Fill Cut Always Comes Up Short

Hi inventables Community,

I am having trouble getting my 1000mm x 1000mm X-Carve to accurately and completely cut a fill using a 1/16" bit.

For example, an 85mm x 85mm square with cut set to “fill” produces a cut area of 84.83mm x 84.97 when using the Inventables 1/16" “blue collar” bit (1.58mm kerf) and 1/16" bit width preset in Easel.

When I use a Kennametal 1/16" bit, which actually has a measured kerf of 1.55mm, the results are even worse: 84.28mm x 84.47mm. I did change the bit width to 1.55mm in Easel prior to starting this cut. It seems that Easel doesn’t recalculate the toolpath based on the custom bit width.

I am using the recommended feed rate and plunge depth for both these cuts.

I need to use the Kennametal bit because the the Inventables bit is not long enough to completely cut through the 1/2" MDF I am using.

I have calibrated my X-Carve to the best of my ability, including:

  1. Squaring the X, Y and X axes
  2. Adjusting all adjustable v-wheels so they are snug but don’t bind
  3. Adjusting the voltages inside the X-Controller with a digital multimeter to give between 2.6A and 2.8A per motor
  4. Restringing the belts so they loop under the belt clip for greater security and stabiility
  5. Adjusting belt tension while motors are closest to the fixed belt clip using a digital scale to measure about 3.75lbs at 1 inch deflection at the mid-point. I also “tfine-uned” the Y axis belts by ear for an exact match in tension
  6. Calibrating the steppers by measuring 450mm of travel and adjusting $100 and $101 as necessary using a stepper calibration spreadsheet
  7. Reading as many of the helpful and informative posts here on the Inventables forum

NOTE: The X axis on my machine deviates ~1mm over a 700mm run. The Y axis does not deviate at all.

Here is a video I put together showing my machine and the outcome of the two cuts I described above (apologies for the shakycam - it’s hard to film and demo at the same time!):

As a newcomer to both X-Carve and CNC in general, I’m stumped and am really hoping someone can point out what I’ve done wrong, or something I can do better.

Thanks for reading!

I think you are right at the edge of Inventable’s claim for accuracy.
I suspect bit deflection also contributing factor.
Please keep in mind that you purchased a hobby machine at a fraction of the cost of an industrial machine.
In working with wood the material can expand or contract more than that.
If you expect tighter results get to know your machine and what it will produce and adjust accordingly.

same bit… how close are you on outside cuts?

Thanks for your reply, Mark. Fair point - definitely makes sense!

I can certainly see how deflection can be a factor when comparing the Kennametal bit to the Inventables bit as it’s longer and thinner, but I don’t yet understand how it comes into play on a square test carve.

My next steps are:

  1. Dig into the forums and learn about deflection
  2. Play with feed rate and router speed
  3. Look for true 1/16" width bits that are 1/2" in length
  4. Test cut my entire project with my Kennametal bit, measure the output and adjust all my cuts accordingly


When determining the kerf, did you measure the bit or did you cut a straight slot and measure the slot? Measuring the slot will provide a more accurate kerf dimension.

Hi BlueLocktite,

Outside cuts have generally come out much better, so much so that I’ve really been stumped as to why fills are so much worse. But to Mark’s point above, maybe deflection is more of an issue on fills than outside cuts.

I’ll try to run a couple outside cuts tonight and post the results.


Hi Robert,

To measure the kerf, I cut a straight slot and measured the slot.


I am curious why you do not use a larger bit for an 85mm square pocket?
I seldom use a bit smaller that 1/8". If fine detail is needed do a two stage carve.

Hi Mark,

There are a few places were I do need fine detail (such as pre-drilling a number of screw holes), but looking over my project again, I think I can accomplish most of it using an 1/8" bit, followed by a fine detail pass. Honestly I’m a bit nervous about a bit change mid-carve, but I’ve got plenty of stock on-hand so it’s worth a try!


I personally, recommend changing the torque reduction dip switches in the controller to off. It gives me a lot more confidence that I am not going to jiggle the mount out of position by accident.

Hi Mark,

I ran two more tests last night with the following results:

1. 2-stage carve
Bit 1: Inventables 1/8" bit - Preset 1/8" bit width
Bit 2: Kennametal 1/16" bit - Custom bit width of 1.55mm

Expected dimensions: 40mm x 85mm
Actual dimensions: 39mm x 84.3mm

2. Single pass carve
Bit: Inventables 1/8" bit - Preset 1/8" bit width

Expected dimensions: 40mm x 85mm
Actual dimensions: 39.54mm x 84.66mm

All cuts were measured with digital calipers.

Getting worse, and far outside of Inventable’s accuracy claim.

Hi Darrin,

Thanks for the great suggestion! Fortunately, the “Lock motors” toggle worked great when I changed bits and held things steady. Accuracy was dead-on. Which makes this “fill accuracy” issue I’m having even more puzzling.


I ran another test this weekend, this time just using the Inventables 1/8" upcut bit (grey collar). It looks like every cut is consistently .5mm short (taking into account acceptable operating tolerances).

Since I’m fairly new to all this and don’t have a lot of past experiences to draw upon, is it possible that backlash and/or deflection could really produce a consistent .5mm discrepancy?

Is there something mechanical I should be adjusting? Belt tension? Controller voltages? Feed rate? Router (Dewalt 611) RPM?