> I am planning to make a milling spindle for my chipmaster lathe. I

Signature
The modular DRO
<http://www.yadro.de>
Nick M?ller <muellernick@gmx.de> wrote:
>> I am planning to make a milling spindle for my chipmaster lathe. I
>
[quoted text clipped - 3 lines]
>
> Nick
Can you explain how to calculate this, please ?
I've got a Westbury-Dore mill fitted with a 1/4 HP single phase motor.
I'd like to change it for a variable speed motor, and have a choice
of a 440W DC motor or a 550W 3-phase motor (both with Eurotherm
controllers). The 3-phase looks a good option, but is it pointlessly big ?
I use cutters up to about 3/8", but would also expect to use a
flycutter. I tend to take very light cuts due to the small size
of the mill, but I'd be interested in knowing what is within the
motor power range.
-adrian
alan@jackary.plus.com - 26 Aug 2006 17:11 GMT
> Nick M?ller <muellernick@gmx.de> wrote:
> >
[quoted text clipped - 20 lines]
>
> -adrian
Adrian,
I modified my Dore Westbury head with a .5hp 3 phase motor via an
inverter woks very well adequare power and much smoother see
http://ph.groups.yahoo.com/group/tom_senior/photos/view/9f33?b=4
Alan
Adrian Godwin - 31 Aug 2006 07:37 GMT
> Adrian,
> I modified my Dore Westbury head with a .5hp 3 phase motor via an
> inverter woks very well adequare power and much smoother see
> http://ph.groups.yahoo.com/group/tom_senior/photos/view/9f33?b=4
> Alan
That's an interesting mod !
For those who aren't members of the yahoo group : the photo shows a
Dore-Westbury head mounted on a horizontal mill's base, replacing
the D-W's vertical shaft. This overcomes the common criticism of the
D-W, that it doesn't maintain alignment when you change height.
Presumably it's also a lot more rigid, as the tall 4" shaft is
no longer there.
-adrian
Mark Rand - 26 Aug 2006 17:19 GMT
>Nick M?ller <muellernick@gmx.de> wrote:
>>
[quoted text clipped - 20 lines]
>
>-adrian
The conventional wisdom is 1 cubic inch of steel per minute per horsepower. I
don't think that I have ever achieved this rate while milling on the lathe
with a 550W motor. Maybe when turning 3" bar down to 2" bar with carbide bits
though.
Mark Rand
RTFM
John Montrose - 26 Aug 2006 20:39 GMT
>I've got a Westbury-Dore mill fitted with a 1/4 HP single phase motor.
>
>I'd like to change it for a variable speed motor, and have a choice
>of a 440W DC motor or a 550W 3-phase motor (both with Eurotherm
>controllers). The 3-phase looks a good option, but is it pointlessly big ?
Others will correct me if this is wrong, but I believe 1 HP is
generally equivalent to 3/4 kW (750W).
If it were me, I'd go for three phase every time as the controllers
can offer loads of useful features such as soft start, jogging, motor
braking, and almost-instant reverse.
I've seen posts recently (admittedly WRT surface grinding) that
suggest 3-phase motors are smoother and hence vibrate less. On a light
mill such as a D-W, this may be an advantage.
Nick Müller - 26 Aug 2006 21:54 GMT
> Can you explain how to calculate this, please ?
OK, lets see:
Math is in metric. :-)
[if I write x//y it means x index y]
given:
Cutter diameter = 10mm
depth of cut = 10mm
number of teeth = 3
I assume rough cutting of MS with reccomended feed per tooth and RPM.
That would be:
feed / tooth (f//t) = 0.016mm
cutting speed (v//c) = 28 m / min
P//c = a//p * f//t * N//c * v//c / 20
with:
P//c : Power f. cutting steel (in kW)
a//p : depth of cut
N//c : number of teeth cutting (with a 3 flute cutter, 1.5 teeth are
cutting in average)
P//c = 10 * 0.016 * 28 * 1.5 / 20 = 0.336kW
All that could be calculated more precise. I tried it, but got lost in
zillions of tables for specific cutter properties, material, dullness of
tool and number of beers.
HTH,
Nick

Signature
The modular DRO
<http://www.yadro.de>
Adrian Godwin - 31 Aug 2006 07:29 GMT
Nick M?ller <muellernick@gmx.de> wrote:
>> Can you explain how to calculate this, please ?
>
[quoted text clipped - 4 lines]
>
> ..etc ..
> P//c = 10 * 0.016 * 28 * 1.5 / 20 = 0.336kW
Thanks for taking this trouble !
That's almost twice the power of the existing motor and less than either
of my alternatives, and the cut is much deeper than I'd normally use.
Which suggests I'm being much too timid (though the mill is probably
not rigid enough for recommended feeds) and any of the motors have
adequate power. I'm not sure what feed rate I can do smoothly with
the manual feed but I suspect that even the existing motor will do
anything I dare attempt.
-adrian
Nick Müller - 31 Aug 2006 08:08 GMT
> Thanks for taking this trouble !
You're welcome!
> That's almost twice the power of the existing motor and less than either
> of my alternatives, and the cut is much deeper than I'd normally use.
Don't forget, that this is the required power, and not the power
consumption of the motor.
Nick

Signature
The modular DRO
<http://www.yadro.de>