClean/10Ease/5Speed/5Cost/5Available/5Total
Spade2215515
Centre9434323
Powerbore7411214
Gedge1251110
Jennings5353420
Forstner for brace 16321113
Forstner for brace 27341116
Famag forstner8443524
Fisch wave7333521
Wood Beaver*2253517

Not what I was expecting either!

The hole nearest the camera in the first photograph was bored by a centre bit. It was consistently the best. It’s also the easiest to sharpen. However there’s one criterion I didn’t measure – consistent sizes between different bits. I’ve got a couple of centre bits that are roughly 5/8″ but that’s not really good enough. I need to be able to match them, consistently to a tenon former of a caliper on the lathe. Centre bits are all old and whilst very easy to find used aren’t consistent. If you’re working on your own and only need one bit you could do a lot worse than get one of these, keep it sharp and match your tenon former to it. It’ll work well.

But if you want half a dozen bits that are interchangeable and match tenons formed on the lathe then the Famag is the one. The Fisch was disappointing. It didn’t chip out but left a fuzzy edge along the grain. Not terrible but the Famag was better.

The biggest surprise was that the modern power bits were better in a brace than the old bits designed for the purpose. Even if cost wasn’t a factor I would be using the Famag.

It’s worth noting that the Jennings excellent at 90º but with even a small angle it produced a lot of tear out.

Most disappointing was the powerbore. I paid a lot of money both to buy it and get it here. Save your pennies.

Winners

*I previously called the Armeg Wood Beaver bit a Wood Owl. I don’t own a 5/8” Wood Owl but I do have one in 1” which I use for drilling dog holes in workbenches. The bit shown here and tested is a 16mm Wood Beaver. Great for drilling fast holes at right angles to flat stock. Not ideal here.

by

Everything I know about screwing

image

The first thing I know is that it’s impossible to resist a ribald pun. Even my normally clean-minded wife couldn’t help a snigger when she asked if I was screwing around in the workshop on my own this evening.

I had some brass, slot-head screws delivered to work today. A colleague looked at them lying on my desk and wondered aloud how you avoid destroying the heads. So I started to tell him. Half way through his eyes glazed over and he wandered off.

 

So for all those who know next to nothing about screwing but actually care:

1. Use a screwdriver that fits. I have a lot of screwdrivers and often pick up cheap old ones when I find them. Each different size of screw head needs a different driver. The tip of the screwdriver should fit so well that it will hold the screw without support. Because most screwdrivers are manufactured to fit a range of screws they don’t work for any particularly well. Grind each screwdriver tip to the size of the slot.

2. Use a screwdriver with a tip with parallel sides. The one at the bottom is manufactured properly. The one at the top is going to get ground to get rid of the taper in the tip. It will end up with a tip that has concave sides. The end will be very close to parallel. Because most of my tools are still in packing boxes this new addition has escaped the grinder for the time being. But its days of tapered mediocrity are numbered.

Tips

 

3. Use a tapered drill for the pilot hole. To be fair I rarely do this. I only have a couple of tapered drill bits and am too mean to buy bits I’m going to use once in a blue moon. However if you want to ensure that your timber doesn’t split under the wedging action of a screw a tapered bit means that the taper in the screw is accommodated. However I always…

4. Use the right sized bit for the pilot hole and drill it full depth. Classic Marine has a useful chart. What do you mean you don’t have a 7/64″ bit?

5. Drill a clearance hole if you want to draw two pieces together. If you think for a moment about the way a screw works it’s obvious that if it goes though a pilot hole in one piece and into a pilot hole in another no matter how hard you drive the screw if will not draw the pieces together if the threads are properly engaged in the upper piece. But if the threads of the screw slide though the clearance hole and catch in the pilot hole of the lower piece then as the head draws up to the upper piece it will pull the two together.

5. Clamp pieces together. If there’s a gap when you screw two pieces together there will always be a gap. If you clamp them tight, drill your pilot hole and then screw them together they’ll remain tight.

6.  When using brass screws use a steel screw first. I’ve lost count of the number of heads I’ve wrung off brass screws. However drilling the right size pilot hole and then cutting threads in the wood with a steel screw reduces the load needed on the brass screw. I wish I did this more.

7. Wax the threads. This is such an easy thing to do and makes so much difference.

Screw and wax

 

I have a small pot of softer wax made from beeswax and turpentine somewhere but it’s hiding in a box so I used candle wax this evening. I’m convinced the softer wax sticks to the screw better and so the effect lasts longer but I may be kidding myself. Certainly the difference between no wax and wax is immeasurably greater than different types of wax.

8.  In corners use a “turn screw”. Which is just an old word for a screwdriver with a flat on the shaft. You can put pressure on the top of the handle and turn the driver with an adjustable spanner. You actually need surprisingly little downward pressure. This means that even in an awkward position you can keep the screwdriver vertical and the tip fully engaged, reducing the chance of it breaking free and damaging the head.

image

 

9. Tighten them up evenly. Your work can shift when screwing it down. To avoid this tighten the screws most of the way. Make sure everything is still where you want it and then tighten them all down bit by bit. If you tighten one in one corner of the workpiece it can spring the opposite corner up in the air making life rather difficult.

image

 

10. Clocking screws is a fool’s errand. You can adjust the countersink hole. But this puts the screws at different heights. You can over tighten some or leave others loose. But this is just self-defeating.  Or you can go to the frankly absurd lengths of putting each screw in your drill press and sanding a fraction off the back of the head, then putting the screw back in the hole to see if it now fits and is “timed” with all the others. Or you could just demonstrate your superior craftsmanship and understanding by correctly tightening each one and then leaving the blessed things alone.

11. A brace with a screwdriver bit is very handy. Use your 6″ brace. The 14″ is asking for trouble. It’s even more important that the bit fits the screw because you’re going to be putting a devil of a lot of torque on it and it’ll skate off without hesitation.

12. If you’re drilling a pilot hole in exterior timber dribble wood preservative in the hole first. My father-in-law will even go the lengths of setting up a tiny funnel into the hole and filling it with preservative and hardener. This then acts as a reservoir to keep feeding the wood as   it soaks up the preservative.

13. In soft wood drill the pilot hole over size and then pour in thinned epoxy. Wax the screw very thoroughly and when the epoxy is green (not completely cured and still fairly soft) drive in the screw.  If you ever want to get the screw out heat the head to soften the epoxy with a soldering iron. I have a gas powered one for cutting rope and it works a treat.

Attributions: I have learnt all of this from other people: my father (who got it from his toolmaker father and his cabinet maker grandfather), my father-in-law, from the online and published works of Chris Schwarz, Bob Smalser, Tim Roussau and Greg Rossel. I use all these techniques and am happy with them, if you’ve got others or improvements let me know. As I remember, learn about and use other techniques I update this page.

St.John