Is there a way to drill dovetails in both sides (bottom and top) of a
bowl blank with a Forstner bit _before mounting the blank on the lathe_
so that the piece will be in line (centered) after reverse chucking)?
Lasers? Vodoo? Luck?


Turn to Safety, Arch
Fortiter


http://community.webtv.net/almcc/MacsMusings

Arch skrev:
Is there a way to drill dovetails in both sides (bottom and top) of a
bowl blank with a Forstner bit _before mounting the blank on the lathe_
so that the piece will be in line (centered) after reverse chucking)?
Lasers? Vodoo? Luck?


Turn to Safety, Arch


(Musing)
However would you line up, Arch?

The way I do it, and I suppose you and a host of others too;
find a spot for my forstner bit, drill a hole,
chuck up and make the reverse hole with a parting tool.

If I am extremely particular, as when I have a full dry and expensive
piece of wood, I then chuck up in the new hole, clean the first one
out with the parting tool - real careful, like - and then reverse
again for a last finish.

After this long and careful procedure, I have two beautiful holes
that I can switch between and rechuck time after time without losing
the center on either side. (I use the Talon, thank you very much.)

Try this on a half-dried piece, and you waste a lot of time and effort
for nothing. Half dried pieces warp as you work.

BjarteR

Hi Arch

Yes you can, however a true dovetail is not a straight sided hole, but
we'll go with that, as I use those with my Oneway chucks.

First take a board and clamp or screw to your drill press table, then
drill a recess, like 1/2" deep.
Next make a piece, ( turned wood or metal ) that fits nicely into that
recess and would stick out above the board by say 1/4", we'll call if
"Filler"
Fits nice ??, OK now take Filler out, and take your bowl blank, drill
a recess 1/4"+ deep, now place Filler into the board's recess, then
place the bowl blank with the recess fitting onto Filler, and now
drill the recess on the other side of the bowl blank, should be close
I think ? ;-)).
Have fun and take care
Leo Van Der Loo


On Aug 1, 4:14 pm, (Arch) wrote:
Is there a way to drill dovetails in both sides (bottom and top) of a
bowl blank with a Forstner bit _before mounting the blank on the lathe_
so that the piece will be in line (centered) after reverse chucking)?
Lasers? Vodoo? Luck?

Turn to Safety, Arch
Fortiter

http://community.webtv.net/almcc/MacsMusings

"Arch" wrote in message
...
Is there a way to drill dovetails in both sides (bottom and top) of a
bowl blank with a Forstner bit _before mounting the blank on the lathe_
so that the piece will be in line (centered) after reverse chucking)?
Lasers? Vodoo? Luck?


Jig, as Leo detailed. Dowel piece of the proper diameter, drill down into
the sacrificial base, then down into the piece without moving the base.
Insert dowel, invert work and bore. Errors possible from raising the head
of the drillpress after boring the reference hole. It might wander a bit
from center.

Have to ask, if the purpose is to mount the piece on the lathe, what do you
hope to gain by doing an operation on the DP rather than the lathe, which is
so easy? What kind of weird thing are you making?

Bjarte, Leo and George,

Very clear instructions re a jig for making "in line" dovecotes,
recesses or just plain ole holes, but never dovetails. One weird
use might be in making off lathe multiple blanks for production line
work, but mostly I just wanted to add another technique for me and
hopefully a few others to know about. I realize that it won't shake the
earth.


Perhaps not this time, but I think it can be useful or at least
interesting for rcw to think outside the bowl from time to time.
No woodturner may ever use the jig, but that wasn't my question and
isn't the same thing as knowing about it.


Thanks for explaining another technique that somebody may find useful
sometime or at least know about it. In deference to Ecnerwal, I won't
mention that there are many ways to skin a cat or brew coffee.

Knowing about this jig is sort of like knowing how to turn cubes on a
lathe or how to finish the tip of a thin spindle held on a spur center
without tail support. Useless info .....maybe, maybe not.


Turn to Safety, Arch
Fortiter


http://community.webtv.net/almcc/MacsMusings

On Wed, 1 Aug 2007 16:14:37 -0400, (Arch) wrote:

Is there a way to drill dovetails in both sides (bottom and top) of a
bowl blank with a Forstner bit _before mounting the blank on the lathe_
so that the piece will be in line (centered) after reverse chucking)?
Lasers? Vodoo? Luck?


Turn to Safety, Arch
Fortiter


http://community.webtv.net/almcc/MacsMusings


hate to get picky, Arch, but how do you make a dovetail with a drill bit??

maybe you're thinking of a straight walled recess?

For a half assed answer, I'd think that your predrilled "bottom" hole might not
still be centered after roughing out the piece... might end up with an
eccentric?

I do the tenon or recess with a bowl gouge and square nosed scraper, but you
could rough out the bowl and then drill your bottom recess with a drill chuck in
the tailstock...


mac

Please remove splinters before emailing

Hi Mac,

Good tip for when a tail stock interferes with cutting a hole with
straight or angled walls for expansion jaws.

Pickying right along, it dovetails nicely (again misusing the word) into
my cautioning that the bottom of a "Forstner bit straight walled recess"
is not usually truly perpendicular to its walls.

Sorry! It's the heat, not the humididy.


Turn to Safety, Arch
Fortiter


http://community.webtv.net/almcc/MacsMusings

Ok, I core everything. I take a rounded bowl blank to the drill press,
and use the proper sized forstner bit to drill a recess, in the
center, about 1/4 to 3/8 inch deep in the top of the blank. I mount
the blank via an expanding chuck (Vicmark), and turn the bottom. I use
a dovetailed scraper to make the recess on the bottom, usually about
3/16 deep, although I never measure. The angle on the dovetail matches
the angle of the jaws on my chuck when the handle and blade and handle
are parallel to the ways, so the angles of the wood and jaws match for
a perfect fit. I do hold the tool so that it just barely touches the
wood on the final cut on the outside of the dovetail. This evens out
that 1/64 of an inch that creates some of the inevitable wobble that
you get when you reverse. When I remove the core, it already has a
centered recess. I finish turn the big bowl, then remount the core.
The chuck never has to come off, and I don't need the tailstock for
stability. Of course, this has taken a few years to work out all the
details, but it works for me.
robo hippy

On Aug 2, 7:59 am, (Arch) wrote:
Hi Mac,

Good tip for when a tail stock interferes with cutting a hole with
straight or angled walls for expansion jaws.

Pickying right along, it dovetails nicely (again misusing the word) into
my cautioning that the bottom of a "Forstner bit straight walled recess"
is not usually truly perpendicular to its walls.

Sorry! It's the heat, not the humididy.

Turn to Safety, Arch
Fortiter

http://community.webtv.net/almcc/MacsMusings

Hi Robo,

That's a good expansion chucking technique for 'hard core turners'.
"Just a pinch between cheek and gums" Arragh!


Turn to Safety, Arch
Fortiter


http://community.webtv.net/almcc/MacsMusings

Arch,
What about "....finish the tip of a thin spindle held on a spur
center...."??

I've a job coming up like that and just did some spindles with difficulty.

For someone who's just used creative juices instead of a fixed pattern, I
found spindle multiples to be quite an exercise.
You WILL learn tool control:-)

TomNie


"Arch" wrote in message
...
Bjarte, Leo and George,

Very clear instructions re a jig for making "in line" dovecotes,
recesses or just plain ole holes, but never dovetails. One weird
use might be in making off lathe multiple blanks for production line
work, but mostly I just wanted to add another technique for me and
hopefully a few others to know about. I realize that it won't shake the
earth.


Perhaps not this time, but I think it can be useful or at least
interesting for rcw to think outside the bowl from time to time.
No woodturner may ever use the jig, but that wasn't my question and
isn't the same thing as knowing about it.


Thanks for explaining another technique that somebody may find useful
sometime or at least know about it. In deference to Ecnerwal, I won't
mention that there are many ways to skin a cat or brew coffee.

Knowing about this jig is sort of like knowing how to turn cubes on a
lathe or how to finish the tip of a thin spindle held on a spur center
without tail support. Useless info .....maybe, maybe not.


Turn to Safety, Arch
Fortiter


http://community.webtv.net/almcc/MacsMusings

Hi Tom,

I've used the fingers of my left hand as a firm steady just behind the
tip, pressing toward the spur center, while cutting with my right hand
at modest speed. Insulate uncallused fingers with paper etc. It worked
for me, but as always: "Gentlemen, start your criticisms".


Turn to Safety, Arch
Fortiter


http://community.webtv.net/almcc/MacsMusings

"Arch" wrote in message
...
Bjarte, Leo and George,

Very clear instructions re a jig for making "in line" dovecotes,
recesses or just plain ole holes, but never dovetails.

OK, real "musing" accepted. If you want instant dovetails, there's always
the router, collar, and template. Though why bother? I'll stick with the
pin chuck for the north and my parting tool/gouge for the south end.

If the hippy were a bit more inclined to use the tailstock as a third hand,
he might squeeze "the inevitable" out of the reversal equation. With a
tapered nose on my live center and that 1" hole to help, I don't have to
settle for a rotating shadow after reversal. Not that it really matters,
since the thinning of the walls will almost surely result in some bulge
along the endgrain.

On Thu, 2 Aug 2007 10:59:32 -0400, (Arch) wrote:

Hi Mac,

Good tip for when a tail stock interferes with cutting a hole with
straight or angled walls for expansion jaws.

Pickying right along, it dovetails nicely (again misusing the word) into
my cautioning that the bottom of a "Forstner bit straight walled recess"
is not usually truly perpendicular to its walls.

Sorry! It's the heat, not the humididy.


Turn to Safety, Arch
Fortiter


http://community.webtv.net/almcc/MacsMusings


I used to use the forstner bits for the recess, Arch, but quit for 2 reasons...

Several bowls with a tiny hole in the bottom because my bowl depth gauge and
it's operator failed to figure on the cone-shaped hole a F-bit leaves in the
middle..

Most of the wood that I evolved into working with was prone to cracking so I
went to more tenon holding and less recess stuff..

OTOH, if you're holding a piece with a recess and it starts cracking on you, the
advantage there is that you can expand the jaws a bit more to open the crack,
flood the crack with thin CA and then relax the pressure on the recess to
"clamp" the crack while the glue dries..

Not the heat, it's the humility.. ;-)


mac

Please remove splinters before emailing

On Thu, 2 Aug 2007 14:24:38 -0400, "Tom Nie" wrote:

Arch,
What about "....finish the tip of a thin spindle held on a spur
center...."??

I've a job coming up like that and just did some spindles with difficulty.

For someone who's just used creative juices instead of a fixed pattern, I
found spindle multiples to be quite an exercise.
You WILL learn tool control:-)

TomNie

Tom.. I would guess that wood/would depend on how the work is being held,
between centers (which I think is what you're doing) or held in a chuck...

I don't know if this applies to your project, but a trick I learned from one of
Dick Sing's pen turning books was to do your final skew work and sanding on all
but the tips, then wrap masking tape around the drive center and the end of the
work...
GENTLY part off the tail stock end and back off the tail stock, then sand the
parted tip using 2 fingers on your "free" hand as a steady rest while you sand
the tip..

I usually follow this with using a finger on my right hand as the "tail stock"
and applying just enough pressure on the end of the work to keep it on the drive
center for parting this off..
Next step is hand sanding the last end that you cut off, unless you're REALLY
good.. *g*


mac

Please remove splinters before emailing