Variac as router speed control?
 

I've got a hunch this is probably a bad idea.
I bought a Milwaukee 5615 fixed speed router and I need to swing a
3/4" roundover bit (~18,000 rpm, according to Jesada). I'm wondering
if I should return this fixed version for the variable speed unit, or
if a 2kw variac will do the job?
Dave

Interious wrote:
I've got a hunch this is probably a bad idea.
I bought a Milwaukee 5615 fixed speed router and I need to swing a
3/4" roundover bit (~18,000 rpm, according to Jesada). I'm wondering
if I should return this fixed version for the variable speed unit, or
if a 2kw variac will do the job?
Dave

You don't want to go there.

I could give you a long explaniation why, but it's late and I'm tired.
Sorry.

What I suggest is you consider something like a table mounted PC 7518.

A 3/4" rounding over bit is nothing to fool around with in a hand held
router, IMHO.

You are probably going to have to probably make multiple passes anyway,
so a table makes it a lot easier and safer.

HTH

Lew

Well, I just got up.
The Variac is a great variable voltage transformer and good for many
things...I might want to buy yours.
The trouble with the router is that reducing the voltage to the router will
reduce the current the motor "can" draw as it loads down in a cut. With
limited current it will sag badly and slow way down...more than you want.
The solid state speed controls are entirely different. They control by
actually turning the voltage off and on rapidly. The great thing is that
they also incorporate a feedback system that senses motor speed and
increases the voltage as required to maintain the speed you want. Just run
your variable speed drill at low speed and take hold of the chuck. You'll
actually feel and hear the torque pulses change as you apply load!
So there you go. Buy the speed control. They are cheap ($12 for mine). Of
course having the control built in is great. I'd do the exchange if I
could.
Wilson
"Lew Hodgett" wrote in message
k.net...
Interious wrote:
I've got a hunch this is probably a bad idea. I bought a Milwaukee 5615
fixed speed router and I need to swing a
3/4" roundover bit (~18,000 rpm, according to Jesada). I'm wondering
if I should return this fixed version for the variable speed unit, or
if a 2kw variac will do the job? Dave

You don't want to go there.

I could give you a long explaniation why, but it's late and I'm tired.
Sorry.

What I suggest is you consider something like a table mounted PC 7518.

A 3/4" rounding over bit is nothing to fool around with in a hand held
router, IMHO.

You are probably going to have to probably make multiple passes anyway, so
a table makes it a lot easier and safer.

HTH

Lew

Interious writes:

I've got a hunch this is probably a bad idea.
I bought a Milwaukee 5615 fixed speed router and I need to swing a
3/4" roundover bit (~18,000 rpm, according to Jesada). I'm wondering
if I should return this fixed version for the variable speed unit, or
if a 2kw variac will do the job?

While a variac is great for fan motors, especially if you go three
phase, it's not a good idea on cutting tools. Go for the variable
speed unit, it will anyway be cheaper then the variac.

--
Dr. Juergen Hannappel http://lisa2.physik.uni-bonn.de/~hannappe
Phone: +49 228 73 2447 FAX ... 7869
Physikalisches Institut der Uni Bonn Nussallee 12, D-53115 Bonn, Germany
CERN: Phone: +412276 76461 Fax: ..77930 Bat. 892-R-A13 CH-1211 Geneve 23

In article ,
Interious wrote:

I've got a hunch this is probably a bad idea.
I bought a Milwaukee 5615 fixed speed router and I need to swing a
3/4" roundover bit (~18,000 rpm, according to Jesada). I'm wondering
if I should return this fixed version for the variable speed unit, or
if a 2kw variac will do the job?
Dave

The 5616, the 2.25 HP VS bigger brother of the 5615 (I own both) is
barely adequate for thr 3/4" r bit... depending on material.
The variac does nothing for 'speed' as such, it just makes it weak,
which is fine for a light bulb.
You will seriously affect the 5615's ability to cool itself as well.

I kind of figured purpose designed speed controls essentially act like
an intelligent constant current source. I thought I would ask about
the variac anyway just to rule the option out with certainty.

I think I'm going to get the 5625-20 and put it in a table for this
job. My experience is with a wimpy old craftsmen router and small
bits. Lots of learning to do.

By the way--I bought a Bosch 3/4" roundover bit at Lowes. Should I
return it for a Whiteside, CMT, etc.? MDF is the current medium.

Thanks to all for interesting responses.
Dave




On Tue, 29 Mar 2005 00:50:47 -0500, Interious
wrote:

I've got a hunch this is probably a bad idea.
I bought a Milwaukee 5615 fixed speed router and I need to swing a
3/4" roundover bit (~18,000 rpm, according to Jesada). I'm wondering
if I should return this fixed version for the variable speed unit, or
if a 2kw variac will do the job?
Dave

The controller is not a constant current source, it's the opposite.
Constant current will give constant torque, so you'd go to max spped with no
load and stop as soon as the load torque corresponded to the current set in
the controller! It IS a (nearly) constant SPEED device. Current can rise
to whatever is needed to maintain speed, or until the motor or controller
blows. With the motor locked, such a controller can deliver full voltage to
the motor, at high current, frying it quickly.
WL
"Interious" wrote in message
...
I kind of figured purpose designed speed controls essentially act like
an intelligent constant current source. I thought I would ask about
the variac anyway just to rule the option out with certainty.

I think I'm going to get the 5625-20 and put it in a table for this
job. My experience is with a wimpy old craftsmen router and small
bits. Lots of learning to do.

By the way--I bought a Bosch 3/4" roundover bit at Lowes. Should I
return it for a Whiteside, CMT, etc.? MDF is the current medium.

Thanks to all for interesting responses.
Dave




On Tue, 29 Mar 2005 00:50:47 -0500, Interious
wrote:

I've got a hunch this is probably a bad idea.
I bought a Milwaukee 5615 fixed speed router and I need to swing a
3/4" roundover bit (~18,000 rpm, according to Jesada). I'm wondering
if I should return this fixed version for the variable speed unit, or
if a 2kw variac will do the job?
Dave

Wilson,
It's a long time since I've studied current and voltage source theory.
I completely take your word for it. Makes sense.
Dave


On Wed, 30 Mar 2005 04:24:40 GMT, "Wilson Lamb"
wrote:

The controller is not a constant current source, it's the opposite.
Constant current will give constant torque, so you'd go to max spped with no
load and stop as soon as the load torque corresponded to the current set in
the controller! It IS a (nearly) constant SPEED device. Current can rise
to whatever is needed to maintain speed, or until the motor or controller
blows. With the motor locked, such a controller can deliver full voltage to
the motor, at high current, frying it quickly.
WL
"Interious" wrote in message
.. .
I kind of figured purpose designed speed controls essentially act like
an intelligent constant current source. I thought I would ask about
the variac anyway just to rule the option out with certainty.

I think I'm going to get the 5625-20 and put it in a table for this
job. My experience is with a wimpy old craftsmen router and small
bits. Lots of learning to do.

By the way--I bought a Bosch 3/4" roundover bit at Lowes. Should I
return it for a Whiteside, CMT, etc.? MDF is the current medium.

Thanks to all for interesting responses.
Dave

I have two Variacs... I wonder what they're worth. I was thinking of selling
them on Ebay, I got them from an estate sale (an electro-chemical engineer's
estate)
Tom

"Wilson Lamb" wrote in message
et...
Well, I just got up.
The Variac is a great variable voltage transformer and good for many
things...I might want to buy yours.
snip