Duff drill bits

I see you tried the unsharpened one!

Bill

Yes. I was interested to see just how badly it cut. It quickly scorched the wood. I was experimenting in a bit of wood similar to what I'll use for the base. (*)

The "whirling drill bit" (the 30 mm one) was most disconcerting. My first thought when I started the electric drill (slowly, before taking it up to normal speed) was that I'd not loaded it into the chuck properly. Then I took it out and looked at it, and thought "that bugger is as bent as a banana".

(*) It so happens that I have another 25 mm drill - a very large (and very long) twist drill, rather than a spade one. But it binds in the wood almost immediately. I'd bought it originally to drill some holes in tree stumps, so my wife could plant some trailing plants in the holes, and found it got stuck very quickly which I attributed to the tree stump wood being damp. But it does it on seasoned, cleanly-cut gate post wood as well. Are those very large twist drills designed to be used in an electric drill, or or you supposed to use them in a brace-and-bit drill which turns very slowly?

They look just like the ones someone else returned!

The thought had occurred to me!

The company that supplied them has apologised and is sending replacements.

Those flat blade things are pretty useless anyway. Far better to get some decent auger bits.

Agreed. And they're dangerous if they hit a nail.

Bill

They are a bit of a bugger for that. The thread pulls them into the work too quickly. They're OK in a pedestal drill because you can control the feed rate. On an electric drill you have to go very slowly and keep pulling back. I have wondered about grinding the thread off part of the pointy bit.

Bill

I'm still persevering with a bulk box of drill bits in assorted sizes that I bought from B&Q, or Wickes, about 15 years ago, where every one of the 20

Ant.

Lack of QA, I'd say. I remember buying several things, in one case jewellers screwdrivers, they were wonderful. Same make a year later, the handle plaiting came off and went into my hand and the screwdriver blades bent. Counterfeit? Who knows. Back in the days of cassettes a company called Dindy used to make them in this country, and they were pretty good for the price. A couple of years down the line, I bought some more. All made in Mexico, all either jammed or had tape that was a shadow of the old ones. The problem is that many companies sub stuff out. I bought a pack of Draper hacksaw blades, the blue ones? Previously they were from Germany, the new ones made in Poland. All of them were either snapping or stripping teeth just while sawing mild steel rod!

Brian

It's the nonsense (nowadays anyway) of "branding". A brand no longer gives any guarantee of source, quality or anything.

Do you really mean twist drill or an auger bit?

Twist drills have cutting geometry for metals rather than wood, though at the small sizes it's not that critical. Not surprised that a 25 mm twist drill binds in wood, especially without a pilot hole.

I wouldn't even try to use an auger bit in a power tool. The screw feed is quite quick and they need a fair bit of torque at low speed.

The cutting action of a twist drill or flat wood bit is more of a scrape than a cut. An auger bit cuts more like a chisel or plane.

I've got smaller sized twist drills designed for wood. they even have a centre point for accurate location. Damned clever these Japs!

It may well be an auger - I was using "twist" to convey the meaning of a spiral thread, in contrast to a flat perpendicular blade of the drill bits that I was initially talking about, not realising that there are two categories of twist-action drill: metal (twist) and wood (auger).

The 25 mm auger drill has a conical thread on the tip to create a pilot hole. The whole drill is about 30 cm long and is bloody heavy - it's a lot better for drilling vertical holes (eg in the top of tree stumps) than horizontal ones where the weight of the drill but would tend to twist an electric drill that is held with its normal handle and hand-hold.

If I need to use it in future, I'll probably buy a brace-and-bit hand drill for greater control at low speed. My electric drill had variable speed and is capable of running at low speed, but the torque at low speed is low and the movement is a bit jerky. I bought the drill bit not realising that it wouldn't cut in the same way as a small drill of 5-10 mm diameter and would need to run very slowly because it draws itself into the wood very quickly.

There are in fact a lot more

Off the top of my head

1. standard cheap twist drill as in metal type
2. flutes masonry drill with hardened 'smasher' carbide head.
3. wood drill auger type with a spiral centre and then a sort of 'planer' edge
4. flat wood drill with a centre spike and angled 'scraper' stile blades.
5. hole saws
6. diamond core drills with no centre at all.

Then there are combo drills with counterbore and countersink...

yes. High torque low speed as for hand brace work

you can make them work well in wood by grinding to much steeper geometry & grinding out most of the dull centre.

I've done a fair bit of that, worked great. Can certainly go wrong though.

NT

Problem with using those in a modern drill is that once the snail bites, it's away at a rate of knots ... I had some oak flooring clamped in the workmate to drill a hole for a radiator pipe, it bit, started cutting, split the wood and then went for my thumb ...

hence you blunt the tip to slow it down. And never run them fast.

NT

Then they don't bite ...

they do only when pushed a bit, so you can control them.

The advantage of their bite-fast approach is it's energy efficient. It also makes them work best at low speed with highish torque - ideal characterisa tics for hand drilling. These days more or less everyone uses them in power drills, so gotta wonder why the mfrs don't make the self driving tips less aggressive.

NT