Auger Bits

Been readying myself to attempt a small timber framing project and have acquired a hand powered boring machine and a t-auger..(bless ebay)..anyways...looking to get some bits and I'm confused between the ship auger bits and the wood boring bits that lets say irwin makes...which are the appropriate ones for working in pine and oak and/or is there a better manufacturer or source

thanks in advance

I recently bought some Bosch ship auger bits(I work for Bosch too). Bosch has two types,type I and type II. I talked to the Bosch marketing people and was told to get the Type I for cleaner holes. Type two are for going through staples and nails if you hit them, and while it does that, it won't leave as clean a hole due to it's more aggressive nature. So the type I 's are the way to go. I am new to timber framing too, so I don't have a lot of experience yet. I have no familiarity with Irwin bits.

Irwin makes some double-spur bits that work fine. I would avoid the ship augers as they tend to tear up the wood. The bits you see in the big-box stores are not usually double spur. Irwin Auger website
Look carefully at the twist pattern and note how it differs from the ship augers.

Admittedly I have not tried my new bits yet as I just recieved them. Yes they have a single cutting edge, but on the opposite side they have a blade knife edge on the outer diameter to score the wood before the cutting edge gets to that section. I think this design is made to prevent tearout. I will try to test one this weekend on a scrap piece when I am out at my shop. Brad

i took a close look at the irwin bits and i am not familiar with the bosch versions but the problem i saw is that the shaft end was completely round and i dont see how that would hold in chuck of my ancient boring machine (snell, i think)..the bit that came with it was 1/3 flat and 2/3 rounded....brad...let me know how it works out for you

Brad- The knife edge to which you refer is what is called a spur. Some bits have a single spur and some have a "double" or "twin" spur. As you said, these are to cleanly cut the fibers on the circumference before the center material is drilled out. Two spurs will generally produce a cleaner hole. Some of the "ship augers" or electricians bits have no spur. Some of these are known as "nail eaters" as the are meant for plowing through wood for wiring or piping and they just need to aggressively hog out material. The nature of the cutting edge (almost square) lends itself to tearing through rough material, even the occasional nail, without losing the "edge". ("edge" is used very loosely here, like the "edge" on a pick-ax!)
Also of interest is the Wood Owl bit. It has three spurs and three flutes. The spurs are shaped a little differently than conventional spurs. They cut extremely well but are a little trickier to sharpen. They sell special files for them. They are also pricey. I don't know if they're adaptable to boring machines (I'm not sure of the shank size). I have only used them for peg holes.

A flat side can easily be ground on to a round shank. It only needs to be enough to allow the chuck screw to grab hold and prevent rotation. Milwaukee makes a spurred 1 1/2" bit that works nicely in my Boss Double Eagle boring machine.

Also refer to Jim Rogers tools in this forum.

Here's what I was taught:

Both of these bits are 1-1/2" auger bits. The one on the top/left is called a "Scotch pattern". The one on the bottom/right is a "Jennings pattern".




Both are double spurred bits. Both have flat cutters that are approximately parallel to the work surface that lift off the chips. Both have lead screws to pull the bit into the wood. The difference is in the location of the spurs. The Jennings spurs hang down below the cutters. They score the circular edge of the chip before the cutter lifts it out. That makes for a cleaner hole. The Scotch spurs stick up above the cutters, and cut the circular edge of the chip at the same time the cutters are lifting up the chip. Becuase it does not have to drive the spurs into the uncut wood, it requires less effort to turn, but it does not cut as clean a hole. In general (I repeat, in general), the Irwin pattern works best with power tools, and the Scotch with hand tools, as the added power for turning the Jennings comes from the motor, not the arms. It's probably not a big deal for a boring machine, but on a T-Auger, every little bit helps!

Note also that in my examples, the Scotch pattern has a more aggressive screw thread, requring fewer revolutions to bore the same depth. Again, with a power tool, more revolutions doesn't make much difference. I think the aggressive screw pattern is also more appropriate for softwoods, the finer pitch thread for hardwoods.

Finally, I agree with Dan, that you should track down Jim Rogers. He knows his stuff, and sells high quality tools. CB.
CB.