520 Fence Is Not Square to the Table Surface

[rlkeeney]

I need to cut 1/8" slots in the end of a piece of wood. While I was figuring out how I wanted to do this, I discovered that the sides of my fence are not square to the table surface. I did a lot of searching, trying to find a fix, but had no luck. How can I fix this?

2026-04-18 11.23.17.resized.jpg (172.74 KiB) Viewed 24359 times

[DLB]

I think the first place I would look is to see if the front and rear rails are correctly positioned relative to the table surface. There are rail alignment jigs sold by Shopsmith and normally provided with upgrades. Having bought a few 520 systems on the used market, I find these jigs to be frequently missing. Do you have them? They are just small aluminum extrusions that let you set the rail height the correct distance below the table surface, two of them thus allowing the rail to be set parallel to the table surface.

- David

[RonKlein]

How about attaching an auxiliary fence, and using thin shims as necessary to square it to the table?
Ron

[rlkeeney]

I think the first place I would look is to see if the front and rear rails are correctly positioned relative to the table surface. There are rail alignment jigs sold by Shopsmith and normally provided with upgrades. Having bought a few 520 systems on the used market, I find these jigs to be frequently missing. Do you have them? They are just small aluminum extrusions that let you set the rail height the correct distance below the table surface, two of them thus allowing the rail to be set parallel to the table surface.

- David

I do have the rail alignment jigs. I don't know why I didn't think about that.

[rlkeeney]

How about attaching an auxiliary fence, and using thin shims as necessary to square it to the table?
Ron

That would be a last resort. The jig I made for making this cut straddles the fence. It is a tight fit.

[chapmanruss]

Robert,

If I am understanding it correctly your problem sound like one another Shopsmith owner has posted about on My Growth Rings. His Fence, like yours for a 520/M7, is slightly angled off 90 degrees from the Table surface. When eliminating other possibilities it appears to be either the Fence Extrusion connection to the Base end of the Fence or the Locks (Locking Bars P/N 518407) which might be causing the slight tilt. He has tried the Fence on the Extension and Floating Tables with the same result.

Sitting on the Table without being locked in place is it out of 90 degrees or does it only occur when locked?

If you haven't checked the alignment of the Fence Rails do so. If out of alignment that could be the problem in your case and a simple fix.

[rlkeeney]

Sitting on the Table without being locked in place, is it out of 90 degrees, or does it only occur when locked?

Either way, it is not square to the table surface.

If you haven't checked the alignment of the Fence Rails, do so. If out of alignment, that could be the problem in your case, and a simple fix.

I have checked the rail alignment twice to be sure. The front rail was a tiny bit low on the left side, and that seemed to be too help a little, but no joy. I aligned the rails on the extension table and checked it there, and it was still not square.

Until now, the only thing I have used the Table saw for has been ripping. I could have been this way when I received it.

[rlkeeney]

Adding another piece to the puzzle: If I turn the fence upside down on the table, it rocks corner to corner. Same on the extension table.

[DLB]

Adding another piece to the puzzle: If I turn the fence upside down on the table, it rocks corner to corner. Same on the extension table.

This seems to indicate a bad fence extrusion.(?) Or two bad tables... I'm pretty confident using the top of a 520 extrusion as a precise flat reference when I need one, what you're seeing is abnormal compared to my experience. But it isn't obvious to me how an extrusion like that goes bad. (I once had a 510 fence that was bowed outward on the reference surface, I didn't understand that one either.)

- David

[rlkeeney]

I did some more testing using a Starrett straight edge.

* The table is dead flat, and no light shows in any direction.
* The fence extrusion is flat on the sides but has a slight upward bow. The ends are higher than the center.

I checked the fence for squareness. It is square all the way around.

I measured the height of the plastic pads using the depth rod on my electronic calipers. I took a bunch of measurements and averaged them together. The right side is 0.1 mm higher than the left.

Update: After doing a little research and asking Grok to do the math for me, I don't think that is enough to cause the out-of-square condition I am seeing.