a drawbore pin question

[David Wadstrup]

Hi,

I'm building a Roubo and will soon be drawboring the rails to the legs. I purchased about a dozen 3/8" hardwood(maple or birch, LeeValley says -- I think the ones I got are birch) dowels to serve as the pins. Now that I have them I'm wondering if maybe birch isn't such a good choice. What do you think? Should I use oak or something else instead?

Thanks!

[Jim Matthews]

Will you also glue the tenon in place, or just use the pin?

If it's just the pin, do a flex test.
Get the pin of your desired length, and get it wet with glue.

See if you can bend it into a U shape without breaking.
If it breaks, your suspicions are confirmed.

The offset is how much in your design?
1/32"?
1/16"?

The pin essentially acts as a spring.

[Andrae Covington]

Jim's advice sounds good. The birch is probably ok if the grain is pretty straight. The problem with commercial dowels is that the grain often wanders off and you get short grain along the dowel, which will be weak in bending. You can be selective about where you saw out short pieces for pegs though.

I think I bought the same dowels when I was building my roubo workbench, but I ended up making my own pegs out of red oak; riven blanks pounded through a shop-made dowel plate.

[Michael Peet]

Personally I would avoid commercial dowels and try to go with riven ones. They will follow the grain and therefore tend to be stronger than the perfect machine-made dowels.

I made mine from ash but oak is also a popular choice.

Mike

[Wilbur Pan]

Riven is best and traditional, but I've made my drawbore pins from 1/4" or 3/8" oak dowel rods from the borg. They come in 36" lengths, and I just cut off the length needed for the drawbore pin. If there is runout in the grain, you'll see that quickly if you bend the dowel a bit. The dowel will easily split before you use it.

[Russell Sansom]

Unless you're putting some really unusual stress on the dowels, the birch should work. In my experience there's more "wedging" going on than "bending," but it matters how much offset, species of wood, size of the tenons, etc.

To put a nice taper on the dowel, there's where the riven ones are so superior, since you can whittle the peg to the perfect taper. With a BORG dowel it's just a matter of luck for the grain to be tame enough to whittle. I've found that each draw-bore experience wants it's own taper. There have been many times when I've looked into the dry-fitted joint, like a leg to a table apron, and It's obvious no dowel is going to go AROUND the too-severe kink I've created. In that case, I taper the dowel on one side and leave it fairly flat on the other. This generally works, even though the full circumference of the dowel probably won't come out the other side if it's a "through" dowel pin. I don't usually bother, but in some cases it's necessary to drill out 1/4" of the tapered part of the pin ( on the back side of the joint ) and replace it with a little button of perfectly circular dowel to cover up the unsightly gap.

[Zach Dillinger]

Your dowels will work, but a riven oak, ash or hickory peg will be better. It doesn't need to be perfectly round; in fact it is better if it is slightly faceted. Tapering is a must, so that it can find its way through the tenon hole and so it can snake through the offset.

[Jim Foster]

I used some commercially available white oak and walnut dowels in my bench, and if I could do it over again, I'd use white oak (since I have a lot of it) and rive them myself. I was surprised how weak the walnut ones were. My bench is solid, so-far, just seems like the dowels were not what I expected.

[Rob Fisher]

...a riven oak, ash or hickory peg will be better. It doesn't need to be perfectly round; in fact it is better if it is slightly faceted. Tapering is a must, so that it can find its way through the tenon hole and so it can snake through the offset.Exactly, I would even specify white oak, as opposed to red.