Arg! Rouhing/finishing passes

I have the worst time trying to change the bit on my Dewalt without having the gantry move a little bit. Once it has been nudged, the finishing pass is ruined before it’s begun. What is the secret? I hold the button, crank the wrench to loosen my roughing bit, and invariably the thing moves a bit, usually on the X axis.

Then of course, my other problem is getting my Z axis to exactly the same point on the surface of the piece once the new tool is installed.

Any tips?

Do you have grbl lock the motors at all times?


Not necessarily locked, but powered.

A rather obvious tip is to not tighten the collet nut so hard next time, just hard enough. Can’t say what the sweet spot in tightening the nut is on the Dewalt, but on my makita I found it doing roughing/finishing on scrap pieces of wood for practice.

I tighten the nut with my hand first, then tap it with a spanner for good measure and luck. Then I tighten it down using the spanner. Just under half a turn, I guess…

There should not be a need for much brute force to loosen the nut to change bits

The GRBL $1 = 255 supposedly works, I set that option just last week or so, but never really had a need for it.

Also, order one of these. These things are GREAT.

I use the exact same one for my Z-Axis zeroing. I replaced the wire with some better stuff and put a 1/4" headphone jack on the end, so it plugs into my enclosure when I need it and back in the drawer when I am finished.

I wasn’t aware of that setting. If I set it, does that mean I can’t manually move the gantry around at all? I know I shouldn’t do that too much anyway, but I often just push it back out of the way at the end of a project. I suppose I can set it for a tool change, then just set it back afterwards, too.

I do need a touchplate. Maybe it’s time to just pick one up. I’m sure there is information all over the forums here on how to install it and use it.

Only when the machine is powered off will you be able to move it around by hand. I use the jog controls to move mine always, I never move it by hand (will it hurt it? Probably not, but not a good habit to get in)

I never turn off the power to the controller (motors) when changing bits. This keeps the motors locked and nearly impossible to move.

Only if the grbl settings are set to $1=255…

Mostly use Easel, so I guess this is already set?

No idea…I don’t use easel, but I did have to set mine, it did not come that way.

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I just make sure I know were my work home position is at. Then if I do move anything changing bits it is easy to position the spindle back where it belongs.

The important thing to know is that you are positioning the exact center if the bit. What I do it set my work home to the lower left corner. Then I position my first bit so that the it is exactly lined up with the left edge and the bottom edge. You can use your finger to feel the edge of the wood and the edge of the bit on left side and front side.

Then the next step is most important - jog the bit half the diameter of the bit to the left and half the diameter forward. This will position the exact center of the bit on the lower left corner.

So if I am using a .25 inch bit, I position the sides of the bit flush with the left and front. Then jog the spindle left .125 left and .125 forward. Then if I change the bit to a .125 for the detail pass it is easy to line it up flush with the sides again but this time I jog it .0625 left and .0625 forward. Now the center of the .125 is in the same exact position as the .25 bit was.

Now that you can position the bit easily you don’t need to be so worried about the spindle moving on a bit change.


Good solution Allen. I usually bore a hole a 0,0. Then, if I lose position, I can manually move the bit to the hole and nestle it in. If you do not have a touch plate yet, you should get one, but until then, chock up your new bit, lower it to just above the surface, loosen the chuck, let it drop to the surface and re-tighten. Do this with all your bits in the same spot on your work piece and you should have no problems.

You are sure right about the touch plate, I have one and it has made setting the Z zero much faster. Once you start using the touch plate you can’t imagine how you survived without it.

I just wish that UGS had the necessary code in it to use the triple edge finder. If you have not seen the triple edge finder it is just a chunk of aluminum with a hole in it designed so that when it is set on your work piece the center of the hole aligns exactly with the corner of the work. With the right software all you need to do is position the bit inside the hole and it will move to each side of the circle left,right, top and bottom and then with some math it can determine the diameter of the bit and exact coords for the center of the hole (which is your work X and Y zero). They all you need to do is use the same edge finder to set the Z zero.

I think that Mach 4 has the software built in to do this. Now if only UGS could do it!

Yes, I have Mach 3, and you just edit the macro for the homing button. Mine is only z-axis though. I could build something, but I don’t really need it. My motors do not budge during bit changes, and I always drill a x,y locator hole.

When I started using my Shapeoko 2, the x,y hole was the best.

If you have homing switches, this makes it very easy.

When you do your original setup always your machine. This sets the machine coordinates.

Next, when you move into your X,Y,Z=0 position, using the controls on UGS, or Easel note what the new coordinates are before you zero your axis’s. I usually just take a picture with my phone.

If you move the spindle during the tool change, you can always return to the same spot for X and Y.

Then you just have to set Z.

I have upgraded my machine so it allows me to turn the motor power for Gshield on and off with a key switch.
Using the switch and a relay, I shut the key switch off and the motors are no longer powered. What is so great about this is that after a panic button attack, you can turn off the motors and the machine wont move!. Its also convienient when you want to get the gantry out of the way :wink:

Good Luck and keep learning.

Mine is set to keep the stepper motors powered so they can not move as I change bits. And I really torque on the collet.
I never manually configured it to do this, it always had.
(I think the “$1” is how much power is sent to the motors to hold them in place when idle? 255 being max?)
I use UGS and once I connect UGS to the XC the steppers power up and everything locks in place.
(When I was first using UGS I had to “reset” the controller between each cut, causing it to cut power to the motors for a second and loosing zeroing. I screwed up every finishing pass I made. So I can empathize! I was so happy when I fixed UGS so this didn’t happen anymore!)

I am not sure how Easel handles this.

If your steppers are still slipping even when powered (at max) you may need to turn up the power on your stepper driver pots.

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The $1 parameter is the amount of time the motors will stay powered when they are idle. A value of 255 tells the controller to always keep the motors powered no matter how long they are idle.

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Ok I’m a newbie. Just got my x carve working today. I made a design on easel and it said the 1/8 bit was too big so I put in a 1/16 bit. I hit carve and my gawd this is going to take HOURS to complete.

May be a stupid question but how do I get easel cut with a bigger bit then switch to a smaller bit for the fine work?? It’s been cutting for 15 minutes now and says its 2% done lol

Hi @MichaelMills
Just ask to be added to the two-stage-cuts easel beta, see below