Spade bits vs auger bits

[Rob Blaustein]

I've used spade bits to drill bigger holes (>3/4 inch diameter) and I don't have auger bits but I've seen them around and was wondering when one uses them vs spade bits or even larger twist bits. When the cable guy ran cable into our house he used a long auger bit--is it better if you need to drill through a thick piece?

[mike holden]

The difference is between scraping a hole and cutting a hole.
The spade bit is a spinning scraper, and takes more effort to cut.
The auger bit has cutting edges and cuts and lifts a chip away, less effort and usually a cleaner cut.
The spade bit is much (much!) cheaper to make and buy, and with powered tools, the effort is pretty much a moot point.
The only other advantage to an auger is that it is self centering and once ligned up and boring, it will go straight. The spade can be somewhat "steered" if needed.
The spade bit wears faster than the auger, so if I were outfitting a crew that needed to drill lots of holes I would outfit them with augers for the longevity.
So to answer your question: It depends!

Dont you love definitive answers? (grin)
Mike

[Jim Becker]

Augers kinda need a beefy driver if you're going to go through a lot! The drill that my electrician uses with them is a very scary machine...takes two hands to hold it! You'll also notice that the augers pull a lot of the chips out which is important when drilling deep holes through thick materials...like building framing. (Interestingly, some of the oldest Neander drill bits I've seen were augers, many of which were used for timber framing)

Spade bits, especially those with the little wings, do a very nice job for larger holes when sharp and can even have a clean exit if you clamp a sacrificial board in place. And they are easier to use hand-held. You don't want to put a big forstner or saw-tooth bit in a portable drill.

[Rob Blaustein]

The spade bits I have are probably low quality since they were part of a $30 Costco bit kit loaded with all sorts of different bits, drivers, etc. I used them to drill holes through some pressure treated 2x's recently and I have to say that after a few holes they were bogging down. As with all of these things, sharpness and quality help, as Jim pointed out. I assume I can just sharpen them by hand with a file, right?

Off topic, but speaking of electricians Jim, I watched my electrician drill a good sized hole through our concrete garage wall the other day using a pretty big Bosch SDS hammer drill with what looked like an auger bit but designed for concrete. As discussed in other threads here, the SDS drill is quite a different beast from your standard hammer drill--it was impressive to watch.

[Jim Becker]

Good points, Rob. I was very happy with the Irwin 3/4" spade bit I bought when I was doing the dog holes in my bench. Very clean...those little wings really do work. And it was fairly easy on the drill, too.

[Dale Lesak]

One thing I don't think anyone touched on is the spade bit is like a brad point bit and the auger is a self feeder. Once it starts drilling hold on. it will drill aggressively until the feed screw clears the other side. I have seen auger bits with the brad point feature :)

[Gary Keedwell]

Also, if you can sharpen it with a file...it is too soft and not worth sharpening.
Gary