I picked up some nice Whiteside compression bits recently. Unfortunately, their tool import data (importing to VCarve Pro) is not even close to accurate. For instance, it loaded with a feed rate of 400 ipm which is just crazy.
I’m using similar bits as a reference point and adjusting the tool data as I see fit. However, I’m interested in pushing it hard to optimize production time, but not so hard I’m breaking bits or starting fires.
I’ve always heard that chip size is a good indicator of good or bad feed rates, but what about temperature? When I light up the bit using an infrared thermometer it doesn’t get much hotter than 108°F. That seems rather cool to me and I would suspect that I could increase feed rate, but I’m not sure what the ideal max temperature for a bit while cutting should be.
I’m wondering if temperature means anything in respect to feed rate or if it’s not a metric useful for modifying tool data?
I would use temperature as a red line where at a certain threshold of heat it would be necessary to back off on the cut — but chip size seems far more useful a guide/gauge.
Interesting question, and a nice can of worms
I guess @spargeltarzan could give us the hard facts here as I suspect the answer is not obvious, but I’ll say this, assuming we are talking about cutting wood, not metal, since you mention a compression bit:
generally speaking, there is a higher chance of ending up with a hot tool when using a chipload that is too small (hence the tool is rubbing rather than cutting), than when using a larger chipload
the lower the temperature, the longer the tool life, so the ideal temperature is as-low-as-practically-possible
I suspect your MRR will be limited by machine rigidity loooong before the tool temperature becomes a concern, assuming appropriate feeds and speeds (which in my religion boils down to proper chipload, indeed)
@WillAdams - Interesting read. It does seem to be relevant to metal machining and not so much wood, as I’m working with. But still some insightful info. Thanks for sharing the article. There are some concepts in there that suggest temperatures can rise due to feed rates being too low.
@Julien - You are correct. I’m carving wood only at this point. I hadn’t considered machine rigidity relative to feed rate, but it makes sense now that I think about it.
I’m not certain, but if an IR Thermometer works similarly to a thermal camera, the bit will simply be reflecting IR wavelengths from around it if it’s shiny carbide. A matte black surface is best. If there is room you could put a piece of gaffers tape on the bit to try and take a measurement of that.
That said, for wood I wonder the same thing. No carpenter with his router table is measuring feeds and speeds. Let 'er rip. I imagine the room for error is much bigger then 6061 aluminium, which would also have a bigger tolerance than for steel, plate, so on and so forth.
I occasionally check the cutter temperature just after a job finishes, with a finger, if the cutter is warmer than my finger after cutting wood then I ask myself what’s wrong with my cutting parameters. I certainly don’t want the cutter hanging around long enough to cause any burn marks on the wood. As Julien says, moving too slowly on wood is generally the heating issue. Adjusting the depth of cut to find the sweet spot of moving fast without causing cutter or machine vibrations is the trick.
I’ve also not had a cutter get noticeably warm cutting Aluminium, except when having an obvious issue overheating the workpiece and once that’s too hot to touch and has started chip-welding to the cutter I suppose the cutter has an excuse to be a little warm.