520 Rip Fence does not lock

[joegez12]

I have a 520 rip fence that I have had troubles locking since I bought my shop smith 16 years ago. I finally decided to try to set it up from the beginning and now I am having trouble getting it to lock at all. I loosen the nut for the front clamp and I can get the bottom lever to go all the way down but I can't get the fence to stay locked. Any suggestions about steps I should be taking to get it to work properly?

[wa2crk]

This is off the top of my head but here goes.
First, adjust the nut for the lower handle clamp so that it just locks. Then adjust the nut for the top handle a little bit at a time until it just locks. All the time the lower handle should remain down and locked. Now check the lock levers and tighten the fence to see if locks and remains in position.
Bill V
PS We like pics if you can post some

[DLB]

A bit of powdered graphite on the cam part of the handle should reduce the amount of effort it takes to lower the handle, and allow you to tighten the nut a bit.

- David

[dusty]

The bottom lever has two functions. One (and I think the most important) is to square the rip fence with with the front rail. The other is to secure the rip fence to that same rail. Once that is done, the upper lever further secures the rip fence (to the rear rail). The two adjustments must be made in tandem to properly secure the fence.

After "locking the fence", can you move the fence by applying lateral force? If so, does the fence move "only" at the outfeed side or does the entire fence move? Your answers to this question should indicate to you which adjustment needs further attention.

Clean but don't lubricate the rails AND inspect the locking levers (fore and aft) for debris or damage.

[joegez12]

Rip Fence Bottom Clamp Lock Position.pdf

Handle is not quite all the way down, rip fence is locked.

(332.71 KiB) Downloaded 678 times

Rip Fence Bottom Handle Fully Down.pdf

Handle is fully down, fence is not locked

(303.46 KiB) Downloaded 669 times

Rip Fence Front Clamp.pdf

Rip Fence Front Clamp with missing chip

(1.96 MiB) Downloaded 643 times

Thank you all for the helpful suggestions.
I vacuumed the rails, the table and the rip fence and added graphite to the cam surfaces. I then adjusted the nuts for the two handles. I can now get the fence to lock in place with no motion but I have an additional question. See the first picture with handle not quite all the way down.

As I push the bottom locking handle down I can get it to go past the point where I get the fence to be locked and then when it goes all the way down the tension releases and the fence is no longer locked. See the second picture with the handle all the way down. Is that the way it should behave?

I also noticed that there is a chip out of the front clamp. See the third picture. Is that affecting the clamping performance?

[joegez12]

Here are the the pictures that I tried to include with my previous submission.

Rip Fence Front Clamp with missing chip

Rip Fence Front Clamp.jpg (59.52 KiB) Viewed 8137 times

Handle is fully down, fence is not locked

Rip Fence Bottom Handle Fully Down.jpeg (89.07 KiB) Viewed 8137 times

Handle is not quite all the way down, rip fence is locked.

Rip Fence Bottom Clamp Lock Position.jpeg (103.33 KiB) Viewed 8137 times

[DLB]

There is nothing other than adjustment to prevent the handle from rotating too far, and it is normal that past a certain point of rotation it loosens the lock. If it was me I would adjust the nut a bit tighter so that the lock is tight enough to prevent that.

Chipped Locking Bar - Assuming that you can achieve satisfactory adjustment and performance this would be low priority to me. The locking surface can't be seen in the pic, it is primarily the bevel on the opposite side of the bar, though it is certainly damaged. I don't think it is causing a problem, but I'd probably order one on my next SS order.

- David

[JPG]

Wind from the direction of zero experience(never had a 520 fence within close sight let alone in hand).

However peering at the exploded diagram, I presume the following.

The locking levers are the same part as on other fence models.

The locking levers have a caming profile that has a slightly reduced radius at the end of their travel.(over the center clamping assumption) That is the result of the radius meeting the straight portion. The wear plate cannot be ignored. It will affect this.

That being so, I presume the adjustment for clamping(nyllock nut) is to tighten just securely with the clamp fully depressed.

I started this post a couple of hours ago. I hope I am not repeating anything that has been posted in the meantime.

[DLB]

The locking levers are the same part as on other fence models.

The locking levers have a caming profile that has a slightly reduced radius at the end of their travel.(over the center clamping assumption) That is the result of the radius meeting the straight portion. The wear plate cannot be ignored. It will affect this.

The 520 locking levers are a different part but functionally similar to the 510 and Bandsaw fence that's based on the 510 extrusion. A difference that I think is in play here is that, in contrast with those other fences, there is no mechanical feature to prevent over-rotation. When it is over-rotated you are no longer on the cam profile, but the behavior is similar.

Reading through this again, I think the originator has an incorrect expectation. The title of the third picture is "Handle is not quite all the way down, rip fence is locked." In reality, I think the handle is past all the way down.

Over rotated

Rip Fence Bottom Clamp Lock Position.jpeg (123.93 KiB) Viewed 8063 times

The part I'm highlighting with a red line should not be rotated beyond 'flat' or parallel to the table. Rotating beyond that point means you are engaging a corner of the handle profile rather than the cam portion. The nylok nut should be adjusted, I believe, while the handle is in that position representing the end the usable cam, but not 'fully depressed' as it would be on those other fences that have a mechanical stop for the lever.

- David

[jsburger]

David, you are correct. There is no mechanical stop. However when the adjustment nut is adjusted correctly you cannot move the handle past the proper lock position.

The first picture shows a properly locked handle(s). The second and third pictures show the handles in the unlocked position. The fence is laying on the table upside down. The short flat section of the cam should rest against the fence casting when locked. That is shown in the fourth picture. If you can move the lever past that point to the long flat section the adjustment nut is way too loose.

When properly adjusted it is impossible to move the lock lever past the proper point. That effectively acts as a positive stop. The lock handle actually clicks to a stop when properly adjusted.