Slipping fence

[hfmann]

JPG - actually it holds pretty well. The rails are completely different from the original tubes. Here's some profile pix of the front and back rails with the fence in place but not locked.

Hal

[JPG]

JPG - actually it holds pretty well. The rails are completely different from the original tubes. Here's some profile pix of the front and back rails with the fence in place but not locked.

Hal
. . .

AHH SO! The tapers make a difference! I had visualized the clamp 'shoe' pressing flat against the 'back' of the rail!.

[keakap]

I just noticed this yesterday in trying a horizontal boring method. When putting some pressure on the hardwood piece with the drill bit, my fence kept slipping away. This is a Mark V 520 with a pro fence upgrade. I always lock the lower fence lever first, then the upper. I tried tightening the nuts on each lever just a little. No matter what, it still slipped. I kept trying with gradual adjustments until it was so tight I could no longer lock down the fence levers.

I checked to make sure the engagement wedges and rails were clean. Also I checked visually for damage to either the wedges and rails. They both looked fine.

The fence is tight enough that normal pressure on the fence from a ripping procedure would not move it. So far this is just happening with the extre pressure imposed with horizontal boring.

Anybody else have this problem? What to do?

Hal

I'm gonna jump right in ('cause I dang near destroyed both hands struggling with this before the "discovery") and plop down my $1.57 ($.02 adjusted for inflation)-- don't "close" (tighten) the fence locks, especially the lower, all the way. And put some graphite loob on the clamp cams.

Then I'll read all of the correct answers.

(Then, armed with that knowledge, I'll go set mine up right.)

[hfmann]

Keap,

I'm not sure where you are saying to apply the graphite. As hard as my levers are to move, sounds like that would help a lot.

ALSO - took the advice to make sure I was using a sharp bit. VOILA! Using a sharp one make a world of difference. And going slow helped a lot too.

Thanks guys.

Hal

[keakap]

Thanks for the pix! I have not seen a 520 rear fence clamp b4. I am amazed the clamp holds at all! There is so little clamp surface area! I assume the black part is a 'skid' that rides on the top of the rear 'rail' and the clamp presses against the rear surface of that rail near the top.

I'm assuming mine is standard. The cams are weird. When you tighten them, they go from loose to tight to less tight in the range of lever motion. One (or at least I) assumed at first that the further you tightened the lever the tighter it all got.
Wrong!
You can tighten the nut from here to doomsday and what you get is raw red hands from trying to tighten the levers, yet if you go all the way down they LOOSEN up again.

Danged idiotic system imhso.
However, it works fine if you simply use the tightest (~half-way down) setting for the really rough stuff.

Caution: I've gotten some strange stuff from SS. For all I know mine is the only one this side of Mars that works this way.

[keakap]

Keap,

I'm not sure where you are saying to apply the graphite. As hard as my levers are to move, sounds like that would help a lot.

A...Hal

As you look at the cam lever when the lock is fully engaged, drop some powdered graphite on the contact surfaces (2 each), then run the cams up and back a couply times to distribute. Most of it will fall off, of course.