UHMW Fences On Accufence Are a Bit Wavy

[Lewis Cobb]

Right, so I am running the dial indictor along the blade and fence with my handly little wooden jig I made for alignment and discover that the UHMW faces on the Bies. Style fence on the PM2000 are anything but flat. I am not so sure it's a big issue and the tech service guys at PM are of the same opinion.

A bit of tinkering over this last weekend revealed that the steel tube is pretty flat - say +/-0.002" - hard to get a good reading as the mill marks where it's machined "flat" cause the needle to bounce around a bit. I also made sure that the holes in the steel tube are big enough to cause at least a little "slop" in the fence when it's slid onto them - so that it's not binding and twisting any when the bolts are tightened down.

It appears that the bolting down of the UHMW faces, causes them to buckle and go "wavy" in between the mounting points. I read bang on 0.000" at the mounting points (well, maybe +/-0.001") but in between I can get +0.005" and -0.004"

A bit of digging with the search function reveals that I am not alone in this discovery but I could not seem to find any solutions. In fact, I came across one posting a while back where a fellow has a Bies. fence with the same wavy problem and those faces are much harder to replace than the accufence ones.

I am not sure this can be corrected with shims as I tried a bit of shimming here and there with only moderate success.

Anyone have this issue and come up with a better face for their Accufence, or perhaps it's just not worth the trouble ?

Thanks,
Lewis

[Doug Shepard]

Yup. They're wavy. Not so bad that I did anything about it for 20 years but just enough that I thought I could do better. I finally switched them to BB phenolic ply (from Woodcraft). See
http://www.sawmillcreek.org/showthread.php?t=115481
starting at post #20.

[Frank Snyder]

I have the same PM2000 and had the same problem. I found that the fence buckled between the bolts once I tightened them, so I elongated the holes in the steel fence which then allowed the subfence to flatten out better. When you tighten the subfence down, think as if you're flattening out a sheet. Start by tightening at one end, and work your way down the line. If you elongated the mounting holes enough, no buckling should occur.

[Lewis Cobb]

Doug - thanks for the link - that gives me some food for thought - one idea - a bit on the extreme side but that's ok - is to call up my buddy who is a machnist and see about fab'ing up some sides from 3/4" aluminum - I can envision some tapped holes for various jigs etc. along with perhaps either some laminate or thin UHMW "tape" on the side faces......if nothing else it would look "trick" :)

Got to be color co-ordinated though - maybe get it black anodized as well.....

There does not seem to be a big deal with this if you lasted 20 years before you changed yours.


Frank - I did bring the holes out, but only enough to allow the side face to slide from side to side a little to ensure I was not binding up as I tightened the bolts down. And on that procedure I did it different - I started in the center and worked alternately out from there - sort of like the head on an engine block. Worth a try to go back and tighten in line like you mention though.

Thanks for the ideas.

[Sam Layton]

Lewis, I have an older PM66 with the PM acc-fence. Mine had thin plywood for the face that was not 90 deg to the table nor was it straight. I removed the sides and found the steel T-square was not perfect as well.

I made new sides out of 3/4" baltic Birch ply, and covered them with Formica. I used aluminum tape (HVAC tape) to shim as needed. My fence is now straight and at 90 deg to the table saw. The 3/4" thickness helps keep things straight I think.

Problem solved.

Sam

[Scott Busse]

I had the exact same issue on my xacta II fence. I replace them with 1/2 baltic birch and now they are straight.