Anyone out there notice any bogging down since they've switched over to
either a spiral cutterhead or one with carbide inserts? The laws of
physics dicatate that since something is ALWAYS in contact with the
wood that you'd need more POWAH. Am I right, or am I right?
I'll tell ya' later.
In the straight case, you have a free spin, then a "whomp" as the whole
blade bites at once.
In the spiral case, you have a continuous but narrower cut.
Likely the total amount of work is similar. You might even need less
power on the spiral cutter as it is a more even load.
I asked the question because I was at a tool dealer today who said that
he doesn't sell any tools with spiral inserts because the companies
don't upgrade their motors when they include the spiral heads - and
that they should because those with such an upgrade really need 30%
MORE power than their straight-bladed counterparts. Sounded fishy to
He carries Delta and General Int'l.
The laws of physics may dictate that something that is always in contact
with the wood would need more power however the laws of physics also dictate
that a shearing action will require less power than a non shearing action.
Perhaps feed rate should be slowed to offset the amount of waste being
generated. Oddly single flute carbide bits cut better and or faster than
double flute bits as there is more room for the waste chips.
Know anything about calculus?
Where you arrive at an answer for the 'whole', by breaking the matter
down into a bunch of smaller pieces, figuring out each piece, and then
"add 'em up" to get the answer for the 'whole' thing.
Apply the same approach to the planer knife. consider the straight
blade as a bunch of little pieces all lined up in a row.
Now, consider the same bunch of little pieces, offset into a spiral.
Is there _any_ difference in the amount/duration of blade contact with
"A numerical answer is left as an exercise for the student."
(I've always wanted to say THAT!! <grin> )
for a true spiral blade, where the cutting edge is at an angle to
the direction of travel of the wood, the energy required is proportional
to the cosine of the angle of the blade to the direction of travel,
multiplied by the blade dimension.
Now, it just happens that said cosine dimension is the same as the
straight-line measure that a straight blade would require for the same
Actually, there *is.**everything* cancels out. you end up with a 1==1
Oh.. a Jointer... I was picturing a spiral router bit. Humm.... LOL...
Did you see the article in the latest Wood magazine on 8" jointers? About
half of them were with some type of spiral head cutter. I do not recall any
complaints about power problems but there was a section that addressed the
cuts that were less than perfect when compared to the standard straight
knife cutter heads. Apparently the manufacturers are aware that the
straight knife leaves a smoother and more uniform surface.
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