Hey All,
I just started cutting circular blanks on my bandsaw and I want to
know if there is a table, or guide that indicates the minimum radius
that can be cut depending on the width of the blade(regardless of the
blade width).

Thanks in advance for your suggestions.
Marc

"marc rosen" wrote: (clip) the minimum radius that can be cut depending on
the width of the blade (clip)
^^^^^^^^^^^^^^^^
It actually depends on the ratio of the width of the blade to the width of
the kerf, which in turn depends on the tooth set. Furthermore, you can
force a tighter radius by doing a little back and fill motion as your cut
progresses.

On Feb 19, 10:20 pm, "Leo Lichtman"
Thanks Leo,
But i know there must be some mathematical limit. I was using a 3/4
inch blade and because of the size log- cherry- I could not get a 12
inch diameter. I think it was closer to 9 inches. It became very
difficult to cut/turn the piece. I replaced the 3/4 with a 1/4 to see
how it would behave and as expected I was able to finsih the cut.
(sadly, this blank had some checks that only became evident upon
turning)
I'm still experimenting but here's a follow up question;
Does anyone free hand cut their blanks or do you use jigs, such as
circle cutters? Am i wasting time freehanding it?
Thanks again,
Marc

wrote:
"marc rosen" wrote: (clip) the minimum radius that can be cut depending on

the width of the blade (clip)
^^^^^^^^^^^^^^^^
It actually depends on the ratio of the width of the blade to the width of
the kerf, which in turn depends on the tooth set. Furthermore, you can
force a tighter radius by doing a little back and fill motion as your cut
progresses.

marc rosen wrote:
On Feb 19, 10:20 pm, "Leo Lichtman"
Thanks Leo,
But i know there must be some mathematical limit. I was using a 3/4
inch blade and because of the size log- cherry- I could not get a 12
inch diameter. I think it was closer to 9 inches. It became very
difficult to cut/turn the piece. I replaced the 3/4 with a 1/4 to see
how it would behave and as expected I was able to finsih the cut.
(sadly, this blank had some checks that only became evident upon
turning)
I'm still experimenting but here's a follow up question;
Does anyone free hand cut their blanks or do you use jigs, such as
circle cutters? Am i wasting time freehanding it?
Thanks again,
Marc

wrote:
"marc rosen" wrote: (clip) the minimum radius that can be cut depending on

the width of the blade (clip)
^^^^^^^^^^^^^^^^
It actually depends on the ratio of the width of the blade to the width of
the kerf, which in turn depends on the tooth set. Furthermore, you can
force a tighter radius by doing a little back and fill motion as your cut
progresses.


Marc,
I have some cardboard disks cut out at 1" diameter intervals. I lay the
biggest that will fit on top of the blank, mark it somehow, and
free-hand cut the pen blanks off ;-)

Mathematically, what you are looking at is the answer to the question of
how much blade at what tangent will fit between two circles (the scrap
and the keeper stock describe two circles ABOUT 1/8" apart.)

If you care to do that math, fine. But I see no reason to bother unless
you are planning on cutting a couple hundred all the same and are
looking to find the "one perfect blade" to make that cut. I, however,
cut one at a time and seldom cut two in a row the same size. Changing to
the ideal blade for each piece is just too much of a hassle with too
little payback.

Frankly, I just make the cut as directly as I can. If the blade is
struggling to make the turn, I widen the kerf and have another go at it.
I might even straighten out the cut and remove that piece of scrap
altogether, then begin the cut anew.

Normally I then take two of the best looking arcs as support for a
center-finder head and mark the APPROXIMATE center. If I take a third or
4th line, there is never exact agreement because I haven't actually cut
a perfect circle. But two lines make an intersection that is close
enough for the next step in the process.

Bill

--
Make yourself an honest man, and then you may be sure that there is one
rascal less in the world.
Thomas Carlyle (1795 - 1881)
http://nmwoodworks.com

"marc rosen" wrote in message
ups.com...
Hey All,
I just started cutting circular blanks on my bandsaw and I want to
know if there is a table, or guide that indicates the minimum radius
that can be cut depending on the width of the blade(regardless of the
blade width).

Perhaps not quite as precise as other answers, but this might help.
http://www.timberwolf1.com/silicon_steel_slection.asp

Got a cutting jig?

"marc rosen" wrote in message
ups.com...
Hey All,
I just started cutting circular blanks on my bandsaw and I want to
know if there is a table, or guide that indicates the minimum radius
that can be cut depending on the width of the blade(regardless of the
blade width).

Thanks in advance for your suggestions.
Marc


Try this link.

(watch the wrap)

http://www.vermontamerican.com/NR/rd...dsawBlades.PDF

Some other interesting info as well. For instance I need to 'break in' my
blades. I didn't know that but it can't do any harm. Will try that next
time.

BillR

Hey Guys,
Thanks for the links and the advice. Yeah, I was getting too
analytical but the tables look helpful if I want to grab a specific
blade to cut out a single. or a series of blanks.
I don't have a cutting jig yet but I am building a circle cutting jig
based on some magazine plans.

I've got a new topic which I'll post momentarilly. Thanks again,
Marc

I use the same method as Bill, I have cardboard discs each slightly bigger. Mark using the biggest and cut parts at a time as the turn of the blade will let me.
Also i have a small hole cut in the center of each cardboard disc which i also mark thus straight off the bandsaw,on with the face plate and tidy up the outside of the blank on the lathe.
Mark

Hello Marc,

There are tables that give the info you need. I am sure they are in
the Machinist
Handbook, but alas, it is at home right now. Some blades have the
info on the back
of the package they come in. Note that I purchase an 82" 1/4 inch
blade and use it
for all my cutting. I have a Jet 1236 so my swing is somehat less
than the big boys.

The procedure I use is as follows:

The log is cut with a rip chain on my chainsaw with the pith being
removed.
This results in 3 or 4 flat pieces (usually).
Sometimes I let them dry for few months, other times I turn green.
I take the flat piece and with a compass mark out the diameter I
want. I make
sure the center point is well marked as well as the diamter. The
piece is
then taken to my bandsaw and sawn. This oft times results in a fairly
good round
piece. The rounded piece is then either turned between centers or
attached to a
faceplate. Swapping out blades for different cuts would be a bit of a
time waster for
me as all my bowls are well within the tolerance of my lathe's swing
and the type of
turning I do.
The only real bit of 'accuracy' I strive for is on the tennon as the
Nova chuck I use
is rather limited in its spread (approx. 1.75 to 2.00). I have the
midi Cole jaws
attached to my other Nova chuck for finishing the bottom.

Bill's suggestion to use cardboard cutouts is a really good one. One
minor improvement
may be to make the cardboard cutouts out of some stiffer more durable
material and
have a hole in the center of the cutouts. The center on the blank can
then be marked
without not much effort.



On Feb 20, 7:40 am, "marc rosen" wrote:
Hey Guys,
Thanks for the links and the advice. Yeah, I was getting too
analytical but the tables look helpful if I want to grab a specific
blade to cut out a single. or a series of blanks.
I don't have a cutting jig yet but I am building a circle cutting jig
based on some magazine plans.

I've got a new topic which I'll post momentarilly. Thanks again,
Marc

Kevin wrote:

Bill's suggestion to use cardboard cutouts is a really good one. One
minor improvement
may be to make the cardboard cutouts out of some stiffer more durable
material and
have a hole in the center of the cutouts. The center on the blank can
then be marked
without not much effort.

I'm sure I cribbed that idea from someone. I do have a hole in the
middle where I tap a nail to mark the center (if I remember to do it).

But the circle I cut isn't going to be especially round, so, whether I
mark the center before or after cutting, it's still gonna carry a fudge
factor with it.

Now Darrell Feltmate ... now there's the man! He says (IIRC) that he
printed concentric circles on a sheet of acetate and can not only select
for size, but also for grain presentation. Seems to me that if you then
punch a hole in the acetate film to mark the center and let the tip of a
crayon pass through to mark the circumference, you'd be in pig heaven!

Once you get out past 8" diameter, though, I think you'll need to either
chum up with someone who has a large format printer or a stack of
cardboard circles. Then, too, there's no law against notching a stick
every inch or so, starting with a nail to use as a center pin.


Bill

--
Make yourself an honest man, and then you may be sure that there is one
rascal less in the world.
Thomas Carlyle (1795 - 1881)
http://nmwoodworks.com


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