BL Touch Settings Question


I’m using BL Touch bracket from Ender 3 V2 BL Touch mount by Bertram69 - Thingiverse
I am using the smith3D firmware on my Ender 3 v2

Do I need to add M851 X-39 Y-7 to my Start Code. And if so does it go before the G29 ;?

This is what I have in my Start Code:

M851 X-39 Y-7 ; BLTouch bracket Offset
G29 ; ABL - BLTouch

The summary for the print is as Follows


Compact BL Touch mount for the Ender 3 V2

Initial version (my preference, unless you use the Creality firmware and don’t want to update the offset):

Offset X = -39, Y = -7

Version with correct offset for Creality firmware:

Offset X = -45, Y = -20

There are two ways to set the X and Y offset:

Add M851 X-39 Y-7 to your start G code
Use Pronterface to execute the exact same command, followed by M500 so that the new offset is stored in the Eprom

OK, I only just got my BLT working, so I’m hardly an expert. That said, my understanding is that once you input the offsets & then issue an M500 command to store the settings, then you don’t need it in the g-code.

Yes you will need to they intended for you to use this mount Ender 3 V2 3DTouch/BLTouch Mount by jkostenov - Thingiverse which has X, Y offsets of X-42.00 Y-10.00 which they built into the firmware. The mount you selected uses X = -39, Y = -7 so you will need to send the gcode commands to your printer at the beginning of your start code otherwise the firmware will use what smith3d programmed in. Or you could just swap the mounts to the one they suggest you use.

@Larry, thanks for the info; it’s interesting. I ran into something similar very recently when trying to override the default ABS Preheat settings in TH3D firmware. I found I had to reset the EEPROM before flashing the modified firmware. Is that an option with the smith3D firmware?

Yeah using the bracket that Smith3D suggests requires that the Guide wheel bolt be used to hold it in place. This bracket has the holes that screw to the plate.
I measured the bltouch pin to the nozzle and it is 39mm.


Looking at those bolts, I can’t help channeling Ryan Reynolds, “Whoa! Easy… e-a-s-y!” :smiley: All kidding aside, I presume they’re what you had available.

The vertical Bolts? They came with the BL Touch… lol
A bit long

Yeah, the ones holding the BLTouch itself :slight_smile:

Not seeing anything about that in there info on there site

I have another question
In the BLTouch package there are 2 springs.
Needless to say there was no instructions and I don’t know what they are for.



The metal bracket that came with my Creality BLT kit is held in place using the 2 bolts that hold the fan shroud in place. It has a fairly large hole that fits around the head of the guide wheel bolt.

Here is what mine looks like

[ATTACH=JSON]{“data-align”:“none”,“data-size”:“full”,“title”:“bltouch cover.PNG”,“data-attachmentid”:6766}[/ATTACH]

Made screw covers for the screws and found a cover for the BL Touch on thingiverse

bltouch cover.PNG

My Creality kit didn’t come with springs. The only thing I could think they would be for is to act as a cushion to protect the BLT probe. Maybe they’re supposed to mount between the top of the BLT and the bottom of its bracket, much like the printbed springs. I would be a little concerned about accuracy with that arrangement, but it might account for the length of the bolts. It might also be to adjust the height of the BLT probe, to get it the same height as the nozzle, or close to it.

The springs are to allow some movement for the BL Touch in case the probe is pushed into the bed to hard which could damage it if the springs aren’t in place but was told it can cause incorrect proble measurments so i didn’t install them myself. That’s why the screws are so long it allows for the springs which i understand hardly no one uses.

Ok Thanks
I was thinking that was what they were for

So Just to be clear

The offset setting go before the G29 or after the g29?

M851 X-39 Y-7 ; BLTouch bracket Offset
G29 ; ABL - BLTouch


G29 ; ABL - BLTouch
M851 X-39 Y-7 ; BLTouch bracket Offset

The G29 code starts the probing of the bed. Before it does that you need to set the correct X,Y offsets otherwise the probing will be done with the x at -42 and Y at -10 which is wrong. so set offsets first then probe

Ok Thanks

Good to know. Up until today I have been printing without that Offset code so Now I hope My prints will be even better. I have been printing with a 3mm difference on x and Y

Coke, no rebounds. :smiley:

I don’t know much about the Smith3d firmware, but I’m pretty sure that you could save the offsets to firmware, including the z-offset. Highly doubt that they would disable saving to eeprom, but who knows. I’ve never put the offsets in my start gcode. If you want to check, you should be able to find the offsets in the menus. Set it to what it should be, save config, turn it off and on again, and check if it’s saved. In fact, you should be able to find out all your mesh readings from the probe as well, all in the menus (unless you’re using a crippled version of Marlin).

Also, I recommend puttin M420 S1 right after G29. This tells it to turn on bed leveling. G29 is supposed to do that also, but there have been buggy revisions of marlin that did not, so I would put it there “just in case,” and it doesn’t hurt anything. Also you can use the M420 commands to turn on the leveling if you decide not to probe every print. The last mesh stored to eeprom can be loaded.