Ok. I am trying to wrap my head around the accumulated error
associated with the 5-cut method. I read somewhere that the
accumulated error increases by a factor of 5 or was it 4? Anyway, I
think both are wrong. I drew up a mock 5-cut in CAD and used an angle
error of 5 degrees. The box is 4" by 4".
Cut1=red line
Cut2=green line
Cut3=orange line
Cut4=yellow line
Cut5=grey line
Cut one:
http://www.garagewoodworks.com/5cut/cut1.jpg
Cut two: Rotate clockwise and cut. Red line is now against the
fence. The distance at the top goes from 0.35 to 0.6440 - Not double,
but close.
http://www.garagewoodworks.com/5cut/cut12.jpg
Cut three: Again rotate clockwise and put the green line against the
fence.
http://www.garagewoodworks.com/5cut/cut123.jpg
Cut four: Rotate and put the orange line against the fence.
http://www.garagewoodworks.com/5cut/cut1234.jpg
Cut five: Rotate and put the yellow line against the fence.
We went from the original 0.35" to the accumulated 1.0". That's an
increase of 2.86".
Not four or five. Am I missing something?
I absolutely need one of those calibrated striking mallets!!! It must be a
home-built as I can't find one at the hardware store.
Ralph
"JayPique" <[email protected]> wrote in message
news:15210733.719.1331290818133.JavaMail.geo-discussion-forums@vbas10...
We do something like that I guess when we tune our sliding table saws. We
take about a 48" square and spin it 4 times and then measure the thickness
of a thin ripping at the front and the back and see if they're the same. If
they are, we've got a nice square cut. If not, we scientifically calculate
the difference and use a calibrated striking mallet to bump it into square.
ish. Works great!
JP
We do something like that I guess when we tune our sliding table saws. We =
take about a 48" square and spin it 4 times and then measure the thickness =
of a thin ripping at the front and the back and see if they're the same. I=
f they are, we've got a nice square cut. If not, we scientifically calcula=
te the difference and use a calibrated striking mallet to bump it into squa=
re. ish. Works great!
JP
On Mar 8, 12:25=A0pm, "John Grossbohlin"
<[email protected]> wrote:
> Two observations/questions...
>
> I thought the accumulated error warning was in terms of angular measures,
> not distance measures. For example, being off by a degree on cutting a mi=
ter
> would yield a 2 degree gap.
Ah, you're right. (slap forehead)
How does one calculate the accuracy level in degrees that the method
will get you? Obviously it depends on the length of the sides and the
delta distance you accept in your fifth cut from front to back.
How close to 90 degrees will I get if I use a 18" square board and
accept a delta of 0.004" on the fifth cut?
(snip)
On Mar 8, 11:56=A0am, [email protected] wrote:
> Ok. =A0I am trying to wrap my head around the accumulated error
> associated with the 5-cut method. =A0I read somewhere that the
> accumulated error increases by a factor of 5 or was it 4? =A0Anyway, I
> think both are wrong. =A0I drew up a mock 5-cut in CAD and used an angle
> error of 5 degrees. =A0The box is 4" by 4".
>
> Cut1=3Dred line
> Cut2=3Dgreen line
> Cut3=3Dorange line
> Cut4=3Dyellow line
> Cut5=3Dgrey line
>
> Cut one:http://www.garagewoodworks.com/5cut/cut1.jpg
>
> Cut two: =A0Rotate clockwise and cut. =A0Red line is now against the
> fence. =A0The distance at the top goes from 0.35 to 0.6440 - Not double,
> but close.http://www.garagewoodworks.com/5cut/cut12.jpg
>
> Cut three: =A0Again rotate clockwise and put the green line against the
> fence.http://www.garagewoodworks.com/5cut/cut123.jpg
>
> Cut four: Rotate and put the orange line against the fence.http://www.gar=
agewoodworks.com/5cut/cut1234.jpg
>
> Cut five: Rotate and put the yellow line against the fence.
>
> We went from the original 0.35" to the accumulated 1.0". =A0 That's an
> increase of 2.86".
>
> Not four or five. =A0 Am I missing something?
Cut 5
http://www.garagewoodworks.com/5cut/cut12345.jpg
"Doug Miller" <[email protected]> wrote in message
news:[email protected]...
> [email protected] wrote in
> news:31710c09-a7cf-4135-a57c-9b3eb5b08cf3
> @s7g2000yqm.googlegroups.com:
>
>> On Mar 8, 12:25 pm, "John Grossbohlin"
>> <[email protected]> wrote:
>>> Two observations/questions...
>>>
>>> I thought the accumulated error warning was in terms of angular
>>> measures,
>>> not distance measures. For example, being off by a degree on cutting a
>>> mi
>> ter
>>> would yield a 2 degree gap.
>>
>> Ah, you're right. (slap forehead)
>>
>> How does one calculate the accuracy level in degrees that the method
>> will get you? Obviously it depends on the length of the sides and the
>> delta distance you accept in your fifth cut from front to back.
>>
>> How close to 90 degrees will I get if I use a 18" square board and
>> accept a delta of 0.004" on the fifth cut?
>
> 89 degrees 59 minutes 50.8 seconds, or 89.9975 degrees.
Seems close enough to 90 to not worry about it... ;~)
[email protected] wrote in news:31710c09-a7cf-4135-a57c-9b3eb5b08cf3
@s7g2000yqm.googlegroups.com:
> On Mar 8, 12:25 pm, "John Grossbohlin"
> <[email protected]> wrote:
>> Two observations/questions...
>>
>> I thought the accumulated error warning was in terms of angular measures,
>> not distance measures. For example, being off by a degree on cutting a mi
> ter
>> would yield a 2 degree gap.
>
> Ah, you're right. (slap forehead)
>
> How does one calculate the accuracy level in degrees that the method
> will get you? Obviously it depends on the length of the sides and the
> delta distance you accept in your fifth cut from front to back.
>
> How close to 90 degrees will I get if I use a 18" square board and
> accept a delta of 0.004" on the fifth cut?
89 degrees 59 minutes 50.8 seconds, or 89.9975 degrees.
[email protected] wrote in
news:[email protected]
om:
> On Mar 8, 2:00 pm, Doug Miller
> <[email protected]> wrote:
>> [email protected] wrote in
>> news:31710c09-a7cf-4135-a57c-9b3eb5b08
> cf3
>> @s7g2000yqm.googlegroups.com:
>> > How close to 90 degrees will I get if I use a 18" square
>> > board and accept a delta of 0.004" on the fifth cut?
>>
>> 89 degrees 59 minutes 50.8 seconds, or 89.9975 degrees.
>
> Hey cool. I'd appreciate it if you could show the equation(s)
> you used. (degrees only)
Sure thing, Brian, here you go:
Accumulated error of 0.004" in five cuts = 0.004 / 5 = error of 0.0008" per
cut.
Error of 0.0008" at a distance of 18" gives the tangent of the
angle at 0.0008 / 18 = 0.000044444444....
Inverse tangent of 0.0000444... (that is, the angle whose tangent
is 0.0000444...) = 0.002546 degrees.
0.0025 degrees deviation from a 90-degree angle 90 +/- 0.0025 =
89.9975 or 90.0025 degrees.
On Mar 8, 5:04=A0pm, Doug Miller <[email protected]>
wrote:
> [email protected] wrote innews:f482e2ee-3fc3-4260-87ae-f5caa0fdb5=
[email protected]
> om:
>
> > On Mar 8, 2:00=A0pm, Doug Miller
> > <[email protected]> wrote:
> >> [email protected] wrote in
> >> news:31710c09-a7cf-4135-a57c-9b3eb5b08
> > cf3
> >> @s7g2000yqm.googlegroups.com:
> >> > How close to 90 degrees will I get if I use a 18" square
> >> > board and accept a delta of 0.004" on the fifth cut?
>
> >> 89 degrees 59 minutes 50.8 seconds, or 89.9975 degrees.
>
> > Hey cool. =A0I'd appreciate it if you could show the equation(s)
> > you used. =A0(degrees only)
>
> Sure thing, Brian, here you go:
>
> Accumulated error of 0.004" in five cuts =3D 0.004 / 5 =3D error of 0.000=
8" per
> cut.
>
> Error of 0.0008" at a distance of 18" gives the tangent of the
> angle at 0.0008 / 18 =3D 0.000044444444....
>
> Inverse tangent of 0.0000444... (that is, the angle whose tangent
> is 0.0000444...) =3D 0.002546 degrees.
>
> 0.0025 degrees deviation from a 90-degree angle 90 +/- 0.0025 =3D
> 89.9975 or 90.0025 degrees.
Thanks Doug. That's actually what I had originally, but I started to
second guess myself. I appreciate your help.
On Mar 8, 2:00=A0pm, Doug Miller <[email protected]>
wrote:
> [email protected] wrote in news:31710c09-a7cf-4135-a57c-9b3eb5b08=
cf3
> @s7g2000yqm.googlegroups.com:
>
>
>
>
>
>
>
>
>
> > On Mar 8, 12:25=A0pm, "John Grossbohlin"
> > <[email protected]> wrote:
> >> Two observations/questions...
>
> >> I thought the accumulated error warning was in terms of angular measur=
es,
> >> not distance measures. For example, being off by a degree on cutting a=
mi
> > ter
> >> would yield a 2 degree gap.
>
> > Ah, you're right. =A0(slap forehead)
>
> > How does one calculate the accuracy level in degrees that the method
> > will get you? =A0Obviously it depends on the length of the sides and th=
e
> > delta distance you accept in your fifth cut from front to back.
>
> > How close to 90 degrees will I get if I use a 18" square board and
> > accept a delta of 0.004" on the fifth cut?
>
> 89 degrees 59 minutes 50.8 seconds, or 89.9975 degrees.
Hey cool. I'd appreciate it if you could show the equation(s) you
used. (degrees only)
Thanks.
Two observations/questions...
I thought the accumulated error warning was in terms of angular measures,
not distance measures. For example, being off by a degree on cutting a miter
would yield a 2 degree gap.
Secondly, I'd think you would see a different distance result if you kept
the side length 4" in your example instead of starting with a 4" square and
making cuts. If you measure the lengths of your final sides in the graphic
they aren't 4". For example, make the first cut, mark off 4" and make a
second cut, mark off 4" and make a third cut, etc. Can you easily mock that
up? I'd be curious to see the difference.
John
<[email protected]> wrote in message
news:93025756-0fed-4527-9f8e-dbb425233dc8@p12g2000yqe.googlegroups.com...
> Ok. I am trying to wrap my head around the accumulated error
> associated with the 5-cut method. I read somewhere that the
> accumulated error increases by a factor of 5 or was it 4? Anyway, I
> think both are wrong. I drew up a mock 5-cut in CAD and used an angle
> error of 5 degrees. The box is 4" by 4".
>
> Cut1=red line
> Cut2=green line
> Cut3=orange line
> Cut4=yellow line
> Cut5=grey line
>
> Cut one:
> http://www.garagewoodworks.com/5cut/cut1.jpg
>
> Cut two: Rotate clockwise and cut. Red line is now against the
> fence. The distance at the top goes from 0.35 to 0.6440 - Not double,
> but close.
> http://www.garagewoodworks.com/5cut/cut12.jpg
>
> Cut three: Again rotate clockwise and put the green line against the
> fence.
> http://www.garagewoodworks.com/5cut/cut123.jpg
>
> Cut four: Rotate and put the orange line against the fence.
> http://www.garagewoodworks.com/5cut/cut1234.jpg
>
> Cut five: Rotate and put the yellow line against the fence.
>
> We went from the original 0.35" to the accumulated 1.0". That's an
> increase of 2.86".
>
> Not four or five. Am I missing something?
>