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I am looking at milling 4140PH (Rc of 30) and from some reading the recommendation is to dry mill with air blast for chip removal as coolant will cause thermal shock to the carbide and early failure. Doing this in a maker space (not my machine) so limited on what I can set up or modify on the machine. I know it has coolant setup but not aware of any provision for air blast. How is this usually done other than just hand holding an air hose to keep the chips away from the cutter?
There is always going to be someone that says no coolant is better in some cases it can be better, roughing 4140 is good to do without coolant, but finishing will give you better tool life and better finish with coolant, and this won't cause thermal shock when finishing, it has a lot to do with speeds / Feeds the Tool being used and the rigidity of the part and the machine plus spindle Hp correct chip load is important, and use max depth of cutQuote:
Originally Posted by Jim27
You would need a spare coolant m code, possibly M7 if the machine only has M8 function. A relay, air valve and manual flow control valve. It could be rigged up using a magnetic base in the work area to clamp the nozzle and spare coolant m code could be programmed ie M7 air on M9 off.Quote:
Originally Posted by Jim27
You could run air and valve externally.
if there is an ample coolant pressure and flow then go with coolant . I've found more times than not that coolant will give the better tool life on inserts or coated end mills . Just provide a lot of coolant at a bit higher concentrate
Maybe coolant is the way to go. I have just read some on carbide thermal shock from coolant but have really no experience to base that on one way or the other. I suppose it is a case of flood with coolant or none (rather than a little coolant where it may get hot when coolant isn't on it and then gets hit with coolant)?
the more coolant the merrier but if you have a decent flow then you should be good to go . If it can push the chips out of the way then you should have enough pressure to keep the tool soaked .
There are a lot of arguments from both sides of the fence , and experiences differ from one another to justify both sides of the argument . Applications vary and so do factors which play into things , but flooding a tool is usually a safe bet for general machining
You’ll be fine running flood coolant and If it’s available I would recommend to do so.
They may not let you hack their machine but it’s possible you can rig up a 120v coil solenoid valve actuated by the M8/M9 output instead of the coolant pump..
The biggest advantage to running dry vs coolant is more the lack of mess, expense, maintenance and degradation of the machine. It all depends on your priorities.
I personally run everything dry in my home shop CNC with just an air nozzle to clear chips and occasionally some tapmagic if I’m drilling aluminum or running a problematic tool path that I know will induce recutting or chip welding.
accelerated tool wear with dry cutting is the trade off.
Oh and you absolutely need to use carbide if your cutting dry. HSS will die a quick death.
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