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Lotsa questions on drawbore mortising

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Forum topic by groland posted 1490 days ago 1653 views 0 times favorited 7 replies Add to Favorites Watch
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groland

117 posts in 2016 days


1490 days ago

I am planning on using 3/8 ” dowels to drawbore mortise some workbench joints in red oak. I will be gluing the joints as well, but my M&T joints are not that tight. The stock is about 3” thick.

I did a test joint today and ran into some problems. I need some advice from those of you who are experienced making this kind of joint.

Problem: hole small or dowels large—first off, the dowel wouldn’t go into the hole. Yes, the bit was a brad point 3/8” bit and the dowels were 3/8. I really pounded on the dowel and it would not go in. I’m wondering now how to tell whether the dowels will fit? I can’t risk gluing up a joint, pounding the dowel and having it fail to go in.

Should the dowel fit into the drilled hole with hand pressure alone? Should you be able to slide it in and out with minimal taps of a hammer? What’s a good rule of thumb here?

Some solutions I can imagine
a.) while the drill bit is in the hole, wiggle the wood a round a bit to slightly enlarge the hole. Seems risky and inconsistent.
b.) sand the dowels smaller-seems tedious and imprecise.
c.) buy one of those gizmos with holes you can pound the dowels through to size them. Are these precise enough to do the job? Any recommendations for good ones?
d.) on another test, I did sand the dowel a lot, then I coated it with a little wax and it slid in much better. Is “waxing” these pins a good idea or a bad idea? Ought the dowels to be glued? Would glue lubricate the dowels while they are being driven in?
Whew! Too many questions, I know.
I have just invested a ton of time in building this workbench and I don’t want to mess up at his last assembly stage!

Many thanks,

George


7 replies so far

View sphere's profile

sphere

109 posts in 1636 days


#1 posted 1490 days ago

I often groove / compress the dowel or peg with vise grips or channel lock pliers prior to glue and pound. Usually just the leading end.

-- Spheramid Enterprises Architectural Wood Works

View uffitze's profile

uffitze

199 posts in 1560 days


#2 posted 1490 days ago

A 3/8” dowel should go into a 3/8” hole without much/any problem.

Correctly done a pegged (drawbored) tenon will have the holes in the mortise piece and the tenon slightly offset. (The peg is actually pulling the tenon into the mortise.) So, in order to get your dowel to go into all three holes, you need to taper the end … the tapered end leads the peg through, and the peg will bend and pull everything tight.

View Gregn's profile

Gregn

1642 posts in 1588 days


#3 posted 1490 days ago

Check out this video on draw bore mortising it may answer a lot of your questions and give you some reference.
http://www.woodworkingchannel.com/dolphin/vidego_video_library.php
Go to the Lie-Nielsen tool works button and click on it. Chris Swartze has a video in 2 parts.

-- I don't make mistakes, I have great learning lessons, Greg

View TheDane's profile

TheDane

3659 posts in 2268 days


#4 posted 1489 days ago

I would not wax the dowels, and IMHO they should be glued.

The dowel rods available at big box stores tend to vary in size … when I built my bench ( http://lumberjocks.com/projects/18261 ) the oak dowel rod from Menards was a skosh over 1/2”. I sanded them down to get a snug fit.

-- Gerry -- "I don't plan to ever really grow up ... I'm just going to learn how to act in public!"

View groland's profile

groland

117 posts in 2016 days


#5 posted 1489 days ago

Sphere, thanks for this good advice!

Uffitze—sorry I didn’t make clear that my tests today were not of drawbore mortises. I just bored a hole into some 1 1/2” oak and tried driving in the dowel. I will certainly taper the ends of my dowels before doing this for real.
Do you have any rule of thumb regarding how tightly the dowels ought to fit—hand tight, tighter than that?

Gregn—thanks for the video suggestions. I shall surely look at them!

3fingerpat—Great tips! I’m thinking 1/16” offset would be good for this application. What would you suggest? I just went on LNs site and ordered their drawbore pins and dowel plate. Thanks for these tips!

TheDane—good information. I bought my oak dowels at The Home Depot. It is wood too. Going to move, swell a bit in humid weather…sizes probably aren’t real exact as you found. Me too!

Appreciate the help guys!

George

View uffitze's profile

uffitze

199 posts in 1560 days


#6 posted 1489 days ago

I see.

Well, I say, make yourself a dowel plate and make your own dowels … that way you’ll know what size drill bit to use.

Hand tight is probably fine … your glue will lube them up similar to the wax idea.

View David Kirtley's profile

David Kirtley

1276 posts in 1602 days


#7 posted 1487 days ago

If I were going to do draw bore it:

You don’t want anything but wood if you are going to glue it. But even the glue is overkill when you are drawboring something on this scale. Also: WARNING WARNING. If you glue the pins, be quick about it. The moisture in the glue will make the pins swell. Faster than your might think.

I would go at most 1/16 offset on something like this. I would also probably use larger pins than 3/8. 1/2 or actually larger. I would personally go as much as 3/4 if the tenons are beefy enough for it. If they are not perfectly round, it will not even show up after driving them through. They will “self fill” as

The pins will be a pretty tight fit to the holes. Point them a bit (like a pencil). If they are through pins, (They will go all the way through both sides) I would make them nice and pointy. More leverage for drawing it tight. This will create the ramp to pull the tenons tight. On this size I would be prepared to do some serious convincing. Probably have my 3lb sledge handy. This is not going to be the job for a little carving mallet.

-- Woodworking shouldn't cost a fortune: http://lowbudgetwoodworker.blogspot.com/

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