|It seems that, no matter what new
tools we come up with, someone always wants a bit that has a smaller
diameter, cuts deeper, and is able to cut a wider variety of materials
without a reduction in performance. As we have pushed our tools ever
smaller we have often run into situations where the data that we were
collecting just did not make sense. Sometimes a tool would last for
thousands of inches, sometimes, in the exact same material, a tool would
snap off as soon as it hit the surface. Tool wear was inconsistent and
edge quality varied from test to test.
After an awful lot of busted carbide, we
discovered that we were making a rather silly mistake. We had always
assumed that, since we were running our tests using very good spindles
(Colombo, NSK, & Westwind) the problems must be with our designs or
the batch of carbide we were using. As it turned out, the problems that
we were chasing were more often than not caused by the spindle, or
rather, the by way that the spindle had been maintained. To make a VERY
long story shorter, suffice it to say that we discovered that if the tapered
spindle bore and/or the collet / toolholders were even the least bit dirty
or corroded, the dynamic and static run-out
(TIR) could vary by as much as
0.005" (0.13mm) between successive tool changes. Run-out of
that magnitude will break bits, cause excessive chatter and can even
shorten the life of the spindle bearings.
While a few of the problems that we discovered
were caused by plain old negligence, the most common was the result of
improper cleaning techniques using alcohol or similar solvents. On the surface, this sounds
like a good idea. The alcohol would dissolve any grime that might
have collected inside the bore allowing it to be removed by a cloth or other
absorbent material. Unfortunately, on closer examination, this procedure
is unwise for a number of reasons.
- Alcohol removes any oil or lubricant, leaving the hardened steel surfaces totally unprotected from humidity and atmospheric pollutants.
- Isopropyl alcohol (which is commonly used) contains as much as 5% water by volume.
After the alcohol strips away any protective oil and flashes off you are left with a layer of water
that will readily attack an unprotected steel surface.
- Removing the layer of oil between the
spindle taper and the collet taper makes it more difficult for the
collet to seat properly during tool loading, potentially increasing tool runout (TIR).
- Removing the layer of oil between the
spindle taper and the toolholder (on machines equipped with automatic tool change) makes it more difficult to eject the toolholder, resulting in the loud hammer sound often heard during tool change.
The result of cleaning the spindle with a solvent, as many people
have discovered, is an ever deepening layer of corrosion and pitting
inside the spindle bore and on the precision ground surfaces of the
collets and tool holders. As the corrosion becomes more pronounced, it
grows increasingly difficult for the collet to seat properly in the
spindle taper, often causing it to torque over to one side or the other.
This is the source of the excessive run-out mentioned above.
We also found that some users were removing the rust with
a ScotchBrite® or steel wool pad. While both of these
materials are quite effective at removing rust, they are also very good
at removing "healthy" material from the hardened tapered
surfaces. It is true that the amount of material actually removed is
quite small. However, when you are cleaning a high-speed spindle with a
TIR specification between 0.000050" - 0.000400" (1.3 - 10 microns),
it does not take many such cleaning cycles to permanently alter the
concentricity of the spindle bore and push the TIR far outside that
Rule of thumb: Do not clean
precision ground surfaces with aggressive abrasives.
Now there is Son of ColletCare® and ColletCare +P+®, a
revolutionary solvent/lubricant that is designed specifically to clean,
lubricate and protect the precision ground surfaces of electric and air
spindles. Combining a solvent, low viscosity lubricant and a small
amount of PTFE / colloidal boron nitride, ColletCare® will clean, polish
and protect the bore and collets of virtually any precision spindle, router, laminate trimmer or
After watching the video, please read the rest of the page for more information.
Flip the Q-Tip®
over and insert the used dry end to wipe any residual ColletCare®
off of the tapered surface.
As the surface dries, the mild abrasive
properties of the cotton tip will polish the surface to a high luster
while leaving behind a monolayer of protective lubricant. This
layer will prevent corrosion and will allow collets and tool holders to
seat easily and securely when drawn into the spindle taper. In addition, the small
amount of colloidal graphite in ColletCare® will find it
way into any pits and scratches in the surface and effectively stop any
corrosive processes that might otherwise survive the cleaning process.
The Star Wars© class animation to the right shows the proper motion to polish the entire spindle taper. Nine or
ten in-out cycles should be enough to thoroughly dry the surface.
If the Q-tip®
is discolored (dirty) when you remove it, get a new one and repeat the
drying step. There will only be a slight gray discoloration on the
cotton tip when the taper is clean and totally dry.
this procedure at least once a week to insure that your spindle bore,
collets and tool holders remain clean and corrosion free.