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Norm Dresner
 
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Default Need advise on reparing broken leg on old wooden desk

During a move I broke one of the wooden legs of a (circa 1940) wooden desk
right where the round turned leg was attached to the square top that forms
the corners of the case. Of course it's not a clean break, though it's not
that jagged either, and I can fit the two halves together by hand quite
closely.

I'm intending to repair the break by drilling for and inserting a metal
"dowel" of some sort as a strength member between the two pieces. I have an
older 3/8" drill mounted in a portable drillpress which I'm pretty sure can
be used to drill the hole into the case part along the axis of the leg quite
accurately. But I have no lathe and I don't see a good way to align the
hole in the tapered rounded leg axially. I have 1/2" (tabletop) drillpress
on which I could tilt the table. I haven't had the table tilted in the last
30 years so I don't know if it will rotate further than the marked 45
degrees but I see no stops that would prevent it from going (close to)
vertical. Since this is a tabletop drillpress, there's not enough room to
put the leg between the chuck and the base, though (it looks like) I can
swing both the head and the table out over the edge of the stand to get
space down to the floor.

I'd like comments, suggestions -- and even constructive flames -- concerning
the following scheme:

1. Swing the head and table around so that they're no longer over the base
but rather clear of it. Measure the taper angle of the leg and set the
table to 90 degrees - taper angle so that the axis of the leg would be
vertical when clamped into a v-block against the table. I think that this
should give me the ability to drill exactly parallel to the axis of the leg.

2. I don't know how to get the exact center of the broken end of the leg
and there's no part that's even close to the exact diameter of any (Fostner)
drill bit I have to use to create a jig, though I guess I could try to
(patiently) use an adjustable circle cutter and chisel out the center to get
a center finder. Any comments or suggestions?

3. I think I can locate the "exact" center of the square end of the broken
leg on the case by "drawing" the two diagonals.

My biggest fear is getting the holes in the leg parts off-center relative to
one another.

Now -- here's another thought on which I'd like comments. Epoxy glue is
significantly stronger than wood. If I can get even a sloppy hole in the
two parts into which I can insert a "spline", I should be able to use the
jagged break to align the leg with respect to the case and a level together
with a custom-cut tapered wedge the same angle as the leg taper clamped to
the leg with a level to get the leg vertical. When the glue sets, the whole
joint will be stronger than the original wood was. _Please comment_.

Thanks in advance.

Norm

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Andy Dingley
 
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On Mon, 02 May 2005 05:20:27 GMT, "Norm Dresner" wrote:

I'm intending to repair the break by drilling for and inserting a metal
"dowel" of some sort as a strength member between the two pieces.


That sounds the right sort of idea, but personally I'd use a wooden
dowel. If you use a strong timber - even a broomstick - rather than
typical decorative dowel stock, then this is a strong enough repair for
a desk. Chairs are always a bit harder, because of the racking forces,
but desks are a nice simple static load.

But I have no lathe and I don't see a good way to align the
hole in the tapered rounded leg axially.


Good bench vice, a hand-turned drill and eyeball it. If you're _SLOW_
then you can do this accurately enough. Using an electric drill _will_
encourage you to squeeze just that little bit too hard when "it's going
well", then you'll screw it up.

Start out by chiselling a flat and square starting plane for the
drillbit..


2. I don't know how to get the exact center of the broken end of the leg


Chisel the middle flat. Then use a pencil and finger to draw a tiny
circle in the centre. Eyeballs are surprisingly accurate, if you take
your time.


My biggest fear is getting the holes in the leg parts off-center relative to
one another.


Of course this will happen, for some tiny value of "off center". What
you actually mean here is "How much gap filling will the glue be doing,
after I've adjusted the hole to allow correct alignment".

If you're averagely careful, then the hole will be close enough to allow
white glue or hide glue (your call) in a nice closely fitting joint.
Don't make it _too_ tight, or you'll squeegee the glue off the dowel as
it goes in (and remember to groove the dowel sides a little too).

If it's sloppy, then change glue. I'd go for epoxy with cellulose fibre
filler in it, maybe microballoons on a valuable piece (easier to
dismantle in the future). Some people might use PU glue, which will gap
fill anything easily, but I've never liked the stuff myself.


I should be able to use the
jagged break to align the leg with respect to the case


That should be sufficient to give you a good result.

For clamp up here, I'd splint a leg that was easy, but not one that
required tapered shims. For doing those I turn the piece upside down and
use a brace on the top part, jury-rigged from a chemistry lab stand and
brackets (these are useful workshop equipment, and worth scrounging if
you ever get the chance)


--
Cats have nine lives, which is why they rarely post to Usenet.
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George
 
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"Norm Dresner" wrote in message
...
During a move I broke one of the wooden legs of a (circa 1940) wooden

desk
right where the round turned leg was attached to the square top that forms
the corners of the case. Of course it's not a clean break, though it's

not
that jagged either, and I can fit the two halves together by hand quite
closely.

I'm intending to repair the break by drilling for and inserting a metal
"dowel" of some sort as a strength member between the two pieces. I have

an
older 3/8" drill mounted in a portable drillpress which I'm pretty sure

can
be used to drill the hole into the case part along the axis of the leg

quite
accurately. But I have no lathe and I don't see a good way to align the
hole in the tapered rounded leg axially.


At least one aspect will be in perpetual shadow, won't it? How about gluing
up, groove in the hidden side, reinforcement inserted.


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Hax Planx
 
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Norm Dresner says...

During a move I broke one of the wooden legs of a (circa 1940) wooden desk
right where the round turned leg was attached to the square top that forms
the corners of the case. Of course it's not a clean break, though it's not
that jagged either, and I can fit the two halves together by hand quite
closely.


Dowel joints have to be exceptionally accurate even under normal
circumstances, but in this case it would have to be perfect. Even a few
thousandths of off would be too much considering the jagged edges have
to meet perfectly. I strongly suggest you forget about that scheme. It
won't work with the tools and techniques you described. The obvious
course of action would be to just glue and clamp the break without any
reinforcement. That's what I would do. It might even be more or less
as strong as the unbroken wood that way, but in any case it would only
break again if you had another major accident. I wouldn't use epoxy
either. The bad thing about epoxy is that once it hardens, it is there
forever. You will have a real mess on your hands of you have a false
start with epoxy. I would use hide glue because it is reversible. If
it doesn't go together right, you could (with some difficulty) take the
joint apart again and reset it. If you feel you must reinforce the
joint, do it after the break is glued together and square. You could
put a spline in the back side as someone else said. If the top is not
in the way or can be removed, you could drill from the top with an
appropriately long bit and add a dowel that way.
  #5   Report Post  
Richard Cline
 
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In article ,
Hax Planx wrote:

Hax has the right idea. Dowling is clearly an invitation to disaster.
Practice hand fitting the pieces dry. If you can get them to fit
together accurately, a simple glue job should be adequate. A
conventional wood glue joint is often stronger than the wood.
Conventional wood glue would give you time to adjust the alignment of
the parts. Hyde glue would give you the opportunity to disassemble.

Dick


Norm Dresner says...

During a move I broke one of the wooden legs of a (circa 1940) wooden desk
right where the round turned leg was attached to the square top that forms
the corners of the case. Of course it's not a clean break, though it's not
that jagged either, and I can fit the two halves together by hand quite
closely.


Dowel joints have to be exceptionally accurate even under normal
circumstances, but in this case it would have to be perfect. Even a few
thousandths of off would be too much considering the jagged edges have
to meet perfectly. I strongly suggest you forget about that scheme. It
won't work with the tools and techniques you described. The obvious
course of action would be to just glue and clamp the break without any
reinforcement. That's what I would do. It might even be more or less
as strong as the unbroken wood that way, but in any case it would only
break again if you had another major accident. I wouldn't use epoxy
either. The bad thing about epoxy is that once it hardens, it is there
forever. You will have a real mess on your hands of you have a false
start with epoxy. I would use hide glue because it is reversible. If
it doesn't go together right, you could (with some difficulty) take the
joint apart again and reset it. If you feel you must reinforce the
joint, do it after the break is glued together and square. You could
put a spline in the back side as someone else said. If the top is not
in the way or can be removed, you could drill from the top with an
appropriately long bit and add a dowel that way.



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Lew Hodgett
 
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Norm Dresner says...


During a move I broke one of the wooden legs of a (circa 1940) wooden desk
right where the round turned leg was attached to the square top that forms
the corners of the case. Of course it's not a clean break, though it's not
that jagged either, and I can fit the two halves together by hand quite
closely.


The easiest approach if I were doing the job would be microballoon
thickened epoxy.

Mask of the areas where you don't want the epoxy and go for it.

I can see absolutely no reason why you would want to take this repair
apart, so don't understand the hide glue approach.

As far as any kind of a mechanical aid approach such as a dowel, I
wouldn't go there.

No matter how you approach doweling for this job, you will never get it
perfectly aligned.

Close, yes, but perfect, no.

BTW, the epoxy will be the strongest repair you can make.

Lew

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Hax Planx
 
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Lew Hodgett says...

I can see absolutely no reason why you would want to take this repair
apart, so don't understand the hide glue approach.


Well, the idea was that he could start over if the first attempt didn't
work out.
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