Router Plate Crown: How much is too much?

[Danny Thompson]

The Bench Dog ProMax Cast iron Extension Wing and ProPlate just arrived, and I can't be any more thrilled! The Triton should be delivered later today, as well. In the meantime, I thought I'd run through the standard checklist and found the ProPlate is perfectly flat across the short dimension, but has a crown across the long dimension. This is my first "real" router table, so I need some counsel from the veterans.

When it comes to crown, how much is too much?
When it comes to Bench Dog ProPlates in particular, do they get any better than this? Has anyone ever received a replacement plate that was flatter than one they returned?

Here are the pics. First, the flat front-to-back shot. Next, the left side of the plate, against which the Starrett is registered. Third, the right side of the plate, which shows the gap. Is this a problem?

Your expertise is much appreciated.

251500251501251502

[Nick Lazz]

My plates are adjustable with set screws around perimeter of plate. I can adjust the height to get it flush with table top....If I'm missing something, I apologize. If you are just checking the plate itself, unmounted...I think I would be a little upset.

Edit: Just spit balling here..., you might want to re-check it after router is mounted. If it is a phenolic plate, the weight may help the crown.

[glenn bradley]

I agree that the router should be attached before you make a final adjustment or judgement. As to how much crown is too much? The answer is the question of how much deviation can you tolerate in your profile? Mating profiles like rail and stile bits won't tolerate much. A bead along a table top will tolerate more visually. Darned flat is best ;-)

[Ole Anderson]

I would expect a ground or milled CI plate that size to be dead on out of the box. At most the thickness of a dollar bill. That almost looks like 1/32", way too much IMO, send it back.

[Jim Riseborough]

Is your square flat?

[Curt Harms]

I think phenolic plates are typically crowned a tiny bit in the long dimension. If it were low in the middle or started out dead flat then sagged in the middle I'd be a lot more upset. I suspect the idea is that the phenolic could sag a tiny bit due to router weight and still not be low in the center. My understanding is that low in the center is a deal killer, slightly high in the center is not. It'd sure be worth a call to Bench Dog.

[pat warner]

Router table top flatness is important for safety and quality.
If the insert or continuous surface is mishapen the work will squirm over the cutter.
That will vary the profile. If the work is not flat and square, a mishapen table may constructively
combine with the defects in the work. That combination of calamities may cause the work to jam, kick back or the cutter may just tear/open the profile.
The goal then is for flatness and no interruptions.
Phenolics are strong but not flat unless remachined.
Acrylic and polycarbonate are reasonably flat but not stiff enough to resist a permanent sag, unless stressed.
Steel & aluminum can be ground to <.001" in flatness/ft.sq..
MDF can be stressed to remain flat and it is one of the best buys with respect to flatness and uniform thickness.
Bottom line: No interruptions (the work should never stop) and flat.
How flat? For joinery: ~+ or .003" max. For decorative cuts: As twisted as your tolerance for sanding out burns and tearout.

[Ken Fitzgerald]

Danny.....mount your router to the plate, put it into the opening and repeat your tests/measurements.

It maybe crowned without a mechanical load and flatten out with the mechanical load.

[Andrew Joiner]

Nothing in my shop is perfectly flat. I've found a slight crown is better than a dip. As close to flat as you can get tends to sag to a dip more often than move skyward. I make my tops so I can adjust a teeny, tiny crown in them.

[Lloyd McKinlay]

Lee Valley manufactures their router table top with a crown. From the website...Many router tables claim to be flat, and some even are, until you mount a router to them and they suddenly become concave. Each Veritas® router table top is a 16" x 24" steel plate that has been hand tuned to have a slight upward curve. This curve is specifically set so that the weight of the router cannot deform the router table to concave. When used with routers up to10 lb, the Veritas router table top will always be slightly convex, with the highest point adjacent to the bit, so your depth of cut will always be exactly as set. Because the plate is steel, it will not sag over time, as many laminate tables will.

[glenn bradley]

Lee Valley manufactures their router table top with a crown. From the website...Many router tables claim to be flat, and some even are, until you mount a router to them and they suddenly become concave. Each Veritas® router table top is a 16" x 24" steel plate that has been hand tuned to have a slight upward curve. This curve is specifically set so that the weight of the router cannot deform the router table to concave. When used with routers up to10 lb, the Veritas router table top will always be slightly convex, with the highest point adjacent to the bit, so your depth of cut will always be exactly as set. Because the plate is steel, it will not sag over time, as many laminate tables will.

I understand that LV and Rousseau do this on purpose. It is a broken logic. Crowning a router plate is like adjusting for drift on your bandsaw. Don't band-aid the symptom, cure the cause. JMHO.

[Chris Padilla]

I understand that LV and Rousseau do this on purpose. It is a broken logic. Crowning a router plate is like adjusting for drift on your bandsaw. Don't band-aid the symptom, cure the cause. JMHO.

Gravity???

[Ole Anderson]

Gravity???

Insufficient plate strength.