Pockets and profiles cutting 1/16" undersize

Machine: X-Carve 1000mm
Router: Dewalt 611
Software: Rhino with RhinoCAM, using X-Carve Post Processor
Tool: 1/4", 2 flute straight router bit (square bottom)
Material: melamine coated particle board (.750" thick)


  • pockets are 1/16" undersize in X and Y direction
  • profiles are undersize by 1/16" in X and Y direction

When I cut rectangular pockets, the X and Y dimensions are short 1/16".
The pockets I’m cutting in my part should be .750" x 2.000", but they come out as approximately 11/16" x 1-15/16".
Some are arranged vertically and some are horizontal… but they measure the same in both orientations.

When the part is cut out using the profile process, the part should measure 21" x 18", but it measures 1/16" short in both dimensions.

With profiling and pocketing being outside and inside operations, respectively… AND with the 1/16" loss being constant, regardless of X or Y direction OR dimension… I’m at a loss.

I’ve measured my tool to ensure it is .250" OD, and it is.

I figured if the tool was undersize, it would impact the pocketing and profiling in opposite ways (pocketing would be undersize and profiling would be oversize), but that’s not the case. :frowning:
I figured if the gantry was twisting or the tool was deflecting, it would impact X and Y differently, but it isn’t. :frowning:

Last night, I tried cutting the pockets .300" deep in two ways to compare… one pocket cut by hogging out all .300" at once, and the other way cutting it in three passes .100" deep per pass. Of course the 2nd one looked better, but the dimensions between sides was the same… 1/16" undersize in both X and Y. :frowning:

I’m at a loss.
Can anyone give me some advice?

I’m going to go through calibration again, this week and see what that yields, but I’m looking for anything before I go too far in any direction.

Thank you, in advance for your help and input.

Oh, and I should mention that these problems exist whether I’m upcutting or climb cutting… or mixed. It doesn’t seem to matter.

Just off the top of my head I am thinking your steps per inch may be off.

Ahh… I see what you’re saying.
I will load up my 1/4" bit, then use manual control, plunge and cut a line in a single direction slowly… then measure the width of that line to determine what the true cut of the tool is, as opposed to just measuring the tool max OD. Got it. I will do that. :slight_smile:

Sadly, the loss didn’t appear to be exponential… but I will double-check when I move forward.
Thank you for your community contribution with the calculator. It’s people like you who make the community special. :slight_smile:

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I’m not familiar with Rhinocam, but I recently discovered that some of CAM solutions from Fusion 360 leave .02" of stock behind by default, unless you uncheck that option. They are assuming you will be adding a finishing pass to remove the rest. Sounds like it could be a similar thing.

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I recently got caught out by this using CamBam. Square profile cuts came out spot on for size but a hole (pocket) was consistently under sized. Turns out I’d selected the finishing option for holes but roughing for the square profiles. Took me a while to figure that one out!

I think we’ve nailed it.
It appears that the Pocketing operations cannot be generated without leaving some amount of stock for a cleanup pass… can’t just do it all at once.
Looking very carefully at the “Global Parameters” under “Cut Parameters” (which global is kind of a misnomer, as I can’t find a way to edit the default/global values for these), I find entries for “tolerance” and “stock”… one appears to be the allowed deviation and the other is an amount of stock to be left (for a cleanup pass)… Tolerance defaults to 0.01" and Stock defaults to 0.025"… explaining the extra material left inside the pockets I’ve cut.
Stock, cannot be set below 0.01"… but if I do a Profiling pass, that operation has a default Stock value of zero… so that’s the ticket. Pocketing cannot be used for finished dimensions… and there is no “finish pocketing” operation… just “profiling” which can be set to inside or outside a curve (pockets or part cutout, in my case).

Bottom line: It appears I will have to come back with a Profiling pass on the ID of my pockets… unless there’s another way.

I can’t explain the missing 1/16" on the outer dimensions of my cutout part, but I will continue investigating… but that’s not as critical as these pockets for tabs to fit inside.

I will perform a test on both the pockets and the outer cutout of the part in the next couple of days and let everyone know how it went.

Again, thank you all for your help… I think we may have this licked. :smiley:

I’m having the same problem. Was that your solution in the end - final pass as a profile inside?

I actually had a couple of problems with getting my finish dimensions to come out right. One was the software I am using (RhinoCAM) leaves a default amount of material on a roughing pass… which can be modified. I was leaving material without knowing it. Once I configured the software the way I needed (education on my part), it worked great.
The other problem I’ve encountered with material not coming out to proper size was when I was using a 1/8" bit with a collet adapter for my Dewalt 611… and the collet didn’t hold the tool firmly or centered… that made my cuts come out wrong. I’ve upgraded to a better collet, and I’ve learned how to set my tools securely… again, education on my part.
I hope this information is helpful. Shout back, if I can be of further help. :slight_smile: