Tool diameter accuracy

[Neale]

No, I don't think that it is a tool compensation problem as the gcode preamble includes G40 which should turn it off. That amount of error is strange - too big for cutter diameter error, I would have thought, but too small for any significant axis calibration error (which I have checked in the past). The error is also pretty much the same, within the limits to which you can measure MDF anyway, along both axes, which I would have thought meant that it's probably not machine bend as I would expect that to vary with axis. However, this is my MDF router, so anything's possible. At least the error is consistent enough that I can tune it out by tweaking cutter diameter in vCarve. Sometimes I have to pretend to be an engineer and not a scientist (it works, dammit, so forget the theory!).
Thanks for the thoughts, guys, and I shall try putting a mike across the plain part of the cutter (3mm single flute on 6mm shank) as a check.
This is what I'm playing with.

It's a cable chain idea based on something I found a while back; it needs reasonably accurate cutting to make it all stay together (no glue or loose fixings) while still being able to articulate.

[JAZZCNC]

It's a cable chain idea based on something I found a while back; it needs reasonably accurate cutting to make it all stay together (no glue or loose fixings) while still being able to articulate.

Don't see the point in cutting these other than the exercise.!! . . . They will cost more in Elecy than they cost. . Lol

The cutting differance will be MDF frame swelling in the morning dew try cutting in afternoon when it's warmed up. .

Now seriously I would check for backlash or end float on the screws and because it's consistant the differance could be the amount of backlash. Try cutting something similair with a larger cutter and see if error is same amount I'd wager it will be.!
After this then check steps per again and make sure it's moving the exact amount it's told. That amount of differance can really only come from either cutter comp or wrong amount of movement, either thru backlash or steps.