520 Fence Is Not Square to the Table Surface

[DLB]

The fence should be square to the mounting rails. Measuring to the rear rail is straightforward. Measuring to the front rail is less so, especially if you have the direct readout indicator on the bottom of the fence. I don't have a great square for that, a Starrett 20 like you have in the first picture is close if you put the base on the fence you can eyeball a small gap between the blade and the highest part of the rail. A larger #20 might get you there, I was using a 4-1/2" one. My thinking here is that this would be informative, identify which end(s), if any, are problematic.

- David

[rlkeeney]

Hopefully, this is what you are talking about. The fence is locked down to the table, and the square is sitting on top of the rail. The photos aren't great, but these are hard shots to capture. I am beginning to think the extrusion has a slight twist end bend.

2026-04-19 10.17.49-1.resized.jpg (105.87 KiB) Viewed 16950 times

2026-04-19 10.19.05-1.resized.jpg (129.28 KiB) Viewed 16950 times

2026-04-19 10.27.58.resized.jpg (136.94 KiB) Viewed 16950 times

2026-04-19 10.29.51.resized.jpg (110.93 KiB) Viewed 16950 times

[DLB]

So it is out of square at both ends, at least when mounted. With the fence upside down, can you see if the hard plastic pad at the outfeed end is square to the extrusion? Then, the same idea on the infeed end to see it the fence mounting surface, two rubber(?) pads, are square to the extrusion. (I haven't worked out how to do this, need something like maybe a large steel parallel in combination with a square.(?)) I think I would try a combination square with two heads, then an additional square, but we don't all have the same stuff. Are the rubber mounting pads in good shape?

- David

[rlkeeney]

Here is what I came up with. I put a level across the pads and used a digital angle gauge zeroed on the bottom of the fence. The difference was 0.1 degrees.

That works out to approximately 1/128 inches or 0.00781 inches. This is insignificant for woodworking purposes. It might be even less as electronic angle gauges are not known for high accuracy.

[chapmanruss]

Robert,

It looks like your problem is different than Robert H at MGR since you have found the Fence Extrusion apparently has a slight twist in it. It may require replacing the MARK 7 / MARK V520 Rip Fence Extrusion P/N 518400 to correct this. Currently that part is not available. Even the complete Fence is not available. Probably all of them are going to new Marks for sale until additional stock comes in.

[rlkeeney]

Robert,

It looks like your problem is different than Robert H at MGR since you have found the Fence Extrusion apparently has a slight twist in it. It may require replacing the MARK 7 / MARK V520 Rip Fence Extrusion P/N 518400 to correct this. Currently that part is not available. Even the complete Fence is not available. Probably all of them are going to new Marks for sale until additional stock comes in.

I'm considering buying a used fence because I have already checked on the replacement parts. I'm hesitant to do so because I bought this fence as a used upgrade on eBay. It was probably like this when I purchased it, but I never used it for any thing tha mattered until now.

[dusty]

I'm sorry but I do not understand the consequences of what you have described. The face of your rip fence is off vertical by such a small amount. Just how does that minimal error impact the accuracy and quality of the resulting cut.

[rlkeeney]

I'm sorry but I do not understand the consequences of what you have described. The face of your rip fence is off vertical by such a small amount. Just how does that minimal error impact the accuracy and quality of the resulting cut.

I need to cut two slots at the ends of a piece of hardwood, centered and parallel to the sides. I made a jig to do this before I discovered the fence was not square to the table. I make the cut in two passes, turning the wood over for the second pass to be sure it is centered. I was hoping to get precise, clean cuts with parallel sides. When using the fence, I get a tapered slot.

Here is what I am making:

Wooden Toy F-4 Phantom Fighter Jet

20260331-070620 009 4480730894 F-4 Phantom Fighter Jet Airplane.jpg (231.25 KiB) Viewed 16477 times

The slots are for the tail section. I have been cutting these with my scrollsaw, cutting slots in 1-3/4-inch-thick hardwood. Cutting slots with a scroll is slow, difficult, and requires sanding and filing to fit.

[DLB]

I'm considering buying a used fence because I have already checked on the replacement parts. I'm hesitant to do so because I bought this fence as a used upgrade on eBay. It was probably like this when I purchased it, but I never used it for any thing that mattered until now.

FWIW I've looked at two fences that I bought used with 520's. Both check square to the table and rails with a square. I'd feel confident buying used but understand your reluctance. I'd also demand a refund if I got a fence that wasn't square to the rails.

Last night I checked one with my angle cube (Wixey) zeroed on the table and the fence reference face measured 90.0 degrees. Going back to your first picture for reference, that gap between square and fence is pretty small at the top but I wouldn't want to guess at how far out of square you actually are. The top of the 520 fence is roughly 3 inches above the table so, assuming I still no how to do math, each 0.005" of gap is about 1/10 of a degree out of square.

- David

[RFGuy]

Not trying to take away from this thread, but just thought I would mention that Andrew Klein did test several digital angle gauges on the market to see which ones met their spec of being accurate to a tenth of a degree or not. He recommends a Lanru DXL360S that is supposedly accurate to one hundredth of a degree. ONLY sharing this post because I haven't seen anyone else try to measure how accurate, or NOT, these digital angle gauges are, so I thought it was worth sharing it on this post for context. IF anyone has found a better comparison for these gauges, I would sure like to see it. Coincidentally I have the Klein and the Wixey in my shop, but will trust the Klein more now. Skip to around the 6 minute mark on the video below to see his comparison: