Routing pressure treated lumber

[sam_ca]

Hello,
My new pressure treated lumber deck is almost finished. I am thinking of going a bit fancy with the railing: I was mainly thinking of rounding edges and using 45deg chamfers.
I am wondering if anyone has tried using a router on pressure treated wood and whether that affects its longevity - or any other concerns from your wealth of experience.
Thanks for the advise and a great forum!

[crokett]

It depends on how much wood you take off. The chemicals are forced into the wood so routing a chamfer or rounding over should not cut into untreated wood. If it does, you can buy the chemicals and retreat it and/or finish the deck with protectant. If you have any crosscut scraps still around you can look at the cut end to see how far into the wood the treatment goes.

[drillman88]

I have routed it after it has dried out with pretty good results, anytime I have tried it wet it tears or leaves a fuzzy finish or a big "burr" at the top edge. Someone else may have had a different experience but mine is to let it dry some before routing.
As long as it sealed properly and the piece is strong enough for its intended use, there should be no adverse effects from routing a profile into treated lumber.

[cabinetman]

I have routed it after it has dried out with pretty good results, anytime I have tried it wet it tears or leaves a fuzzy finish or a big "burr" at the top edge. Someone else may have had a different experience but mine is to let it dry some before routing.
As long as it sealed properly and the piece is strong enough for its intended use, there should be no adverse effects from routing a profile into treated lumber.

My thoughts too. Depending on how wet and thick the wood is it may take weeks or longer to dry out. Make a note of any defects like knots, sappy grain, and voids before routing.
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[Uncle Cracker]

Ditto the above comments, plus one: Make sure you clean and dry your router and bits after working with PT. Any moisture residue will rust your stuff if you leave it on there.

[LarryG]

+1 on cleaning and drying your router thoroughly, and I would go one step further on the bits by using cheapies that I would regard as disposable after the PT job was finished. Something like the $5 green Woodcraft bits, say.

Unless the material is really well-dried you will probably want to use an edge guide attachment on your router, wherever possible. Obviously you don't want to try to machine PT that's still dripping wet, but trying to use bearing-guided bits on material that is even slightly wet or squishy will surely be an exercise in frustration.

[cabinetman]

Ditto the above comments, plus one: Make sure you clean and dry your router and bits after working with PT. Any moisture residue will rust your stuff if you leave it on there.

I agree with cleaning. Bits and router should be cleaned after any procedure is done, even if it's just blowing out with an air hose, and cleaning bits with something like CMT 2050.

Bearing guided bits can leave an indenture on soft woods, and their path on any edge should be checked for any deviations like debris, knots/knotholes, voids, literally anything that would misguide the bearing. On softwoods, if a groove is being left by the bearing, an edge guide should be used.

Bearing machine screw should be checked for being tight before using. The bearing should be checked for free spin with no roughness to the rotation of the bearing when done with the router unplugged and the bearing turned with the finger. Bearing lubricants help their life even for those called "sealed bearings".

IMO, wet wood should not be routed, and I wouldn't use a guide as an alternative to accomplish the procedure.
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