Temperature Warping Powermatic Fence Plates?

[Porter Friedman]

As its gotten colder here over fall and winter, I have noticed the nylon side plates of my PM-1000 table saw fence to be much more warped than normal. I know that with this style fence, its pretty acceptable for the nylon to have very minor "hills and valleys" where the bolts are holding the side plates to the fence. However, now that its cold in my shop, the side plates are so warped its causing binding on the blade and riving knife. This is especially prominent at the end of the fence, where the nylon side plates are pretty flared out.

My shop is not heated or anything and currently is in the high 30's to low 40's outside...


Has anyone else experienced this? Has anyone found a solution other than heating my shop? For the last project, I would bring the fence inside before using it, but suffice to say its REALLY annoying to have to bring your fence inside to warm up before every cut.

[Lee Schierer]

Plastic has to have a means to move as the temperature changes. Plastic changes dimensions pretty significantly with temperature, so when you mount it to metal you have to make allowances for the expansion and contraction, just like you have to allow for wood movement with humidity changes. You might need to slot the holes for the fasteners than attach the plastic to the metal frame.

[Porter Friedman]

Thanks Lee.. Anyone else experienced this? Seems that with as many PM saws out there, I cant be the only one.

[Curt Harms]

Make new faces out of something like laminate covered MDF or something like that? I had no idea plastic moved that much with temperature change.

[Lee Schierer]

Make new faces out of something like laminate covered MDF or something like that? I had no idea plastic moved that much with temperature change.

The Coefficient of Linear Thermal Expansion (http://www.engineeringtoolbox.com/linear-expansion-coefficients-d_95.html) of cast iron is 10.8 (10-6 m/(m K))*), Nylon is 72 (10-6 m/(m K))*), pvc is 50.4 (10-6 m/(m K))*), polyethylene is 200 (10-6 m/(m K))*)

For a temperature change from 100 down to 32, a 30" long cast iron piece will shrink about .012" in length the polyethylene will shrink almost 1/4"

[Dick Mahany]

I made a router table fence out of some very slippery plastic material (UHMW) about .75" thick, and experienced the same thing. I changed over to a MDF fence and laminated a Formica sheet to it and it stays flat and stable. My Biesemeyer fence on my Unisaw also had MDF/laminate faces and were very stable. I think the plastic faces may have been intended to provide minimal friction, but a smooth Formica type surface INHO is just as good in that respect.