Which wood bits for straight large holes in a pillar drill?

[Triggaaar]

Well, in a normal drill with a drill guide.

I've got to make a couple of dozen 20mm d, 3" long straightish holes in softwood, and I'm confused by the number of bit options available. There's:
Flat (spade?) bits
These 'wood beavers' http://www.axminster.co.uk/armeg-armeg- ... rod801632/
Auger bits
Forstner bits
Self-feed wood bits

The holes are just to go through some 3x2 for a rope bridge I'm making, so they don't need to be perfect, but I don't want them going off line.

I guess auger bits would work, but I find they go blunt incredibly quickly (I've probably not used them properly). Would those wood beavers be a good option?

Thanks

 

[9fingers]

Forstner bits are about the only choice for 3" diameter holes in my book. Get the saw tooth type.
A normal electric drill in a stand ( I assume you mean) is not likely to be able to go slow enough with sufficient torque for such a bit so enlist the help of someone with a decent large pillar drill. You can also get forstners with hexagonal flats on the shank which make gripping them in a chuck much easier.

Bob

 

[Triggaaar]

Forstner bits are about the only choice for 3" diameter holes in my book.

Oops, holes will be between 20 and 25 mm, 3" long (through 3x2). I've edited the OP. Thanks for the reply though.

 

[9fingers]

OK Most of the bits you mention will do the job, as will a decent hand drill in a stand on low speed.
Clamp on some scrap wood on the exit side to prevent ugly break out.
If you got the forstner bit route, make sure the shank is long enough to have a reasonable part in the chuck and 3" plus projecting.
Don't buy cheap forstner sets - most are cr4p. mode flat spade bits are surprisingly goos and dead easy to re-sharpen with a file.
Don't labour on with a blunt tool, you will get a ragged hole, some burning and soften the tool bit.

hth

Bob

 

[Phil Pascoe]

An auger should be no problem - drill from both sides, rather than have the holes come out off centre. Many augers benefit trom a touch up with a needle file, but they shouldn't blunt quickly - because of the lead screw they'll stall rather than burn. I'm glad you're not trying to drill 3" holes in 3" timber, though.
Bits with lead screws don't tend to work well in drill stands though, they pull the tool too quickly.(afterthought)

 

[Triggaaar]

Thanks guys

Clamp on some scrap wood on the exit side to prevent ugly break out.

Good idea. I was thinking of drilling from both side, but I wasn't thinking about break out, I was simply thinking of getting the entry and exit in the correct place.

mode flat spade bits are surprisingly goos and dead easy to re-sharpen with a file.

I should have a old spade bit lying around, maybe I should buy a file first.[/quote]

An auger should be no problem - drill from both sides, rather than have the holes come out off centre.

Probably the best plan, thanks.

Many augers benefit trom a touch up with a needle file, but they shouldn't blunt quickly - because of the lead screw they'll stall rather than burn.

I have some knackered auger bits, I'll see if there's some sharpening demos on youtube.

Bits with lead screws don't tend to work well in drill stands though, they pull the tool too quickly.(afterthought)

Mmm. So Axminster drill guide (which I don't own yet) and flat bits, or auger/beaver bits and do it by hand? Or ignore the pulling problem, and stick and aggressive but in the drill guide? I searched the forum for 'beaver' and found (among other things) some who'd used a pillar drill with wood beavers for their bench dog holes, and that had worked well, but it was a substantial pillar drill.

 

[chipmunk]

If you haven't got a suitable drill bit then I'd suggest these from Screwfix....

http://www.screwfix.com/p/disston-multi-angle-drill-bit-20mm/85864

Used in a pillar drill you can ignore the multi-angle capability, they'll drill straight.

But they come very sharp and IMHO are a great compromise between a spade bit and a forstner and won't break the bank. They don't have a screwpoint and if you drill onto a piece of scrap wood the cutting spurs will go a long way to prevent any break-out even if you go straight through. Unlike many Forstners or sawtooth bits they come with a decent length shank.

HTH
Jon

 

[Triggaaar]

If you haven't got a suitable drill bit then I'd suggest these from Screwfix....

http://www.screwfix.com/p/disston-multi-angle-drill-bit-20mm/85864

Used in a pillar drill you can ignore the multi-angle capability, they'll drill straight.

Well I'm going to screwfix today, with 10% off, hence me trying to make a quick decision. Do you think those are better than the flute bits? http://www.screwfix.com/p/armeg-wood-be ... 22mm/67835

I might try and get a file and sharpen some of the bits I have though.

 

[chipmunk]

Well the Armeg Woodbeaver bits have a screw so aren't going to be easy to use in a pillar dril IMHO.

The feed rate is out of your control and can easily produce break-out unless you can back out the bit before it gets through - and this really requires reverse in anything but the softest timber which isn't usually available on pillar drills.

but if you already have a spade bit of the right size I'd give that a go first. A cheap set of needle files like these would probably do the trick...

http://www.screwfix.com/p/forge-steel-150mm-needle-file-set-6pcs/66936

Although it's yet another £8 or so.

Drill through until the point emerges on the back and then turn over and drill from the back to prevent break-out.

HTH
Jon

 

[custard]

If you were to look at the working practises of ten woodworkers I bet you'd find that at least six or seven of them has never ever sharpened a drill bit, which is odd given that drill bits blunt really fast.

You say you have a couple of dozen 3" holes to drill, let's say that adds up to six foot or more of drilling. Even in softwood I think you'd see a big difference in quality and ease of drilling between the start and end of that job, especially if you hit a few knots along the way. In other words, whatever drill bit you use be prepared to sharpen it two or three times as work is progressing.

So my vote would be a spade bit, not because it's particularly sophisticated, but because it's a breeze to keep in tip top condition!

 

[Triggaaar]

I only like screwfix when I really know what I'm getting, and then I only buy when the price is right, as they're a bit like DFS - drill for sale for £400 that are £200 everywhere else, so they can put them on half price and call them a bargain. When you know what you're getting and what you're paying, it can be good.

I've spoken to Axminster about sharpening bits and they recommend these:
http://www.axminster.co.uk/axminster-ax ... for=200219
They look like a good idea, what do you think?

I'll have a go with some spade of auger bits I have to start with.

I'm also planning to get the cheap Axminster drill guide: http://www.axminster.co.uk/axminster-ax ... prod22269/
I'll use it so rarely I don't think it's worth me getting a proper pillar drill. The only annoying thing is that the only drill I have that'll fit it is an old bosch green drill that isn't accurate (bit wobbles), but I assume once it's going it'll be straight enough.

 

[Triggaaar]

I'll use it so rarely I don't think it's worth me getting a proper pillar drill.

What would you know I'm having doubts and wondering if I should be getting a pillar drill.

I'll post in tool reviews.

 

[xy mosian]

If you are going to use some variety of Flat Bit, or indeed sharpen one, then choosing a bit with 'spurs' will give a nice clean entry.
xy

 

[9fingers]

I'll use it so rarely I don't think it's worth me getting a proper pillar drill.

What would you know I'm having doubts and wondering if I should be getting a pillar drill.

I'll post in tool reviews.

Some nice old British cast iron will be far far superior to anything Axminster or others are bringing in from Chaiwan and possibly less money. Startrite, Meddings, Fobco, Pollard, Progress etc to name but a few excellent makes. usually a good few on ebay.

Bob

 

[Eric The Viking]

+1 for sharpening spade bits - easy to do and makes a world of difference. The steel quality also matters though. I had a wide one bend, just behind the flat where the shaft is narrowest. I think that it heated up so much it lost the temper and softened. When they're cheap steel and start to lose their edge, they go over pretty quick. So like chisels it's hone little and often. They are also prone to wander when used across the grain, particularly in fast-grown softwoods, with really prominent and spaced growth rings. The blade gets pushed around by the grain, and there's nothing in the bit design to force it to keep to a straight cylinder.

I'm sure you can get good quality ones - Bosch do them ISTR. I've tried the cheap ones from the likes of Screwfix. I wouldn't do so again!

On auger bits - don't use them in a pillar drill. You can't run them at slow enough speeds to be safe. They do work in battery drills pretty well though. I've just made 24 x 9" holes in Glulam beams with a 600mm x 1/2" one. It needed fewer battery changes than I expected (10.6V Bosch kit). As long as you're happy you can drill square to the surface by eye it's fine, but once you've gone 1/2" in you're effectively committed and you can't change the line. I use a square held against the surface if it's critical. 20mm would be fine that way.

It's worth mentioning that lip+spur augers don't really work in the same way as flat bits or ordinary twist drills. Assuming you're drilling across the grain, once the spur has cut the fibres, the 'lip' splits them away. The lip doesn't really cut as much as cleave, and so doesn't really get blunt very quickly either.

You may need to touch up the end of the spur, as that does blunt, but it's arguably an easier sharpening job than a flat bit, especially on the bigger sizes. Augers are pretty rubbish in end grain or in man-made board* though, because the fibres aren't aligned so that the system can work properly.

These posh multi-fluted jobbies are probably wonderful in the right application. I think they're intended to cut fast in site work for plumbers, sparks and so on. From the ones I've seen, and I haven't used them, the bevel angle is pretty steep, more like a flat bit. As a consequence you'll have four "blades" to sharpen at a time, although they should last twice as long. Also, being a half-way house between spade and auger, they ought to run straighter in difficult timber and not wander. Personally I can't see the advantage - I'd go for control over speed every time.

Hope some of that's helpful.

E.

*Glulam beams have end-to-end orientated grain like normal timbers.

 

[xy mosian]

Nicely put Eric, a good summation. On the subject of eye-balling a straight hole square to the surface, once the hole is started I tend to try to keep the shaft of the flat bit in the centre of the hole I can see. This on the grounds that to drift off line the shaft must move over to one side. Not as accurate as a square but good enough for a lot of work.
xy

 

[Eric The Viking]

I quite agree XY, I do the same.

I was using a square with a really long auger bit. I was drilling through the centre line of pairs of beams, separated by 3/8" ply. The hole overall was about 7" or 9" deep, and it had to be straight as they're load-bearing.