What is the least amount of brake rotor material (in metric and
inches) that a rotor on a 2000 Ford Taurus should be at which will
allow machining without exceeding the manufacturer recommended minimum
tolerance?

Also, I am interested in determining the average amount of material
(in metric and inches) that is machined off a rotor that is going to
be re-used.

Thank you in advance for your assistance!!!!

kdk1966-ga:

Amazingly, I have not been able to find a reliable on-line reference
to the "machine to" thickness for the brake rotors on a 2000 Ford
Taurus. This information is usually stamped into the hub of the rotor
for easy reference; however, I cannot find any references to the
actual value online, and I do not have a catalog available at the
moment with this information. So, I did the next best thing (and it's
something that you can do as well if you wish to verify my
information); I called up my local 'jobber' parts store, and asked!

The counter-person was kind enough to check out the value stamped into
the side of a new rotor for me. That value is 1.01 in (25.66 mm).

In case you are interested, here is a website that shows the tools
used to measure this thickness properly:

http://www.mytoolstore.com/kd/kdbrak09.html

I can also point you to this link that can help you with the second
part of your Question:

http://members.aol.com/carleyware/library/procut3b.htm

If you scroll down to the FORD NOTES section, you will see that Ford
recommends a minimum cut depth of 0.002 in (0.05 mm), and a maximum
cut depth of 0.008 in (0.20 mm).

Please note the information regarding the difference between "machine
to" thickness, and "discard" thickness. The number stamped on the
rotor for Ford applications is the "machine to" thickness, which is
the value that you are asking about.

The 'average' is a difficult number to state authoritatively, since
the actual amount cut depends on the roughness of the surface that is
being machined. Most reputable shops, if they determine that the
rotors do need to be machined (and note that Ford does NOT recommend
machining rotors unless there is noticeable problems), will survey the
depth of the grooves, and use the minimum-possible cut depth.

I hope this answers your question!

Regards,

aht-ga
Google Answers Researcher

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Request for Answer Clarification by kdk1966-ga on 25 Feb 2004 08:40 PST

I appreciate you answer; however, I am not trying to determine the
"machine to" thickness for the brake rotors (it?s stamped on the
rotor).  Instead, I?m trying to determine the minimum amount of
thickness that can be remaining on the rotor prior to machining so
that the manufacturer?s minimum tolerance is not exceeded after
machining.  Please help!!!

---

Clarification of Answer by aht-ga on 25 Feb 2004 12:02 PST

Based on the information provided by Ford during the Brake Symposium
mentioned above in:

http://members.aol.com/carleyware/library/procut3b.htm

the rotor can only be safely machined down to 1.01 inches before there
is no longer enough material left on the rotor to last the service
life of a set of brake pads.

The 'minimum thickness' before machining is completely dependent on
the depth of the grooves in the rotor that you are trying to machine
out. Each cut must be at least 0.02 inches deep, no more than 0.08
inches deep. The 1.01 inch value is for a machined, smooth surface.
Prior to machining, the actual thickness varies across the face of the
rotor due to the grooves.

To determine the minimum thickness prior to machining for any specific
rotor,  you or your technician, using one of the gauges illustrated in
the 'mytoolstore' link, should measure the minimum thickness across
the face of the rotor where the groove is, and determine that the
remaining minimum thickness (ie. at the bottom of the deepest groove)
is greater than 1.01 inches, and the deepest groove is at least 0.02
inches deep (in reality, you would not machine so shallow a groove).
If so then it is still safe to machine the rotor to remove the groove
as the final cut must be at least 0.02 inches deep. If, for example,
the groove is 0.1 inches deep, and you measure that the remaining
thickness at the bottom of the groove is 1.01 inches, then you can
machine that side of the rotor down to 1.01 (ie. the bottom of the
groove) safely.

Where things get complicated is when both sides of the rotor are
grooved, and you want to machine both sides. The only accurate way to
know if you can still safely machine the rotor is to machine one side
flat, then measure the grooves on the other side and see if you are
still going to be greater than 1.01 inches after machining to the
bottom of the deepest groove on the second side. Another way, that
avoids the first machining pass, is to use a more complex brake lathe
with an integrated datum point that lets you measure both sides
relative to a common reference point, then calculate accordingly.

So, have I made it clear that there is no single "minimum thickness
before machining" number that can be used as a rule? And that rather,
you need to use the "machine to" thickness compared to the thickness
measured at the bottom of the deepest grooves? If there are grooves on
both sides that you want to machine out, then it's more complicated.

Hope this helps,

aht-ga
Google Answers Researcher

Excellent ... thank you so much for your insights aht-ga