Drawboring: How much offset is enough?

[Joe A Faulkner]

I’m looking at the photo enlarged, and frankly, it looks pretty tight. There is a slight gap at the right side, but it also appears quite tight through the center area. From what I can see, it looks like maybe the gap is just a reflection of the fit. Oak has such open pores that an open pore next to the shoulder could seem to be a gap. Unless you can get a piece of paper between the joint, I’d say it’s good to go.

I'm with Phil. Looking closely at the edge of the receiving board, it looks like if you put a straight edge across that edge there would be a gap due to the open grain and/or perhaps minor void in the edge itself. Not to discount the auger bit theory.

[Malcolm Schweizer]

If you used glue, then the problem may be there was not enough room in the mortise for the glue and it pooped in the back of the joint, preventing the tenon from fully seating. This is especially true if you used epoxy, which has less compression and less absorption into the wood than yellow wood glue. No matter what glue, if the joint was especially tight, glue could have compressed into the back of the joint and prevented a tight fit.

Don’t feel bad- guess how I know all of the above!

Edit- that’s “pooled” and not “pooped”! Darned auto-correct.

[Jim Koepke]

Fun fact: (That many of you, maybe all of you, already know). Auger bits are slightly oversized!

This tells a bit about that:

https://sawmillcreek.org/showthread....t-About-Augers

Usually auger bits are in the range of 0.015" oversized.

There are also auger bits that are DNO (Dead N*ts On) for doweling.

Edit- that’s “pooled” and not “pooped”! Darned auto-correct.

LOL! Didn't realize the typo (correction) until you mentioned it.

Glue as occasionally "pooped" on my efforts at woodworking.

jtk

[Matthew Hutchinson477]

That would be another cause of what you are seeing.

It is also a good reason for using riven and tapered pins. Then the hole size accuracy isn't as important.

Though in reality many of my draw boring was done with store bought dowel stock and drilled with a brace and a bit sized for doweling.

jtk

I actually have a piece of 3/8" A2 steel that I am planning on making into a dowel plate so good thing I figured this out before making said plate. If you were to make dowels to use with auger-bored holes would you think sizing up by 1/64" would be enough? Or would you go bigger?

[Jim Koepke]

I actually have a piece of 3/8" A2 steel that I am planning on making into a dowel plate so good thing I figured this out before making said plate. If you were to make dowels to use with auger-bored holes would you think sizing up by 1/64" would be enough? Or would you go bigger?

If possible multiple sizes would be made.

Another approach to getting good results is some dowel plates will have slightly oversized holes to pre-shape the dowels. They end up smoother that way.

If you are going to do a lot of doweling you might want to look for bits that are closer to actual size. My recollection is there are some Stanley Handyman bits in a Russel Jennings style that are dead on size. One problem is in many stores that sell dowels the dowels vary in size and are not always running with the grain like riven wood does.

jtk

[Patrick Chase]

If you used glue, then the problem may be there was not enough room in the mortise for the glue and it pooped in the back of the joint, preventing the tenon from fully seating. This is especially true if you used epoxy, which has less compression and less absorption into the wood than yellow wood glue. No matter what glue, if the joint was especially tight, glue could have compressed into the back of the joint and prevented a tight fit.

Both epoxy and wood glue are incompressible. The difference is that glue dries by evaporation and loses volume, whereas epoxy solidifies by cross-linking and doesn't shrink.