I had one off those once, before receive my 611 mount. I was kick starting stock spindle until chew my thumb.
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Sure sometimes you lose a little skin, but small price to pay for having so much fun.
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OoopsâŚmistyped, meant to say 1/4" bit. Although I do have a 1" bit with a 1/4" shank that I used to flatten my wasteboard.
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Weâre just teasing you. Just a little break. 
Most of chattering, deflection and/or bad edges on the cuts we found were Vwheel bearings space between two. If bearings inside that plastic can move back and forward, you will have problems. I found proper washers finally to make them solid like a rock after deinstall/install zillion times. Now Iâm cutting like a butter. Unless, if I forget to insert bit further in, just leaving enough bit exposed for my job, this time starts deflecting on climb.
Spent a bit more time trying to figure this out and here is where I got too.
Cut 10 x 30mm circle pockets, after cutting each one I adjusted the steps per mm on the grbl settings, I finally got the right settings which produced an accurate 30mm pocket.
I then proceeded to cut a square contour 55mm x 100mm but this was then out by 0.5-1mm.
At this point I decided to measure the diameter of the slot made by my cutter. Now I have measured and remeasured my cutter using callipers and I have been setting my tool diameter to 6.4mm. However the diameter of the slot in the wood was 6.2mm, therefore I must be measuring the cutter wrong somehow.
I havenât had the chance to run some more tests with this new tool diameter but I am hoping this will explain a few of the inaccuracies.
What are you using to measure you cutter. A 0-25mm micrometer is best. digital calipers are prone to errors.
You are seeing a 6.2 slot do to tool deflection. If you set up a test that cuts a 6.5 slot cut down the center first and then cut on each side .25 mm and then measure the slot. I think you will see a slot that measures 6.5.
Dave
I was indeed using a digital caliper, I know they are not as accurate but I donât think that was the reason for the inaccuracy, more so my ability to measure the cutter correctly.
It does make me wonder how to measure cutters accurately, I donât want to have to make a cut each time and then measure the gap produced. From this experiance I can only assume that it is best to measure each tool to confirm its actual cutting diameter rather than going off the manufacturers specification. This cutter was one from Trend, the cutting diameter was 6.85mm in the spec, however after measuring I realised it is 6.2mm. It hasnât had a whole lot of use either, only some light work on MDF.
I put all my grbl settings back to the inventables defaults and re ran my tests and my circular pockets are now almost dead on, and the square tests are within 0.1mm. So I think this has solved my problem.
Surely tool deflection couldnât ever result in a smaller slot/cut diameter, it would have the opposite effect and end up in a larger slot?
Youâre correct, deflection would cause a larger slot.
Iâve measured my bits and have their info written down next to their storage slots. Iâve had the ball-end endmills from Inventables come anywhere from .122" to .126", so just pick one to use and stick with it. I measured mine with the digital calipers since itâs the best I have, but the results are at least repeatable with them.
When you say you set your grbl settings back to default, does that include the x and y steps/mm? I think I saw a thread somewhere that stated that after calling Inventables, the recommendation was to leave the x and y steps/mm at the default 40 and not change it as it was âthat way for a reasonâ. I am thinking to give that a shot as a last effort to get my accuracy where it should be.
Yup it does, actually the x and y steps/mm where the only settings I changed. I increased them until my pockets were correct, but then I noticed the machine was not cutting correct when cutting out a square. So I figured the defaults (40 for both) must be fine, I canât imagine they would ship the carve with those settings unless they were valid.
Have you tried cutting a slot with your cutter and measuring it to get a diameter for your cutter? After i did that I found my measurements that I took from the cutter itself to be wrong. Measuring the cutter was quite difficult as you have to make sure you are holding the callipers at the right angle and make sure the tool bit is at the correct orientation depending on where the cutting blades are.
Good to know. I will try to give that a shot this afternoon and see what happens. Also, I did finally figure out measuring the bit is mostly a waste of time, rather make some cuts and measure the slot (or several slots). Much more consistent results. Thanks.
Ok, so changed back to the defaults of 40 steps/mm for both x and y, and it looks like things are much, much better. Cut a 1/4" hole and actually got a perfect 1/4" hole. I will play with the square cuts and see if they are better as well, based on the success with the simple 1/4" hole (have not been able to successfully do this until just now), I am assuming monkeying around with the steps/mm is not the best idea, at least for me.
Quick update. Just made a quick knob. Assumed my bit was exactly 1/4". Measured my hex nut and bolt. Made up the knob in Vcarve with maybe .005" extra width for fit. Absolutely perfect fit of the hex nut and bolt. So, the lesson I learned from all of this, tune your machine (belts, pulley, alignment, stiffening, etcâŚ) but donât mess with the steps/mm. Once I set those back to default, this thing cuts perfectly. Time to stop tweaking and tuning and move forward with fun projects. Thanks again to everyone for your thoughts and ideas.
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I seem to be having a very similar issue. I have a Dewalt 611, and VCarve Desktop. Tried to cut two pieces of 1/2" ply so they could intersect with each other. My 1/2" slots ended up 0.46" and 0.47", and would not join. The calipers measure the thickness of the ply to .501".
After reading this post, I tried to cut a square and found that an On-line cut with a V-bit would yield accurate dimensions, but an outside cut with an 1/8" single flute upcut left me 0.04" short in X AND Y of my 3" square. That tells me something is off by 0.02" with using my .125" bit.
Did anyone have more success with improving their tolerances? Is making a test cut with each bit and measuring the kerf the best way to set tool diameter settings in VCarve?
make sure you measure your bit with something reasonably accurate. A bit advertised at a certain diameter can be off quite a bit.
I have been using a set of digital calipers. I know they are not as accurate as a micrometer, but they are at least consistent. The 1/8" bit used as described above measured .115, and I used that as the actual bit diameter for calculating the Gcode.
the next thing you should run as a test is a a simple straight line and then take an inside measurement of the cut. This will tell you what kind of run out you may have.
I ran the straight line. I am getting an inside measurement of .133". When I use that as my bit size in VCarve, I get a cut my 2" square has a tolerance of +/- 0.010" or better. Pocket and Profile paths are within the same tolerance. It seems that the tool selector in VCarve wants the dimensions for my actual kerf, not necessarily the bit diameter? Thanks for helping me understand - I am still new to this. Let me know if I am still missing a step.
if I understand you correctly, that is a difference of .018 between the bit diameter and the width of the cut. That is quite a bit of run out.