Drawboring in softwood

[MarkDennehy]

Folks, quick question - if you're drawboring an M&T joint in softwood, should you use a softwood peg as well? Would a hardwood peg punch through the offset bit of the tenon on its way through the hole instead of deforming round it and applying the pressure?

 

[No skills]

Interesting question that I'd also like to know the answer to

I'd be worried that a softwood dowel would break, hmm..

 

[Phil Pascoe]

I'd have thought a softwood peg would deform too easily.

 

[ColeyS1]

For a drawbore to work it only has to be offset by a very small amount. I guess the only issue with a softwood drawbore might be that it'll shrink more than a hardwood one so not be very good at keeping the joint tight once it's shrunk.
I posted a thread years ago about a drawbore machine I made. When i was an apprentice i hated planing em tapered by hand- probably cause I use to plane my fingers off [SMILING FACE WITH OPEN MOUTH] it's certainly made it a almost pleasurable task making them now. A tapered drawbore is so much better than just a dowel imho.

Coley
Edit - drawbore jig
draw-bore-guide-draw-bore-maker-t42140.html

 

[ED65]

I think the rule of thumb is that the peg should be hardwood. But I don't think softwoods are ruled out entirely, big difference if you made them from a good piece of fir compared to a weedy bit of pine. And obviously yew is hardwood-hard.

As I suspected Christopher Schwarz has looked at this in detail and he says definitively in his workbench book he says "Make the pins from the toughest wood you can." his preference being white oak.

Would a hardwood peg punch through the offset bit of the tenon on its way through the hole

It might if you didn't whittle or pare a slight taper on the tip.

 

[Jacob]

I've done loads of old windows where M&Ts are pegged but I doubt they were draw bored - more likely just clamped tight and drilled through.
If you can do this you don't need to draw bore.
Draw bore is an alternative to clamping for difficult shapes so if you don't need to then don't. Typically a stair stringer to newel post with 5/8" round dowel (often either pitch pine or oak) done through a dowel plate from riven blanks for straight grain.
The window pegs were usually oak or pitch pine, square (riven) about 1/4" but you would hardly know as by the time they are hammered through a round hole they've also got rounded off. Though there are tell tails such as the "apple seed" shape you sometimes see at the end on the driven side - where the peg is harder along the ring marks and doesn't squash equally all round.

 

[Phil Pascoe]

I wonder if sometimes people see pegged joints and presume they are draw bored?
I had sashes in my old house that were a bit shaky - when I investigated during a serious redec. I found that they were pegged with twigs - which obviously had shrunk on drying.

 

[Jacob]

I wonder if sometimes people see pegged joints and presume they are draw bored?
I had sashes in my old house that were a bit shaky - when I investigated during a serious redec. I found that they were pegged with twigs - which obviously had shrunk on drying.

The square riven pegs do look like twigs when they work their way out 100 or more years later.

 

[Phil Pascoe]

Definitely twigs - the centres were hollow where the pith dried out.

 

[deema]

Some woods react with each other to create stains, so the best course of action is IMO to use the same wood for any draw pegs. If you select the diameter to take into account the wood you compensate for any weakness in both the peg and the compressibility of the wood making up the M/T. A small diameter hardwood peg in a very soft wood will only apply a certain pressure due to the M/T wood compressing under pressure, the result a poor clamping pressure. Equally using the same species helps with finishing hardwood in most cases is not good for instance at taking paint. It also ensures that the wood reacts the same to moisture.

Again it's my opinion that the glue on M/T in Windows often fails after a number of years and the windows are held together by the draw peg. I often find that when a sash has rotted, usually the rails, and if it needs restoring due for instance to graded listing requirements that once the draw pegs are drilled out (or tapped out with straight drift) the window will fall apart.

 

[ColeyS1]

A small diameter hardwood peg in a very soft wood will only apply a certain pressure due to the M/T wood compressing under pressure, the result a poor clamping pressure.

I don't understand that. If you've got a hole in a tenon and an offset hole in the mortice, surely pushing something hard, thats round and tapered will try and cause the holes to line up, creating a nice squeezed up joint ?

Coley

 

[deema]

Hi Coley,
Your absolutely correct, it will compress the joint to a point depending on the species of wood. Softwood is relatively soft and compresses under pressure / tension. To minimise the compression you have to make the diameter of the draw rod larger in a soft wood compared to a harder wood.

 

[Jacob]

Just in case anybody has missed the point - you don't draw bore anything if you can clamp it.
It's just for difficult objects - stair string to newel at an angle, funny shaped chair legs you can't get a clamp on etc.
To make it work everything has to be a good push fit first or the draw bore pin might split the tenon. Then the actual dowel just pulls up the last fraction of an inch to close the gap.
It doesn't make a stronger joint and is best avoided if you don't need to do it.

.....it's my opinion that the glue on M/T in Windows often fails after a number of years....

yes but only if the paint work is neglected.

 

[paulrockliffe]

The jig looks neat. I presume you didn't have access to a lathe, otherwise you would have made it as a lathe attachment? Seems the most obvious way to do it if you can.

 

[No skills]

I think I have read that draw boring was also used as an alternative to clamps which in dark and distant times could be very expensive.

 

[ColeyS1]

Hi Coley,
Your absolutely correct, it will compress the joint to a point depending on the species of wood. Softwood is relatively soft and compresses under pressure / tension. To minimise the compression you have to make the diameter of the draw rod larger in a soft wood compared to a harder wood.

Or just hammer the tapered drawbore in a bit more.

Coley

 

[ColeyS1]

The jig looks neat. I presume you didn't have access to a lathe, otherwise you would have made it as a lathe attachment? Seems the most obvious way to do it if you can.

I've got a lathe but couldn't think of an easy way for repeatability. The drawbores are quite long and if the speeds not quite right that's turning the square blank, you either end up with a very poor finish (if it's too slow) or it completely disintegrates from flexing too much.
I was interested how Appleby made there tapered pellets and thought he might have had a few suggestions that I could have used for my drawbore jig. Apparently it was a trade secret and he couldn't share photos or info ! A bit of googling and I found photos of there setup on t'internet anyway [SMILING FACE WITH OPEN MOUTH AND SMILING EYES] it's the flexing that causes complications.
Come to think, I think using just the end of the router cutter caused less flex as it seems to slice the wood better.

Coley

 

[Jacob]

A very common trad way with dowels is to split a blank (for straightness of grain) and to hammer it through a dowel plate. They come out a bit rough and not perfectly straight but that's fine for a dowel as long as the grain is straight so it won't collapse when being hammered home.
Faster and a lot easier than turning!

 

[ColeyS1]

But not tapered Jacob - Bit like pellets, tapered ones are better cause you're guaranteed a nice snug fit.

Coley

 

[No skills]

Can't you rig up something like the veritas taper cutter? (Jumbo pencil sharpener).