Surfacing and zeroing

Do you need to set the z axis to zero before the surfacing starts?

Yes, Technically, you need to set the XY TOO, but I assume your doing it from the
middle

No. I was going to use the instructions with gSender and start in the back left. I can zero set everything with a 1/4" endmill and then switch to the surfacing bit.

@Psal217050 You are correct, Pete. Follow the instructions on the surfacing tab and set X0Y0 to the left rear corner. As for Z0, you can use any bit you like to set X0Y0, but when setting Z0, you must use the bit that you will use to do the actual surfacing. Unless your 1/4" end mill has precisely the same extended length from the collet as your surfacing bit, you cannot use your 1/4" end mill to set Z0, then switch to your surfacing bit to do the surfacing.

I use the 1/4" to set x and y and z, then I rezero the z using the bit that I am using. I know I can do x and y separately but I don’t. Is there a xy zero for the probe, I don’t remember.

right my bad, I havent used it in a while.

but correct, Follow the instructions.

as a General Rule, ZY and Z have to always be set.

For Surfacing, you dont really need to be exact. just close enough. (on the X&Y

I will say though, a 1/4 inch bit is acceptable, however the bigger you go, its going to go faster.

for a 1/4 shank there are a few options available, .75"" and 1" is the largest I have seen. for my 1/2 in shank I am able to go to 2" and I have heard of larger.

Also, watch your step over, you want it to be large enough not to leave a trail, but small enough for it not to run for hours.

I dont own this bit, so I am not making a recommendation.
I have a similar 2" version, but I like it because the blades are removable and sharpenable.

https://www.amazon.com/Spoilboard-Surfacing-Flattening-Woodworking-BINSTAK/dp/B08SKYYN7P/ref=sr_1_2_sspa

@Psal217050 Yes, there is an XY0 option for the probe in gSender