Router table top deflection ????

[Greg Parrish]

Can't say I'm very happy right now. After two days working on enclosing my stand I flipped my table upright to start working on drawers and noticed the Jessem Mast-R-Top didn't look flat. Put a straight edge on it and it's not flat.

So, before I totally freak out, how much deflection would be acceptable. I can't easily get the top off without taking my whole stand apart. Ugh.............. Not a happy camper right now.

Thanks for input.

http://txbonds.zenfolio.com/img/s/v-2/p2594376540-4.jpg

http://txbonds.zenfolio.com/img/s/v-2/p2594274653-3.jpg

[Nick Decker]

I can't say what's considered acceptable, but that looks like too much to me. Is it sagging with the weight of the router and lift, or is that just "as is"?

[Nick Decker]

Also is that a precision straight edge or just a ruler of some kind?

[Greg Parrish]

<p>
It is a carpenter square that appears straight against my tablesaw and jointer cast iron tops.</p>
<p>
The router lift lift is not actually mounted yet so the deflection is not due to the router weight. I built the stand with everything upside down and the top on a flat surface. It is using the factory Jessem stand mounts with only the legs swapped out for the incra stand legs. I also added in additional supports On either side of the router hole to help support top and to form dust collection.</p>
<p>
It appears to have bent due to the thin material where the track is embedded but that may not be why I&#39;m fairly certain the top had to come like this.</p>

[Nick Decker]

If you're sure the straight edge is straight, I'd take it apart and take a similar picture with the top just lying on a flat surface. Send it to Jessem and ask what they can do. Bummer, I know, but I'm guessing they'll make it right.

[Greg Parrish]

Tried a few different edges and then decided to measure the gap. At the widest point the gap measured 0.025". That still seem like too much now that we have a measurement and not just the picture showing the light under the straight edge? Thanks.

http://txbonds.zenfolio.com/img/s/v-2/p2594517650-4.jpg

http://txbonds.zenfolio.com/img/s/v-2/p2594517627-4.jpg

[David Wong]

I would remove the top and check the underside to see if the screw holes where the top is screwed to the table are clean and flat. Perhaps some excess material is holding the table proud along the edges. Also check to see how flat the metal supports are with your straightedge, before you put on the table.

I have a Kreg router table, and I had to shim under the table surface at several locations to get it to a flatness I was happy with.

[Greg Parrish]

Ugh....... Hoped to avoid that as based on how stand cabinet is designed I can't get to the top screws due to the cabinet sides. I'll have to take the upper framing off too.

Im tempted to add two layers of 3/4" mdf under the phenolic top to give it more support. Any reason I couldn't screw the phenolic down from the top to make leveling easier if I drilled and countersunk the screw holes?

[Greg Parrish]

Well, good news and bad.


good news is that once removed and sitting on my outfeed table, the router top appears to be nearly perfectly flat.

Bad ad news is that means my stand/cabinet is causing the stress on the top and I'll have to rethink it and maybe start over.

[Ellery Becnel]

Can you shim where the areas are causing the deflection. Mainly at the screw locations. This may avoid redoing your cabinet.
Just a thought.

Ellery Becnel

[Nick Decker]

Hard to give advice since I don't know the design of your stand and how it attaches to the top, but I wouldn't drill any holes down through the top side of the top. That's just creating something for your work to snag on as it moves across the table, regardless of how well you countersink the screws.

[John Lankers]

I don't know how exactly and at how many points the top is attached to the cabinet, but I would install the screws in sequence (think truck wheel), 1st snug them all up then come back and give each screw another 1/8 turn while checking for flatness, shim if necessary - repeat til done.

[Mike Berti]

Is it possible that somehow the cutout in the table top is too narrow and is pressuring the Jessem plate creating that concave surface?

[john lawson]

I have found that most router table tops are not flat. My experience is that all the magic happens in front of the router bit, so what I do is make sure there is no gap between the workpiece and the router bit. I do this in two steps. First check the router plate for flat. If it is then check the plate along with the table. Usually the table will sag in the middle and plate will be low. In the first picture this looks to be the case. I will then decide if I need to raise the PLATE ONLY to eliminate the gap. That means that my plate may be slightly high and may cause a bump. If it's too much of a bump consider filing down the bump so you can feed the work smoothly. Remember, the only thing that affects the quality is the flatness at the router bit and if you achieve that everything else won't matter. If the router plate is not flat I would want to return it. That is hard to fix.

If your table is flat today it may not be in 6 months or a year so keep this in mind. I know this may not be what you want to hear but for me the idea is what works, and most wood or MDF router table tops are susceptible to this condition. Good luck whatever you decide

[Chris Parks]

There needs to be a move to change the design of router tables so th top does not have to support the weight of the router and lift but I can't see it happening any time soon. if a CNC motor is used and side mounted the sagging top issue goes away completely and a lot of money gets saved because the lift is not needed. The link shows a commercially made version of this which some people have copied with their own design, notice how the height change is done, simple and neat.....

https://vimeo.com/117246317

[Mike Cutler]

Is it possible to use a fairing compound and level it? Then maybe apply a nice Baltic birch top.
You really want that table top flat.
.025?is actually more than you think. If two pieces have to mate together, you could end up off by .050

[Greg Parrish]

Thanks guys. Due to other obligations I was forced to walk away from it after the weekend so I've had time to think on it. The top sits flat once removed. Here is what I've deduced after the fact. The stand assembly is applying pressure once I built the cabinet into it. In other words, the cabinet is so tight of a fit that it is putting stress onto the legs and stringers that screw to the bottom of the table top. This stress was actually enough that it was pulling and pushing on the top enough to deform it.

The way I designed the stand means that I can't get to the screws that go into the table while the stringers are bolted to the legs. Im Going to have to modify the top connection slightly and what I think I've decided to try first is to install a double layer of 3/4" mdf on top of the stand and then apply my phenolic top to that. Should give a nice flat, thick backing for my phenolic to rest on.

Will continue to to think about it as I may ultimately scrap it and start over n the cabinet design but we will see.

[Mike Berti]

You are right. (Unlike other fields, the woodworking community is very conservative and slow to accept new changes).
I was thinking of building a router table with a tilting top, but with the router attached to the sides (or bottom), not the top. I can build it, but the problem is that I can’t install a router lift. All commercial lifts have the rectangle plate on the top. The only alternative is building a DIY lift.

[Chris Parks]

You are right. (Unlike other fields, the woodworking community is very conservative and slow to accept new changes).
I was thinking of building a router table with a tilting top, but with the router attached to the sides (or bottom), not the top. I can build it, but the problem is that I can’t install a router lift. All commercial lifts have the rectangle plate on the top. The only alternative is building a DIY lift.

I can't see the lift being a big problem, a side mounted CNC spindle(s) is lifted and lowered with the panel it is attached to as in my linked video. If the top does not have a router attached to it then all sorts of possibilities open up. It can be removeable by lifting it off locating pins, it does not have to be hugely heavy and thick etc. Water cooled spindles are a lot more quiet than routers which is another big plus.