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Drawbore vs Parallel Clamp ?

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Forum topic by Holbs posted 05-08-2018 04:55 AM 686 views 0 times favorited 15 replies Add to Favorites Watch
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Holbs

1960 posts in 2178 days


05-08-2018 04:55 AM

I’m getting near that stage in a project (joinery bench) that I will be using 3.5” long 3/8” dowel pins for mortise/tenon and bridal joints (2 for each joint). I’ve never done drawboring before but have long enough parallel clamps.
If I went drawbore, my luck with douglas fir has not been all that great for planing and chiseling things smooth 100%. I would be afraid the drawing down of the tenon would split/crack the douglas fir tenon with my luck.
If I went clamp, I would clamp the mortise piece into the tenon, then drill 3/8” hole and mallet in the dowel.
So my question is…. if the idea being drawboring is to bring the mortise shoulder tight up to the tenon… wouldn’t I get the same action by using the correct parallel clamp?

-- The Carpenter Bee is derived from the Ancient Greek word wood-cutter


15 replies so far

View jmos's profile

jmos

869 posts in 2518 days


#1 posted 05-08-2018 11:57 AM

Yes. I think your analysis is sound. If you glue and clamp, it will do largely the same thing as drawboring. Pegging the joint will give you some back-up in case the glue fails; but I think it’s mostly cosmetic.

-- John

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OSU55

1870 posts in 2138 days


#2 posted 05-08-2018 12:14 PM

I suspect a drawbore would create more for force in the joint, but your plan is sound, especially since you are using fir. Good drawbore joints dont have to have glue.

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bondogaposis

4996 posts in 2500 days


#3 posted 05-08-2018 12:48 PM

The purpose of draw boring is not to save on clamping but rather a mechanical feature that will hold the joint together in 50 years when the glue fails. If the project is not an heirloom type project then it makes no difference whether you draw bore or not.

-- Bondo Gaposis

View Tony1212's profile

Tony1212

229 posts in 1883 days


#4 posted 05-08-2018 02:05 PM

Full disclosure: I’ve only done 16 drawbore joints in my life.

When I was building my workbench, I used both glue and drawboring (and clamps to tighten things up so the hole in the tenon was in the right place). I figured that even if the wood of the tenon did split, the mortise is tight enough and there’s enough glue, that the tenon won’t be able to unseat from the pin. Keeping the joint tight as the wood continues to dry.

For instance, if there’s a single split in the tenon (with the grain from the draw bore hole to the end), there’s no way the tenon would be able to spread out enough to slip past the pin. The mortise would prevent it.

If there’s a double split in the tenon at the top and bottom of the draw bore hole, the glue should hold it together enough that nothing can slide apart.

Yeah, draw bores are supposed to allow you to not use glue and clamps, but I figure if you’ve got em, use em. If nothing else, the draw bore should allow you to take the clamp off and still keep the joint tight until the glue dries. And if you DO get a double split, you’ll know it right away and the glue is already in the joint, so you won’t have to disassemble everything to glue it up.

-- Tony, SW Chicago Suburbs

View Loren's profile

Loren

10477 posts in 3796 days


#5 posted 05-08-2018 03:45 PM

I’ve never made a drawbore joint but I
have a few ideas. Back in the day, hide
glue was the only wood glue around and
joints had to fit quite well because it
doesn’t fill gaps. Pinning joints could be
a hedge against glue failure.

Draw bored joints are obviously used in
timber framing where the joints don’t
fit well enough for glue, clamping is awkward,
and the joints and shapes of things are
changing all the time anyway because it’s
done over a period of weeks. I could see
some crossover applications to making larger
furniture pieces, especially if the wood was
less than ideally seasoned.

I’d tend to avoid experimenting with the technique
on softwood furniture joints personally, especially
if I could close the joint with a clamp and a
modern glue was being used.

View jmartel's profile

jmartel

8158 posts in 2299 days


#6 posted 05-08-2018 03:55 PM

If anything, doing it in Fir would be more beneficial as that has a tendency to compress much easier. It would be more difficult in a hard wood that doesn’t compress. I’ve broken tenons when drawboring before. You only need about 1/32” of offset to make the joint.

If you don’t want to risk it, then clamp the crap out of it, drill your holes, put the pegs in. Should work just fine. Your plan shouldn’t have any issues.

-- The quality of one's woodworking is directly related to the amount of flannel worn.

View rwe2156's profile

rwe2156

3094 posts in 1629 days


#7 posted 05-08-2018 03:58 PM

Historically, I think the drawbore was used without glue. In fact, there was a lot of furniture built with no glue whatsoever.

Today with modern glues, the most common reason for the drawer bore is a breadboard or large timber frame-type joinery which doesn’t use glue.

In your case, so longs as your joinery is good, I think drawer bore is a bit overkill. Besides that, it doesn’t lend itself as well with softwood.

Bottom line: Gluing and pinning will suffice.

-- Everything is a prototype thats why its one of a kind!!

View Woodknack's profile

Woodknack

12369 posts in 2529 days


#8 posted 05-08-2018 05:43 PM

Draw bore is pre-industrial woodworking and still a nice technique but completely unnecesary if you have decent clamps.

-- Rick M, http://thewoodknack.blogspot.com/

View Holbs's profile

Holbs

1960 posts in 2178 days


#9 posted 05-09-2018 12:52 AM

I have Jorgensen Cabinet Master 48”+ clamps x 4 along with 4 Bessey.
I think I’ll try drawboring without clamps (or maybe a little help with the clamps). Reading up on Christopher Schwarz article able drawboring is…inspirational.
I even went a step further and just purchased 3/8” and 1/4” drawbore pins from Lee Valley. Doesn’t hurt :)
I’ll toss in glue to cover bases.

-- The Carpenter Bee is derived from the Ancient Greek word wood-cutter

View Aj2's profile

Aj2

1732 posts in 1947 days


#10 posted 05-09-2018 03:06 AM

Draw boring is a good trick to have in your bag. One advantage is it allows you to assemble parts with out using clamps. This is a good way to check the fit and make changes on complicated builds.
I used draw bored tenons on some fancy gates. And some small tables with a gunstock joint
It’s also good to have at least two draw bore tools. Just remembered to suggest that you rive your wood and don’t worry if they look snakey or crooked this will work to your advantage

-- Aj

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Holbs

1960 posts in 2178 days


#11 posted 05-09-2018 04:06 AM

Thanks for the replies, folks. The yes/no answers made me dig deeper into the subject of drawboring.
Yes, I will go drawboring for all joints. If I simply clamp and peg… it plays no part structurally. If I drawbore, it will forever keep the peg squeezing the tenon downwards.
Besides, gives good practice :)

-- The Carpenter Bee is derived from the Ancient Greek word wood-cutter

View rwe2156's profile

rwe2156

3094 posts in 1629 days


#12 posted 05-09-2018 02:01 PM

Holbs, Unless you’re not gluing the joint, or using hide glue maybe, drawboring offers no advantages over pegging with today’s modern glues.

If you dug deeper did you come across anything about the use of draw boring without glue? Because I’m quite certain that’s where it originated (and still used to day in breadboards and timber framing.

Go ahead and do it, but you’re making more work for yourself unless you just want to practice, then OK.

-- Everything is a prototype thats why its one of a kind!!

View Rich's profile

Rich

3668 posts in 738 days


#13 posted 05-09-2018 02:06 PM


Holbs, Unless you re not gluing the joint, or using hide glue maybe, drawboring offers no advantages over pegging with today s modern glues.

- rwe2156

For anything other than Rosie O’Donnell’s chair, hide glue is sufficiently strong on its own.

http://www.oldbrownglue.com/images/articles/HowStrongisYourGlue_FWW.pdf

-- Half of what we read or hear about finishing is right. We just don’t know which half! — Bob Flexner

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Holbs

1960 posts in 2178 days


#14 posted 05-09-2018 02:22 PM

RWE..you are correct. Everyone says there is no need for glue when using drawbore pegs. Yet, most do out of…habit?

-- The Carpenter Bee is derived from the Ancient Greek word wood-cutter

View Woodknack's profile

Woodknack

12369 posts in 2529 days


#15 posted 05-09-2018 05:00 PM

“Modern glue” (PVA) was discovered about a century ago and has been used in woodworking for about 60 years. And like Rich says, hide glue is very strong. Tight joinery is produced everyday without draw boring, that said, it’s a good technique. I pin all mortise and tenon joints, sometimes I offset the holes a bit and sometimes I don’t.

-- Rick M, http://thewoodknack.blogspot.com/

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