Probe AND a Fence?

Hi All,

I am 100% a beginner and I am about to do my first cut in the next week or so. However, for the life of me, my little brain cannot figure out what the purpose of a fence is if I have a touch probe. Can someone please shed some light on this? My brain is hurting trying to figure this out. I have an Aerospace Engineer for a brother. Yet, my brain is the size of a baby acorn.

A fence can help keep the workpiece square. A corner probe will not do that alone


OHHHH! Meaning it won’t move around easily? Well, the piece will be secure with whatever you secure it with, but the fence will make your piece square to the corner? At least I think that is what you are getting at, but if you probe the piece, will it not be in the correct position if you are probing the same piece?

I’ll use the commission I’m working on now as an example: Office Nameplates

I precut the name plates to 12x4"x0.375" Red Oak. I’ll set up a fence to hold the piece square then laser the name and logo on it after I locate a corner (once). The design will be square on the piece and I can quickly exchange to the next one and finish the job quickly.

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a fence is nice if you do repeated work, since you only need to know where in X/Y the fence is once.

probing is mostly also about Z, and the thickness is not something a fence will help you with.
A fence does also help you getting things square, which is a nice bonus… I have had too many cases where I did not get the wood perfectly square, and then some far corner of the work was … well outside of the wood. Not Funny.

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OHHH! I get it. Thanks so much. I am 90% sure I am having the ah ha moment. So, this may not be useful every single time, but if it is set up then you only have to find the corner once. If the fence is set on the lower left hand side, that is technically your zero if that is how you set it up. So you can do multiples of one thing without having to reset everything. This may sound like mush…what I have typed, but in my head, it is processing. Also, if I am doing a one off…it would not necessarily be useful, but it could be useful depending on what kind of one off I am doing.

for one offs it’s useful to make sure you’re parallel/square to the cnc…

Yes! Thanks! I got it now. So that is how it would be useful with one offs! Thanks…I NEED ONE NOW hahaa. I will make one soon. Myers Woodshop seems to have a nice one.

Myers does have a nice fence, but if it is set too far into the lower left corner you will eventually have a problem with needing to clamp a piece in that area.

So, you need to consider clamping when you place a fence on your table.

Also, you will often need to carve right up to the edge on a piece, so the height of a fence will be important.

I’ve used some printed “fence tools” from Pwncnc that have been very useful.

I was worried about losing some of my cutting space and needing to clamp on the left side or the bottom and that is a great recommendation in your link. Wow! Thanks.

The probe will find you a single point to call zero (this establishes the Work Coordinate System or WCS). This point is stored as a set of coordinates based off of your machine home position (called Machine Coordinate System or MCS, which is really only referenced in the controller software as I understand it). This offset zero point, WCS, is what you set up in carbide create when you create a job. It’s where the program bases all of its positions on. You probe at the machine to align the WCS to a corner of your work.

The problem is that if you are working with a piece you won’t be cutting the outline of in that setup on the CNC, it becomes quite hard to make sure the material is aligned with the MCS with just the WCS established by the probe. Fences solve this problem along with allowing you to quickly and repeatably find the WCS zero point for batch work. A practical example is something like @wb9tpg said, where the finished item is being placed in the CNC and you need to be sure the finished edges line up with the MCS. You need to be sure the names aren’t crooked, and if you’re making a lot of them, a fixture like a fence will help.

You can definitely make you fence on your own machine a others suggested, but remember it needs to align to the MCS! Machining the fence faces in place on the machine is a way of being certain everything is lined up. To make a fence you can remove, you’ll need to set up some other reference features on the wasteboard for your fence to align to. I use dowel pins on my wasteboard for this purpose.

While you’re starting out it’s easiest just to use the double sided tape (better yet use taped surfaces held with super glue! ) for workholding and cut your outlines in the same setup.

Hope this helps over complicate things🙃

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This is great advice and best practice.

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This is all very thorough and great advice. Thank you so much for helping me to come out of the fog on this.

I made the Myers fence, cam clamps and spoil board. I do not use the fence too much but I do use the L brackets and the cam clamps a lot. I do sometimes use the fence and Myers designed a cutout in the corner of the fence for the touch prove. When I made my spoil board I batch cut 2 more besides the original. When the time comes to replace my spoil board I just have to knock out the Tee nuts and reuse them. I went with the 5/16" length Tee nuts to give my self room to level and tram the spoil board a few times. You have to get shorter 1/4=20 bolts when you tram and level your spoilboard. The first time I cut my spoil board I was having problems with cutting height. I figured out that the longer bolts were pushing up on the spoil board and making my work piece higher in some places than others. Additionally I got nylon 1/4-20 bolts for the fence in case I was cutting close to the edge of material and hit the fence.

You can also use a v bit and carve a grid on your waste board to square your pieces. Mine are set 2 inches apart and like .02 deep and traced them with a pencil so I can see them better.


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