Why isn't my router table flat?

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Forum topic by KnickKnack posted 07-01-2012 10:39 AM 2714 views 0 times favorited 24 replies Add to Favorites Watch
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992 posts in 2290 days

07-01-2012 10:39 AM

Topic tags/keywords: router table insert plate router table insert plate question

I’ve been lucky enough to be able to move to a large-than-cupboard-sized workshop, and one of my first tasks was to make a new (version 3) router table.
I do almost everything on my router table (which is why it’s the only tool you can see in the ‘shop), and I thought I’d treat myself to a “manufactured” router table insert plate, rather than using the “hole in a bit of plywood” approach I’ve used before.
I’ve always found TrendUK to be a reliable company – I like their bits and they ship to Portugal with no fuss. So I thought I’d buy their plate…

Full specifications of which you can find here.

Feature 6 on the list is…
”Moulded with slight crown (0.8mm) for distortion free cuts.”

They’re right – it isn’t flat – my straight edge rocks slightly, but nicely, when on the crown of the plate.

So – I have 2 questions…
  1. Can someone explain to me how a non-flat plate aids in producing “distortion free cuts”?
    I just find it weird to use – not very very weird, just a bit weird – and I’d like to know if there’s some benefit (I can see the insert rings could be useful, but I don’t use big bits and a single sized hole was never an issue for me), and if so, how I reap that benefit, before I remove it and just drill a hole like I’ve done before.
  2. Aside from the removable rings, are router table insert plates really any better than “just a hole”, and if so, why?

Thanks in advance for the wisdom I know will be brought to bear here on my behalf.

-- "Do not speak – unless it improves on silence." --- "Following the rules and protecting the regulations is binding oneself without rope."

24 replies so far

View b2rtch's profile


4351 posts in 1772 days

#1 posted 07-01-2012 11:00 AM

Myself I just installed a brand new router table and an insert.
I cannot figure out how a non-flat insert would help you make better cuts.
Why don’t you ask the manufacturer of the insert what its theory is?

When I click on the link above I get this:
Product Not Found

Sorry the product you have requested is no longer available.

This could be the answer to your question.
May be this design just doesn’t work very well.
Is it working for you?
If not, can you return it?
You should ship a carton of Port wine my way, I love it.

-- Bert

View NiteWalker's profile


2710 posts in 1301 days

#2 posted 07-01-2012 11:08 AM

The general idea is that the crown would flatten out when the router is attached.

I don’t know who came up with this idea, but 1, if it’s necessary there’s an inherent weakness/problem with the router plate design, and 2, they probably never used a router table.

The trend plate looks a lot like the jessem plate, also “designed” with a slight crown. The rings are a major PITA to remove.

In regards to your second question, if you can make due with a single sized hole, and get your table absolutely flat, then a plate offers no real advantage except for easy removal of the router. You can rout a recess on the underside of the table where the router goes to lessen the thickness that the router mounts to, giving you more depth.

I plan on buying the incra aluminum magnalock plate. I do use a variety of different sized bits, and I like how easy the rings are to swap out and you can adjust them to be level with the top via set screws. A very well made plate, I’m just not a big fan of the gold color, but whatever works.

-- He who dies with the most tools... dies with the emptiest wallet.

#3 posted 07-01-2012 11:19 AM

I have the Veritas steel router table plate and it too, is deliberately and ever so slightly crowned.
Here’s the reasons.
First of all, many routers are heavy and can cause the router table top to sag just enough so that the work has to ride down in the depression and then back up out the other side. That makes an irregular pattern on the work.
The other reason is that wood isn’t always perfectly flat, so if the table is crowned at the point where the bit works the wood, the ends of the workpiece don’t raise the work in the middle.

That’s what the folks at Lee Valley said when I bought it and it has always worked well for me.
Incidently, I like the steel top because I use the Magswitch devices to secure the fence and featherboards in front of the fence.

Check out this link to their page :

-- Will trade wife's yarn for tools.

View Tyrone D's profile

Tyrone D

314 posts in 1057 days

#4 posted 07-01-2012 11:31 AM

I remember reading about the Jessem:
Someone had a crowned plate and called Jessem and they sent some bars to reinforce it.

-- --Tyrone - BC, Canada "Nothing is ever perfect, we just run out of time."

View AaronK's profile


1398 posts in 2188 days

#5 posted 07-01-2012 02:10 PM

in my old home built router table, eventually it ended up being concave where the router was. What happens then is that the depth of cut depends on pressure across the router bit… not what you want. a small crown would seem to work against this – i could see it being very handy.

View PineChopper's profile


175 posts in 921 days

#6 posted 07-01-2012 02:41 PM

My first question would be; is it made in China. If it is then that is also most likely your answer too.
If not, are all the bolts torqued the same during assembly?

View bondogaposis's profile


2697 posts in 1075 days

#7 posted 07-01-2012 02:59 PM

I imagine it is slightly crowned to accomodate the weight of the router. It should be flat after it is in place w/ the router hanging on it.

-- Bondo Gaposis

View Gene Howe's profile (online now)

Gene Howe

5939 posts in 2152 days

#8 posted 07-01-2012 03:07 PM

I use the inserts because, if I use a feather board pushing down on the work, a larger hole will allow the front corner to sometimes dip into the hole. AND, a close to zero clearance makes my “in the fence” DC system work a lot better.
The Jessem solid anodized aluminum plate is an excellent plate. Comes with the lift, though.

-- Gene 'The true soldier fights not because he hates what is in front of him, but because he loves what is behind him.' G. K. Chesterton

View KnickKnack's profile


992 posts in 2290 days

#9 posted 07-01-2012 03:44 PM

My first question would be; is it made in China. If it is then that is also most likely your answer too.
If not, are all the bolts torqued the same during assembly?

I know not where it was made, but it is designed to have this 0.8mm rise in the middle.

When I click on the link above I get this: Product Not Found
Strange – it works for me, the full URL is…

I’ve thought some more about this – say I’m routing a thin square slice out of a 10mm square length of wood – this drawing, to scale, shows the angle I’m going to be getting!

that’s a long long long way off 90°

I also find it strange when I have a longish piece of perfectly flat wood, that it’s only actually on the table at one end. And, as I route along it, at some point it’s going to “tip” from being down on one side of the table to the other side.

I agree with Aaron – slightly raised is way better than slightly dipped.

As for the weight arguments – well – that may be true, but it seems to be a “one size fits all” approach – I imagine some routers weigh a lot more than others (mine is pretty light).

I have written to Trend, drawing their attention to this discussion – we’ll see what they have to say.

Thanks for the replies – it seems I’m not going crazy after all!

-- "Do not speak – unless it improves on silence." --- "Following the rules and protecting the regulations is binding oneself without rope."

View crashn's profile


519 posts in 1189 days

#10 posted 07-01-2012 04:17 PM

I have both the Jessum and Incra plates (and lifts). The incra is far and above a better product and the magna inserts rock.

-- Crashn - the only thing I make more of than sawdust is mistakes

View Karson's profile


34902 posts in 3124 days

#11 posted 07-01-2012 04:55 PM

I made a fix for my sagging router table about 4 years ago. It still works fine.

I also assume that it’s for flex under a heavy router.

-- I've been blessed with a father who liked to tinker in wood, and a wife who lets me tinker in wood. Southern Delaware †

View Sawkerf's profile


1730 posts in 1792 days

#12 posted 07-01-2012 05:06 PM

Think about the geometry of the table and bit. If the table were slightly depressed at the bit, you would either have to use quite a bit of downward pressure to get your cut – or put up with slight variations in the profile depth.

With a slight crown, the wood will be at the correct height at the bit without using excessive downward pressure. The wood will “roll” slightly as it passes the bit, but always be at the correct height.

A perfectly flat table would be ideal – if the workpiece was also perfectly flat. A workpiece with a slight bow would route better on a crowned table than a flat (or depressed) one.

-- Adversity doesn't build reveals it.

View Joe Lyddon's profile

Joe Lyddon

7883 posts in 2776 days

#13 posted 07-01-2012 07:13 PM

I would NOT want such an insert plate in my router table…

Mine would have to be FLAT with the table…
... and the table would be strong & reinforced so that it would NOT warp / sag.

... just my opinion…

-- Have Fun! Joe Lyddon - Alta Loma, CA USA - Home: ... My Small Gallery:"

#14 posted 07-02-2012 10:53 AM

Plywood is flexible. So is plastic and most any other material usable for this purpose.
Suitable reinforcement with these materials, designed to prevent ANY deformation would be rather clumsy. By that I mean large, thick and still, a discernable flex could be measured because of the stresses caused by a 10 pound router working a large bit at 20,000 rpm or more.
So, just as semi trailers that carry large loads are arched so they do not sag under load, a good, well designed router table top can make good use of the idea.
The idea of starting out with a perfectly flat table and having it remain flat under working conditions is a great idea, but I’m afraid it’s not very practical.
I bought my Veritas table with full knowledge that it was slightly arched and additionally, for the excellent router attachment device that allows me to remove and replace the router and not have to fuss with centering it.
I believe we have all stated our beliefs and preferences.
So I’m going to bow out of this thread.


-- Will trade wife's yarn for tools.

View Joe Lyddon's profile

Joe Lyddon

7883 posts in 2776 days

#15 posted 07-02-2012 05:54 PM

If the bottom of the table is reinforced with vertical ribs, it does wonders to keep it flat.

-- Have Fun! Joe Lyddon - Alta Loma, CA USA - Home: ... My Small Gallery:"

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