I'm thinking of buying a Foredom power tools and would like any opinions
on the advantages/disadvantages of their motors.
Basically, they have three types of motors:
1) L - high-torque/low-speed motor (no HP rating is given for this model)
2) TX - 1/3 HP with top speed of 15,000 rpm
3) S - 1/6 HP with top speed of 18,000 rpm
There seem to be heavy duty versions of the three above, as well.
Basically, I see doing just some light carving and polishing-prepping of
metals. I used to have a Foredom that I bought in the 1980s and never
found myself thinking it lacked power. I have a Dremel now which slows
down the second it touches anything.
Does anyone know if having 3,000 more RPMs has any advantage? Seems
like a 20% speed gain, but may not be noticeable.
The high torque/low speed model is said to be perfect for stone-setting,
wax carving and other low speed applications demanding precise control.
Are the faster ones too powerful?
Lastly, I'm probably going to get a handset other than their clunky
standard one, I remember thinking the standard one was just too fat to
manipulate well with the thumb-fingers.
John Poole
hmm... is there any case for high speeds, e.g. 10,000 to 18,000 rpms?
On reflection, I realize that as the diameter of the tool gets smaller,
the RPM must increase to keep the cutting speed constant. It looks like
for buffing (and I do metal work at times), having the high RPM for
small buffs is needed.
A six inch (6") buff running at 1725 rpms will have a surface speed of
approximately 2,710 ft./min.
Using the formula:
Speed (ft/min)
RPM = -----------
Circumference (ft) [Pi * Diameter]
I solve to:
1725 * (22/7 * 6 * 1/12) =~ 2,710 ft/min
To get the same sort of speed on a 1/2" buff, I'll need to calculate the
RPM:
I solve to:
2,710/(22/7 * 1/2 * 1/12) = 20,700
For a 1/4" buff, the RPM needed would be 41,400!
(Wikipedia is our friend: http://en.wikipedia.org/wiki/Cutting_speed)
So, I agree that for wood cutting the high RPMs is not desirable. If I
want to have buffing capability for a very small diameter buff, then the
high RPM becomes desirable.
charlieb wrote:
> If by "high torque" you mean the motor with the gear reduction
> unit on top with the flex shaft coming off it - that'll give you
> the torque - mechanically that you probably could use - spinning
> a bur at 6-10K won't speed up how fast it cuts much - and can
> burn our wood if you push into the "cut" hard. The high torque,
> low rpms will cut faster - with more control.
>
> There is another approach that will give you both higher torque
> AND the ability to go up to higher rpms. Old Foredom flex shaft
> set ups used a "carbon pile" variable resistor to control the
> motor speed - basically bleeding off current before it gets to
> the motor - think of the old sewing machine foot pedal things.
> The "solid state" foot controls have a "full wave rectifier" in them
> that gives you more torque at low rpms where the carbon
> pile/ sewing machine pedals wouldn't.
>
> Think of a sine wave and you're only getting "power" on the
> "UP" side
> .
> /\
> -----/ \--------/--
> \ /
> \/
>
> The rectifier "flips" the "DOWN" side over
> and makes it "UP". At high rpms the effect
> isn't noticable. But at low rpms, relative to
> the old "resistor" foot pedals, you get not
> quite double the power where you notice the'
> difference - at low speed.
> .
> /\ /\
> -----/ \-/ \---
>
> I've had a Foredom for a LONG time - it's only 1 amp
> so that's less than 1/6th hp - with the SR-1
> full wave rectifier foot speed control. I've ground
> metal with it, wood, plastic and an occassional finger.
> I'e used it with small dental burs, larger "bone burs",
> small circular saw blades and recently with one of
> those reciprocating handpieces yoy insert carving
> gouges in. NEVER bogged it down.
>
> If you're working at chainsaw carving size, you
> might look into ArborTech's reciprocating
> attachment for die grinders and hand held
> disk sanders/grinders. They're in the 1/4 to
> 1/2 hp range. You'll snap and inserted gouge
> before you bog one of them down.
>
> charlie b
On May 22, 11:11 pm, "John L. Poole" <[email protected]> wrote:
> I'm thinking of buying a Foredom power tools and would like any opinions
> on the advantages/disadvantages of their motors.
>
> Basically, they have three types of motors:
> 1) L - high-torque/low-speed motor (no HP rating is given for this model)
> 2) TX - 1/3 HP with top speed of 15,000 rpm
> 3) S - 1/6 HP with top speed of 18,000 rpm
>
> There seem to be heavy duty versions of the three above, as well.
>
> Basically, I see doing just some light carving and polishing-prepping of
> metals. I used to have a Foredom that I bought in the 1980s and never
> found myself thinking it lacked power. I have a Dremel now which slows
> down the second it touches anything.
>
> Does anyone know if having 3,000 more RPMs has any advantage? Seems
> like a 20% speed gain, but may not be noticeable.
>
> The high torque/low speed model is said to be perfect for stone-setting,
> wax carving and other low speed applications demanding precise control.
> Are the faster ones too powerful?
>
> Lastly, I'm probably going to get a handset other than their clunky
> standard one, I remember thinking the standard one was just too fat to
> manipulate well with the thumb-fingers.
>
> John Poole
I like my 1/6HP model and have never needed more power. I have the
smaller handset too, but usually use the 44T with a 1/4" chuck for
main hogging off wood. Main benefit of having more than one handpiece
is to leave different chucks in each and not have to change when going
from one shank size to another. It is a lot easier to switch
handpieces than it is to change the chucks. I also have a Dremel with
shaft, and a super micro-motor tool for detail work. All that- and I
don't even like power carving! I like carving birds in tupelo though-
and that requires rotary power: http://www.woodworks-by-donna.com/sculptures-of-birds.html
Donna Menke
If by "high torque" you mean the motor with the gear reduction
unit on top with the flex shaft coming off it - that'll give you
the torque - mechanically that you probably could use - spinning
a bur at 6-10K won't speed up how fast it cuts much - and can
burn our wood if you push into the "cut" hard. The high torque,
low rpms will cut faster - with more control.
There is another approach that will give you both higher torque
AND the ability to go up to higher rpms. Old Foredom flex shaft
set ups used a "carbon pile" variable resistor to control the
motor speed - basically bleeding off current before it gets to
the motor - think of the old sewing machine foot pedal things.
The "solid state" foot controls have a "full wave rectifier" in them
that gives you more torque at low rpms where the carbon
pile/ sewing machine pedals wouldn't.
Think of a sine wave and you're only getting "power" on the
"UP" side
.
/\
-----/ \--------/--
\ /
\/
The rectifier "flips" the "DOWN" side over
and makes it "UP". At high rpms the effect
isn't noticable. But at low rpms, relative to
the old "resistor" foot pedals, you get not
quite double the power where you notice the'
difference - at low speed.
.
/\ /\
-----/ \-/ \---
I've had a Foredom for a LONG time - it's only 1 amp
so that's less than 1/6th hp - with the SR-1
full wave rectifier foot speed control. I've ground
metal with it, wood, plastic and an occassional finger.
I'e used it with small dental burs, larger "bone burs",
small circular saw blades and recently with one of
those reciprocating handpieces yoy insert carving
gouges in. NEVER bogged it down.
If you're working at chainsaw carving size, you
might look into ArborTech's reciprocating
attachment for die grinders and hand held
disk sanders/grinders. They're in the 1/4 to
1/2 hp range. You'll snap and inserted gouge
before you bog one of them down.
charlie b