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Original poster: Edward Wingate <ewing7-at-rochester.rr-dot-com> 

Tesla list wrote:
 > Original poster: Terry Fritz <teslalist-at-twfpowerelectronics-dot-com>
 > Hi Ed,

 > Try cutting 6-4 titanium with tool steel :o))  I just get the hardest bits
 > I can since that will do everything no matter what.  In my case, they last
 > forever since I will never use them hard enough to dull the cobalt.  Of
 > course, machine shops have to worry with the economics, but not a concern
 > here.  But nowadays, most of my titanium (and phenolic) cutting is done by
 > the waterjet shop...


I don't know what the designation 6-4 is, but we machined a lot of
titanium for NASA and with the right speeds, feeds and coolant, high
speed steel cutters worked just fine.

 > >high speed or carbide. On the subject of machining, here's one for you
 > >to ponder. :^) Carbide cutters are the only kind to use on 99.9% of
 > >plastics.
 > Plastics (like high-grade UMHW) need super aggressive super razer sharp
 > cutters.  I do use two flute tool steel for that.  Maybe I need to look
 > into carbide instead since the steel does dull.

High speed steel dulls quickly on plastic because the heat generated on
the cutting edge can't be conducted away due to the plastic's poor
thermal conductivity and the heat literally burns the sharp edge off.
Carbide cutter edges can withstand the heat better and don't break down
as quickly. With glass filled materials like G-10 and Ultem (the
material from he--) all cutting tools take a beating, but carbide still
has a bit of an advantage.

   I tend to break carbide
 > (maybe I should not use them in the hand drill so much :o)))  Cobalt is
 > very strong but you have to jump into the fox hole if they do shatter!!  I
 > always get Ti-N coating too which is worth the cost.  Shopping for the
 > mills is easy too, I just look for the most expensive ones ;-))  But in my
 > case, the cutters are the cheapest part of the whole milling thing.  My
 > brand new Starrett 12 inch calliper just set me back $250!!  Hey, gota have
 > it :o))

But the Starrett caliper isn't considered to be an expendable tool.
Unless, of course, you plan to use it under water. :^)

Titanium nitride coated tools are worth the extra cost for many

Ed Wingate RATCB

 > Cheers,
 >          Terry