Ok, got my new jointer. Never used one before, so I've been reading
about proper technique. I've had great results in my short time, but
need info on face jointing a bowed board.
I understand that you put the concave side down, but what is
preventing one from putting downward pressure which *could* flatten
the board (temporarily) as it runs over the knives? How much pressure
is enough to prevent the board from flying?!?!
George wrote:
>
> Regardless of length, what you're looking for is to take off the high spots
> before you try to get a full surface.
A hand plane #5, #6 or maybe even a #7 - with a sharp iron set for
minimal shavings will take of high corners on the convex side of a
cupped board or the opposing high corners of a twisted board.
Take off some, check to see if "you're there yet" and repeat until
the board doesn't rock when you alternately press down on opposite
corners. Then alternately press down on the center of each end
and see if the board still rocks.
Pictures explain better so have a look here and on the
next page. Cutting "with the grain" instead of "against
the grain" will also save you some grief and that's
on the second page. Nora Hall - a woodcarvers uses
The Broom Analogy. If you want to cut off some bristles
with a knife, cut from the broom handle end towards
the working end of the bristles. If you try it the other
way ...
http://home.comcast.net/~charliebcz/CabProcess3.html
> What you're going to do is set the
> high spot on the outfeed table, where the knives won't even hit it, put
> pressure over the place where the board does hit the table, and feed.
>
> Best outcome does both ends (by reversing and following the same procedure)
> before the middle, though walking up the board will eventually give a wedge
> with a flat surface.
>
> A twisted board wants the opposite corners worked before the full end(s),
> which is(are) worked before the full face.
>
> "Larry Bud" <[email protected]> wrote in message
> news:[email protected]...
> > Ok, got my new jointer. Never used one before, so I've been reading
> > about proper technique. I've had great results in my short time, but
> > need info on face jointing a bowed board.
> >
> > I understand that you put the concave side down, but what is
> > preventing one from putting downward pressure which *could* flatten
> > the board (temporarily) as it runs over the knives? How much pressure
> > is enough to prevent the board from flying?!?!
Swingman gave good advise... I'd add that if jointing a board with a
significant amount of cup, bow or twist to reduce length or width to allow
for a couple inches oversize to reduce the amount of wood removed (maximize
thickness). The board (width) can be edge glued to regain the working width
you need.
The length should be a few inches over size (don't necessarily joint an 8'
board when you need 3').
Tom
<snipped>
you put the concave side down, but what is
> preventing one from putting downward pressure which *could* flatten
> the board (temporarily) as it runs over the knives? How much pressure
> is enough to prevent the board from flying?!?!
Regardless of length, what you're looking for is to take off the high spots
before you try to get a full surface. What you're going to do is set the
high spot on the outfeed table, where the knives won't even hit it, put
pressure over the place where the board does hit the table, and feed.
Best outcome does both ends (by reversing and following the same procedure)
before the middle, though walking up the board will eventually give a wedge
with a flat surface.
A twisted board wants the opposite corners worked before the full end(s),
which is(are) worked before the full face.
"Larry Bud" <[email protected]> wrote in message
news:[email protected]...
> Ok, got my new jointer. Never used one before, so I've been reading
> about proper technique. I've had great results in my short time, but
> need info on face jointing a bowed board.
>
> I understand that you put the concave side down, but what is
> preventing one from putting downward pressure which *could* flatten
> the board (temporarily) as it runs over the knives? How much pressure
> is enough to prevent the board from flying?!?!
"Larry Bud" wrote in message
> I understand that you put the concave side down, but what is
> preventing one from putting downward pressure which *could* flatten
> the board (temporarily) as it runs over the knives? How much pressure
> is enough to prevent the board from flying?!?!
The answer: just enough pressure to keep it moving in the right direction.
That will generally NOT be enough to push the bow down, applied mostly to
the outfeed table after enough of the board has gone through.
With waxed infeed and outfeed tables, you'll find that fairly light pressure
is not only possible, but easily achieved.
IME, the trick to easier jointing, without years of practice, is to cut your
stock to rough project length before jointing.
IOW, 24" boards are much easier to mill accurately than 60" boards.
--
www.e-woodshop.net
Last update: 11/06/04
On Mon, 22 Nov 2004 09:37:34 -0600, "Swingman" <[email protected]> wrote:
>"Larry Bud" wrote in message
>
>> I understand that you put the concave side down, but what is
>> preventing one from putting downward pressure which *could* flatten
>> the board (temporarily) as it runs over the knives? How much pressure
>> is enough to prevent the board from flying?!?!
>
>The answer: just enough pressure to keep it moving in the right direction.
>That will generally NOT be enough to push the bow down, applied mostly to
>the outfeed table after enough of the board has gone through.
>
>With waxed infeed and outfeed tables, you'll find that fairly light pressure
>is not only possible, but easily achieved.
>
>IME, the trick to easier jointing, without years of practice, is to cut your
>stock to rough project length before jointing.
>
>IOW, 24" boards are much easier to mill accurately than 60" boards.
And you end up with thicker boards... More spare material to go
through the thickness planer.
TWS
On 22 Nov 2004 07:11:12 -0800, [email protected] (Larry Bud)
wrote:
>I understand that you put the concave side down, but what is
>preventing one from putting downward pressure which *could* flatten
>the board (temporarily) as it runs over the knives?
Good technique mainly. You _can_ do this, but you shouldn't. It
doesn't really matter that much, because for the first passes of a
really bowed board, even a little deflection still won't contact the
board into the knives. This idea of "ironing the board flat" and all
its resultant problems is mainly with thicknessers, where their
powered rollers really will squash the middle of a bowed board down,
regardless.
if the board is badly twisted, then ask yourself why, will it twist
again, and is this really a board you want to be bothering with for
fine work ? Construction work doesn't need jointing, boards that
twisted once might carry on doing so after I've spent time and effort
on working them. I don't say "fire wood pile for anything with a
twist in it", but I do usually find that twisty stock ends up sawn
either narrower or shorter before I try flattening it. You can also
save timber this way, as it's better to lose a little length than an
awful lot of thickness.
> How much pressure is enough to prevent the board from flying?!?!
Depends a lot on your push board / push paws. You need a few of
these, so if you don't already have them, make some out of plywood
scraps. Then use rubber mousepad material on the bottom surface to
give extra friction with minimal down pressure. This is better than
the standard issue foam, because although that works well, it breaks
up very quickly. For some jobs, use a push board with a small ledge
at the tail end of it.
When making them, glued dowel construction is good. Don't use screws
or nails. One day you _will_ put a push board into the knives, and you
don't want this to be any noisier than it has to be....
--
Smert' spamionam