1/8" Bit cutting deeper then other bits

After Cutting something like shapes, letters or doing a text on text using a 1/4" bit then switching to a smaller 1/8" bit and cutting around the first shape or text, or text on text, the 1/8" bit cuts about .05 in deeper then the 1/4 bit. I even cut the 1/8" inside the 1/4" grove. I have touched off several time with the 1/8in bit (used different bits too) with the same results. I use the touch off block that comes with the Onefinity. Yes I tried the original side of the block up then flipped it over and the same thing happened. The depth of cut is consistently off so it should not be in the block. Both bits are compression bits so one is NOT a ball end and another an End Mill. Difference really shows up after you stain it. I use Vectric V-carve Pro 11 and newest firmware update to controller. Any ideas? Thanks for your time and thoughts.

Looks like an error arising from your vectric programme settings. Check depths of cuts, biard thickness etc. Have you looked at the gcode to see what z depths are being asked for?

If you are unfamiliar with gcide Can you set up and run a “mini version” of what you are trying to achieve and share the gcode if that also fails.

I was thinking about all the different things and I will recheck the things suggested including the tip of the cutting tools. If I get a chance today or tomorrow I will send the gcode here. I am kinda familiar with gcode. Great idea. thanks.

Are you probing in the same reference point for both bits?
Are you using an adapter for the 1/8 bit or is it tapered?

I looked everything over. All the settings for the bits are correct in the software. I looked at the g-code and everything there is correct, both bits go down to .25. Yes I touched off at the exact same spot and no adapter for the 1/8" bit and it is not tapered. I do not think that would make a difference on depth but everything is worth a try. I will try slowing the bits down to about 40ipm currently at 80ipm. I took pictures but of course I can not find the attach file anywhere in here. I made a simple square and pentagon shape then used the 1/4" and cut on line, then changed to the 1/8 bit and made the same cut so that it would cut in the same path as the 1/4 bit. You can see the difference in height. I will just keep trying. Thanks for your suggestions

Have you tried 1/4 bit cut, take bit out, put it back in (do everything like you woukd if you were putting 1/8 back on), touch off probe, run gcode, something very close to what you would do with the 1/8 bit but such that you can see a difference , say stop the cut half way).

Yes I did try this and no success. On one occasion I had to run the “1/4” in bit three times before it would cut down to the level it should. On a pocket toolpath It would cut down around the shape leaving the center area a little higher then the outline of the shape. I kept running the same tool path until on the third try it finally cut the center section down low enough to match the outer shape. Figures I get the POS Machine. Time to tear it down and start over. Thanks for your help.!!!

I dont think you need to tear anything down, until you understand your issue.

Did you measure, with a caliper/micrometer, the thickness of your touch probe, and verify it against the setting measurements?

Are you touching the probe, in the same orientation (recessed or flipped) for both bits, each time (not differing the process)?

I think this is solvable, if you go over your process, and possibly your program info in extreme detail.

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Is there a chance your material is moving after you remove stock from the piece? The other issue could be one of bit deflection (but less likely)

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No. I thought of this but it is consistent all the way around. Removing a 1/4 wide cut of material in the shape of a square only .10 deep is not enough material removal to change the shape of the whole board. Then running the 1/8 in. bit in the same path and it cut a little deeper. Nice thought though. Thanks.

Gary - have you checked to see if your relative offset in the Z-axis is exactly the same after you probe between bit changes?

That is, after you do your Z-axis probing fot bit changes and the controller retracts the bit (so you can remove the probe), the height of the bits above the zero-plane of the workpiece should be exactly the same on the controller’s display.

Second thought: you said running a second toolpath to the same depth can be ~0.05" lower OR higher than the previous toolpath. Do I have that right? Is that 0.05" measured with a micrometer or a guesstimate?

Can you run some test cuts with standard upcut endmills? Same higher and lower Z-axis problem between different toolpaths?

(I’m wondering if you might have a tramming problem or maybe you have slop in your Z-axis: collet, bearings, rotor,…)


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Hey Mark. Great questions. I did not measure the distance manually after the bit change but looked at the numbers on screen and they were exactly the same. I did measure the 0.05 difference with a micrometer. Sure I can run the same thing using up cut bits.
These are small name plates 4"x6" along with just a simple square and octagon so I tried them in different areas of my cutting area and same result. Last night I added a 1/16" bit to the toolpath for the stacked text and in the preview window of the toolpaths I could see where the 1/16" bit was cutting lower then the 1/4" and 1/8" bits. I ran out of time so I did not actually get to cut those. Going to try today. There are no offsets, I usually try to set to lower left corner but also tried to set x0y0 to center of board and zeroed off center using touch plate. Great ideas so I will manually measure what the actual withdrawal after probing is. Thanks for your ideas. starting to think I need to reinstall Vectric Program after what I saw last night with 1/16" bit. Enjoy the weekend.

Just re-reading this, and did I get this right: the 1/8" bit cuts lower than the 1/4" bit, and the 1/16" bit lower than the 1/8" bit? Like they cut deeper the smaller the diameter? Have you checked that the tool setups are correct, or that youre using the right ones, especially if they were manually created?

Of all the causes mentioned so far, like tramming or slop in the z-axis, I can’t see where they would correspond to increasing depth of cut with smaller diameter tools except possibly one thing. If your distance per step on the Z axis were wrong (it thinks its shorter than it is), would the depth be increasingly off the further it traveled? But, for that to make a difference here, the tool would need to be a ball end, I’d think.

Sorry, maybe I’m just thinking out loud, but perhaps it will trigger someone else’s thoughts.

Sounds to me that the program is thinking that you are using a V bit hence trying to set a different depth to get the same width cut. I know, not likely but the only time I have ever seen different depths for different width bits.

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Solved. DAAHHH. After Looking at everything two or three times, I was working on another project with much thinner wood. While trying X,Y,Z Zeroing I noticed the touch off block was not quite down in contact with the wood below. Turns out the plug going into the touch off block was just touching my squaring/cornering block (attacked to my spoil board) that is only 1/8-1/4" thick but just enough to keep the plug and touch off block about .05 off the work piece. So any Z Zero in the lower left corner would be off by .05" until I touched off in the center of the project (for the 1/8" bit). It is always the simple things that always get you. Thanks for every ones help and suggestions


I have proven this with younger cuts of woods… There is always a certain amount of tension relief , especially when large amounts of mat’l are removed, as proven by white papers from Boeing Tacoma mills. My Manufacturing Dean was a programmer for them (Airbus structural parts, from 10’ x 30’ billets, 12" thick) and always tweaked large billets of T6061 before cuts. They always warped upon release from fixtures, but he was a guru and passed this on for us. I see it pronounced in woods like I said. Difference there being a few thou to tens of thou… That being said, I also am true to the paper setting for zeroing unless I have an auto tool changer. Regardless of "settings. the proof is in the actual stock.