High Speed Spindle for SIEG X2 - Finally a Solution

Looking for an affordable high speed spindle for your SIEG X1, X2,
or X3 - or for any bench milling machine? I've been looking for one
for over a year, and finally found one at KDN Tool.

I first looked at the NSK Astro-E 250, which sells for over $2,000.
I can buy 18 of the KDN Tool high speed spindles for the price of
one NSK Astro-E 250. The solutions I found on ebay, the internet,
and in the discussions on Yahoo CAD-CAM-EDM-DRO group, DIY-CNC
group, hf47158toCNC group, Irk-torquemax group, X-Series-Mills
group, and CNCNet came close, but not quite close enough in price,
power, number of collet sizes, reliable collet chuck design for
small end mill shanks, air cooling, variable spindle speed,
commercial designed spindle nose bearings, low spindle run out,
quiet running, and a fairly good duty cycle for long jobs.

I've got it on order - 5,000 to 20,000 rpm with six collets 1/32" to
1/8" - for $170, which includes the mounting bracket for the SIEG
X2. You will find it on www.kdntool.com

Finding the KDN Tool spindle has been quite an adventure. When I
first got into CNC, I determined that I would not be primarily
making conventional machine parts, but would be engraving, and
sculpting plastic, aluminum, and brass. I was surprised to learn
that I would need a high speed spindle, for the same reason that PWB
drilling, and engraving applications demand. The very small
diameter end mills require the high speed. My stock SIEG X2 at
2,500 rpm needed to be stretched up to 20,000 rpm. No way. I
looked at high speed routers (collet limited to one size), air
driven spindle motors (too noisy), hand pieces for manual grinding,
engraving, sculpting (not enough power or too expensive), and die
grinders (one speed).

The breakthrough for me was when I found an article by Paul
Frederickson and David Grimes of The Precise
Corporation, "Increasing Torque For A High Speed Spindle", in MMS
Online. They published a formula to determine the cutting torque
required, and a Power equation. The cutting torque equation is:
Torque (N-m)= Depth of cut (mm) x Width of cut (mm) x Feed rate ( mm
per tooth ) x Number of teeth per revolution x Machinability Torque
Factor

Machinability Torque Factor – aluminum (0.145), brass (0.29), and
steel (0.435).
I wrote Paul Frederickson and he graciously told me the process for
determining the Feed rate ( mm per tooth ), and told me the factor
for brass. He said that, "a good rule of thumb to start with is 1%
of tool diameter per tooth".

So a 1/32" ( 0.794 mm ) dia end mill, 0.4 mm deep cut, 0.008 mm feed
rate per tooth, and 2 teeth results in Torque ( N-m ) of 0.0007
aluminum, 0.0015 brass, and 0.0022 steel. The power in watts for
the KDN Tool spindle at 20,000 rpm is 1.5 aluminum, 3.0 brass, and
4.6 steel. The KDN Tool spindle has a 100 watt capability.

For a 1/8" ( 3.175 mm ) dia end mill, 1.6 mm deep cut, 0.032 mm feed
rate per tooth, and 2 teeth results in Torque (N-m) of 0.046
aluminum, 0.093 brass, and 0.139 steel. The power in watts for the
KDN Tool spindle at 20,000 rpm is 97.2 aluminum, 194.4 brass, and
291.6 steel. So for brass and steel either the depth of cut needs
to be reduced, or the speed needs to be decreased to 10,289 rpm for
brass, and 6,859 rpm for steel.
Power ( kw ) = ( Torque (N-m) x rpm ) / 9,550

When I tried to adapt some of the other solutions to my SIEG X2 I
was stunned to find out that it is a major production to remove
the "Spindle box" casting part # 49 from the "Spindle box seat"
casting part # 63, which rides the column Z axis vee way. Part #49
is bolted through the back of part # 63, and you can't see the bolt
heads, because the are covered by the Z axis column vee way.
Aggghhh!

Wait till you see KDN Tool's solution. It's just right for me, I
don't need all of the X axis travel.

Bill Perun