Auger bits

[lowell holmes]

Jim Koepke drilled holes with an auger bit and then inserted dowels in the holes leaving them proud on the saw bench he made. (See the current string Jim posted about making the saw bench)

As a matter of discussion, I’m making the observations below. This is not to question Jim's work. I’ve had discussions with woodworkers about this before, but I have found no common knowledge. I've never found any one that was aware of this.

I have an Irwin set of auger bits that was my Dad’s. It is a 13 bit set in an oak case. The booklet that was in the case has a 1971 copyright date. On page 5 of the booklet, it states:
“All auger bits, except those made especially for doweling work, are ground approximately 1/64” oversize. This is done so that holes bored for bolts, pipe, cable, etc. can be bored with the same size bit (8/16” hole for a ½” bolt) and a snug fit will result. Dowel bits are made close to actual size so dowels will fit snug.”

I have a doweling jig, and the auger bits will not fit in the jig, so I tend to believe the Irwin information. My auger bits are in fact 1/64" oversize. I’ve also experienced that dowels bought to use are oversize so they will not be loose in an auger bored hole.

Jim’s dowels don’t look loose in the pictures.

Does anyone have a comment to make about this (even if it really doesn't matter.) :)

[Jim Koepke]

I guess I could comment. In my thread, "A Bit About Augers" a bunch of #8 bits are measured with the results being between 0.500" and 0.512".

I also know that there are many types of dowels available. I have seen them in poplar, oak and cedar in just one store. If you go into crafts stores you will find even more.

Another problem may be that a lot of these things are not coming from China or Indonesia. If they are made metric and then sold to the nearest size, it could be trouble for us neanders.

For my smaller bits, there are a few of each size so that I can check for the closest match of bit for dowel.

If I see a decent bit at a yard sale at a decent price, I almost always will buy it. I have seen a lot that get left behind.

jim

[Eric Brown]

Lowell, if you look at the bits closely with calipers you will find that they actually taper, with the cutting end being largest. Most bits are slightly oversized when they start life, but everytime you sharpen the spurs they get a little smaller in diameter as the very tips of the spurs get shorter.

It's not much, but a dozen or so sharpenings could make the difference.

Also consider that dowel bits typically are not used on deep holes so they don't require as much (if any) taper. They start life very close to the stated size.

Now for your consideration is the interesting fact that most dowels are made oversized. Not only that but moisture can make them swell and become ovalish.

So unless you use a dowel plate and make your own dowels, it's best to just try what you have and make adjustments.

Eric

[lowell holmes]

This does help put it into perspective. Matching your auger bit and dowel to be used works for me. I do have some old bits that are redundant and I haven't valued them. I will now inventory, clean and sharpen them.

I was not aware of the taper.

I've considered making a dowel plate. I think I will go ahead and do it.