Drill for making 24mm auger holes

[badgerjockey]

Hi all.
I recently put up an oak sleeper retaining wall in my garden and now want to finish it off by interlocking the three wooden layers using some hardwood dowel pegs hammered into augered holes.

The wall comprises three 200mm wide sleepers on top of each other laid on their short 100mm wide side. It is supported by uprights to which they have been coach bolted (stainless).

I have already augered several 12mm holes through the bottom two (400mm) into which I rammed some 700mm stainless rods so there was a foot in the ground. I’d like to now connect the top two layers with wooden dowel.

Trouble is, while my cordless drill (40nm torque) was fine augering the 200mm 12mm holes for the coach bolts, it struggled a little with the 400mm for the steel rods. It made it in the end by pouring some oil into the threads of the bit and taking it slow, clearing out the wood dust.

I even tried my friends blue Bosch 1100W mains hammer drill but it had the same issue. I was surprised at this, I thought it would make mincemeat of the augering. Obviously it wasn’t on hammer mode!

All this makes me apprehensive about doing the 24mm x 400mm augers. Would you guys have any tips for getting this done? What drill would you go for?

The bits I’m using are these. https://www.toolstation.com/long-auger-bit-set/p35978
The 12mm was surprisingly good!

Thanks

H

 

[^woody^]

Use a flat bit

 

[badgerjockey]

Thanks. I considered using a flat bit, but the reasons against are:

-the longest I could find was 400mm. I'd need a bit longer than this to get through both timbers and account for the length in the chuck.
-To my knowledge, auger bits give a straighter hole, or are at least more resistant to wandering which is what I'd want for making such a long dowel hole.

 

[^woody^]

Use a flat bit extension.

They drill straight holes.

 

[opps]

I think you need @JobAndKnock to recommend a suitable option. The man knows more about tools than anyone I have personally ever encountered.

 

[Munroast]

Yep, J&K will be along to tell you what you really need, but in the mean time I am going to have a guess a a Ships-Auger (the drill dont have a centre shaft), they clear the debris out faster than anything else I have used, I guess they where design for heavy timbers log before cordless arrived.
(I'm curious now what J&K has to say now)

 

[Deleted member 174758]

Would you guys have any tips for getting this done? What drill would you go for?

The bits I’m using are these. https://www.toolstation.com/long-auger-bit-set/p35978
The 12mm was surprisingly good!

To re-iterate what I may well have said already:

1. Learn to sharpen your auger bits, especially the spurs which are the bits which do the vital work of severing the fibres. Not difficult, but necessary as tough timbers like oak, teak, iroko, etc can blunt an auger bit quickly, very quickly and even new bits can be a bit blunt. Wet timbers in particular can cause problems.

2. Cheap 2nd rate Chinese no-name auger bits are often made with variable quality steel and the sharpening is often hit and miss to boot. Personally, I won't waste time on them, as in a given batch you might be lucky and get a good one, but you are just as likely to get a bad one. The bigger the diameter the worse they are in my experience. You cannot ever make a silk purse out of a sow's ear. The big names like Fisch, Heller, Bahco, Bosch, etc are generally good to go straight out of the package - if you use them correctly. You can still pick up bargains on eBay, you know.

3. If you can't drill a 24mm hole with an 1100 watt drill then there are two common user errors, namely:-

(i) the bit simply isn't sharp enough

(ii) the drill is being run at too high a speed - so don't just stick it in first gear and pull the trigger. A speed of 150 to 200 rpm is what I'd start with and I'd vary the speed (probably downwards) until I hit a "sweet spot" where the bit self feeds. In wet timbers the bit may not self feed properly, so extra pressure may be required to get it to cut. Either way there may be spelching at the stsrt of the hole unless the bit is run slowly in reverse for a few turns to allow the nickers to sever the fibres

I have used a Bosch GSB2-21 1100 watt 2-speed drill to bore many hundreds of holes in hard timbers over recent years with auger bits (mainly 12 to 16mm holes for joist sistering and 16 to 26mm for lock mortises, but most recently some 32mm diameter holes in 150 year old rock hard pitch pine for steel tension rods and where the bits incidentally refused to self feed).

 

[Deleted member 174758]

...I am going to have a guess a a Ships-Auger (the drill dont have a centre shaft), they clear the debris out faster than anything else I have used, I guess they where design for heavy timbers long before cordless...

Traditional hand auger bits were found in two main patterns, "Irwin pattern", with a solid centre, and "Jennings pattern", which are effectively centreless. These are two flute drill bits. A single flute version of the Jennings pattern bit was developed, the "L’Hommedieu pattern", and many so-called "machine pattern" (sometimes called "Lewis pattern") auger bits are partly based on that design and the Jennings pattern (although modern bits are machined from solid billets of steel, not hand twisted from a flat piece of red hot metal)

Technically a ship's auger bit is made from HSS steel, as opposed to the tool steel normally used. This allows the bits to drill through soft iron, soft steel and brass fixings (e.g. screws) embedded in, for example, deck timbers without completely losing the cutting edge, but it comes at the cost of them being more difficult to sharpen (they need carborundum instead of auger bit files) and you can never get such a sharp edge on HSS as you can on tool steel. Note therer are versions both with and without spurs - no spur drills allow you to start holes at a greater angle, but comes at the cost of the hole not being as neat with more spelching at the edges.

 

[badgerjockey]

Thanks for the response, Job.

The bits I’ve used do have a central shaft. The 12mm bit has been surprisingly good but, I suspect, has become a bit duller as you suggest. That’s after about ten 400mm holes in oak.

The hammer drill in question was indeed the GSB21-2, too. It certainly was not on high speed, I took it very slowly after learning my lesson getting the bit stuck with my ordinary combi drill! But it surprised me that it seized up at the same point as the smaller drill. I guess it must be the cutting edge…

So, how to go about sharpening the bit?

Also, should I be surprised that my small Dewalt cordless combi and the GSB both have a max torque rating of c.40NM? Wouldn’t one assume the GSB was capable of more turning power?

Also, any tips on lubricating the auger - what’s best? And is there any point? It did seem to help before.

Thanks again.

 

[chirpychippy]

Personally I would drill with a 6mm Auger slowly then a 12mm slowly, last chance of burning your drill out.

 

[badgerjockey]

Ok, can you work up the sizes using auger bits? I’d have thought that it’s hard to centre them seeing as the cutting edge is flat and the screw spur would be lost in the previously cut hole.

 

[Notch7]

Ok, can you work up the sizes using auger bits? I’d have thought that it’s hard to centre them seeing as the cutting edge is flat and the screw spur would be lost in the previously cut hole.

No you can’t.

 

[Deleted member 174758]

... it surprised me that it seized up at the same point as the smaller drill. I guess it must be the cutting edge…

Or maybe the lands are filled with waste? You aren't going to be able to drill all that far in solid oak without reversing the bit out and clearing it from time to time.

So, how to go about sharpening the bit?

Short, sharp (no pun intended) and to the point. For general work you don't absolutely need the diamond card file (a few hundred years worth of woodworkwrs did without them, after all). The biggest aggro is getting hold of an auger bit file - try Workshop Heaven or Amazon

Wouldn’t one assume the GSB was capable of more turning power?

Not if the bit was jammed solid with swarf. See my comments above

Also, any tips on lubricating the auger - what’s best? And is there any point? It did seem to help before.

You could just rub some candle wax on the outsides of the bit (not the cutting edge) and maybe treat the lands with something like dry lubricant (PTFE spray) or even furniture polish (basically paraffin wax)

 

[Notch7]

You need a huge amount of torque to drill a screw thread auger bit.

Ive got some Armeg beaver drill bits and an 18volt drill struggles a bit.


Have you tried Erbauer bits from screwfix - I buy Erbauer router bits and they are fantastic, superior in my opinion to Trend.

I would get a set of needle files and sharpen your auger

Erbauer Auger Bit 14 x 400mm

Order online at Screwfix.com. For large diameter drilling in wood, corkscrew design pulls bit through the wood. FREE next day delivery available, free collection in 5 minutes.

www.screwfix.com

 

[badgerjockey]

This is all great advice. Thank you Job and notch. Trouble with the 400mm bits is that it won’t be long enough to go all the way through as some of it will be in the Chuck.

I’ll try it all out tomorrow and will report back. And I’ll see what files I can get my hands on.