[TCML] Machining Question - Techniques for Cut-Off Sawing

[BunnyKiller]

Hey Daniel...

what type of vertical mill are you getting?  That can be the deciding 
factor..
as far as cut-off saws most offer 10 thousands of an inch "perfection" 
(.010") with a metalic blade and carbide cutter tips ( pretty much 
depends on material being cut)
if you use the granulated abrasive type blade, expect about .050 - .080" 
"perfection"for metals ( dont use on plastics).  I prefer a good bandsaw 
with a carbide tipped blade ( 3/4" wide blade or 1" ) best used on soft 
non ferrious metals ( Cu, brass, Al) and plastics
to do the job ( but then again a 3/4" blade runs about 200$)

Chop saws are great for metallics ( granulated abrasive), soft copper 
thru hi carbon steels, but they suk for plastics... (EXCEPT when you 
change the blade to a  carbide tipped wood working blade  80 -120 tooth 
...cuts all plastics, no gumming)

best bet is to cut about .10-.250" longer than what you need and mill 
.050-.100" off of each side to be veryyy close to what you expect.
Depending on your choice of mill, you can see anywhere between .0005 to 
.002" of "perfection". I have worked with CNC Bridgeports that can do 
.0005" tolerance over 36" length and worked with some Chinese made 
models that only offer .005 over 8" length. A word on plastics, acetyls 
are more stable than ethelynes when doing machine work.... I have seen 
acetyls behaive more like aluminun and HDPE's go absolutely crazy on the 
mill, warp like all get out due to localized heating ....

As far as cutting "soft materials, it all depends on the type of blade 
and cutting speeds used to cut said materials. Copper and brass can be 
cut with a fast blade speed , soft steels and hard aluminums can be done 
with medium speeds with a water based lubricant, hard steels and hi 
carbon usually need slower speeds and an oil based lubricant, plastics 
are a totally differenty monster do deal with, acetyls like faster 
speeds, ethelynes a slow speed due to heating problems and gumming when 
run at medium to hi speeds. Plastics can be a real problem if they are 
"pre-stressed" they have a tendency to close up on the blade as they are 
being cut.

wow  hmm  okay a synopsis, soft metals and plastic need hi to medium 
speed with a carbide tipped blade, low carbon and hard copper alloys ( 
brass etc) medium speed either tungsten or abrasive cutter, hi carbon or 
exotic steels.. granulated metal cutting blade... but expect some 
localized heating at cut point ( monel will tend to turn blue at cut 
point to about .200" from actual cut point)

yup its not that easy to cut something if you want a good 
tolerance.....    :)

cut it thick  mill off the rest :)

If you are planning on soft metals and plastics, consider a compound 
miter saw.... might be a bit cheaper  Roybi has one for 99$


Scot D


Mccauley, Daniel H wrote:

> 
>Just getting around to finally investing in a vertical mill, and am
>looking at what options there are for a cut-off saw.
>Do you typically just make a rough cut and then use the mill to
>"perfect" the cut, or get the best possible cut right off the bat
>using a cut-off saw?
>
>Dewalt and Milwaukee (as well as others) sell some inexpensive metal
>chop-saws, but not sure how well they work for soft metals like
>aluminum, brass, etc... and plastics.
>
>Any help appreciated!
>Thanks!
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