Drawboring white pine

[Mikey R]

Hi,

Im in the process of building the legs of a bench, laminated from B&Qs finest softwood 2 x 4s. The legs are approximately 90mm x 115mm, the stretchers are approx 95mm x 40mm with 18mm thick tennons on the ends. This is my first bit of real joinery, and Im quite pleased with the result so far. I will be drawboring the tennons into the morices in the legs, but I would like some advice on what specie to use for the pegs.

The options from the offcut box are either hard maple, american ash or black cherry.

I am leaning towards cherry pegs, in 10mm holes, offset by 2mm or so. I suspect that the harder, stiffer maple and ash would do more damage to the soft pine than they would help.

Does this sound reasonable?

 

[Dibs-h]

To be able to drawbore you need to have sufficient relish (the bit of the tennon after the pin) otherwise you'll destroy the tennon. As you are using pine and the tennons are quite thin i.e. 18mm - I would be wary of drawboring them.

If you look at my Truss Joints thread on projects - Simon posted some stuff about the nbr of diameters (of the pin) that it was recommended that you had before the pin (to the shoulder) and after (i.e. the relish).

https://www.ukworkshop.co.uk/forums/view ... c&start=15

3rd from last post.

HIH

Dibs

 

[Chems]

I drawer bored some pine tenons less than 18mm with white oak.

Click for larger an you should be just about to make them out, 2 per tenon.



Its very strong, no glue used except on the pegs.

 

[wobblycogs]

I really like that seat Chems and am tempted to have a crack at making one myself. Do you find that the top corners of the legs stick into you are you sit on the seat though? Looks like they could be a bit uncomfortable.

 

[Chems]

If your bum was as wide as the gap it would yes. Have enough stuffing to get up above the pointy bits or make the top parts a little lower. But this one isnt uncomfortable luckily.

 

[Mikey R]

To be able to drawbore you need to have sufficient relish (the bit of the tennon after the pin) otherwise you'll destroy the tennon. As you are using pine and the tennons are quite thin i.e. 18mm - I would be wary of drawboring them.

If you look at my Truss Joints thread on projects - Simon posted some stuff about the nbr of diameters (of the pin) that it was recommended that you had before the pin (to the shoulder) and after (i.e. the relish).

https://www.ukworkshop.co.uk/forums/view ... c&start=15

3rd from last post.

HIH

Dibs

Thanks for the link Dibs, I found this line interesting:

A rough guide to pegging given by Steve Chappell
"When the tenon is in tension, the pegs should be 4 times the peg diameter from the loaded edge"

My stretcher tennons are 65mm long, so if I use a 10mm peg, and drill 12mm from the edge of the leg (advice from Chris Schwarz Workbench book), then this allows me just over 40mm of 'relish', or 4 times the peg diameter. This is cutting it rather fine though! I might go for 8mm pegs, which is annoying as I dont have an 8mm drill bit.

I drawer bored some pine tenons less than 18mm with white oak.

Click for larger an you should be just about to make them out, 2 per tenon.



Its very strong, no glue used except on the pegs.

Thanks Chems, could you tell me how much you offset the holes in the tennons? Im aiming for around 2mm, but maybe this is too much on soft pine.

I might need to make a trial mortice and tennon, and see if it holds up to being drawbored.

 

[Chems]

Less than that, about 1mm to 1.5.

I suggest you test on a bit of scrap before hand and use a clamp to aid the pulling together as this doesn't work as well on pine as it does on hardwoods as the tenon inside just deflects and dents around the hole ending up with the peg snapping

I found this out the hard way.

 

[Mikey R]

thanks for the heads up Chems!

Of course, the other alternative is to cut new stretchers with thicker tennons and enlarge the mortices to match. Maybe 25mm would be a better choice.

Ive got enough material left over, but i'd rather not spend another weekend cutting these joints.

 

[bodgermatic]

Impending threadjack, sorry

I'm doing breadboard ends on my workbench build at the moment, and having read this thread I'm concerned that my tenons aren't long enough. The material is beech, the tenons are currently 30mm deep by 500mm wide. Do I need longer tenons to consider draw boring them?

 

[Mikey R]

Do I need longer tenons to consider draw boring them?

This is where I was getting confused - last night I had a read through the Nicholson Bench chapter in the Workbench book, and the stretchers are drawbored into the legs. But on that bench, the tenons are way shorter than on either the Roubo or the Holtzapfel, and the bench still seems to hold up to regular use.

Are breadboard ends normally drawbored? I thought they are pegged, but not with an offset. Also, the holes are elongated to allow the top to move accross the grain. I saw this on a Woodwrights Shop back episode, cant remember which one though.

 

[bodgermatic]

Are breadboard ends normally drawbored? I thought they are pegged, but not with an offset. Also, the holes are elongated to allow the top to move accross the grain. I saw this on a Woodwrights Shop back episode, cant remember which one though.

Yes, the frontmost hole won't be elongated, the others will - so that the front edge stays where it is and the movement occurs at the back edge. I was going to go for a very slight offset in the holes to get the joint to pull up tight, probably not as much as you would for a standard M&T though.

 

[milkman]

You can always clamp up the joint as hard as you dare then drill it. When you relax the clamps the draw bore will be in place.

 

[bodgermatic]

You can always clamp up the joint as hard as you dare then drill it. When you relax the clamps the draw bore will be in place.

That sounds like a good plan, it takes the uncertainty out of determining the right amount of offset. Thanks milkman!

 

[SeanG]

When I drawbored pine for my garge doors the wood was way too soft to pull together when the pins (softwood dowl) were hammered in.

I offset by 1 to 2mm clamped up hard and fitted te pins.

Been up a year now with no movement.