Crown in router table top

[Rob Holcomb]

My router table build is coming along nicely but when I built my top (2 sheets of 3/4" ply covered with laminate) it developed a slight crown. Over the length of it (36") it measures about 1/16". I haven't done the cutout for the router plate yet as the Incra Mast R Lift hasn't arrived yet. It's due to be delivered tomorrow. Do you think the crown will settle down with the weight of the plate, lift assembly and Porter Cable 7518 router? The router weighs 14.5 pounds and the lift with plate weighs 18 pounds. I plan on adding cross braces to the cabinet to eliminate sag once I know exactly where to place them but if the crown doesn't settle down from the cutout and weight of the lift and router, would it be appropriate to screw the top down to the cross braces? I really don't want to do this because to remove the top would then require removal of the screws but having a top that's flat is so important. What are your thoughts?

Thanks,

Rob

[Jeff Duncan]

I doubt the crown will settle much in 1-1/2" material, but it's easy enough to find out. Find something that weights approx. the amount of the router and pop it on the middle of the table!

My guess is it's barely going to move at all. If that's the case I'd put some nice structural ribs on the bottom of the top to pull the crown down....no glue though! Even if is sags over time you can still loosen the screws and strategically place shims to get her flat again.

good luck,
jeffD

[Peter Kuhlman]

If I remember correctly - big IF!!
Seems Lee Valley has a router table and the top is deliberately crowned as this does 2 things -
--helps compensate for any droop from the router weight
--makes sure that the wood is absolutely at the surface of the table top right where the cutter is operating.

I would be far more concerned with a dished top. 1/16" of rise over 36" length is extremely minimal and may very well work to your advantage.

[frank shic]

a dished top can cause you tons of grief if you mill long pieces of stock. took me years to figure out why the cut profile would taper towards the ends :/

[Rob Holcomb]

Thanks Guys! I've been fretting over this since I noticed the crown. I'll see how things go and hopefully my worries will end up being not a big deal.

[Caspar Hauser]

I crowned my router table by adding thin washers between the top (reclaimed corian) and the aluminium braces. As mentioned it helps in bringing the workpiece and cutter together where it matters.

CH

[mreza Salav]

I'm in the middle of making my router table and have made the top out of two 3/4" MDF laminated with fomica laminated on top.
It will house a PRL lift with 3.5HP router (which are heavy). I found that the 38" top I've made can be made to move so I suspect your's will be easy to pull down from underneath too.
I've made my base fairly strong and I am going to screw it to the top, shims will be used (if needed) to flatten the top.

[frank shic]

a crown is way better than a dish. you can at least put more pressure on the piece as it passes over the router plate and not worry about it getting thrown off by the higher edges that you'd encounter in a dished situation. show us pics!!!

[Peter Aeschliman]

Agreed. 1/16" over 36" and with the added weight of the router and lift assemblies, you'll be fine. Dish would be a much bigger problem.

[Rob Holcomb]

Frank, I'm still waiting for the Incra Mast R Lift to be delivered (Supposed to arrive today) and plan on getting in the shop this evening to continue with the build. If I think about bringing my camera out to the shop, I'll snap some pics this evening and post them. Thanks everyone for the advice about my crown situation. I feel better about how things will be turning out now that you've all set my mind at ease.