Slipping fence

hfmann · Post by **hfmann** » Mon Nov 15, 2010 5:01 pm

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

judaspre1982 · Post by **judaspre1982** » Mon Nov 15, 2010 6:45 pm

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DT aka Agent Orange is a POS
Liar Liar his wonky comb over is on fire

hfmann · Post by **hfmann** » Mon Nov 15, 2010 7:00 pm

Dave,

Wow -fast response. Thanks.

The 520 fence upgrade replaced the rails and provided a sturdier fence with two clamping handle locks. The first was the same as the prior model, squaring the fence and locking onto the tube. The second lever provides another measure of firmness by clamping down on the back rail.

I hadn't really thought about using some auxiliary clamps. I'm sure that would work.

Dont know if this is the case, but I was hoping that there was something I wasn't doing properly, or some little adjustment that would make it good.

Thanks again for the good idea. That'll certainly get me through the next time I have to use that method.

Thanks again

Hal

john · Post by **john** » Mon Nov 15, 2010 7:48 pm

Hal:

I have experienced this problem on my 510, and like Dave mentioned I have used a clamp to secure the back end of the fence.

Good luck.

John

judaspre1982 · Post by **judaspre1982** » Mon Nov 15, 2010 8:05 pm

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judaspre1982 · Post by **judaspre1982** » Mon Nov 15, 2010 8:11 pm

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SDSSmith · Post by **SDSSmith** » Mon Nov 15, 2010 8:29 pm

hfmann wrote: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

By slowly tightening each of the two nuts, you have done what I would expect to cure the problem. One thought is that there may be some foreign material (like wax) on the rails that may be reducing the coefficient of friction between rail and fence lock. Another thought is to make sure your drill bit is sharp and make sure you let the bit do the work (try not to force the bit), clearing chips often.

FYI, there is no equivalent piece on the 520 fence like the one on the far end lock of the 510 fence. On the 510 fence, the plastic piece increases the friction between the rear fence rail and the back fence lock.

dusty · Post by **dusty** » Tue Nov 16, 2010 6:32 am

hfmann wrote: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 do not believe you can solve this problem by adjusting the fence lock any tighter. In fact, you may want to back it off a little so that it works properly as a "rip fence lock" and then reassess the problem. The first thing I would do is make certain that the drill bit is sharp and the drill speed is correct (slow) - (real slow).

Drill the hole slowly - don't rush it. Quill pressure should be very little more than what is required to keep the drill bit in constant contact.

hfmann · Post by **hfmann** » Tue Nov 16, 2010 9:24 am

This is a huge help guys. Here's 2 pix of the fence front and back locking wedges from the underside.

Your advice about loosening up the nuts a little to make it more "user friendly" and working slow with a sharp bit makes a lot of sense to me. I'm going to give that a try tonight.

Hal

JPG · Post by **JPG** » Tue Nov 16, 2010 9:38 am

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.