chaniarts wrote in
:


and if you put the router down in a slightly skewed position on the
next one than the previous one, you don't get a repeatable width dado
because the router base may not be circular.


If you can replace your router's baseplate, you can get (make?) one with a
flat edge. If you have two parallel flat edges, then you can just adjust
your jig to accomdate.

Puckdropper
--
Make it to fit, don't make it fit.

On Dec 14, 3:35*pm, Swingman wrote:
On 12/14/2012 2:03 PM, Greg Guarino wrote:









On 12/14/2012 1:54 PM, Peter Bennett wrote:
On Thu, 13 Dec 2012 21:38:15 -0600, -MIKE-
wrote:

On 12/13/12 8:19 PM, Peter Bennett wrote:
My router dado jig doesn't need guide bushings or a top bearing bit -
it guides the router base.

each side of the guide consists of two pieces - a wide piece of 1/4"
plywood that the router rides on, and a (straight!) piece of 1/2"
plywood, or similar piece of solid wood glued on top.

Before the first use, run the router along the jig with the base
against the 1/2" board, so the router bit can trim the 1/4" plywood to
the correct size.

The jigs we're discussing adjust for the thickness of the board that
will go into the dado.
If I understand correctly, all your jig does is allow you to line up
perfectly with a marked line, like a circular saw rip guide.

No - my dado jig uses two pieces as described, joined similarly to the
Woodwhisperer's dado jig, but it uses the router base as the guide,
rather than requiring a guide bushing or a bearing on the bit. (maybe
I should take a picture of it, and post it somewhere...)

Now that sounds like the idea I had. The two guides are separated by a
distance equal to the diameter of the router base plus the thickness of
the stock to go in the dado, right? The router base rides along one
guide first, then the other? I figured if I did this the first pass
would cut a dado in the pieces that join the two guides together,
thereby giving me registration marks to line up the cut with. The
pattern bit idea sounds even more foolproof though, at least to my
untutored ear.

All basically the same principle ... the edge of the router plate in
this one takes the place of the bearing in the top bearing bit method,
or the edge of the guide bushing in the other method.

IMO, the problem with the all the router methods boils down to the use
of a wooden jig, which is prone to the dimensional instability of wood;
and/or the concentricity of a router plate; either with the potential to
effect accuracy over time.

How often do we get to use the word "concentricity" in a sentence?
Google groups even puts a squiggly line under it.

I don't have the table saw option. But I was wondering about both of
those potential problems too. I think that the small imperfection
would probably not be out of place when compared with my general level
of work (sigh), but I'd be perfectly happy to avoid it. I wonder if I
couldn't make the edges that the bearing rides on out of something
more "dimensionally stable"; maybe strips of aluminum set into slots
(or rabbets) in both guide edges, just a little proud of the wood
edge.

On 12/15/12 9:30 AM, Greg Guarino wrote:
On Dec 14, 3:35 pm, Swingman wrote:
On 12/14/2012 2:03 PM, Greg Guarino wrote:









On 12/14/2012 1:54 PM, Peter Bennett wrote:
On Thu, 13 Dec 2012 21:38:15 -0600, -MIKE-
wrote:

On 12/13/12 8:19 PM, Peter Bennett wrote:
My router dado jig doesn't need guide bushings or a top bearing bit -
it guides the router base.

each side of the guide consists of two pieces - a wide piece of 1/4"
plywood that the router rides on, and a (straight!) piece of 1/2"
plywood, or similar piece of solid wood glued on top.

Before the first use, run the router along the jig with the base
against the 1/2" board, so the router bit can trim the 1/4" plywood to
the correct size.

The jigs we're discussing adjust for the thickness of the board that
will go into the dado.
If I understand correctly, all your jig does is allow you to line up
perfectly with a marked line, like a circular saw rip guide.

No - my dado jig uses two pieces as described, joined similarly to the
Woodwhisperer's dado jig, but it uses the router base as the guide,
rather than requiring a guide bushing or a bearing on the bit. (maybe
I should take a picture of it, and post it somewhere...)

Now that sounds like the idea I had. The two guides are separated by a
distance equal to the diameter of the router base plus the thickness of
the stock to go in the dado, right? The router base rides along one
guide first, then the other? I figured if I did this the first pass
would cut a dado in the pieces that join the two guides together,
thereby giving me registration marks to line up the cut with. The
pattern bit idea sounds even more foolproof though, at least to my
untutored ear.

All basically the same principle ... the edge of the router plate in
this one takes the place of the bearing in the top bearing bit method,
or the edge of the guide bushing in the other method.

IMO, the problem with the all the router methods boils down to the use
of a wooden jig, which is prone to the dimensional instability of wood;
and/or the concentricity of a router plate; either with the potential to
effect accuracy over time.

How often do we get to use the word "concentricity" in a sentence?
Google groups even puts a squiggly line under it.

I don't have the table saw option. But I was wondering about both of
those potential problems too. I think that the small imperfection
would probably not be out of place when compared with my general level
of work (sigh), but I'd be perfectly happy to avoid it. I wonder if I
couldn't make the edges that the bearing rides on out of something
more "dimensionally stable"; maybe strips of aluminum set into slots
(or rabbets) in both guide edges, just a little proud of the wood
edge.


I think, as others have also suggested, the best bet is a bearing bit
with a plywood jig.
A strip of hardwood for the nearing to ride against insures a smoother
surface. This type of jig only needs to be dimensionally stable from the
time you clamp it down until the time your cut the dadoes. :-)

Of course there's always the option of using a couple of these guide
clamps with a bearing bit....
http://www.rockler.com/product.cfm?page=25134
Use the first one to clamp along a marked line on one side of the dado,
using squaring attachment blocks. Use the second one to "sandwich" the
material that will go into the dado, clamping against the squaring
blocks of the first guide clamp. Cut the dadoes, running the router
along the flat tops of both guide clamps.


--

-MIKE-

"Playing is not something I do at night, it's my function in life"
--Elvin Jones (1927-2004)
--
http://mikedrums.com

---remove "DOT" ^^^^ to reply

On Sat, 15 Dec 2012 10:57:01 -0600, -MIKE-
wrote:



I think, as others have also suggested, the best bet is a bearing bit
with a plywood jig.
A strip of hardwood for the nearing to ride against insures a smoother
surface. This type of jig only needs to be dimensionally stable from the
time you clamp it down until the time your cut the dadoes. :-)

A problem I see with using a template (top bearing) bit, is that the
jig would have to be very thick - the shortest cutter length on Lee
Valley's template bits is 1 inch, so the jig would have to be at least
an inch thick, to allow a minimum depth of cut of 1/8".


--
Peter Bennett, VE7CEI
peterbb (at) telus.net
GPS and NMEA info: http://vancouver-webpages.com/peter
Vancouver Power Squadron: http://vancouver.powersquadron.ca

On 12/15/2012 10:57 AM, -MIKE- wrote:

I think, as others have also suggested, the best bet is a bearing bit
with a plywood jig.
A strip of hardwood for the nearing to ride against insures a smoother
surface. This type of jig only needs to be dimensionally stable from the
time you clamp it down until the time your cut the dadoes. :-)

Don't ignore Murphy ... she always strikes somewhere around the next to
the last one.

(That's right, "she" ... nothing but a female could be that heartless to
your last piece of irreplaceable $tock)

--
eWoodShop: www.eWoodShop.com
Wood Shop: www.e-WoodShop.net
https://plus.google.com/114902129577517371552/posts
KarlCaillouet@ (the obvious)

-MIKE- wrote:

Of course there's always the option of using a couple of these guide
clamps with a bearing bit....
http://www.rockler.com/product.cfm?page=25134

I see that those are "new & improved". I hope so. I bought a couple years
ago, used them once and have never used them again. Why? Because they
deflected. Even with modest sideways pressure from the router base.

--

dadiOH
____________________________

Winters getting colder? Tired of the rat race?
Maybe just ready for a change? Check it out...
http://www.floridaloghouse.net

Greg Guarino wrote:

IMO, the problem with the all the router methods boils down to the
use of a wooden jig, which is prone to the dimensional instability
of wood; and/or the concentricity of a router plate; either with the
potential to effect accuracy over time.

How often do we get to use the word "concentricity" in a sentence?
Google groups even puts a squiggly line under it.

I don't have the table saw option. But I was wondering about both of
those potential problems too. I think that the small imperfection
would probably not be out of place when compared with my general level
of work (sigh), but I'd be perfectly happy to avoid it. I wonder if I
couldn't make the edges that the bearing rides on out of something
more "dimensionally stable"; maybe strips of aluminum set into slots
(or rabbets) in both guide edges, just a little proud of the wood
edge.

Somewhere out there exists a great forest. The trees are getting in the
way.

Greg, your jig will work just fine as is. I would worry more about being
abducted by aliens from outer space than I would about the dimensional
stability of the ply in your jig. Hell, you are making a dado *IN* plywood.
How about the stability of that? We are working wood and there is a pretty
fair amount of leeway.

Ditto any lack of concentricity in the router base plate. If it is out of
round, make one that *does* have the bit centered. Or a square one.

There is something to be said for square as each side can be at a different
distance from the center. If one side is, say, 1/16 different it becomes
easy to make a cut that is 7/16 or 9/16 or whatever without having to have a
bit that size. Same thing for 1/8. And if you need a way to take off just
a skosh from something, 1/64. Or less.

--

dadiOH
____________________________

Winters getting colder? Tired of the rat race?
Maybe just ready for a change? Check it out...
http://www.floridaloghouse.net

On 12/15/12 12:22 PM, Peter Bennett wrote:
On Sat, 15 Dec 2012 10:57:01 -0600, -MIKE-
wrote:



I think, as others have also suggested, the best bet is a bearing bit
with a plywood jig.
A strip of hardwood for the nearing to ride against insures a smoother
surface. This type of jig only needs to be dimensionally stable from the
time you clamp it down until the time your cut the dadoes. :-)

A problem I see with using a template (top bearing) bit, is that the
jig would have to be very thick - the shortest cutter length on Lee
Valley's template bits is 1 inch, so the jig would have to be at least
an inch thick, to allow a minimum depth of cut of 1/8".


There are lots of cheap flush trim/pattern buts that have a 1/2"-5/8"
cutting depth.
But yeah, if you want to use a bit you already own, you may just add
some thickness to the jig.


--

-MIKE-

"Playing is not something I do at night, it's my function in life"
--Elvin Jones (1927-2004)
--
http://mikedrums.com

---remove "DOT" ^^^^ to reply

On 12/15/12 1:00 PM, Swingman wrote:
On 12/15/2012 10:57 AM, -MIKE- wrote:

I think, as others have also suggested, the best bet is a bearing bit
with a plywood jig.
A strip of hardwood for the nearing to ride against insures a smoother
surface. This type of jig only needs to be dimensionally stable from the
time you clamp it down until the time your cut the dadoes. :-)

Don't ignore Murphy ... she always strikes somewhere around the next to
the last one.

(That's right, "she" ... nothing but a female could be that heartless to
your last piece of irreplaceable $tock)


+1


--

-MIKE-

"Playing is not something I do at night, it's my function in life"
--Elvin Jones (1927-2004)
--
http://mikedrums.com

---remove "DOT" ^^^^ to reply

On 12/15/12 1:35 PM, dadiOH wrote:
-MIKE- wrote:

Of course there's always the option of using a couple of these guide
clamps with a bearing bit....
http://www.rockler.com/product.cfm?page=25134

I see that those are "new & improved". I hope so. I bought a couple years
ago, used them once and have never used them again. Why? Because they
deflected. Even with modest sideways pressure from the router base.


Yes, not all of those are the same. I just used that page as an example
of what I was talking about.
I had issues with them developing a "memory" at locations one might
often, repeatedly clamp, like say, 24" and 36", making it difficult to
adjust slightly away from the often used spot.

I've seen some from other suppliers that are much more rigid, sideways.


--

-MIKE-

"Playing is not something I do at night, it's my function in life"
--Elvin Jones (1927-2004)
--
http://mikedrums.com

---remove "DOT" ^^^^ to reply

On 12/15/2012 1:45 PM, dadiOH wrote:

Somewhere out there exists a great forest. The trees are getting in the
way.

You missing the point?

Those who take the time and effort to cut a dado with the precision
under discussion in this thread, are fooling themselves if they
consider/take into account, and understand, ALL factors that can effect
the precision they are pursuing.

Anyone sneering at the effects of a lack of "concentricity" when using a
router jig that relies on a reference edge, better first go cut a bunch
of dovetails with one and see how long that attitude lasts.

--
eWoodShop: www.eWoodShop.com
Wood Shop: www.e-WoodShop.net
https://plus.google.com/114902129577517371552/posts
KarlCaillouet@ (the obvious)

"Swingman" wrote:

You missing the point?

Those who take the time and effort to cut a dado with the precision
under discussion in this thread, are fooling themselves if they
consider/take into account, and understand, ALL factors that can
effect the precision they are pursuing.

Anyone sneering at the effects of a lack of "concentricity" when
using a router jig that relies on a reference edge, better first go
cut a bunch of dovetails with one and see how long that attitude
lasts.
---------------------------------------------
See what the man has to say about the subject.

www.patwarner.com


Lew

On 12/15/2012 3:24 PM, Lew Hodgett wrote:
"Swingman" wrote:

You missing the point?

Those who take the time and effort to cut a dado with the precision
under discussion in this thread, are fooling themselves if they
consider/take into account, and understand, ALL factors that can
effect the precision they are pursuing.

"if they DON'T ... " is missing,

Anyone sneering at the effects of a lack of "concentricity" when
using a router jig that relies on a reference edge, better first go
cut a bunch of dovetails with one and see how long that attitude
lasts.
---------------------------------------------
See what the man has to say about the subject.

www.patwarner.com


To be more precise, the second paragraph:

http://www.patwarner.com/collarguide.html


--
eWoodShop: www.eWoodShop.com
Wood Shop: www.e-WoodShop.net
https://plus.google.com/114902129577517371552/posts
KarlCaillouet@ (the obvious)

On Wednesday, December 12, 2012 3:02:53 AM UTC-8, Swingman wrote:
Greg Guarino wrote:

, is it OK

to make dadoes in both sides of the center divider, as long as none of

them are in line with each other?

Perfectly OK to make dadoes in both sides of the center divider, even if
they are in line with each other, as long as you fill them with shelf.

I'd add a caveat, there ought to be LONG GRAIN extension of the central
ply through the thinned region. It's possible to orient the plywood
so that thinning it leaves only/mainly one ply, with grain parallel to the shelf.
That's gonna break REAL easy. Maybe won't survive attempted assembly.

On 12/15/2012 4:54 PM, whit3rd wrote:
On Wednesday, December 12, 2012 3:02:53 AM UTC-8, Swingman wrote:
Greg Guarino wrote:

, is it OK

to make dadoes in both sides of the center divider, as long as none of

them are in line with each other?

Perfectly OK to make dadoes in both sides of the center divider, even if
they are in line with each other, as long as you fill them with shelf.

I'd add a caveat, there ought to be LONG GRAIN extension of the central
ply through the thinned region.

OK, which ply is the "central" ply?

Most, if not all plywood has an odd number of plys by design,
specifically to mitigate warping.

It's possible to orient the plywood
so that thinning it leaves only/mainly one ply, with grain parallel to the shelf.
That's gonna break REAL easy.

Not so sure about that, especially if the dado fits what's going into it.

Maybe won't survive attempted assembly.

That's a pretty strong statement ... got anything to back it up with?

Literally thousands of this type joint under my belt and have never
seen, or heard of any instance, of that happening.

All that means nothing in the greater scheme of things, basically, I'll
continue to take my chances that, providing everything fits as spec'ed,
it ain't gonna happen.

--
eWoodShop: www.eWoodShop.com
Wood Shop: www.e-WoodShop.net
https://plus.google.com/114902129577517371552/posts
KarlCaillouet@ (the obvious)