Machining PVC Block

dulltool17

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This might actually be my first "I need help" post......

I have a block of PVC that's 3" x 6" x 3/4" thick.
I need to reduce the thickness to 11/16" (0.688 +/-0.005)

I have a Grizzly combo machine with enough travel and a mill vise.
Here are the cutting tools at my disposal:
-1/2" Endmill
- boring head and a variety of carbide bars

I'm thinking of using the boring head and my smallest boring bar as a fly cutter (which, BTW, I've never done with any material) taking 2-3 passes per cut depth to keep vibration to a minimum.

Anyone got advice on RPM and Depth of cut?
Other suggestions?
 
I think either would work, but the cutter has to be sharp with a good shear angle to get a decent finish. A dull cutter just kind of mushes and melts its way through the plastic. As far as speed, run slower than you think you should, unless you can crank the feed handle at about 40 IPM.

A wood router bit would be my first choice, they have a cutting geometry that is pretty well suited to plastics.
 
Thanks, Jim. I do have wood router bits. Hadn't thought of using them.
 
I have used a fly cutter to machine nylon and pvc with great success using a HS cutter a 1/16" minimum radius point with positive rake. It is a 2" diameter with the tool bit set in a 45 degree fly cutter. Flooded with wax base coolant. 100 to 250rpm. Feed rate slow to get and excellent finish. Depth of cut ? till it cuts nice. Stay away from the carbide, you need a lot of positive rake in the tool.
 
Use flood coolant if possible, I often turn 16"+ CPVC rounds and it improves the finish a good deal, dish washing soap diluted in water sprayed on with a hand spray bottle works well, dish soap and water also works well on aluminum cast jig plate if you are not plowing through it when roughing.
MIC 6 and similar materials.
 
This would be the perfect excuse opportunity to buy a fly cutter.;)
 
With what you have. I d go boring head but I Think it would be a god time to make your own flycutter. Easy peasy and another shop tool. Just grind your tool so there is a leading angled edge that shears the cut and material supports the cut to not blowout on the edge. Consider clamping pressure. I d get close then reclamp with minimal pressure than finish to square and not be affected by clamping pressure to distort.
 
V. Sharp HSS edge cuts best. As others have said, avoid carbide. Biggest issue is how you hold it. Clamp it in such a way that won’t alter the machined dimensions when you release the clamping force.


Mal
AKA The Felsted Skiver
 
Thank you, all, for the ideas. I'm off for a vacation, so I'll see what I can concoct after I get back.
 
V. Sharp HSS edge cuts best. As others have said, avoid carbide.

I get excellent surface finishes on CPVC with carbide insert tooling, chip control is a problem however, I do not see how HSS tools would solve this.
Please explain.
 
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